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A crucial factor influencing the mass balance of the West Antarctic Ice Sheet is the Amundsen Sea Low (ASL), a climatological low‐pressure region situated off the West Antarctic coast. However, albeit the deepening of the ASL since the 1950s has been attributed to anthropogenic forcing, the multi‐decadal variability of the ASL remains poorly understood, because of a lack of long observations. Here, we apply a newly developed data assimilation method to reconstruct the ASL over 1870–2000. We study the forced and internal variability of the ASL using our new reconstruction in concert with existing large ensembles of climate model simulations. Our findings robustly demonstrate that an atmospheric teleconnection originating from the tropical Indo‐Pacific is the main driver of ASL variability at the multi‐decadal time scale, with resemblance to the Interdecadal Pacific Oscillation. Since the mid‐20th century, anthropogenic forcing has emerged as a dominant contributor to the strengthening of the ASL. Plain Language Summary: Changes in the West Antarctic Ice Sheet mass balance (i.e., the difference between the gain and loss of ice mass) are partly influenced by large‐scale winds, and in particular, a climatological low‐pressure feature located off the West Antarctic coast called the Amundsen Sea Low (ASL). Yet, although the long‐term strengthening of the ASL since the mid‐20th century has been demonstrated to be related to anthropogenic forcing, our understanding of the variability of the ASL on time‐scales of decades is poorly known. In this paper, we therefore investigate the origins of this variability since 1870, and quantify the relative contributions of human‐caused climate changes and natural variability of the climate system. For this purpose, we use several ensembles of model simulations as well as new climate reconstructions that combine paleoclimate records with model simulations using a statistical method. Our results indicate that the multi‐decadal variability of the ASL is strongly driven by tropical variability in the Indo‐Pacific through atmospheric connections between this region and the Amundsen Sea. Our reconstruction, when compared with a large ensemble of model simulations, indicates that since 1950, human‐induced climate forcing has become a dominant driver of long‐term ASL variability, contributing equally to tropical variability. Key Points: The large‐scale atmospheric circulation in West Antarctica exhibits a strong multi‐decadal variability superimposed by a 20th‐century trendThe multi‐decadal variability of this large‐scale atmospheric circulation is strongly governed by the Indo‐Pacific tropical variabilitySince 1950, anthropogenic forcing has emerged as a key driver of the long‐term change of this atmospheric circulation [ABSTRACT FROM AUTHOR]

After days of intense solar activity, active region AR3664 launched seven CMEs toward Earth producing an extreme G5 geomagnetic storm commencing at 17:05 UT on 10 May 2024. The storm impacted power grids, disrupted precision navigational systems used by farming equipment, and generated aurora seen around the globe. The storm produced remarkable effects on composition, temperature, and dynamics in the Earth's thermosphere that were observed by NASA's Global‐scale Observations of the Limb and Disk (GOLD) mission and are reported here for the first time. We use synoptic disk images of ΣO/N2 and neutral temperature (at ∼160 km) measured by GOLD to directly link dynamics resulting from the storm with dramatic changes in thermospheric composition and temperature. We observe a heretofore unseen spatial morphology simultaneously in ΣO/N2, neutral temperature, and total electron content. Equator‐to‐pole temperature differences reach 400 K with high latitude peak neutral temperatures near 160 km exceeding 1400 K. Plain Language Summary: On Saturday 10 May 2024, the sun launched a wave of energized plasma toward the Earth. A large disturbance in the Earth's magnetic field associated with the solar wind resulted in an extreme geomagnetic storm. The storm impacted power grids, disrupted navigational systems used by farming equipment, and produced aurora seen around the globe. The storm produced remarkable effects in the Earth's upper atmosphere that were observed by NASA's Global‐scale Observations of the Limb and Disk (GOLD) mission. In this letter, we use images measured by GOLD to directly link atmospheric dynamics resulting from the May 10–12 superstorm with dramatic changes in composition, temperature, and global circulation in the Earth's upper atmosphere. We observe previously unseen structure in the upper atmosphere associated with equator‐to‐pole temperature differences exceeding 400 K. Peak neutral temperatures near 160 km exceed 1400 K at high latitudes. Key Points: GOLD disk images of ΣO/N2 and neutral temperature link storm time dynamics with changes in thermospheric composition and temperatureWe observe a previously unseen spatial morphology in ΣO/N2, neutral temperature, and total electron contentPeak equator‐to‐pole temperature differences exceed 400 K but relax to pre‐storm conditions well before ΣO/N2 [ABSTRACT FROM AUTHOR]

We investigate the position and intensity changes of the Intertropical Convergence Zone (ITCZ) over Asia (50°E−135°E) relative to the preindustrial period annually and seasonally during the Last Interglacial (LIG), Last Glacial Maximum (LGM), and mid‐Holocene (MH) using available models from phases 3 and 4 of the Paleoclimate Modeling Intercomparison Project. The multi‐model mean shows that the June–July–August ITCZ variations generally dominate the annual changes. The Asian ITCZ shifts northward over western Asia and southward over the eastern side in both the LIG and MH, and the opposite occurs in the LGM. Its intensity varies with longitude similarly for the LIG and MH and generally weakens in the LGM. Precipitation changes associated directly with ITCZ indices are primarily caused by the dynamic term in the LIG and MH, while both dynamic and thermodynamic terms play roles in the LGM, with major contributions from the convergence components. Plain Language Summary: As an intense rain belt, the Intertropical Convergence Zone (ITCZ) has an important influence on the regional climate, particularly over Asia. However, its future and past behaviors remain unclear. Based on multi‐model experiments, we investigate Asian ITCZ changes in location and intensity during the past three typical periods: the interglacial periods of the Last Interglacial and the mid‐Holocene and the glacial period of the Last Glacial Maximum. The Asian ITCZ overall strengthens and regionally moves northward over the western part and southward over the eastern part during the two interglacial periods relative to its preindustrial state, which are generally opposite to the position and intensity changes in the glacial period. These ITCZ changes are directly caused by uneven precipitation changes, which are dominated by atmospheric circulation changes during interglacial periods and additionally contributed from water vapor content changes during glacial periods, primarily through the vertical motion of air. Key Points: Asian Intertropical Convergence Zone (ITCZ) shifts northward over western Asia and southward over the eastern side in Last Interglacial (LIG) and mid‐Holocene (MH), and the opposite occurs in Last Glacial Maximum (LGM)Asian ITCZ intensity varies with longitude similarly for LIG and MH, while it weakens during LGMDynamic term dominates the ITCZ‐related precipitation changes in LIG and MH, while both dynamic and thermodynamic terms play roles in LGM [ABSTRACT FROM AUTHOR]

At mid‐latitudes, a narrow band of near‐surface wind convergence (NSWC) overlies the western boundary currents in long‐term climatology as a response to steep sea surface temperature gradients. The underlying dynamics shaping mean convergence in the mid‐latitude region have been investigated in detail. In polar regions, surface temperature gradients are intense along the sea ice edges. However, literature concerning NSWC near sea ice edges is limited. This study investigates time‐mean NSWC along sea ice edges and its shaping processes, focusing on the Greenland Sea, based on atmospheric reanalysis. In cold‐season climatology, positive NSWC overlies the sea ice edge, resulting in a localized upward motion reaching the free atmosphere. The mean NSWC was insensitive to sea ice thickness and surface roughness in the regional model. This study suggests that, in addition to local atmospheric boundary processes, extreme NSWC events play a vital role in shaping the mean distribution. Although these features are similar to those along the Gulf Stream, atmospheric fronts appear to play a relatively minor role in the Greenland Sea. Instead, the frequent cyclone generation near the sea ice edge and the anticyclonic circulation over Greenland in conjunction with the transient synoptic circulation seem essential. In the warm season, positive NSWC was virtually missing in the Greenland Sea, unlike in the Gulf Stream region, reflecting the shallow virtual temperature response to the surface thermal forcing. This study contributes to understanding the mechanisms by which sea ice variability affects large‐scale atmospheric circulation in remote regions. Plain Language Summary: Previous studies have argued that sea ice variability in Arctic regions could affect large‐scale atmospheric circulation in remote regions. However, the underlying mechanisms remain unclear. A deeper understanding of the impact of sea ice on the local atmosphere will aid in revealing these mechanisms. The present study investigates small‐scale (less than 1,000 km) atmospheric features close to sea‐ice edges, where surface temperature gradients are intense and can exert distinct impacts on the atmosphere. In the winter, the sea‐ice edge distinctly modulates the near‐surface wind, leading to an narrow band of intense upward wind. This upward wind reaches the middle of the atmosphere, suggesting that these features could relate to the effect of sea ice variability on large‐scale atmospheric circulation in remote regions. The physical processes modulating the mean near‐surface winds near the sea‐ice edge are found to be similar to those along the warm currents at the western edge of the basins (such as the Gulf Stream). However, atmospheric fronts appear to play a less important role. Instead, the frequent cyclone generation near the sea‐ice edge and the combination of the clockwise near‐surface wind around Greenland and near‐surface wind blowing from the ocean to sea‐ice regions appear essential. Key Points: A distinct band of mean near‐surface wind convergence overlies the sea ice edge in the Greenland Sea during winterThe mean near‐surface wind convergence along the sea ice edge is insensitive to ice thickness and surface roughness in a numerical modelThe anticyclonic circulation over Greenland and transient synoptic circulation are essential for shaping the time‐mean wind convergence [ABSTRACT FROM AUTHOR]

We analyze the impact of a disintegrated Greenland Ice Sheet (GrIS) on the global climate through steady-state simulations with the MPI-ESM (Max Planck Institute for Meteorology Earth System Model). This advances our understanding of the intricate feedbacks between the GrIS and the full climate system. Sensitivity experiments enable the quantification of the individual contributions of altered Greenland surface elevation and properties (e.g., land cover) to the atmospheric and oceanic climate response. Removing the GrIS results in reduced mechanical atmospheric blocking, warmer air temperatures over Greenland and thereby changes in the atmospheric circulation. The latter alters the wind stress on the ocean, which controls the ocean-mass transport through the Arctic Gateways. Without the GrIS, the upper Nordic Seas are fresher, attenuating deep-water formation. In the Labrador Sea, deep-water formation is weaker despite a higher upper-ocean salinity, as the inflow of dense overflow from the Denmark Strait is reduced. Our sensitivity experiments show that the atmospheric response is primarily driven by the lower surface elevation, whereas altered Greenland surface properties mostly amplify but also counteract few of the changes. The lower Greenland elevation dominates the ocean response through wind-stress changes. Only in the Labrador Sea, altered Greenland surface properties dominate the ocean response, as this region stores excessive heat from the Greenland warming. The main drivers vary vertically: The elevation effect controls upper-ocean densities, while surface properties are important for the intermediate and deep ocean. Despite the confinement of most responses to the Arctic, a disintegrated GrIS also influences remote climates. The altered climate in response to a GrIS disintegration also constrains a potential ice-sheet regrowth to high-bedrock eastern Greenland. [ABSTRACT FROM AUTHOR]

Detecting and interpreting long-term changes in typhoon translation speed in observations remains challenging, contrasting with increased confidence in the poleward migration of typhoons. Here, I show a significant relationship between the basin-wide translation speed and the latitudinal position of tropical cyclones in the western North Pacific over 1980–2023. First, because tropical cyclones move faster at higher latitudes, the significant poleward migration (80 km/decade) increases the yearly basin-wide translation speed by 5% over the period. This effect reduces the detectability of a slowing trend. Second, the basin-wide translation speed solely contributed by regional translation speed has slowed by 18%, mostly in the late stage of the cyclone lifecycle. The translation speed slowdown and the poleward migration are likely caused by the same climate drivers through the interconnected large-scale atmospheric circulation between the tropics and subtropics. My findings suggest exacerbated tropical cyclone-related risk in the subtropical regions in a changing climate. [ABSTRACT FROM AUTHOR]

Progress in understanding the impact of mesoscale variability, including gravity waves (GWs), on atmospheric circulation is often limited by the availability of global fine-resolution observations and simulated data. This study presents momentum fluxes due to atmospheric GWs extracted from four months of an experimental "nature run", integrated at a 1 km resolution (XNR1K) using the Integrated Forecast System (IFS) model. Helmholtz decomposition is used to compute zonal and meridional flux of vertical momentum from ~1.5 petabytes of data; quantities often emulated by climate model parameterization of GWs. The fluxes are validated using ERA5 reanalysis, both during the first week after initialization and over the boreal winter period from November 2018 to February 2019. The agreement between reanalysis and IFS demonstrates its capability to generate reliable flux distributions and capture mesoscale dynamic variability in the atmosphere. The dataset could be valuable in advancing our understanding of GW-planetary wave interactions, GW evolution around atmospheric extremes, and as high-quality training data for machine learning (ML) simulation of GWs. [ABSTRACT FROM AUTHOR]

White dwarfs offer a unique opportunity to search nearby stellar systems for signs of life, but the habitable zone around these stars is still poorly understood. Since white dwarfs are compact stars with low luminosity, any planets in their habitable zone should be tidally locked, like planets around M dwarfs. Unlike planets around M dwarfs, however, habitable white dwarf planets have to rotate very rapidly, with orbital periods ranging from hours to several days. Here we use the ExoCAM global climate model to investigate the inner edge of the habitable zone around white dwarfs. Our simulations show habitable planets with ultrashort orbital periods (P ≲ 1 day) enter a "bat rotation" regime, which differs from typical atmospheric circulation regimes around M dwarfs. Bat rotators feature mean equatorial subrotation and a displacement of the surface's hottest regions from the equator toward the midlatitudes. We qualitatively explain the onset of bat rotation using shallow water theory. The resulting circulation shifts increase the dayside cloud cover and decrease the stratospheric water vapor, expanding the white dwarf habitable zone by ∼50% compared to estimates based on 1D models. The James Webb Space Telescope should be able to quickly characterize bat rotators around nearby white dwarfs thanks to their distinct thermal phase curves. Our work underlines that tidally locked planets on ultrashort orbits may exhibit unique atmospheric dynamics, and guides future habitability studies of white dwarf systems. [ABSTRACT FROM AUTHOR]

Snow cover on the Qinghai-Tibet Plateau significantly impacts the climate, hydrology, and ecology of China and East Asia. Current studies mainly use snow cover days to describe its duration, overlooking the snow's discontinuous nature. This study analyzes snow phenology and the spatiotemporal distribution of continuous snow cover events on the Qinghai-Tibet Plateau from 1961 to 2019. The findings indicate that continuous snow cover days better capture the temporal discontinuity of snow cover compared to snow cover days. The contribution and continuity are lower than regions like North America, Europe, Northeast and Xinjiang in China, indicating poorer snow cover continuity on the Qinghai-Tibet Plateau. Additionally, we found that temperature and precipitation, especially autumn temperatures and spring and winter precipitation, significantly impact various snow indices. Wind speed also significantly impacts snow cover, particularly in autumn. Atmospheric circulation indirectly affects the snow cover discontinuity by influencing temperature and precipitation. [ABSTRACT FROM AUTHOR]

Globally available and highly vertically resolved wind fields are crucial for the analysis of atmospheric dynamics for the benefit of climate studies. Most observation techniques have problems to fulfill these requirements. Especially in the tropics and in the Southern Hemisphere more wind data are required. In this study, we investigate the potential of radio-occultation (RO) data for climate-oriented wind field monitoring in the tropics, with a specific focus on the equatorial band within ± 5° latitude. In this region, the geostrophic balance breaks down, due to the Coriolis force term approaching zero, and the equatorial-balance equation becomes relevant. One aim is to understand how the individual wind components of the geostrophic-balance and equatorial-balance approximations bridge across the Equator and where each component breaks down. Our central aim focuses on the equatorial-balance approximation, testing its quality by comparison with ERA5 reanalysis data. The analysis of the zonal and meridional wind components showed that while the zonal wind was well reconstructed, it was difficult to estimate the meridional wind from the approximation. However, we still found a somewhat better agreement from including both components in the zonal-mean total wind speed in the troposphere. In the stratosphere, the meridional wind component is close to zero for physical reasons and has no relevant impact on the total wind speed. In general, the equatorial-balance approximation works best in the stratosphere. As a second aim, we investigated the systematic data bias between using the RO and ERA5 data and find it smaller than the bias resulting from the approximations. We also inspected the monthly-mean RO wind data over the full example year of 2009. The bias in the core region of highest quality of RO data, which is the upper troposphere and lower stratosphere, was generally smaller than ± 2 ms-1. This is in line with the wind field requirements of the World Meteorological Organization. Overall, the study encourages the use of RO wind fields for regional-scale climate monitoring over the entire globe, including the equatorial region, and also showed a small improvement in the troposphere when including the meridional wind component in the zonal-mean total wind speed. [ABSTRACT FROM AUTHOR]

The width of the Inter-Tropical Convergence Zone (ITCZ) affects tropical rainfall, Earth's albedo, large-scale circulation, and climate sensitivity. To better understand the ITCZ width and its effects on global climate, we present a protocol to force changes in ITCZ width in climate models. Starting from an aquaplanet configuration with a slab ocean, adding surface heat fluxes in the deep tropics forces the ITCZ to narrow, and subtracting them causes it to widen. The protocol successfully generates changes in ITCZ width in all four climate models used in this study. ITCZ width in each model responds linearly to forcing magnitude and sign. Comparing across the four climate models, a response to varying ITCZ width that is remarkably consistent among models is the ITCZ strength, which is greater the narrower the ITCZ. On the other hand, the effect of varying ITCZ width on climate sensitivity is divergent among our four models, varying even in sign. Results from this pilot study highlight the connections between surface fluxes, ITCZ width, and the wider climate. A comprehensive model intercomparison project (MIP) has the potential to advance understanding of both the physical processes shaping ITCZ width and its influence on remote atmospheric circulations and global climate. [ABSTRACT FROM AUTHOR]

The quantitative characterization and prediction of localized severe weather events that emerge as coherences generated by the highly non-linear interacting multivariate dynamics of global weather systems poses a significant challenge whose solution is increasingly important in the face of climate change where weather extremes are on the rise. As weather measurement systems (multiband satellite, radar, etc) continue to dramatically improve, increasingly complex time-dependent multivariate 3D datasets offer the potential to inform such problems but pose an increasingly daunting computational challenge. Here we describe the application to global weather systems of a novel computational method called the Entropy Field Decomposition (EFD) capable of efficiently characterizing coherent spatiotemporal structures in non-linear multivariate interacting physical systems. Using the EFD derived system configurations, we demonstrate the application of a second novel computational method called Space-Time Information Trajectories (STITs) that reveal how spatiotemporal coherences are dynamically connected. The method is demonstrated on the specific phenomenon known as atmospheric rivers (ARs) which are a prime example of a highly coherent, in both space and time, severe weather phenomenon whose generation and persistence are influenced by weather dynamics on a wide range of spatial and temporal scales. The EFD reveals how the interacting wind vector field and humidity scalar field couple to produce ARs, while the resulting STITS reveal the linkage between ARs and large-scale planetary circulations. The focus on ARs is also motivated by their devastating social and economic effects that have made them the subject of increasing scientific investigation to which the EFD may offer new insights. The application of EFD and STITs to the broader range of severe weather events is discussed. [ABSTRACT FROM AUTHOR]

Identifying seismic CH4 anomalies via remote sensing has been verified as a legitimate method. However, there are still some problems, such as unknown reliability due to the complex characteristics of seismic anomalies. In this study, a multi-dimensional and multi-scale methane seismic anomaly extraction process for remote sensing was constructed with the Robust Satellite Technique (RST) based on the Atmospheric Infrared Sounder (AIRS) CH4 data and then applied to the 2023 Türkiye–Syria earthquake. This study obtained the two-dimensional temporal–spatial distribution of methane anomalies and temporal variation in the anomaly index. Based on this, the three-dimensional profile structure of the 8-day methane anomaly was extracted to determine the reliability of the anomaly. Finally, based on the daily methane anomaly, combined with atmospheric circulation and backward trajectory analysis as auxiliary tools, the influence of air mass migration was excluded to enhance the accuracy of CH4 anomaly determination. The results show that the three-dimensional anomalous structure is consistent with the geological characteristics of tectonic activities, and it appears as a "pyramid" or "inverted pyramid" type in a three-dimensional space. The anomalies caused by air mass migration can be eliminated by combining them with synoptic-scale circulation motion. The time series calculated at the epicenter or a certain point in a region may not accurately reflect the influence of regional or specific tectonic activity in the atmosphere. Thus, the optimal determination of the range and magnitude of atmospheric anomalies caused by tectonic activities is a difficult task for future research. [ABSTRACT FROM AUTHOR]

Atmospheric gravity waves (GWs) can strongly modulate middle atmospheric circulation and can be a significant factor for the coupling between the lower atmosphere and the middle atmosphere. GWs are difficult to resolve in global atmospheric models due to their small scale; thus, GW observations play an important role in middle atmospheric studies. The climatology of GW variance and momentum in the low-latitude mesosphere and lower thermosphere (MLT) region are revealed using multiple meteor radars, which are located at Kunming (25.6°N, 103.8°E), Sanya (18.4°N, 109.6°E), and Fuke (19.5°N, 109.1°E). The climatology and longitudinal variations in GW momentum fluxes and variance over the low-latitude region are reported. The GWs show strong seasonal variations and can greatly control the mesospheric horizontal winds via modulation of the quasi-geostrophic balance and momentum deposition. The different GW activities between Kunming and Sanya/Fuke are possibly consistent with the unique prevailing surface winds over Kunming and the convective system over the Tibetan Plateau according to the European Centre for Medium-Range Weather Forecasts (ECMWF), Reanalysis v5 (ERA5) data, and outgoing longwave radiation (OLR) data. These findings provide insight for better understanding the coupling between the troposphere and mesosphere. [ABSTRACT FROM AUTHOR]

The earliest Asian summer monsoon onset (SMO) occurs in the Bay of Bengal (BoB), heralding the coming of the rainy season. In late April or early May, the strong sea surface temperature (SST) diurnal variation accompanied by ocean surface warming triggers the SMO. However, this observed diurnal cycle intensity cannot be reasonably simulated by state‐of‐the‐art climate models, resulting in a spurious delayed SMO. To address this issue, the SST diurnal cycle parameterized by a diagnostic sublayer scheme was incorporated into a climate model named FIO‐ESM v2.0. The large diurnal amplitude of SST contributes to surface warming and changes atmospheric circulation. Consequently, the high‐pressure anomaly at high levels and an inverted trough at low levels promote more convective activity, triggering an earlier SMO. Our findings improve the ability of climate models in simulating the evolution of the Asian monsoon system. Plain Language Summary: Asian summer monsoon onset (SMO) accompanied by the coming of the rainy season has a significant impact on the lives and livelihoods of more than half of the world's population. However, state‐of‐the‐art climate models struggle to capture the major features of SMO accurately. The simulated diurnal amplitude of sea surface temperature (SST) is much smaller compared with observation, resulting in a cold bias in SST and a delayed SMO in the Bay of Bengal (BoB). Here, we incorporated a diagnostic sublayer parameterization into the climate model to account for the effect of a strong diurnal cycle. The SST in the BoB increases, and more convective activities are promoted in response to the warmer underlying surface. Changes in monsoon circulation create favorable environmental conditions for an advanced SMO. Considering the effect of strong diurnal variation provides a solution to reduce common biases of the climate model in simulating SMO. Key Points: The spurious delayed Asian summer monsoon onset (SMO) is improved by including the effect of large sea surface temperature (SST) diurnal amplitude in a climate modelStrong diurnal variation of SST contributes to upper ocean warming in the Bay of Bengal before the Asian SMOLarge‐scale circulation with favorable conditions for convection activity in response to ocean warming triggers an advanced monsoon onset [ABSTRACT FROM AUTHOR]

This study explores the added value (AV) of a regional Earth system model (ESM) compared to an atmosphere-only regional climate model (RCM) in simulating West African monsoon (WAM) rainfall. The primary goals are to foster discussions on the suitability of coupled RCMs for WAM projections and deepen our understanding of ocean–atmosphere coupling's influence on the WAM system. The study employs results from dynamical downscaling of the ERA-Interim reanalysis and Max Plank Institute ESM, low resolution (MPI-ESM-LR), by two RCMs, atmosphere only (REMO) and REMO coupled with Max Planck Institute Ocean Model (MPIOM) (ROM), at ∼25-km horizontal resolution. Results show that in regions distant from coupling domain boundaries such as West Africa (WA), constraint conditions from ERA-Interim are more beneficial than coupling effects. REMO, reliant on oceanic sea surface temperatures (SSTs) from observations and influenced by ERA-Interim, is biased under coupling conditions, although coupling offers potential advantages in representing heat and mass fluxes. Contrastingly, as intended, coupling improves SSTs and monsoon fluxes' relationships under ESM-forced conditions. In this latter case, the coupling features a dipole-like spatial structure of AV, improving precipitation over the Guinea Coast but degrading precipitation over half of the Sahel. Our extensive examination of physical processes and mechanisms underpinning the WAM system supports the plausibility of AV. Additionally, we found that the monsoonal dynamics over the ocean respond to convective activity, with the Sahara–Sahel surface temperature gradient serving as the maintenance mechanism. While further efforts are needed to enhance the coupled RCM, we advocate for its use in the context of WAM rainfall forecasts and projections. [ABSTRACT FROM AUTHOR]

Summer drought over northern Asia (NA) seriously threatens the local fragile ecological environment and social economy development. In this study, using the standardized precipitation evapotranspiration index (SPEI), we first identify the dominant modes of interannual variability in summer drought condition over NA and then explore the atmospheric patterns responsible for the formation of the modes. The results show that the first empirical orthogonal function (EOF1) mode of summer SPEI over NA exhibits a meridional dipole pattern, which is influenced primarily by the polar–Eurasian teleconnection (POL) and circumglobal teleconnection (CGT) patterns. Under the influence of negative POL and positive CGT patterns, there is an anomalous anticyclone (cyclone) over northwestern Siberia (Lake Baikal to Northeast China). Such atmospheric circulations lead to meridional dipole patterns in air temperature, moisture condition, vertical motion, and cloud cover over NA, favoring decreased (increased) precipitation and increased (decreased) potential evapotranspiration over northern (southern) NA, finally contributing to the formation of EOF1. The second EOF (EOF2) shows an approximate zonal dipole pattern, which is influenced by the British–Baikal Corridor (BBC) and Scandinavia (SCA) teleconnection patterns. The positive BBC and SCA patterns can lead to an anomalous anticyclone over the Ural Mountains and a cyclone over Lake Baikal. Such atmospheric circulations result in a zonal dipole pattern in precipitation and potential evapotranspiration over NA through changing the local moisture condition, air temperature, and radiation, consequently favoring the formation of EOF2. Fitting analysis indicates that the aforementioned atmospheric factors can explain 76% (55%) of the interannual variability of EOF1 (EOF2). [ABSTRACT FROM AUTHOR]

The models that participated in the Coupled Model Intercomparison Project (CMIP) exhibit large biases in Arctic sea ice climatology that seem related to biases in seasonal atmospheric and oceanic circulations. Using historical runs of 34 CMIP6 models from 1979 to 2014, we investigate the links between the climatological sea ice concentration (SIC) biases in September and atmospheric and oceanic model climatologies. The main intermodel spread of September SIC is well described by two leading EOFs, which together explain ∼65% of its variance. The first EOF represents an underestimation or overestimation of SIC in the whole Arctic, while the second EOF describes opposite SIC biases in the Atlantic and Pacific sectors. Regression analysis indicates that the two SIC modes are closely related to departures from the multimodel mean of Arctic surface heat fluxes during summer, primarily shortwave and longwave radiation, with incoming Atlantic Water playing a role in the Atlantic sector. Local and global links with summer cloud cover, low-level humidity, upper or lower troposphere temperature/circulation, and oceanic variables are also found. As illustrated for three climate models, the local relationships with the SIC biases are mostly similar in the Arctic across the models but show varying degrees of Atlantic inflow influence. On a global scale, a strong influence of the summer atmospheric circulation on September SIC is suggested for one of the three models, while the atmospheric influence is primarily via thermodynamics in the other two. Clear links to the North Atlantic oceanic circulation are seen in one of the models. [ABSTRACT FROM AUTHOR]

Frequent drought has posed widespread, large-scale and extremely severe impact on the ecological environment under global climate and human activities. This study aims to analyze the spatiotemporal dynamic evolution of drought in China. A threshold of -0.5 was chosen to identify drought conditions. A raster was set as the drought state at standardized precipitation evapotranspiration index (SPEI) less than -0.5. The start and end times of drought were varied for each raster within a single event, indicating the dynamic and evolving drought. At the same time, some rasters exited the drought states, while others entering. The contribution rates of drought to rasters were calculated at a given time, in order to capture the dynamic changes in drought. Three perspectives were considered: the extent of drought impact, duration, and severity. The SPEI was then used to assess the drought, in order to introduce the concept of persistent drought rasters. Large-scale and persistent drought events were identified to investigate the spatiotemporal dynamic evolution from 1961 to 2020, together with their response mechanisms to the atmospheric circulation. The research findings can be summarized as follows: 1) A total of 47 events occurred between 1961 and 2020. The 1970s witnessed the highest frequency of large-scale persistent drought events, with 10 occurrences, while the 2000s and 2010s each experienced 9 such events. The average duration of these drought events was 7.14 months, with the longest average duration in the 1960s at 11.83 months. The average extent was 28.66%, with the highest average extent index reaching 33.75% in the 2000s.The average severity was -2.86 for the 47 large-scale persistent drought events. Between 1980 and 2010, the average area affected by persistent drought events each decade showed a continuous expanding trend. Between 1970 and 2020, the average duration of persistent drought events each decade was concentrated between 4 to 8 months. 2) Before the 1990s, the lag time of Oceanic Niño Index's impact on spring precipitation was 3 and 9 months. From then on, the ONI's influence on summer and autumn precipitation extended to 6, 9, and 12 months. Once La Niña events occurred, there was the decrease in the spring precipitation, thereby increasing the frequency of spring droughts in China. 3) There was a resonance period of 16-48 months between ONI and SPEI3 during the years 1961-1976, 1980-1988, 1994-2001, and 2006-2020. The ONI index also demonstrated the strongest correlation with SPEI3 in this timeframe. While the WP index exhibited the weakest correlation with SPEI3 during the same periods.The research results help further understand the causes and patterns of drought in China, thereby enhancing the scientific basis and precision of drought prevention and mitigation policies. [ABSTRACT FROM AUTHOR]

Radar detection technology has been used to observe meteors since the last century. According to the echoes of electromagnetic waves scattered by meteor trails, the drift velocity of meteors is calculated to research the atmospheric dynamics characteristics in their distribution height. In this paper, complementary code sequences are applied to a Very High Frequency (VHF) ionospheric sounding system. Unlike the common VHF meteor radar, the system parameters can be set with a pulse duty cycle, allowing for flexible adjustment of detection range. At the same time, the detection frequency can also be adjusted within a certain range, breaking through the traditional fixed frequency detection mode. Moreover, by employing a miniaturized antenna array composed of an orthogonal dipole antenna for the VHF receiving, the system takes account of the requirements of the inversion algorithms of meteor radar and the detection need for the irregularities sounding concurrently, achieving the function of detecting multiple targets. Therefore, the system is called the Wuhan VHF Comprehensive Sounding (WHCS) system. This system has the function of integrating transmission and reception, which can be directly detected by a single station or synchronously detected through the separation of transmission and reception. This system has the function of internal channel calibration to compensate for the phase error of meteor echoes. Through further analysis of the detection data, the height distribution of meteors, as well as typical echoes of ionospheric irregularities, were obtained. The experiments verified the availability of the system scheme and its engineering application significance. [ABSTRACT FROM AUTHOR]

Ocean circulation plays an important role in the formation and occurrence of extreme climate events. The study shows that the periodic variation of ocean circulation under strong wind stress is closely related to climate oscillation. Ocean circulation is a nonlinear dynamic system, which shows complex nonlinear characteristics, so the essence behind ocean circulation has not been clearly explained. Therefore, the response and evolution of the circulation system to wind stress are studied based on the bifurcation and catastrophe theories in nonlinear dynamics. First, the quasi-geostrophic gyre equation and the normalized gravity model are introduced and developed to study ocean circulation driven by wind stress, and solved using the Galerkin method. Then, the bifurcation and catastrophe behaviors of the system governed by the low-order ocean circulation model during the change in wind stress intensity and the coexistence of multiple equilibria in the circulation system are studied in detail. The results show that saddle and unstable nodes appear in the system after a cusp catastrophe. With the change in model parameters, the unstable node becomes the unstable focus, and then the subcritical Hopf bifurcation occurs. The system forms a bistable interval when the system undergoes a catastrophe twice, and the system shows hysteresis. In addition, multiple equilibrium states are coexisting in the circulating system, and the unstable equilibrium state always changes into a stable equilibrium state through vortex movement. Therefore, there is a route for the system to induce short-term climate oscillation, that is, in the multi-stable equilibrium state of the system, the vortex oscillates after being subject to small disturbances, and then triggers climate oscillation. [ABSTRACT FROM AUTHOR]

Large-scale meteorological events (e.g. cyclones), referred to as synoptic events, strongly influence weather predictability but still cannot be fully characterised in the Arctic region because of the sparse coverage of measurements. Due to the fact that atmospheric dynamics in the lower stratosphere and troposphere influence the ozone field, one approach to analyse these events further is the use of space-borne measurements of ozone vertical distributions and total columns in addition to conventional parameters such as pressure or wind speed. In this study we investigate the link between cyclones and changes in stratospheric ozone by using a combination of unique measurements during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) ship expedition, ozone profile and total column observations by satellite instruments (OMPS-LP, TROPOMI), and ERA5 reanalysis data. The final goal of the study is to assess whether the satellite ozone data can be used to obtain information about cyclones and provide herewith an additional value in the assimilation by numerical weather prediction models. Three special cases during the MOSAiC expedition were selected and classified for the analysis. They are one "normal" cyclone, where a low surface pressure coincides with a minimum in tropopause height, and two "untypical" cyclones, where this is not observed. The influence of cyclone events on ozone in the upper-troposphere lower-stratosphere (UTLS) region was investigated, using the fact that both are correlated with tropopause height changes. The negative correlation between tropopause height from ERA5 and ozone columns was investigated in the Arctic region for the 3-month period from June to August 2020. This was done using total ozone columns and sub-columns from TROPOMI, OMPS-LP, and MOSAiC ozonesonde data. The greatest influence of tropopause height changes on ozone contour levels occurs at an altitude between 10 and 20 km. Moreover, the lowering of the 250 ppb ozonopause (at about 11 km altitude) below 9 km was used to detect cyclones using OMPS-LP ozone observations. The potential of this approach was demonstrated in two case studies where the boundaries of cyclones could be determined using ozone observations. The results of this study can help improve our understanding of the relationship between cyclones, tropopause height, and ozone in the Arctic and demonstrate the usability of satellite ozone data in addition to the conventional parameters for investigating cyclones in the Arctic. [ABSTRACT FROM AUTHOR]

Persistent winter aerosol pollution frequently occurs in the Sichuan Basin (SCB) due to its unfavourable weather conditions, such as low wind, wetness, and cloudiness. Based on long-term observational data analyses from 2015–2021, it has been found that the four representative stations in the SCB often simultaneously experience PM2.5 pollution accompanied by variations in meteorological conditions above 850 hPa , which indicates a connection between regional winter air pollution in the SCB and large-scale synoptic patterns. The dominant 850 hPa synoptic patterns of winter in the SCB were classified into six patterns using T-model principal component analysis: (1) strong high pressure in the north, (2) east high–west low (EHWL) pressure, (3) weak high pressure in the north, (4) a weak ridge of high pressure after the trough, (5) a low trough (LT), and (6) strong high pressure. Pattern 2 characterized by the EHWL pressure system, and Pattern 5, featured with LT, was identified as having key synoptic patterns for the beginning and accumulation of pollution processes. Pattern 1, characterized by a strong high pressure in the north, was the cleanest pattern associated with reduced PM2.5 concentrations. The EHWL and LT patterns were associated with a remarkably high cloud liquid content attributed to upper southerly winds introducing humid air. Clouds reduce solar radiation through reflection and scattering, resulting in more stable stratification and aerosol accumulation. This cloud radiation interaction (CRI) was more pronounced in the LT pattern due to denser isobaric lines and stronger southerly winds than in the EHWL pattern. Numerical simulation experiments utilizing WRF-Chem indicated that there is an upper-level heating during afternoon and surface cooling in the morning forced by the aerosol radiation interaction (ARI) under the EHWL and LT patterns. Additionally, strong surface cooling in the evening influenced by valley winds could be found. With wet and cloudy synoptic forcing, ARI directly affects the stability of the boundary layer and is modulated through CRI inhibition. For example, Chongqing exhibited lower PM2.5 concentrations and stronger ARI compared to the western and southern SCB due to lower cloud liquid content and weaker CRI inhibition on the ARI. The CRI inhibition caused a 50 % reduction in solar radiation and boundary layer height during the daytime under the LT pattern, which was larger than that under the EHWL pattern. This study comprehensively analysed the spatial disparities in cloud inhibition on the ARIs, their impacts on the boundary layer structure, and the discrepancies of these interactions under different synoptic patterns during pollution processes. The findings have important implications for the effective management of pollution processes in cloudy and foggy weather. [ABSTRACT FROM AUTHOR]

The climate characteristics of remote rainfall events in Taiwan from September to February over 41 years (1980–2020) are studied. These events are induced by the interaction between the northeasterly flow and the typhoon's outer circulation. Our findings reveal that rainfall in northeastern Taiwan becomes more prominent when tropical cyclones move to the remote rainfall‐prone area, located in the north Philippine area to the northern South China Sea, and when the background northeasterly wind speed exceeds 7 m s−1. Under these criteria, the confluence of the typhoon's outer circulation and the northeasterly flow creates a convergence area that enhances rainfall in northeastern Taiwan, increasing the occurrence of moderate to extreme rainfall (ER) events. This leads to an average enhancement in rainfall amount of 80–220 mm per day. Additionally, when typhoons are in the remote rainfall‐prone area, there is a greater than 20% chance for events with maximum rainfall over 200 mm day−1 to occur, particularly in the region of 20°–22°N, 116°−124°E, and north to Luzon Island. In this area, the occurrence rate can exceed more than a 45% chance. The highest risk of ER events occurs between 20°–22°N and 118°−120°E, with a probability of over 90%. Notably, the convergence area for the Taiwan cases does not necessarily coincide with the baroclinic forcing as that associated with remote rainfall events observed in Japan, Korea, and North America. Plain Language Summary: We studied a particular pattern of rainfall in Taiwan that occurs between September and February over a 41‐year period (1980–2020). Our research found that when tropical cyclones (TCs) are far from Taiwan and there is a strong northeasterly wind, it causes more rainfall in northeastern Taiwan. This can lead to moderate to extreme rainfall, with an increase in rainfall of 80–220 mm per day. When tropical storms are in a specific area north of Luzon Island, there is a higher chance of heavy rain, with some places receiving more than 200 mm per day. The highest probability of extreme rain events occurs when TCs are in a specific area between 20°–22°N and 118°−120°E, where the chance of extreme rain in Taiwan is over 90%. It happens because the TC circulation meets with the northeasterly flow and creates a convergence area. It's important to note that the way remote rainfall events happen in Taiwan may not be the same as in Japan, Korea, and North America. Key Points: Northeastern Taiwan experiences heavy rainfall as tropical cyclone (TC) move toward North South China Sea while northeasterly flow >7 m/sTyphoons' outer flow and the northeasterly convergence enhanced remote rainfall events to 80–220 mm/dayAbove 45% of events with max daily rainfall over 200 mm occur when TCs are in the 20°–22°N, 116°–124°E area and north to Luzon Island [ABSTRACT FROM AUTHOR]

During the dry season, river flow gradually diminishes, and surface water flow dries up. Therefore, the investigation of runoff during the dry season is of great practical significance for rational water allocation and water resource management. Based on hydrological station data from the Xijiang River Basin (XRB) from 1961 to 2020, this study examines the trend and periodic characteristics of dry-season runoff, identifies fluctuation and variability in dry-season runoff, and investigates the main circulation factor combinations influencing dynamic changes in dry-season runoff. The results indicate the following: (1) the characteristics of dry-season runoff variations are basically consistent across sub-basins in the XRB during the study period, with the minimum (21.96 × 108 m3) and maximum (54.67 × 108 m3) average monthly runoff occurring in February and October, respectively; (2) interannual-scale dry-season runoff exhibits periodicity of 3.53 years and 7.5 years; (3) using the Bayesian estimator of abrupt seasonal and trend change algorithm (BEAST), a seasonal abrupt point with a probability of 20.5% occurs in 1983, and the confidence interval for this abrupt point is from 1980 to 1986; (4) based on the cross wavelet approach, solar sunspots are identified as the primary circulation factor contributing to dry-season runoff in the XRB, exhibiting a significant 8–14 years resonance cycle of negative correlation with runoff during the high-energy phase from 1972 to 2006. These findings offer a new perspective on understanding the evolution of dry-season runoff and circulation factor variations, which are crucial for accurate prediction, early warning, and rational allocation of water resources during the dry season. [ABSTRACT FROM AUTHOR]

Precipitation plays a crucial role in the hydrological cycle and is vital for water resources management, climate change research, and ecosystem conservation. Precipitation stable isotopes serve as the 'fingerprints' of precipitation, which can clearly trace the formation, transport, and subsequent processes of precipitation. However, due to the scarcity of precipitation stable isotope data, we face challenges of temporal discontinuity and spatial heterogeneity when studying it at large to medium scales. Therefore, we compiled precipitation hydrogen and oxygen stable isotope data (δ18O and δ2H) from 2059 global sites spanning from 1961 to 2023, totaling 141,624 records. Our study indicates significant variations of global precipitation stable isotopes both spatially and temporally. Spatially, the isotopic composition of precipitation in different regions varies significantly due to factors such as geographical location, underlying surface conditions, and atmospheric circulation. Temporally, δ18O and δ2H show decreasing trends, while d-excess shows an increasing trend, with the impact of global temperature rise being very apparent. This precipitation stable isotope dataset provides robust support for our understanding of global precipitation changes and climate change. Through further investigation of precipitation stable isotope data, we hope to uncover more mechanisms and influencing factors of precipitation processes, providing a more accurate basis for the assessment and prediction of climate and water resource changes. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) are anomalously warm events that profoundly affect climate change and local ecosystem. During the summer of 2012 (June-September), intense MHWs occurred in the tropical Indian Ocean (TIO) concurrently with an unseasonable positive Indian Ocean Dipole (pIOD) event. The MHW metrics (duration, frequency, cumulative intensity and maximum intensity) were characterized by northwestward-slanted patterns from west Australia to the Somalia coast. The analysis confirmed that these MHWs were closely associated with the unseasonable pIOD 2012. The weakening of Western North Pacific Subtropical High and strengthening of Australian High in spring induced an interhemispheric pressure gradient that drove two anticyclonic circulation patterns over the eastern TIO. The first anticyclonic circulation featured cross-equatorial wind anomalies from south of Java to the South China Sea/Philippine Sea, which led to strong upwelling off Sumatra-Java during the subsequent summer. The second anticyclonic circulation excited downwelling Rossby waves that propagated from the southeastern TIO to the western TIO. Thus, downwelling in the western pole and upwelling in the eastern pole led to a strong pIOD event peaking in summer, namely, the unseasonable pIOD 2012. These downwelling Rossby waves deepened the thermocline by more than 60 m and caused anomalous surface warming, thereby contributing to the occurrences of MHWs. With the development and peak of the unseasonable pIOD 2012, anomalous atmospheric circulation transported moisture from the TIO to the subtropical Western North Pacific (WNP), favoring a strong cyclonic anomaly that profoundly affected the summer monsoon rainfall over the subtropical WNP. This study provides some perspectives on the role of pIOD events in summer climate over the Indo-Northwest Pacific region. [ABSTRACT FROM AUTHOR]

The heat storage capacity of Southern Ocean (SO) buffers future atmospheric warming but differs vastly across climate models. Reducing its projection uncertainty is vital for understanding and evaluating future global sustainability. Using Coupled Model Intercomparison Project Phase 6, we show that the present-day SO high-latitude easterly wind anomalies induced by El Niño is an effective constraint for the projected increase in SO heat content. Models simulating weaker El Niño-induced easterlies generate more equatorward atmospheric teleconnection in the present day. Under global warming, these models have greater capacity in the poleward shift of atmospheric circulation, thus generate stronger future increase in El Niño-induced high-latitude easterlies, slowing the SO heat storage by weakening the northward Ekman transport that underpins the dynamical process for SO heat storage. However, most models overestimate the present-day El Niño-induced easterlies, implying that alleviating this bias would reduce future SO heat storage, thus exacerbating atmospheric warming. [ABSTRACT FROM AUTHOR]

Humid heat extreme (HHE) is a type of compound extreme weather event that poses severe risks to human health. Skillful forecasts of HHE months in advance are crucial for developing strategies to enhance community resilience to extreme events1,2. This study demonstrates that the frequency of summertime HHE in the southeastern United States (SEUS) can be skillfully predicted 0–1 months in advance using the SPEAR (Seamless system for Prediction and EArth system Research) seasonal forecast system. Sea surface temperatures (SSTs) in the tropical North Atlantic (TNA) basin are identified as the primary driver of this prediction skill. The responses of large-scale atmospheric circulation and winds to anomalous warm SSTs in the TNA favor the transport of heat and moisture from the Gulf of Mexico to the SEUS. This research underscores the role of slowly varying sea surface conditions in modifying large-scale environments, thereby contributing to the skillful prediction of HHE in the SEUS. The results of this study have potential applications in the development of early warning systems for HHE. [ABSTRACT FROM AUTHOR]

The atmospheric circulation significantly influences the snowpack over mid-high-latitude Eurasia. This study examines the characteristics of the leading subseasonal variability mode of boreal winter sea level pressure (SLP) with 20-80-day period and its relationship with snowpack over mid-high-latitude Eurasia, using the fifth generation of European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data and different snowpack datasets. The SLP leading mode, characterized by a monopole pattern with a strong surface anomalous high centered near the Ural Mountains, exhibits a barotropic structure and extends from the surface to the tropopause. Above SLP and geopotential height anomalies propagate southeastward from the Barents-Kara Sea to East Asia. This leading SLP mode contributes to surface air temperature (SAT) and snowfall circulation anomalies over mid-high-latitude Eurasia. The latter two both directly influence on snowpack anomalies in situ. Over high latitude region, snowfall circulation anomaly is the dominant factor to control the snow depth anomaly. Over middle latitude region, both SAT and snowfall circulation anomalies lead to the snowpack anomaly. Furthermore, the response of snow depth to the leading subseaonal SLP mode occurs 2–5 days earlier than the response of snow cover to the same mode over middle latitude region. In addition, it is suggested that the Arctic Oscillation (AO), East Atlantic/West Russia (EAWR) and Polar/Eurasia (PEU) pattern may contribute to the development of the leading SLP mode and subsequently influence snowpack anomalies. [ABSTRACT FROM AUTHOR]

The spatial propagation patterns of meteorological drought events (MDEs) and underlying mechanisms contribute to elucidating and forecasting drought evolution. In this study, gridded MDEs in the Yangtze River Basin (YRB) throughout the entire year, wet season and dry season were extracted from 3-month Standardized Precipitation Evapotranspiration Index (SPEI-3) series. Event synchronization (ES) and complex networks (CN) were employed to construct the MDE synchronization networks and MDE spatial propagation networks for various periods. The former were utilized to identify MDE synchronized subregions where MDEs co-occur and co-evolve in the YRB, while the latter were used to quantify the MDE spatial propagation patterns over both the basin and its subregions. The driving mechanisms behind MDE spatial propagation were further investigated by diagnosing the concomitant drought-inducing climate systems. The findings reveal the presence of four MDE synchronized subregions during the wet season and five subregions during the entire year and dry season. These subregions exhibited distinct spatial propagation patterns of MDEs, aligning with overall findings across the YRB. Notable differences were observed between wet and dry seasons, with various subregions exhibiting distinctive spatial propagation patterns during each season. These patterns are driven by variations in the controlling atmospheric circulation systems, leading to anomalies of wind patterns and moisture distribution, ultimately resulting in deficient moisture supply. The variations of tropical sea surface thermal conditions, influences of the Tibetan Plateau and MDE self-propagation triggered by land–atmosphere feedback are considered as three primary influencing factors for MDE spatial propagation in the YRB. [ABSTRACT FROM AUTHOR]

This study investigates the potential role and mechanism of the quasi-biennial oscillation (QBO) in influencing the relationship between the stratospheric polar vortex (SPV) and surface air temperature (SAT) over Eurasia during boreal early winter. Our results show that there are variations in the SPV-related SAT anomalies over Eurasia between different phases of QBO, i.e., SAT anomalies exhibit a south- north pattern (colder south and warmer north over Eurasia) in easterly phase of QBO (EQBO) compared to westerly phase of QBO (WQBO) in strong SPV years (SSPV), while a northeast-southwest pattern (colder northeast and warmer west over Eurasia) in weak SPV years (WSPV). On average, the contributions of SPV and QBO to SAT anomalies are approximately 29.4% and 12.6%, respectively. Further analysis suggested that these SAT differences between EQBO and WQBO under different SPV conditions are associated with the corresponding atmospheric circulation in the troposphere over Eurasia. The south-north pattern of SAT anomalies during SSPV is attributed to a stronger amplitude of the anomalous anticyclone in western Eurasia, which shifts westward, and the eastward shifting of anomalous cyclonic center in northwestern Eurasia in EQBO. But the southwest-northeast pattern during WSPV is related to anomalous cyclone over western Eurasia and the eastward shifting of anticyclone over northwestern Eurasia in EQBO. These tropospheric circulation anomalies are influenced by the propagation of planetary waves induced by QBO. The SPV weakens in EQBO compared to WQBO, which is accompanied by the strengthened (weakened) low-latitude waveguide and reinforced (shifting southward) subtropical jet stream during SSPV (WSPV) years. The different responses of subtropical jet are mainly related to the tropopause and the meridional temperature gradient around the tropopause caused by QBO via the meridional circulation and Holton-Tan relationship. [ABSTRACT FROM AUTHOR]

The evolution of temperature anomalies in the North Atlantic (15° N – 70° N 80° W – 8° W) is analyzed. The results are based on the decomposition of the GECCO3 (1948–2018), ORA-S5 (1979–2018) and SODA3.12.2 (1980–2017) oceanic reanalyses data using extended empirical orthogonal functions. The leading pattern during the entire 16–month period (January–April of the next year) in the 0–300 m layer is a tripole, with temperature anomalies of the same sign in the tropical and high latitudes and the opposite sign in the subtropical gyre. The evolution of the leading pattern shows the deepening of temperature anomalies in winter, their preservation with a maximum in the summer seasonal thermocline (~ 65–90 m) and partial weakening in the subsurface layer in summer, and their emergence on the ocean surface in the subsequent autumn–winter season. The temporal evolution of the reemergence of the tripole pattern of the sea surface temperature anomalies (SSTAs), explained by the first extended principal component (EPC1), is in good agreement with the variability of the main atmospheric circulation mode over the North Atlantic on interannual scales – the North Atlantic Oscillation (NAO), especially after 1979. The recurrence of SSTAs is found in all three centers of action of the tripole pattern. In the subpolar and midlatitude centers of action, the reemerging signal maximum appears in the subsurface layer in late summer and early autumn and in the subsequent autumn–winter season ~ 2/3 of this signal occurs at the surface. In the subtropical center of action, the reemerging signal maximum appears in the mixed layer in winter–spring and in the subsequent autumn–winter season ~ 1/2 of this signal occurs at the surface. For the subtropical center of action, a moderate correlation was found between the regional EPC1 and the mixed layer depth and the wind stress modulus over a 16–month period. Recurrence of temperature anomalies in all centers of action of the tripole structure from January 2014 to April 2015 associated with the repeated positive NAO phase is shown. [ABSTRACT FROM AUTHOR]

The mid-Piacenzian Warm Period (MPWP, ~ 3.264–3.025 Ma) is the most recent example of a persistently warmer climate in equilibrium with atmospheric CO2 concentrations similar to today. Towards studying patterns and dynamics of a warming climate the MPWP is often compared to today. Following the Pliocene Model Intercomparison Project, Phase 2 (PlioMIP2) protocol we prepare a water isotope-enabled Community Earth System Model (iCESM1.2) simulation that is warmer and wetter than the PlioMIP2 multi-model ensemble (MME). While our simulation resembles PlioMIP2 MME in many aspects we find added insights. (1) Considerable warmth at high latitudes exceeds previous simulations. Polar amplification (PA) is comparable to proxies, enabled by iCESM1.2's high climate sensitivity and a distinct method of ocean initialization. (2) Major driver of warmth is the downward component of clear-sky surface long-wave radiation ( Δ T rlds _ clearsky ). (3) In iCESM1.2 modulated dominance of dynamic (δDY) processes causes different low-latitude (~ 30 S°–10°N) precipitation response than the PlioMIP2 MME, where thermodynamic processes (δTH) dominate. (4) Modulated local condensation leads to lower δ18Op across tropical Indian Ocean and surrounding Asian-African-Australian monsoon regions. (5) We find contrasting changes in tropical atmospheric circulations (Hadley and Walker cells). Anomalous regional meridional (zonal) circulation, forced by changes in tropical-subtropical (tropical) diabatic processes, presents a more comprehensive perspective than explaining weakened and expanded Hadley circulation (strengthened and westward-shifted Walker circulation) via static stability. (6) Enhanced Atlantic meridional overturning circulation owes to a closed Bering Strait. [ABSTRACT FROM AUTHOR]

Using fifth-generation ECMWF Atmospheric Reanalysis (ERA-5) we investigate the topical changes in global teleconnection with seasonal precipitation dynamics in the backdrop of climate change particularly for the recent 20 years (L20:2002 to 2021) with respect to the previous 20 years (F20: 1982–2001). It unveils a considerable decrease in both monsoon and pre-monsoon precipitation over the Northwest Himalaya (NWH) in the Indian region and a decline in winter precipitation over the Tibetan Plateau (TP). Statistically robust K-S test shows notable changes (5% significance level) in the regional distribution of the atmospheric parameters in parts of the High Mountain Asia (HMA) region in recent decades (L20). Further, a weakening of the North Atlantic Oscillation (NAO) and El-Nino Southern Oscillation (ENSO) influence on precipitation pattern is noted in the L20 (2002–2021) compared to the F20 (1982–2001) years over parts of the HMA region. A regional heterogeneity is perceptible among different parts of HMA i.e. NWH in the Indian region and the TP. The NWH precipitation shows a diametrically opposite relation with the NAO index for winter precipitation in L20 (correlation coefficient R= -0.18, sample size: 240) compared to a positive correlation in F20 (correlation coefficient R = 0.15, sample size: 240) which is significant at 5% significance level. The plausible reasons for such a diametrical change in the relationship during winter are addressed by examining the changing signature of the subtropical jet stream and its relationship with NAO and ENSO. Sea surface temperature shows cooling of the tropical Pacific and the resulting weakening in El-Nino signatures in recent years. Our results point to the noteworthy changes in the atmospheric circulation pattern over the HMA region in recent decades which is attributed to the alteration in the global teleconnection patterns and subsequent their association with the precipitation distribution over the HMA region. This study would be useful for an improved understanding of the precipitation dynamics over the HMA region and global teleconnections in the future. [ABSTRACT FROM AUTHOR]

Empirical orthogonal function (EOF) and correlation analyses were employed to investigate the winter and spring snow depth in Eurasia and its relationship with Eastern China precipitation based on the observed and reanalyzed data from 1980 to 2016. The results show that the winter and spring snow cover in Eurasia not only highlights a decreasing trend due to global warming (the first EOF mode, its variance accounted for 24.4% and 22.6% of the total variance) but also exhibits notable interdecadal variation (the second EOF mode, its variance accounted for 10.2% and 11.5% of the total variance). The second EOF mode of winter snow depth in Eurasia is characterized by a west-east dipole pattern. It was observed that the spatial correlation pattern between the EOF2 of Eurasian snow depth and summer precipitation in China closely resembles the meridional quadrupole structure of the third EOF mode of summer precipitation in China. This pattern is characterized by excessive rainfall in Northeast China and the lower-middle reaches of the Yangtze River, and less rainfall over the Yellow River basin and southern China. The EOF mode of spring snow depth not only reflects the declining trend but also regulates precipitation in Eastern China. The possible mechanisms by which snow depth causes changes in soil moisture and subsequently affects atmospheric circulation are then explored from the perspective of the hydrological effects of snow cover. Decreased (Increased) snow depth in Eurasia during the winter and spring directly leads to diminished (increased) soil moisture while increasing (decreasing) net radiation and sensible heat flux at the surface. The meridional distribution of surface temperature also exhibits a dipole pattern, leading to enhanced subtropical westerly jet in the upper troposphere. The Eurasian snow cover anomalies pattern triggered an anomalous mid-latitude Eurasian wave train, which strengthened significantly in the Western Siberian Plain. It then splits into two branches, one continuing to propagate eastward at high latitudes and the other shifting towards East Asia, thereby impacting precipitation in Eastern China. This work indicates that the second EOF mode of Eurasian snow cover can impact the precipitation variability in Eastern China during the same period and in summer on an interdecadal scale. [ABSTRACT FROM AUTHOR]

The Earth System is warming due to anthropogenic greenhouse gas emissions which increases the risk of passing a tipping point in the Earth System, such as a collapse of the Atlantic Meridional Overturning Circulation (AMOC). An AMOC weakening can have large climate impacts which influences the marine and terrestrial carbon cycle and hence atmospheric pCO 2 . However, the sign and mechanism of this response are subject to uncertainty. Here, we use a state-of-the-art Earth System Model, the Community Earth System Model v2 (CESM2), to study the atmospheric pCO 2 response to an AMOC weakening under low (SSP1-2.6) and high (SSP5-8.5) emission scenarios over the years 2015–2100. A freshwater flux anomaly in the North Atlantic strongly weakens the AMOC, and we simulate a weak positive pCO 2 response of 0.45 and 1.3 ppm increase per AMOC decrease in Sv for SSP1-2.6 and SSP5-8.5, respectively. For SSP1-2.6 this response is driven by both the oceanic and terrestrial carbon cycles, whereas in SSP5-8.5 it is solely the ocean that drives the response. However, the spatial patterns of both the climate and carbon cycle response are similar in both emission scenarios over the course of the simulation period (2015–2100), showing that the response pattern is not dependent on cumulative CO 2 emissions up to 2100. Though the global atmospheric pCO 2 response might be small, locally large changes in both the carbon cycle and the climate system occur due to the AMOC weakening, which can have large detrimental effects on ecosystems and society. [ABSTRACT FROM AUTHOR]

The Siberian High (SH) is one of the most prominent wintertime circulation systems in the Northern Hemisphere. The variability of the intensity of the SH during the boreal winter has been extensively studied, while the reasons behind its formation remain largely elusive. This study investigates the interannual variation and underlying mechanisms of the SH formation, especially the three-dimensional circulation and associated surface boundary conditions. Early SH formation is usually accompanied by a Eurasian teleconnection (EU)-like pattern and a strengthened subtropical westerly jet, and opposite conditions are true for a delayed SH formation. Boundary conditions, including North Atlantic sea surface temperature (NASST) anomalies and the high-latitude Central Eurasia snow-cover extent (HCESCE) anomalies could modulate SH formation by affecting the overlying atmospheric circulations. Specifically, anomalously cold NASSTs can result in an anomalous equivalent barotropic anticyclone via diabatic heating and transient eddy forcing. Such an anomalous anticyclone and related divergence anomalies in the upper troposphere act as effective atmospheric Rossby sources, triggering a downstream propagating atmospheric teleconnection with a pattern similar to that of a positive EU-like wave train, favoring the early formation of the SH. In addition, the reduced HCESCE warms the overlying atmosphere, thus weakening the atmospheric baroclinicity and transient eddy activities over the SH region. These weakened eddy activities can intensify the EU-like pattern via vorticity forcing and strengthen the subtropical westerly jet via the eddy–mean flow interaction. The processes for the impacts of the NASST and HCESCE anomalies on the formation of the SH can be verified by a series of numerical simulations. [ABSTRACT FROM AUTHOR]

In this study, we examine the long-term variability in the western North Pacific (Philippine Sea) summer monsoon (WNPSM) from the 1880s to the present. To determine the sea surface temperature (SST)-induced atmospheric variability, atmospheric general circulation model (AGCM) ensemble simulations are conducted with the observed SST. For the AGCM experiments, we use two convection schemes and SST datasets to examine the uncertainty in the convective parameterization and robustness of the simulated atmospheric response. In the AGCM simulation (T42; approximately 300-km horizontal resolution, 3-member ensemble in each), interdecadal variability can be seen as a cyclonic anomaly in the 1890s–1930s. This cyclonic anomaly is robust to different convection schemes and SST datasets. The observed rainfall over the land demonstrates consistent features. In our AGCM ensemble simulations, sensitivity experiments with several SST patterns show that the interbasin effect (i.e., contribution of tropical Indian Ocean and Atlantic) played a key role in the WNPSM cyclonic anomaly during the 1890s–1930s. Further, idealized SST experiments show that reduction in SST over the tropical Indian Ocean and Atlantic causes the WNPSM cyclonic anomaly. Additionally, using high-resolution AGCM experiments (T119; approximately 100-km horizontal resolution, 4-member ensemble in each), we investigate the increase in tropical cyclone (TC) activity over the western North Pacific during the 1890s–1930s. However, variability of the TC activity is sensitive to the convective parameterization. [ABSTRACT FROM AUTHOR]

Recent Greenland ice-sheet melt constitutes a considerable contribution to global sea-level rise. Observations indicate an approximate zero mass balance of the ice sheet until the late 1990s, after which a strong increase in melting occurred. This cannot be attributed linearly to gradually-increasing global warming. Instead the abrupt shift has been linked to atmospheric circulation changes, although causality is not fully understood. Here we show that changes of atmospheric waves over Greenland have significantly contributed to the shift into a strong melting state. This is evident after having applied a newly-developed methodology effectively decomposing atmospheric flow patterns into parts associated with waves of different scales such as Rossby waves and smaller perturbations. The onset of a westerly-flow reduction, consistent with anthropogenic Arctic warming, affected transports by atmospheric waves and led to a decrease in precipitation and an increase in surface warming, contributing to ice-sheet mass loss, in particular over the southwestern regions. As such, the Greenland ice-sheet melt is an example of a climate response non-linearly coupled to global warming. [ABSTRACT FROM AUTHOR]

The features of large-scale atmospheric circulations, storm tracks, and the mean flow–eddy interaction during winter Pacific–North American (PNA) events are investigated using National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data at subseasonal time scales from 1979 to 2022. The day-to-day variations of storm-track activity and streamfunction reveal that storm-track activity varies along the evolution of mean flow. To better understand storm-track variability with the mean flow–eddy interaction, further exploration is made by analyzing local energy energetics. The changes in horizontal and vertical baroclinic energy conversions from background flow correspond to the storm-track anomalies over the North Pacific, indicating that the anomalies in storm tracks are due to the anomalous mean flow associated with PNA patterns impacting energy conversion through mean flow–eddy interaction. Eddy feedback driven by vorticity and heat fluxes is analyzed. This provides a concrete illustration of how eddy feedback serves as a positive factor for the upper-tropospheric circulation anomalies associated with the PNA pattern. Significance Statement: The background flow plays a crucial role in governing storm-track dynamics. Our emphasis is on the Pacific storm tracks (PST) and their relation to Pacific–North American (PNA) patterns at subseasonal time scales. We unveil the relationship between anomalies of PST and PNA patterns using local energetics and eddy feedback on a day-by-day basis. It is noteworthy that the evolution of anomalous storm tracks during PNA events is the manifestation of mean flow–eddy interaction. Additionally, we provide detailed confirmation of the impact of anomalous storm tracks on large-scale anomalies associated with the PNA pattern. [ABSTRACT FROM AUTHOR]

Understanding the variability of Antarctic sea ice is still a challenge. After decades of modest growth, an unprecedented minimum in the sea ice extent (SIE) was registered in summer 2017, and, following years of anomalously low SIE, a new record was established in early 2022. These two memorable minima have received great attention as single cases, but a comprehensive analysis of summer SIE minima is currently lacking. Indeed, other similar events are present in the observational record, although they are minor compared to the most recent ones, and a full analysis of all summer SIE minima is essential to separate potential common drivers from event-specific dynamics in order to ultimately improve our understanding of the Antarctic sea ice and climate variability. In this work, we examine sea ice and atmospheric conditions during and before all summer SIE minima over the satellite period up to 2022. We use observations and reanalysis data and compare our main findings with results from an ocean–sea ice model (NEMO–LIM) driven by prescribed atmospheric fields from ERA5. Examining SIE and sea ice concentration (SIC) anomalies, we find that the main contributors to the summer minima are the Ross and Weddell sectors. However, the two regions play different roles, and the variability of the Ross Sea explains most of the minima, with typical negative SIE anomalies about twice as large as the ones in the Weddell Sea. Furthermore, the distribution of SIC anomalies is also different: in the Weddell Sea, they exhibit a dipolar structure, with increased SIC next to the continent and decreased SIC at the sea ice margin, while the Ross Sea displays a more homogenous decrease. We also examine the role of wintertime sea ice conditions before the summer SIE minima and find mixed results depending on the period: the winter conditions are relevant in the most recent events, after 2017, but they are marginal for previous years. Next, we consider the influence of the atmosphere on the SIE minima, which is shown to play a major role: after analyzing the anomalous atmospheric circulation during the preceding spring, we find that different large-scale anomalies can lead to similar regional prevailing winds that drive the summer minima. Specifically, the SIE minima are generally associated with dominant northwesterly anomalous winds in the Weddell Sea, while a southwesterly anomalous flow prevails in the Ross Sea. Finally, we investigate the relative contribution of dynamic (e.g., ice transport) and thermodynamic (e.g., local melting) processes to the summer minima. Our results indicate that the exceptional sea ice loss in both the Ross and Weddell sectors is dominated at the large scale by thermodynamic processes, while dynamics are also present but with a minor role. [ABSTRACT FROM AUTHOR]

Arctic summer sea ice has shrunk considerably in recent decades. This study investigates springtime sea-ice surface melt onset in the Laptev Sea and East Siberian Sea, which are key seas along the Northeast Passage. Instead of region-mean melt onset, we define an index of melt advance, which is the areal percentage of a sea that has experienced sea-ice surface melting before the end of May. Four representative scenarios of melt advance in the region are identified. Each scenario is accompanied by a combination of distinct patterns between atmospheric circulation, atmospheric thermodynamic state, sea-ice cover (polynya activity), and surface energy balance in May. In general, concurrent with faster melt advance are a warmer and wetter atmosphere, less sea-ice cover, and surface energy gains in spring. Melt advance can be potentially used in the practical seasonal prediction of summer sea-ice cover. This study suggests the interannual and interdecadal flexibility of spring circulation in the lower troposphere and the significance of seasonal evolution in the Arctic. [ABSTRACT FROM AUTHOR]

The Kingdom of Saudi Arabia (KSA) is characterized by a desert climate, with rainfall mainly occurring during the cooler months (November–April) and sometimes in conjunction with intense extratropical systems that can cause serious damage and casualties. Given the vast size of KSA, there are gaps in understanding the association between large‐scale atmospheric circulations and local organized rainfall events, and in characterizing the diversity of this association. To address these gaps, we analyse an in‐house 5‐km horizontal grid spacing regional atmospheric reanalysis that has been specifically generated for the Arabian Peninsula to explore the mechanisms behind the organized rainfall events over KSA. Nine major regions with distinct climate regimes were objectively selected to represent KSA rainfall climatology. The results demonstrate that organized thunderstorms over KSA only occur under sufficient moisture and environmental instabilities. Mesoscale convective systems responsible for organized rainfall generally develop and propagate with low‐level moisture flow from the nearby seas (the Red Sea to the west and Arabian Gulf to the east) toward the desert. In the central part of KSA, the most frequent physical mechanism responsible for rainfall is winter extratropical influence, followed by spring extratropical–tropical interactions, and spring tropical influence. The east coast is characterized by two rainfall modes: a continuous southwest–northeast rain corridor and concentrated southwestern rain. Large‐scale organized convection following three physically distinct mechanisms (extratropical, transition and tropical) is revealed along the west coast. [ABSTRACT FROM AUTHOR]

Investigating the physical mechanism behind the formation of summer heat-drought weather (HDW) in the Yangtze River Basin (YRB) holds significant importance for predicting summer precipitation and temperature patterns in the region as well as disaster mitigation and prevention. This study focuses on spatiotemporal patterns of July–August (JA) HDW in the YRB from 1979 to 2022, which is linked partially to the preceding May–June (MJ) Antarctic Oscillation (AAO). Key findings are summarized as follows: (1) The MJ AAO displays a marked positive correlation with the JA HDW index (HDWI) in the southern part of upper YRB (UYRB), while showing a negative correlation in the area extending from the Han River to the western lower reaches of the YRB (LYRB); (2) The signal of MJ AAO persists into late JA through a specific pattern of Sea Surface Temperature anomalies in the Southern Ocean (SOSST). This, in turn, modulates the atmospheric circulation over East Asia; (3) The SST anomalies in the South Atlantic initiate Rossby waves that cross the equator, splitting into two branches. One branch propagates from the Somali-Tropical Indian Ocean, maintaining a negative-phased East Asia–Pacific (EAP) teleconnection pattern. This enhances the moisture flow from the Pacific towards the middle and lower reaches of the Yangtze River Basin (MYRB-LYRB). The other branch propagates northward, crossing the Somali region, and induces a positive geopotential height anomaly over Urals-West Asia. This reduces the southwesterlies towards the UYRB, thereby contributing to HDW variabilities in the region. (4) Partial Least Squares Regression (PLSR) demonstrated predictive capability for JA HDW in the YRB for 2022, based on Southern Ocean SST. [ABSTRACT FROM AUTHOR]

We report on a novel fluid dynamics experiment configuration based on a modified version of the differentially heated rotating annulus, a widely used laboratory model of the large-scale mid-latitude atmospheric circulation. Through applying an azimuthally (zonally) inhomogeneous, dipole-like thermal boundary condition—imitating a permanent "day side" and "night side" in the rotating setting—we explore the character of the flow patterns emerging at different values of the zonal temperature contrast and rotation rate. This configuration may prove to be a useful minimal model of the large-scale atmospheric circulation of tidally locked exoplanets. [ABSTRACT FROM AUTHOR]

In the current environment of climate change, the precipitation situation of marine islands is particularly valued. So, this study explores precipitation characteristics and mechanisms over Sri Lanka in the background of the western Indian Ocean using satellite and reanalysis datasets based on 40 years (from 1981 to 2020). The results show that the highest precipitation occurs between October and December, accounting for 46.3% of the entire year. The Indian Ocean sea surface temperature warming after 2002 significantly influences precipitation patterns. Particularly during the Second Inter-Monsoon, the western Indian Ocean warming induces an east–west zonal sea surface temperature gradient, leading to low-level circulation and westerly wind anomalies. This, in turn, results in increased precipitation in Sri Lanka between October and December. This study used the Trend-Free Pre-Whitening Mann–Kendall test and Sen's slope estimator to study nine extreme precipitation indices, identifying a significant upward trend in extreme precipitation events in the Jaffna, arid northern Sri Lanka, peaking on 9 November 2021. This extreme event is due to the influence of weather systems like the Siberian High and intense convective activities, transporting substantial moisture to Jaffna from the Indian Ocean, the Arabian Sea, and the Bay of Bengal during winter. The findings highlight the impact of sea surface temperature warming anomalies in the western Indian Ocean and extreme precipitation events, anticipated to be more accentuated during Sri Lanka's monsoon season. This research provides valuable insights into the variability of tropical precipitation, offering a scientific basis for the sustainable development of marine islands. [ABSTRACT FROM AUTHOR]

Due to its high short-term global warming potential (GWP) compared to carbon dioxide, methane (CH4) is a considerable agent of climate change. This research is aimed at analyzing data on methane gathered at the GAW (Global Atmosphere Watch) station of Lamezia Terme (Calabria, Southern Italy) spanning seven years of continuous measurements (2016–2022) and integrating the results with key meteorological data. Compared to previous studies on detected methane mole fractions at the same station, daily-to-yearly patterns have become more prominent thanks to the analysis of a much larger dataset. Overall, the yearly increase of methane at the Lamezia Terme station is in general agreement with global measurements by NOAA, though local peaks are present, and an increase linked to COVID-19 is identified. Seasonal changes and trends have proved to be fully cyclic, with the daily cycles being largely driven by local wind circulation patterns and synoptic features. Outbreak events have been statistically evaluated depending on their weekday of occurrence to test possible correlations with anthropogenic activities. A cross analysis between methane peaks and specific wind directions has also proved that local sources may be deemed responsible for the highest mole fractions. [ABSTRACT FROM AUTHOR]

Extreme precipitation events induced by tropical cyclones have increased frequency and intensity, significantly impacting human socioeconomic activities and ecological environments. This study systematically examines the spatiotemporal characteristics of these events across Hainan Island and their influencing factors using GsMAP satellite precipitation data and tropical cyclone track data. The results indicate that while the frequency of typhoon events in Hainan decreased by 0.3 events decade−1 from 1949 to 2020, extreme precipitation events have increased significantly since 2000, especially in the eastern and central regions. Different typhoon tracks have distinct impacts on the island, with Track 1 (Northeastern track) and Track 2 (Central track) primarily affecting the western and central regions and Track 3 (Southern track) impacting the western region. The impact of typhoon precipitation on extreme events increased over time, being the greatest in the eastern region, followed by the central and western regions. Incorporating typhoon precipitation data shortened the recurrence interval of extreme precipitation in the central and eastern regions. Diurnal peaks occur in the early morning and late evening, primarily affecting coastal areas. Typhoon duration (CC_max = 0.850) and wind speed (CC_max = 0.369) positively correlated with extreme precipitation, while the pressure was negatively correlated. High sea surface temperature areas were closely associated with extreme precipitation events. The atmospheric circulation indices showed a significant negative correlation with extreme precipitation, particularly in the western and central regions. ENSO events, especially sea surface temperature changes in the Niño 1 + 2 region (−0.340 to −0.406), have significantly influenced typhoon precipitation characteristics. These findings can inform region-specific disaster prevention and mitigation strategies for Hainan Island. [ABSTRACT FROM AUTHOR]

High‐elevation, low‐relief continental plateaus are major topographic features and profoundly influence atmospheric circulation, sediment transport and storage, and biodiversity. Although orogenic surface‐uplift mechanisms for modern continental plateaus near known plate margins like Tibet are well‐characterized, they cannot account for examples in intracontinental settings like the Colorado Plateau. In contrast to canonical plate‐tectonic uplift mechanisms, broad‐scale hydration‐induced metasomatism of the lower crust has been suggested to reduce its density and increase its buoyancy sufficiently to contribute to isostatic uplift. However, the relationships between key petrophysical properties in these environments are not fully quantified, which limits application of this model. Here, we develop a series of petrological models that describe the petrological and topographic effects of fluid–rock interaction in non‐deforming continental crust of varying composition. We apply an open‐system petrological modelling framework that utilizes reactive‐transport calculations to determine the spatial and temporal scales over which mineralogic transformations take place compared with the magnitude of infiltration of aqueous fluids derived from devolatilization of subducting oceanic lithosphere. The buoyancy effect of hydration‐induced de‐densification is most significant for metabasic lower crust, intermediate for metapelitic crust, and minimal for granodioritic crust. We apply these results to a case study of the ~2 km‐high Colorado Plateau and demonstrate that under ideal conditions, hydration of its lower–middle crust by infiltrating aqueous fluids released by the Farallon slab during Cenozoic low‐angle subduction could have uplifted the plateau surface by a maximum of ~1 km over 16 Myr. However, realistically, although hydration likely has a measurable effect on surface tectonics, the uplift of orogenic plateaus is likely dominantly controlled by other factors, such as lithospheric delamination. [ABSTRACT FROM AUTHOR]