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In semi-arid northeastern Brazil, where water is scarce, rainforest refugia can be seen along the coastal relief, where the trade winds bring in humidity from the Atlantic Ocean, or further inland, at the Araripe plateau where water comes from aquifer resurgence. In order to reconstruct past changes in water resurgence and in their associated vegetation types, we analyzed pollen, charcoal, and trace elements from sediment cores collected in the permanent swamps created by the resurgences. Our high temporal resolution analyses show that the vegetation was more sparse and drier than today until 2700 cal yr BP. Between 2700 and 2000 cal yr BP, palm swamp and evergreen forest tree taxa started to expand, suggesting an increase in water resurgence. At 2000 cal yr BP, the moist forest with Mauritia expanded and fire activity changed from mixed to woody fuel particles. During the last 200 cal yr BP, a decrease in the palm tree Mauritia flexuosa, an expansion of Poaceae and an increase in macrocharcoal particles are attributed to an increase in anthropogenic activities in the Araripe Basin. The Late-Holocene climatic trend seen at Araripe mirrors that of eastern Brazil and has controlled the aquifer activity, including during the major droughts that affected the region. This is highly relevant for the application of public policies that rely on the aquifers of Araripe for the 21st century. [ABSTRACT FROM AUTHOR]

The equatorward contraction of tropical precipitation, commonly referred to as the "deep‐tropical contraction", is witnessed in the paleoclimate simulations of the early Eocene. However, the mechanism driving this contraction is still unclear. Based on the energetics framework of the Intertropical Convergence Zone (ITCZ) and the decomposition method of the latent heat flux along with the simulations of a climate system model, CESM1.2, we proposed a novel mechanism responsible for the "deep‐tropical contraction" in the early Eocene. The greenhouse gases‐induced sea surface warming amplifies the sensitivity of evaporation to surface wind speed changes through Clausius‐Clapeyron scaling, leading to an interhemispheric asymmetric enhancement of the latent heat flux. To maintain hemispheric energy balance, the cross‐equatorial atmospheric energy transport must be reduced during the solstice seasons. As a result, the solstitial location of the ITCZ shifts equatorward, causing the "deep‐tropical contraction" in the early Eocene. Plain Language Summary: The early Eocene is the warmest epoch in the last 65 million years, with a global mean temperature 9°C–23°C higher than the preindustrial period. According to state‐of‐the‐art climate models, the tropical rainfall contracted toward the equator during this extremely warm period. However, the physical mechanism causing this phenomenon remains unclear. In this study, we examined the hemispheric energy balance in the early Eocene that causes the equatorward contraction of tropical precipitation. A novel mechanism underlying this phenomenon is revealed. Based on the climate modeling of CESM1.2, we show that the GHG‐induced warmth enhances the sensitivity of evaporation to surface wind speed changes in the early Eocene. Thus, the stronger tropical trade wind in the winter hemisphere will drive out stronger latent heat flux than in the summer hemisphere. This interhemispheric asymmetric response reduces the interhemispheric heating contrast in the solstice seasons. As a result, the ascending motion in the tropical atmosphere migrates toward the equator, finally decreases the width of tropical precipitation in the early Eocene. Key Points: The "deep tropical contraction" in the early Eocene is caused by the equatorward migration of the seasonal ITCZThe equatorward migration of the solstitial ITCZ location in the early Eocene is due to decreased cross‐equatorial energy transportThe enhanced wind‐evaporation effect in the early Eocene reduces the cross‐equatorial atmospheric energy transport in the solstitial seasons [ABSTRACT FROM AUTHOR]

Tropical free‐tropospheric humidity plays a crucial role for the Earth's radiative balance and climate sensitivity. In addition to atmospheric humidity, stable water isotopes can provide important information about the hydrological cycle. We use the isotope‐ and water tagging‐enabled version of the COSMOiso model to determine isotopic fingerprints of diagnosed moisture pathways over the western tropical Atlantic (WTA). A convection‐permitting, high‐resolution (5 km) nudged simulation is performed for January–February 2020. During this period, the target region is characterized by alternating large‐scale circulation regimes with different humidity and isotope signatures. Moist conditions in the middle troposphere (300–650 hPa) are associated with moisture transport from the south, east, southeast, as well as evaporation from the North Atlantic, while dry conditions correspond to extratropical transport from the north and west. To predict the contribution of different moisture sources, we used a statistical model based on the local specific humidity and temperature as predictors and obtained an R‐squared (R2) of 0.52. Adding water isotopes improved the prediction (R2 = 0.73), showing that isotopes provide unique information on moisture sources and transport patterns beyond conventional local observations. [ABSTRACT FROM AUTHOR]

The Pacific meridional mode (PMM) is one of the dominant coupled modes in the northeastern tropical Pacific (NETP), characterized by strip-like sea surface temperature (SST) anomalies spanning from Baja California to the central equatorial Pacific. While the majority of the El Niño events follow a positive PMM, only a few La Niña events are preceded by a negative PMM. Such an asymmetric activity of PMM before the onset of El Niño–Southern Oscillation (ENSO) was previously attributed to the inherent nonlinear response of the wind–evaporation–SST (WES) feedback to trade winds in the NETP. Through data analysis and coupled model experiments, we pointed out that PMM is in fact a highly symmetric phenomenon, and the asymmetry of PMM before the ENSO onset thus must be associated with ENSO. On the one hand, the nonlinear response of deep convection over the equator to symmetric ENSO forcing in the central equatorial Pacific permits a stronger Pacific–North America (PNA) pattern in El Niño years than in La Niña years. On the other hand, since the majority of La Niña events are preceded by a sharp decay of an El Niño, the warm equatorial SST anomalies associated with the preceding El Niño provide another source to trigger PNA before the La Niña onset. The two mechanisms modulate the trade winds and heat fluxes in NETP more heavily before the La Niña onset than the El Niño onset and equally contribute to PMM asymmetry before the ENSO onset. [ABSTRACT FROM AUTHOR]

This study investigates thermal circulations on Reunion Island (21°07'S 55°32'E), focusing on the complex terrain of the region. Observations from the BIO‐MAÏDO campaign, along with 2 days of high‐resolution simulation using the MesoNH model, were analyzed to understand the thermally‐driven mechanisms. This simulation was conducted with a horizontal resolution of 100 m and employed a vertically stretched grid, achieving a resolution of 1 m at the lowest levels. Two distinct wind regimes were identified, characterized by katabatic flows prevailing within a 30 m thick layer during nighttime, and an anabatic flow manifesting within a layer spanning from 150 to 200 m during the daytime. The simulation was confirmed through validation with surface measurements, and thus enabling a detailed study of thermal breeze circulations. Results reveal that the intensity of trade winds significantly influences the development of thermal circulations. Complex layered structures in the atmosphere were also identified. At an intensity of 7 m s−1, trade winds impede the development of thermal circulations atop the slope, and result in the emergence of a convergence zone between local and regional circulations. The analysis of the breeze establishment period indicates that the katabatic flow stabilizes in 35 min, quicker than the anabatic flow, which takes 110 min. Momentum and heat budget analysis provide insights into the primary drivers of thermal circulations: buoyancy acceleration, influenced by local surface heating during anabatic flow onset, and local surface cooling during katabatic flow onset. Plain Language Summary: This research explores thermal circulation in the northwestern region of Reunion Island, an area significantly influenced by the return flow of the trade winds, the trade winds themselves, and breezes. Data from the BIOMAÏDO campaign and simulation using the MesoNH model were employed to analyze the heat‐driven air movements in this specific region. The study identified two distinct wind patterns: a downward katabatic flow within a 30 m layer and a diurnal anabatic flow occurring between elevetions of 150–200 m. Validation through surface measurements corroborated the model simulation, facilitating a detailed analysis of thermal breeze circulations. The results indicate that strong directional winds significantly influence air movement patterns. At a speed of 7 m s−1, these winds inhibit upward air movement along the slopes, creating a convergence zone between local and larger‐scale wind patterns. Analysis of the breeze establishment periods indicated a faster stabilization of katabatic flow at 35 min compared to 110 min of anabatic flow. Momentum and heat budget analysis revealed the primary drivers: buoyancy acceleration, influenced by local surface heating during anabatic flow and by local surface cooling during katabatic flow. Key Points: Trade winds strongly impact thermal circulations on Reunion Island, creating complex atmospheric structuresKatabatic flow stabilizes faster (35 min) than anabatic flow (110 min), affecting the island's thermal breeze patternsBuoyancy acceleration, local surface heating, and cooling play significant roles in driving thermal circulations [ABSTRACT FROM AUTHOR]

Aim: The aim of this study is to understand the development of windsports and the challenges faced by wind-based leisure activities. Methods: The socio-historical dynamics behind the development of wind leisure are analysed on the basis of specialised tourism blogs, as well as a field study carried out in the Northeast Region of Brazil, combining ethnographic observations and semi-structured interviews with 6 wind leisure enthusiasts. All the data is processed using the serious leisure perspective tools developed by Stebbins, and the body ecology tools developed by Andrieu et al. Results: The results show that wind sports provide a dual continuum. First of all, there are the practitioners, from Neophyte to Devotee Worker. Then there is the junction between land, water and air, where wind practices ensure a dual aesthetic. On the one hand, riders are united by a community of flow, emotion and sensation mediated by their relationship with the wind and the creation of play materials (waves, lagoons, trade winds). On the other hand, the tourist development of these practices serves a political narrative based on postcard aesthetics, enabling wind concessions to be traded for the development of wind farms. Conclusion: this original research calls for a more systematic exploration of wind practices and the hybridisation of natural elements, which seems to illustrate the crisis that modern sport and its institutions are going through today. [ABSTRACT FROM AUTHOR]

Pacific islands are widely exposed to several strong wave events all year long. However, comprehensive analyses of coastal vulnerabilities to wave climates and their extremes are often lacking in those islands. In the present paper, the wave climate around the reef of New Caledonia is analyzed using a 28-year simulation performed with the Wave Watch III model, and accounting for realistic wind intensity forcing from tropical cyclones. Four mean wave regimes are defined with clustering methods, and are shown to vary along the reef depending on its main orientation. The western reef is mostly exposed to energetic south-western swells (significant height over 1.5 m, peak period of ~ 12 s) generated in the Tasman Sea that are reinforced during austral winter. The northern sector and the Loyalty Islands, are hit by shorter waves (~ 8 to 9 s period) coming from the south-east to the north-east, with height ranging on average from 0.8 m in the Loyalty Channel to 1.5 m at the northern tip of the Grande Terre reef. These waves mainly result from the south-eastern trade winds that blow over the central south-western Pacific all year long. In austral summer, additional swell remotely generated by both the extra-tropical westerlies and the north-eastern trade winds of the northern hemisphere reach the north-eastern reef of the archipelago. These wave regimes also strongly vary in response to the interannual El Niño-Southern Oscillation. El Niño events tend to increase the frequency of the south-western swell regime in austral spring and fall, and of the south-eastern trade wind waves in austral summer. In contrast, during La Niña, waves generated in the northern hemisphere are more likely to reach New Caledonia all year long. Finally, extreme wave events and their return periods were assessed. Wave amplitude reaching 7 m is estimated to occur every 100 years. On the west and southern tip of the Grande Terre reef, extreme waves are 80% of the time westerly waves generated by storms in the Tasman Sea or in the Coral Sea, while on the eastern reefs (Loyalty Islands and Channel), 70% of the extreme wave episodes are associated to tropical cyclone-induced waves. During La Niña episodes, more tropical cyclones pass by New Caledonia, increasing their contribution to extreme wave events along the western and southern coasts of the island. Conversely, in El Niño conditions, the exposure to tropical cyclone-induced waves is predominantly concentrated on the northeastern side. [ABSTRACT FROM AUTHOR]

This study addresses the global shift towards renewable energy due to the increasing demand driven by socioeconomic development. With finite fossil energy sources, there's a growing interest in oceanic renewable energy, estimated at 76 million MW. The Amazon, with its significant potential, particularly from predictable tidal currents in estuaries, stands out. The Inner Continental Shelf of Amapá, influenced by factors like water discharge (5,7 × 1012 m3.year− 1) and trade winds (speed: 5–10 m.s− 1) as well as Meso and Macrotidal, is a notable region. The paper focuses on hydrodynamic simulations considering different tidal scenarios and aims to assess the energy potential of tidal currents. Using the SisBaHiA two-dimensional hydrodynamic model, the study evaluates power density in key areas. The spring-neap cycle simulations identify promising zones in the Varador channel—upper section (tidal current velocity of 1,53 m.s− 1– 1.835 W.m− 2) and lower section (tidal current velocity of 1,12 m.s− 1 – 720,03 W.m-2). Notably, the upper Varador channel near the Inferno ¨igarapé¨ (Maraca Island) exhibits greater energy density, highlighting its potential in both spring and neap cycles. This research contributes valuable insights into the renewable energy potential of tidal currents in the Amapá region, supporting sustainable energy development. [ABSTRACT FROM AUTHOR]

Abstract The frequencies of marine heatwaves and thermal coral bleaching events (CBEs) over the Great Barrier Reef (GBR) continue to increase with five mass CBEs reported since 2016. While changes in the local meteorology, such as reduced wind speeds and decreased cloud cover, are known to heat the shallow reef waters, little consideration has been given to the overriding synoptic meteorology. The 2022 CBE, occurring under La Niña conditions, saw ocean temperatures at Davies Reef increase 1.9 $$^\circ \hbox {C}$$ ∘ C over 19-days and subsequently cool 2.1 $$^\circ \hbox {C}$$ ∘ C back to seasonal norms over eight days. This event was found to be triggered by repeated Rossby wave breaking disrupting the local trade winds, thus inhibiting the latent heat flux. Latent heat fluxes, the primary driver of the event, tripled as the trade winds returned via rapid coastal ridging. These same synoptic features are concurrent with the historic Lismore flooding located hundreds of kilometres south of the GBR.

From 1979 to 2022, the summer monsoon precipitation has increased by a substantial 40% over Northwest India compared to the 1980s. This wetting trend aligns with the future projections of the Coupled Model Intercomparison Project 6 (CMIP6). The observationally constrained reanalysis data indicates that significant sea surface warming in the western equatorial Indian Ocean and the Arabian Sea is likely driving this increase in rainfall by enhancing the cross‐equatorial monsoonal flow and associated evaporation. We demonstrate that the strengthening of the cross‐equatorial monsoon winds is due to the rapid warming of the Indian Ocean and the enhanced Pacific Ocean trade winds, which result from the poleward shift and expansion of the Hadley cell. These strengthened winds boost the latent heat flux (evaporation), leading to increased moisture transport to Northwest India. Plain Language Summary: From 1979 to 2022, the summer monsoon precipitation has increased by a substantial 40% over Northwest India compared to the 1980s. The analysis suggests that a noticeable warming of the sea surface in the western equatorial Indian Ocean and the Arabian Sea could be causing this increase in rainfall. This warming strengthens the winds crossing the equator in the Indian Ocean and increases evaporation. The study also shows that the monsoon winds are strengthened due to the rapid warming of the Indian Ocean and the enhanced Pacific Ocean trade winds. These stronger winds cause more evaporation, which means more moisture is carried from the ocean to the land, leading to increased monsoon rainfall. Key Points: Large increase in summer monsoon precipitation over Northwest IndiaThe strengthening of the monsoon winds and the Indian Ocean warming drives increasing evaporationPoleward shift and expansion of high‐pressure belts and the Indian Ocean warming are responsible for the strengthening of winds [ABSTRACT FROM AUTHOR]

The doldrums are regions of low wind speeds and variable wind directions in the deep tropics that have been known for centuries. Although the doldrums are often associated with the Intertropical Convergence Zone (ITCZ), the exact relationship remains unclear. This study re‐examines the relationship between low‐level convergence and the Atlantic doldrums. By analyzing the frequency distribution of low wind speed events in reanalysis and buoy data, we show that the doldrums are largely confined between the edges of the ITCZ marked by enhanced surface convergence. While the region between the edges is a region of high time‐mean precipitation, low wind speed events occur in the absence of precipitation. Based on these results, we hypothesize that low wind speed events occur in regions of low level divergence rather than convergence. Plain Language Summary: The doldrums, an area between the trade winds formerly feared by mariners because of its low wind speeds and variable wind directions, have largely disappeared from mention in the scientific literature. The most commonly given explanation for the existence of the doldrums, according to which the weaker surface winds result from the upward circulation of the trade winds, can only be true when averaged over timescales of days or weeks. In this study, we re‐examine this region and its relationship to the convergence of the trade winds. We show that although low wind speed events occur in the region where the trade winds meet and precipitation rates are high on average, they occur precisely when there is no precipitation. This leads us to the hypothesis that these regions of low wind speeds are characterized by sinking rather than rising air. Key Points: The doldrums are confined to the area of time‐mean convergence of the Atlantic Intertropical Convergence Zone (ITCZ)The frequency distribution of low wind speed events peaks between the edges of the ITCZ, which are characterized by increased convergenceLow wind speed events within the ITCZ occur when precipitation is absent, suggesting they coincide with local low‐level divergence [ABSTRACT FROM AUTHOR]

Understanding the causes for discrepancies between modelled and observed regional climate trends is important for improving present-day climate simulation and reducing uncertainties in future climate projections. Here, we analyse the performance of coupled climate models in reproducing regional precipitation trends during the satellite era. We find statistically significant observed drying in southwestern North America and wetting in the Amazon during the period 1979–2014. Historical climate model simulations do not capture these observed precipitation trends. We trace this discrepancy to the inability of coupled simulations to capture the observed Pacific trade wind intensification over this period. A linear adjustment of free running historical simulations, based on the observed strengthening of the Pacific trade winds and modeled ENSO teleconnections, explains the discrepancy in precipitation trends. Furthermore, both the Pacific trade wind trends and regional precipitation trends are reproduced in climate simulations with prescribed observed sea surface temperatures (SST), underscoring the role of the tropical Pacific SST patterns. [ABSTRACT FROM AUTHOR]

The tropical arm of Atlantic Multidecadal Variability (AMV) influences climate worldwide, yet the mechanisms generating it remain unclear. Here, we examine experiments with sea surface temperature (SST)‐restoring in the extratropical North Atlantic in multiple models and use mixed‐layer heat budgets to elucidate the important mechanisms. Our results demonstrate that the tropical AMV is driven by wind‐mixed‐layer‐SST feedback. The evolution has two phases with tropical AMV SST anomalies growing from April to October and decaying from November to March. The amplitude of the growth phase surpasses that of the decay phase, resulting in overall tropical Atlantic warming during positive AMV phases. During summer, positive SST anomalies in the extratropics weaken the trade winds, resulting in a shallower mixed‐layer with reduced heat capacity. Subsequent absorption of climatological shortwave radiation in this shallower mixed‐layer then causes SSTs to warm, generating the tropical AMV. Importantly, anomalous surface heat‐fluxes make modest contributions to tropical AMV in these experiments. Plain Language Summary: The North Atlantic sea surface temperature (SST) has fluctuated significantly over periods of decades to multiple decades, a phenomenon known as the Atlantic Multidecadal Variability (AMV). It influences climate worldwide; however, questions remain about how it evolves. This study highlights the vital role of upper ocean processes, particularly the depth of oceanic mixed‐layer, in generating the tropical part of the AMV. Here, we analyzed SST‐restoring climate model experiments in which a surface temperature anomaly is added over the extratropical North Atlantic Ocean. The evolution features a summer growth phase and a winter decay phase, with stronger growth leading to overall warming during positive phases of the tropical AMV. In summer, prevailing trade winds weaken and induce a shallower depth of oceanic mixed‐layer. This leads to the absorption of solar energy in a reduced volume of ocean water, resulting in the warming of SST and the development of a positive phase of tropical AMV. Interestingly, changes in heat‐fluxes over the ocean surface and related mechanisms make little contribution to the development of tropical AMV in these experiments. These results emphasize the importance of accurate upper‐ocean processes for the simulation of AMV in coupled climate models. Key Points: Tropical Atlantic Multidecadal Variability (AMV) is driven by wind‐mixed‐layer‐sea surface temperature (SST) feedback in extratropical SST‐restoring experimentsWeakening of trade winds in summer induces a shallower mixed‐layer, reducing ocean heat capacity and generating positive tropical AMVChanges in surface heat‐fluxes or associated mechanisms are not responsible for tropical AMV in these experiments [ABSTRACT FROM AUTHOR]

Climatic impacts of historical volcanism are principally tied to the eruption size, while observation versus model discrepancies have been commonly attributed to the uncertainties in paleo‐reconstruction or malpresentation of volcanic aerosols in models. Here we present convergent evidence for significant compensation effect of ocean latent heat (LH) in balancing the tropical volcanic‐induced heat loss, by introducing an effective perturbation ratio which is found to decrease with increasing eruption magnitude. Four LH compensation hot spots overlapping with the trade wind regions are identified, together with three western boundary currents regions with intensified LH loss. Comparison between the 1258 Samalas and 1452 Unidentified eruptions suggests considerable modulation of the concurring El Nino‐Southern Oscillation on LH anomaly, which is further verified by CESM large ensemble sensitivity experiments. This study depicts how the interplay between the ocean and the atmosphere could contribute to the overall resilience of the climate system in the face of volcanic disturbances. Plain Language Summary: Large volcanic eruptions drive significant climate perturbation and the resulting cooling generally decreases with increasing eruption size, especially over the surface and upper ocean. In this study we introduce an effective volcanic perturbation ratio, defined as the ratio between the surface net flux anomaly and the volcanic‐induced shortwave flux anomaly, and analyze its relationship with the eruption magnitude. Our results, based on tree‐ring reconstructions and the CESM‐LME simulations, suggest that the effective ratio gradually decreases with the increasing shortwave perturbation, and the reduction of latent heat (LH) flux from ocean to atmosphere balances a significant portion of the volcanic‐induced net surface heat loss. LH varies with wind speeds and vertical specific humidity gradient. We identify four LH compensation effect hot spots which highly overlap with the trade wind regions, and three western boundary currents regions with intensified ocean latent heat loss. We run sensitivity experiments using the 1815 eruption of Mount Tambora as a test case, and find that the ENSO responses accompanying the eruption could modify the LH compensation effect. Key Points: Volcanic‐induced temperature responses do not scale linearly with the eruption sizes in both reconstruction and model simulations with same aerosol ‐ radiative treatmentOcean latent heat (LH) flux plays an important role in compensating volcanic‐induced radiative heat loss which enhance with growing eruption sizeInternal climate variability such as ENSO inserts significant influence on LH's compensation role through the wind‐evaporation‐SST feedback [ABSTRACT FROM AUTHOR]

Lahar deposits resulting from the eruption of Ambae (Vanuatu) in 2017–2018 were transformed into black sand beaches at the discharge points of water flow paths. This occurrence represents a novel and unreported phenomenon for Ambae. This study proposes that the combination of steep slopes generally 20–25% with relatively short flow paths (5–10 km) and substantial ash accumulation at the summit facilitated the rapid transfer of material from the volcanic summit to the coastal zone, providing the energy necessary for the gradual seaward extension of the coastline and the formation of beaches. The occurrence of this phenomenon is limited to specific areas, contingent upon the distribution of ash deposits on the summit. The western section of the crater's summit has predominantly accumulated ash, partially due to the consistent presence of trade winds. This region coincides with the origins of the flow paths supplying the lahar zone. Since 2018, the newly formed beaches persist, offering promising prospects for the island's development, including the identification of freshwater sources. The study also delves into the most destructive event of the eruption and proposes that a combination of the lahar and landslide events precipitated the destruction of the village of Waluembue. Paradoxically, the lahar's arrival preceded the landslide, providing a warning call to the inhabitants and giving them crucial time to evacuate before the catastrophic impact. [ABSTRACT FROM AUTHOR]

This study analyzes fluctuations in the atmospheric boundary layer height (aBLH) over a Caribbean island using hourly measured and model-interpolated data from the 2019–2023 period. Our focus is the mean structure, diurnal cycle, and aBLH correlation with meteorological parameters on the leeward coast at Mayaguez (18.2 N, 67.1 W). The mean diurnal cycle of the aBLH increases from 300 m near sunrise (07:00) to 1200 m by 13:00 because of turbulent heating. Summer-time thermal circulations lead to a 3 °C increase in near-surface dewpoint temperature (Td) that propagates upward to 3000 m by 16:00. A case study demonstrates how mid-day trade winds turn onshore and generate significant rainfall and river discharge across the island. The context for this study is provided by a 24 yr cluster analysis that identifies rainfall over the island's northwest interior driven by upstream heating. Analysis of linear trends from 1979 to 2023 shows that Td declined by −0.02 °C/yr above 1500 m because of large-scale subsidence. However, cool interior forests transpire humidity and instill contrasting trends that may amplify climate extremes. A better understanding of entrainment at the top of the atmospheric boundary layer could be critical for managing future water resources in Caribbean islands. [ABSTRACT FROM AUTHOR]

It remains unresolved whether the La Niña-like sea surface temperature (SST) trend pattern during the satellite era, featuring a distinct warming in the northwest/southwest Pacific but cooling in the tropical eastern Pacific, is driven by either external forcing or internal variability. Here, by conducting a comprehensive analysis of observations and a series of climate model simulations for the historical period, we show that a combination of internal variability and human activity may have shaped the observed La Niña-like SST trend pattern. As in observations, SSTs in each model ensemble member show a distinct multi-decadal swing between El Niño-like and La Niña-like trend patterns due to internal variability. The ensemble-mean trends for some models are, however, found to exhibit an enhanced zonal SST gradient along the equatorial Pacific over periods such as 1979–2010, suggesting a role of external forcing. In line with this hypothesis, single-forcing large ensemble model simulations show that human-induced stratospheric ozone depletion and/or aerosol changes have acted to enhance the zonal SST gradient via strengthening of Pacific trade winds, although the effect is model dependent. Our finding suggests that the La Niña-like SST trend is unlikely to persist under sustained global warming because both the ozone and aerosol impacts will eventually weaken. [ABSTRACT FROM AUTHOR]

This study investigates the representation of the Tropical Atlantic zonal and meridional modes of sea surface temperature variability, as well as precipitation in western Sahel, northeast Brazil, Amazon and equatorial Atlantic in a set 40 CMIP6 models under the historical period in both full-forcing historical simulations (hist-full) and the Detection and Attribution Model Intercomparison Project (DAMIP) single-forcing simulations: historical natural (hist-nat), historical aerosol (hist-aer) and historical greenhouse gases (hist-GHG). The mean state and variability represented in the CMIP6 historical full forcing simulations is compared to observations. The mean state and long term trends in the single forcing simulations is analysed and compared against the full-forcing and control simulations. Results show that there is a warm bias in the Atlantic Cold Tongue region observed in previous CMIP versions which persists in CMIP6. The models simulate higher mean precipitation rates than observations in northeastern Brazil and eastern equatorial Atlantic, while they present a negative bias overall in Amazon and Sahel regions. For the Detection and Attribution Model Intercomparison Project (DAMIP) experiments, aerosols lead to a decrease in climatological mean precipitation in the Amazon region while greenhouse gases lead to a warming trend in SSTs accompanied by a slight weakening of trade winds. Statistically significant long-term precipitation trends are observed only in Sahel region for the full-forcing simulations. [ABSTRACT FROM AUTHOR]

For nearly half a century, marine ecosystems in the Pan-Caribbean region have degraded due to pollution from oil and its hydrocarbons, solid waste, toxic substances and nutrients, with different kinds of pollution occurring in one or more places. Marine pollution in one country not only harms the development of its own marine economy, but also causes uncontrollable transboundary environmental impacts on neighboring countries. There are three major sources of marine pollution in this region. First, land-based activities are the main cause of marine pollution, as the coastal waste from daily life and production has been discharged into the sea intentionally or inadvertently, leading to large-scale pollution. Second, marine activities such as submarine hydrothermal, oil drilling, gas extraction and transit shipping impact the marine ecological environment in natural or man-made ways. Third, special natural activities such as trade winds and ocean currents further aggravate the spread of pollution. Marine pollution seriously affects the socio-economic development of the Pan-Caribbean region, especially tourism and fishing industries vital for local people's survival. Marine pollution in the Pan-Caribbean region is not only a regional issue, but also an international concern calling for the active attention and response from the global community. [ABSTRACT FROM AUTHOR]

The Amazon rainforest (ARF) is threatened by deforestation and climate change, which could trigger a regime shift to a savanna‐like state. Whilst previous work has suggested that forest resilience has declined in recent decades, that work was based only on local resilience indicators, and moreover was potentially biased by the employed multi‐sensor and optical satellite data and undetected anthropogenic land‐use change. Here, we show that the average correlation between neighboring grid cells' vegetation time series, which is referred to as spatial correlation, provides a more robust resilience indicator than local estimations. We employ it to measure resilience changes in the ARF, based on single‐sensor Vegetation Optical Depth data under conservative exclusion of human activity. Our results show an overall loss of resilience until around 2019, which is especially pronounced in the southwestern and northern Amazon for the time period from 2002 to 2011. The results from the reliable spatial correlation indicator suggest that in particular the southwest of the ARF has experienced pronounced resilience loss over the last two decades. Plain Language Summary: The Amazon rainforest (ARF) is Earth's most biodiverse ecosystem, crucial for regulating global and regional climate through water recycling and carbon uptake. Several studies suggest that ongoing deforestation, land‐use changes, and climate change induced shifts in rainfall patterns could trigger an abrupt regime shift from the current rainforest to a low‐treecover state. Here, we investigate the resilience of the ARF vegetation based on remotely sensed Vegetation Optical Depth, particularly useful in high‐biomass areas such as the ARF. The main feedback mechanism, essential for potential tipping, is moisture recycling. The trade winds bring in moisture from the Atlantic Ocean to South America's east, where it precipitates. Much of this moisture re‐enters the atmosphere via evapo‐transpiration and is transported further west, thereby establishing a moisture regime supporting the rainforest. The induced spatial coupling results in the spatial correlation being a reliable indicator of resilience. We compare changes in the spatial correlation to changes in the two classic indicators. The greatest resilience loss is detected in the southwestern Amazon, which has been identified as a highly‐coupled sub‐system since it is reliant on recycled moisture from upstream the trade winds, hence making the spatial correlation a particularly suitable and trustworthy resilience indicator there. Key Points: We quantify changes in Amazon resilience by investigating satellite data that has been carefully selected to avoid known sources of biasSpatial correlation of vegetation time series reliably shows resilience changes in spatially coupled systems such as the Amazon RainforestThe Amazon forest is losing resilience, especially in the southwestern Amazon, a region which has high demand on recycled moisture [ABSTRACT FROM AUTHOR]

At mesoscale, trade wind clouds organize with various spatial arrangements, shaping their effect on Earth's energy budget. Representing their fine‐scale dynamics even at 1 km scale climate simulations remains challenging. However, geostationary satellites (GS) offer high‐resolution cloud observation for gaining insights into trade wind cumuli from long‐term records. To capture the observed organizational variability, this work proposes an integrated framework using a continuous followed by discrete self‐supervised deep learning approach, which exploits cloud optical depth from GS measurements. We aim to simplify the entire mesoscale cloud spectrum by reducing the image complexity in the feature space and meaningfully partitioning it into seven classes whose connection to environmental conditions is illustrated with reanalysis data. Our framework facilitates comparing human‐labeled mesoscale classes with machine‐identified ones, addressing uncertainties in both methods. It advances previous methods by exploring transitions between regimes, a challenge for physical simulations, and illustrates a case study of sugar‐to‐flower transitions. Plain Language Summary: Clouds are a fundamental player affecting our planet's energy balance, making their accurate representation crucial in climate models. One open question is how they organize on a scale of a few 100 km (mesoscale) in the tropical northern Atlantic region east of Barbados. Satellite observations can help to categorize these clouds, but previous methods had limitations in capturing the full range of cloud arrangements and transitions between different cloud forms. We have introduced a novel approach that utilizes machine learning and geostationary satellite data to address this issue. Our machine learning model autonomously learns to recognize various cloud patterns and distributions. We conducted a comparative analysis between the categories generated by the machine and those identified by human experts to understand the strengths and weaknesses of both methods. Additionally, we explore a case study where clouds undergo a transformation, changing from a structure resembling sugar to one resembling flowers. This particular transformation was found difficult to capture with physical simulation before. The clear signatures of the transition identified by our machine learning approach can help to better understand cloud evolution, which is crucial for improving climate models and predicting how cloud behavior may change in a changing climate. Key Points: Mesoscale cloud organization can be taxonomized by a two‐step deep learning approach in the feature space continuumComparing seven machine‐identified classes with humans' four recognized categories underlines the significance of uncertainty estimatesNew diagnostic is provided to analyze the temporal transition between regimes, as illustrated for human‐labeled sugar‐to‐flower regimes [ABSTRACT FROM AUTHOR]

This work is carried out in the Republic of Congo. The aim is to identify extreme events during the rainy season from the analysis of tendencies, based on abrupt changes in meteorological parameters recorded in 2015 and 2016 by the meteorological office during the passage of extreme rainfall events. We observed changes in temperature, relative humidity, and atmospheric pressure being respectively above 6˚C, 40%, 2 hPa or below 4˚C, 20%, and -2 hPa. Through a principal component analysis of the local hourly tendencies at each station, we were able to discover 49 extreme rainy events occurring during the March–April and October–November periods. The spread of tendencies is different in the south and the north of the equator due to meteorological factors such as CAPE, Madden–Julian oscillation, Walker circulation, local oceanic influence, and the forest cover of the Congo Basin. The coastal city of Pointe-Noire shows more homogeneous tendencies as observed at the station of Ouesso in the north of the equator with the influence of monsoon and forest. Also, the stations of Dolisie and Brazzaville, despite their location in the south of the equator, showed greater variability. Indeed, Dolisie undergoes the combined effects of the relief of Mayombe (900 m) and the trade winds of the southwest. Brazzaville is under the effect of the southwest trade winds which becomes progressively unstable landward with stronger convection and is on the trajectory of certain squall lines which are developed from the reliefs of the east of the Democratic Republic of Congo. [ABSTRACT FROM AUTHOR]

Three supervised neural network cloud classification routines are applied to daytime MODIS Aqua imagery and compared for the year 2018 over the North Atlantic Ocean. Routines surveyed here include the Morphology Identification Data Aggregated over the Satellite-era (MIDAS), which specializes in subtropical stratocumulus (Sc) clouds; sugar, gravel, flowers, and fish (SGFF), which is focused on shallow cloud systems in the tropical trade winds; and the community record of marine low-cloud mesoscale morphology supported by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) dataset, which is focused on shallow clouds globally. Comparisons of co-occurrence and vertical and geographic distribution show that morphologies are classified in geographically distinct regions; shallow suppressed and deeper aggregated and disorganized cumulus are seen in the tropical trade winds. Shallow Sc types are frequent in subtropical subsidence regions. More vertically developed solid stratus and open- and closed-cell Sc are frequent in the mid-latitude storm track. Differing classifier routines favor noticeably different distributions of equivalent types. Average scene albedo is more strongly correlated with cloud albedo than cloud amount for each morphology. Cloud albedo is strongly correlated with the fraction of optically thin cloud cover. The albedo of each morphology is dependent on latitude and location in the mean anticyclonic wind flow over the North Atlantic. Strong rain rates are associated with middling values of albedo for many cumuliform types, hinting at a complex relationship between the presence of heavily precipitating cores and cloud albedo. The presence of ice at cloud top is associated with higher albedos. For a constant albedo, each morphology displays a distinct set of physical characteristics. [ABSTRACT FROM AUTHOR]

The propagation of sea surface temperature (SST) anomalies along the equatorial Pacific Ocean during El Niño shifted around the late 1970s, previously propagating westward from the eastern Pacific and shifting to eastward propagation from the central Pacific. This shift has been attributed to decadal changes in the mean state of the equatorial Pacific. This study examined the influence of the subtropical South Pacific on the decadal variation in El Niño zonal propagation through the utilization of observational data and extensive simulations with coupled climate models. We showed that El Niño induced by the positive South Pacific Subtropical Dipole mode (pSPSD) started in the eastern Pacific and developed westward. The mean trade winds in the southeastern Pacific were stronger before the late 1970s, leading to a stronger pSPSD through enhanced wind–evaporation–SST feedback. Then, the pSPSD could trigger westward propagating El Niño. Contrarily, weaker pSPSD did not induce El Niño events after the late 1970s. El Niño initiated from other processes and propagated eastward. Our study reveals the modulation of the subtropical South Pacific on the decadal shift of El Niño propagation. [ABSTRACT FROM AUTHOR]

The North Pacific Oscillation (NPO) serves as a pivotal atmospheric circulation pattern within the North Pacific. It has a considerable influence on the climate of East Asia and North America in the North Pacific Basin, and can also affect the climate of more distant regions via the atmospheric teleconnections. Our study has revealed a significant eastward shift of the southern lobe of the NPO from 178°E to 155°W during the boreal winter (November–December–January–February–March, NDJFM) after 1993/1994 in observations. The eastward shift of the NPO after 1993/1994 leads to stronger subtropical northeasterly trade winds during the boreal winter over the eastern North Pacific. As the strongest climatic factor influencing the strength of the wind-evaporation-sea temperature (WES) feedback mechanism, the enhanced subtropical northeast trade winds after 1993/1994 stimulate a more efficient WES feedback mechanism over the eastern North Pacific. Furthermore, the intensification of the WES feedback mechanism after 1993/1994 subsequently enhances the influence of the NPO on the tropical Pacific sea surface temperature (SST). [ABSTRACT FROM AUTHOR]

Trade wind clouds are ubiquitous across the subtropical oceans, including the Great Barrier Reef (GBR), playing an important role in modulating the regional energy budget. These shallow clouds, however, are by their nature sensitive to perturbations in both their thermodynamic environment and microphysical background. In this study, we employ the Weather Research and Forecasting (WRF) model with a convection-permitting configuration at 1 km resolution to examine the sensitivity of the trade wind clouds to different local forcings over the GBR. A range of local forcings including coastal topography, sea surface temperature (SST), and local aerosol loading is examined. This study shows a strong response of cloud fraction and accumulated precipitation to orographic forcing both over the mountains and upwind over the GBR. Orographic lifting, low-level convergence, and lower troposphere stability are found to be crucial in explaining the cloud and precipitation features over the coastal mountains downwind of the GBR. However, clouds over the upwind ocean are more strongly constrained by the trade wind inversion, whose properties are, in part, regulated by the coastal topography. On the scales considered in this study, the warm-cloud fraction and the ensuant precipitation over the GBR show only a small response to the local SST forcing, with this response being tied to the surface flux and lower troposphere stability. Cloud microphysical properties, including cloud droplet number concentration, liquid water path, and precipitation, are sensitive to the changes in atmospheric aerosol population over the GBR. While cloud fraction shows little responses, a slight deepening of the simulated clouds is evident over the upwind region in correspondence to the increased aerosol number concentration. A downwind effect of aerosol loading on simulated cloud and precipitation properties is further noted. [ABSTRACT FROM AUTHOR]

The upper water‐column dynamics and surface productivity variability in the Northeastern Atlantic Ocean across the Marine Isotope Stage (MIS) 7 interglacial complex is not well understood. Here, we present high‐resolution planktic foraminiferal proxies combined with Artificial Neural Network based‐sea‐surface temperature (SST) and ice‐rafted detritus records from International Ocean Discovery Program Site U1385, SW Iberian Margin for the intervals representing MIS 8 deglaciation, MIS 7 interglacial complex and MIS 6 glacial inception. The long‐term SST pattern is modulated by insolation and precession parameters across the MIS 7 interglacial complex and is superimposed by the millennial‐scale variability (stadials at ∼250, ∼243, ∼230, ∼221, ∼203, ∼196 and ∼192 ka). The regional SST records indicate high temperature gradient (∼6°C) between the sub‐polar North Atlantic Ocean and the SW Iberian Margin during MIS 7d which enhanced the moisture transport from mid‐to‐high latitudes. Further, low obliquity with low insolation induced cooling at high latitudes and promoted the expansion of ice‐sheets during MIS 7d. Comparison of our faunal proxies with the published marine and terrestrial records from SW Europe and western Mediterranean Sea suggested a weakening and southward shift of Azores High (AH) pressure system, similar to the present‐day (−) NAO‐like atmospheric configuration during the early phases of MIS 7e, MIS 7c and MIS 7a, resulting reduced surface productivity of SW Iberian Margin. During the late phases of MIS 7e, MIS 7c and MIS 7a, the AH pressure system strengthened and shifted northward causing the intensification of the trade winds, a scenario similar to present‐day (+) NAO‐like atmospheric configuration, which resulted in high surface productivity of SW Iberian Margin. Key Points: Long‐term sea‐surface temperature (SST) trend across the Marine Isotope Stage (MIS) 7 interglacial complex is modulated by insolation and precessionHigh SST gradient between sub‐polar North Atlantic and SW Iberian Margin and low obliquity enhanced the expansion of ice‐sheets during MIS 7dSurface productivity during MIS 7e, MIS 7c, & MIS 7a is driven by a NAO‐like atmospheric configuration [ABSTRACT FROM AUTHOR]

Sea surface temperature (SST) across the Coral Sea is tightly coupled to the regional and larger‐scale ocean circulation and climate. Continuous records that reflect past changes in Coral Sea SST in high resolution are missing, however. Here, we present Mg/Ca‐ and alkenone‐based SST reconstructions from the northwestern Coral Sea that cover the past 130 kyr. Our SST estimates vary in line with southern hemisphere high latitude climate variability, linked to atmospheric CO2. Combining the newly generated with published records, we find that the SST changes across the Coral Sea show a large spatial heterogeneity during the last glacial‐interglacial cycle. Particularly prior to 60 ka, precession exerts a discernible influence on the meridional SST gradients across the Coral Sea, as well as between the Coral Sea and southern Western Pacific Warm Pool. We posit that these changes are linked to the regional trade winds and the South Pacific subtropical gyre circulation, and/or to changes in the El Niño Southern Oscillation. Key Points: SST evolution across the Coral Sea was spatially heterogenous during the last glacial‐interglacial cycleSST in the NW Coral Sea varies in line with southern hemisphere high latitude climate and atmospheric CO2Precession modulates meridional SST gradients, via its effect on the regional trade winds, ENSO and the South Pacific subtropical gyre circulation [ABSTRACT FROM AUTHOR]

The mesoscale eddy characteristics of the Mozambique Warm Current were investigated by detecting and tracking satellite altimetry data from 2010 to 2019. A total of 1,086 eddies were identified in the Mozambique Channel, comprising 509 cyclonic eddies and 577 anticyclonic eddies. The results revealed that the bay area on the northwest coast of Madagascar was the main hotspot of eddy generation, and the mean amplitude and radius of the anticyclonic eddies in the Mozambique Channel were 24.23 cm and 82.7 km, respectively, which are larger than those of the cyclonic eddies. Local wind forcing had a significant impact on the formation of mesoscale eddies in the Mozambique Channel. In winter, the wind stress in the northern and southern areas of the Mozambique Channel exhibited a strong correlation with the distribution of eddy kinetic energy (EKE), where both monsoonal winds in the north and trade winds in the south could facilitate mesoscale anticyclonic eddy formation. In addition, the variability in the number of anticyclonic and cyclonic eddies in the Mozambique Channel may have exerted a significant influence on the seasonal anomalous fluctuations in local sea surface temperatures (SSTs). This study presented a novel analysis of the mesoscale eddy characteristics in the Mozambique Channel. [ABSTRACT FROM AUTHOR]

Ocean acidification, caused by the absorption of carbon dioxide (CO2) from the atmosphere into the ocean, ranks among the most critical consequences of climate change for marine ecosystems. Most studies have examined pH and CO2 trends in the open ocean through oceanic time-series research. The analysis in coastal waters, particularly in island environments, remains relatively underexplored. This gap in our understanding is particularly important given the profound implications of these changes for coastal ecosystems and the blue economy. The present study focuses on the ongoing monitoring effort that started in March 2020 along the east coast of Gran Canaria, within the Gando Bay, by the CanOA-1 buoy. This monitoring initiative focuses on the systematic collection of multiple variables within the CO2 system, such as CO2 fugacity (fCO2), pH (in total scale, pHT), total inorganic carbon (CT), and other hydrographic variables including sea surface salinity (SSS), sea surface temperature (SST) and wind intensity and direction. Accordingly, the study allows the computation of the CO2 flux (FCO2) between the surface waters and the atmosphere. During the study period, stational (warm and cold periods) behavior was found for all the variables. The lowest SST values were recorded in March, with a range of 18.8-19.3°C, while the highest SST were observed in September and October, ranging from 24.5-24.8°C. SST exhibited an annual increase with a rate of 0.007°C yr-1. Warmer months increased SSS, while colder periods, influenced by extreme events like tropical storms, led to lower salinity (SSS=34.02). The predominant Trade Winds facilitated the arrival of deeper water, replenishing seawater. The study provided insights into atmospheric CO2. Atmospheric fCO2 averaged 415 ± 4 µatm (2020-2023). Surface water fCO2sw presented variability, with the highest values recorded in September and October, peaking at 437 µatm in September 2021. The lowest values for fCO2sw were found in February 2021 (368 µatm). From 2020 to 2023, surface water fCO2sw values displayed an increasing rate of 1.9 µatm yr-1 in the study area. The assessment of fCO2sw decomposition into thermal and non-thermal processes revealed the importance of SST on the fCO2sw. Nevertheless, in the present study, it is crucial to remark the impact of non-thermal factors on nearshallow coastal regions. Our findings highlight the influence of physical factors such as tides, and wind effect to horizontal mixing in these areas. The CT showed a mean concentration of 2113 ± 8 mmol kg-1 and pH at in-situ temperature (pHT, IS) has a mean value of 8.05 ± 0.02. The mean FCO2 from 2020 to 2023 was 0.34 ± 0.04 mmol m-2 d-1 (126 ± 13 mmol m-2 yr-1) acting as a slight CO2 source. In general, between May and December were the months when the area was a source of CO2. Extrapolating to the entire 6 km² of Gando Bay, the region sourced 33 ± 4 Tons of CO2 yr-1. [ABSTRACT FROM AUTHOR]

The Amazon Continental Shelf (ACS) is a shallow region (< 100 m), with a maximum width of 330 km, which encloses the northern portion of the Brazilian continental shelf and has great ecological and climatic importance on a global scale. Although important scientific efforts have been made to understand the hydrodynamics of the ACS and the dispersion of the Amazon River plume, there are still few studies that address surface oceanic water intrusion into the ACS. This study describes the existence of preferential surface oceanic water intrusion pathways into the ACS along 3 sectors: Maranhão (MA shelf), Pará (PA shelf) and Amapá (AP shelf). The analysis is based on: (i) 306 surface drifter trajectories along 1344 km of the ACS (provided by the Global Drifter Program) and (ii) 20 years of Lagrangian simulations (with Parcels model forced by currents from the reanalysis GLORYS). The results show that the MA shelf sector is the main pathway for surface oceanic water intrusions into the ACS, corresponding to 56% of the intrusions, followed by PA shelf (43%) and AP shelf (1%). During the austral summer, intrusions occur with a higher frequency in PA and AP shelf. The MA shelf shows weak seasonality in the intrusions. The temporal variability of particle intrusion rates into the ACS is directly related to the variability of the trade winds, and the meso-scale circulation associated with the North Brazil Current and the North Equatorial Countercurrent. [ABSTRACT FROM AUTHOR]

The BIO-MAÏDO (Bio-physicochemistry of tropical clouds at Maïdo: processes and impacts on secondary organic aerosols formation) campaign was conducted from 13 March to 4 April 2019 on the tropical island of Réunion. The main objective of the project was to improve understanding of cloud impacts on the formation of secondary organic aerosols (SOA) from biogenic volatile organic compound (BVOC) precursors in a tropical environment. Instruments were deployed at five sites: a receptor site, Maïdo Observatory (MO) at 2165 m a.s.l. and four sites along the slope of the Maïdo mountain. Observations include measurements of volatile organic compounds (VOCs) and characterization of the physical, chemical and biological (bacterial diversity and culture-based approaches) properties of aerosols and cloud water. Turbulent parameters of the boundary layer, radiative fluxes and emissions fluxes of BVOCs from the surrounding vegetation were measured to help interpret observed chemical concentrations in the different phases. Dynamical analyses showed two preferred trajectory routes for air masses arriving at MO during the daytime. Both trajectories correspond to return branches of the trade winds associated with upslope thermal breezes, where air masses likely encountered cloud processing. The highest mixing ratios of oxygenated VOCs (OVOCs) were measured above the site located in the endemic forest and the highest contribution of OVOCs to total VOCs at MO. Chemical compositions of particles during daytime showed higher concentrations of oxalic acid, a tracer of cloud processing and photochemical aging, and a more oxidized organic aerosol at MO than at other sites. Approximately 20 % of the dissolved organic compounds were analyzed. Additional analyses by ultra-high-resolution mass spectrometry will explore the complexity of the missing cloud organic matter. [ABSTRACT FROM AUTHOR]

Using two decades of data from 12 low-income countries in West Africa, we show that dust carried by harmattan trade winds increases infant and child mortality. Health investments respond to dust exposure, consistent with compensating behaviours. Despite these efforts, surviving children still exhibit negative health impacts. Our data allow us to investigate differential impacts over time and across countries. We find declining impacts over time, suggesting adaptation. Using national-level measures of macroeconomic conditions and health resources, we find suggestive evidence that both economic development and public health improvements have contributed to this adaptation, with health improvements playing a larger role. [ABSTRACT FROM AUTHOR]

Grasses are one of the most successful and dispersed plant families worldwide and their environmental and economic values are widely acknowledged. They dominate the landscape of Cabo Verde, the southernmost and driest archipelago of Macaronesia, and are relevant natural resources for local populations, but a comprehensive evaluation of their distribution patterns is still lacking. In this study, we aim to evaluate the potential effects of climate change using the long‐term data concerning grass distribution in Cabo Verde and the widely recognized climatic variability of this archipelago, which entails a huge irregularity in spatial and temporal rainfall. We identified two contrasting climatic periods (wet, from 1929 to 1968, and dry, from 1969 to 2007) and gathered all the information available from the bibliography, herbaria, and fieldwork concerning spontaneous grass species recorded in Cabo Verde during those two periods, which amounted to 107 taxa. This information was then used to disclose the patterns of grass diversity as related to climatic and topographic variables (altitude and windward vs. leeward aspects). Different altitudinal shifts in the distribution patterns of grass species assemblages and an assemblage specific to the wet period were revealed by comparing the two climatic periods. The role of exposure in delimiting the altitudinal distribution of the various assemblages was highlighted; the trade winds clearly determine the distribution of grass assemblages. We detected shifts in the distribution of grass assemblages according to the climatic periods (related to the macroclimate) and local topographic factors (associated with mesoclimates). Also, functional traits (i.e., annuals vs. perennials, C3 vs. C4 grasses, and tropical vs. temperate species) were found to vary between wet and dry periods, as well as with altitude and with slope aspect. Understanding species distributions and the role of the climatic variability of Cabo Verde is crucial to predicting how climate change will affect them and thus to support effective management and conservation actions. [ABSTRACT FROM AUTHOR]

In the northeastern tropical Atlantic, a region of high potential vorticity (PV) determines the size of the exchange window for the interior thermocline flow of the subtropical cell via its variations in strength and extent. Variability of this PV barrier has the potential to impact the ventilation of the tropical Atlantic on decadal timescales. Here, the impact of the North Atlantic Oscillation (NAO) on the PV barrier related to isopycnals within the thermocline of the subtropical‐tropical Atlantic Ocean is assessed from Argo observations for the time period of 2006–2022. Relative to the negative NAO phase (2009–2010), during the positive NAO phase (2014–2019), the North Atlantic subtropical high and the northeast trades are intensified. Satellite‐derived wind stress curl shows increased upwelling/downwelling on the equatorward/poleward side of the trade wind zone, respectively. In the subtropical‐tropical Atlantic, a symmetric pattern of isopycnal heave is observed: rising isopycnals within 20°N and 20°S and sinking poleward of that. With rising isopycnals, the PV barrier in the northeastern tropical Atlantic becomes stronger. Analyses of geostrophic velocities and the Sverdrup streamfunction show that during the positive NAO phase there are increased equatorward velocities at thermocline level along the western boundary and reduced velocities through the interior as a result of intensified northeast trades and therefore a strengthened PV barrier. Intensified trades lead to enhanced subduction of thermocline waters and, independent of that, to a strengthened Equatorial Undercurrent transport as observed at the mooring site at 0°, 23°W, likely via the pulling effect of the subtropical cells. [ABSTRACT FROM AUTHOR]

Observations of column water vapor in the tropics show significant variations in space and time, indicating that it is strongly influenced by the passage of weather systems. It is hypothesized that many of the influencing systems are moisture modes, systems whose thermodynamics are governed by moisture. On the basis of four objective criteria, results suggest that all oceanic convectively coupled tropical depression (TD)-like waves and equatorial Rossby waves are moisture modes. These modes occur where the horizontal column moisture gradient is steep and not where the column water vapor content is high. Despite geographical basic-state differences, the moisture modes are driven by the same mechanisms across all basins. The moist static energy (MSE) anomalies propagate westward by horizontal moisture advection by the trade winds. Their growth is determined by the advection of background moisture by the anomalous meridional winds and anomalous radiative heating. Horizontal maps of column moisture and 850-hPa streamfunction show that convection is partially collocated with the low-level circulation in nearly all the waves. Both this structure and the process of growth indicate that the moisture modes grow from moisture–vortex instability. Last, space–time spectral analysis reveals that column moisture and low-level meridional winds are coherent and exhibit a phasing that is consistent with a poleward latent energy transport. Collectively, these results indicate that moisture modes are ubiquitous across the tropics. That they occur in regions of steep horizontal moisture gradients and grow from moisture–vortex instability suggests that these gradients are inherently unstable and are subject to continuous stirring. Significance Statement: Over the tropics, column water vapor has been found to be highly correlated with precipitation, especially in slowly evolving systems. These observations and theory support the hypothesis that moisture modes exist, a type of precipitating weather system that does not exist in dry theory. In this study, we found that all oceanic tropical depression (TD)-like waves and equatorial Rossby waves are moisture modes. These systems exist in regions where moisture varies greatly in space, and they grow by transporting air from the humid areas of the tropics toward their low pressure center. These results indicate that the climatological-mean distribution of moisture in the tropics is unstable and is subject to stirring by moisture modes. [ABSTRACT FROM AUTHOR]

Spaceborne synthetic aperture radar (SAR) has been widely acknowledged for its advantages in collecting ocean surface measurements under all weather conditions during day and night. Despite the strongly nonlinear imaging process, SAR measurements of ocean waves provide an invaluable resource for studies into wave dynamics at the global scale. In this study, we take advantage of a newly defined parameter, the mean cross-spectrum (MACS) at a discrete wavenumber along the sensor line-of-sight axis, to further investigate the ocean wave properties. With the range peak wavenumber extracted from the MACS profile, together with the collocated model winds, the inverse wave age (iwa) is estimated. As an indicator of local wind–wave coupling, the global map of the iwa depicts a distinct pattern, with larger iwa values observed in the storm tracks. In addition to the mean, stronger variability in the iwa is also found in the storm tracks, while the iwa remains relatively steady in the trade winds with lower variability. This makes the SAR-derived iwa a significant parameter in reflecting the varying degrees of wind–wave coupling in variable geographical locations across the ocean basins. It will help to promote the practical application of SAR measurements, as well as advancing our understanding of ocean wave dynamics. [ABSTRACT FROM AUTHOR]

The paradigm shift towards sustainable energy sources has propelled research into enhancing the efficiency and reliability of power systems. This study introduces an advanced methodology for optimal power flow (OPF) by integrating the skill optimization algorithm (SOA) with considerations for open-access trading of wind farms and the integration of electric vehicle (EV) fleets. In order to improve exploration features of SOA, opposition-based learning (OBL) is used for diversifying the population. The proposed ISOA-based OPF model addresses the optimization of power flow in a multi-objective framework, aiming to minimize generation cost and minimize transmission loss while accommodating the open access trading between wind farms and EV fleet demands. The incorporation of open-access trading enables the effective utilization of surplus wind energy among interconnected power systems, fostering grid resilience and sustainable benefits. Simulation results on standard IEEE 30-bus and 57-bus test systems validate the efficacy of the proposed approach, showcasing improved system performance, reduced cost and power losses, and enhanced utilization of renewable resources in modern power grids. In the IEEE 30-bus, fuel costs are $803.13/hr standard and $935.2408/hr with extra trading. In the IEEE 57-bus, costs are $37589.34/hr standard and $37628.8/hr with additional trading. These results align with benchmarks, showcasing the method's efficacy in intricate problem-solving. [ABSTRACT FROM AUTHOR]

Abstract From 1979 to 2022, the summer monsoon precipitation has increased by a substantial 40% over Northwest India compared to the 1980s. This wetting trend aligns with the future projections of the Coupled Model Intercomparison Project 6 (CMIP6). The observationally constrained reanalysis data indicates that significant sea surface warming in the western equatorial Indian Ocean and the Arabian Sea is likely driving this increase in rainfall by enhancing the cross‐equatorial monsoonal flow and associated evaporation. We demonstrate that the strengthening of the cross‐equatorial monsoon winds is due to the rapid warming of the Indian Ocean and the enhanced Pacific Ocean trade winds, which result from the poleward shift and expansion of the Hadley cell. These strengthened winds boost the latent heat flux (evaporation), leading to increased moisture transport to Northwest India.

Sea surface temperature (SST) gradients are a primary driver of low‐level wind convergence in the east Pacific Inter‐Tropical Convergence Zone (ITCZ) through their hydrostatic relationship to the surface pressure gradient force (PGF). However, the surface PGF may not always align with SST gradients due to variations in boundary layer temperature gradients with height, that is, the boundary layer contribution to the surface PGF. In this study, we investigate the observed northern hemisphere position of the east Pacific ITCZ using a slab boundary layer model (SBLM) driven by different approximations of the boundary layer virtual temperature field. SBLM simulations using the entire boundary layer virtual temperature profile produce a realistic northern hemisphere ITCZ. However, SST‐only simulations produce excessive equatorial divergence and southern hemisphere convergence, resulting in a latitudinally confined double ITCZ‐like structure. Observed virtual temperature gradients highlight the importance of northward temperature gradients strengthening with height from the equator to 15°S below the trade wind inversion (TWI). Our interpretation is that the equatorial cold tongue induces relatively weak high surface pressure and double ITCZ‐like convergence because the resulting layer of cold air is shallow. Concurrently, relatively strong high surface pressure spreads out in the southern hemisphere due to interactions between stratocumulus clouds and the ocean surface. Together, the equatorial cold tongue and the TWI/stratocumulus clouds enable a more northern hemisphere dominant ITCZ. Thus, we provide evidence of a dynamical link between the equatorial cold tongue, low clouds, and double ITCZs, which continue to be problematic in Earth system models. Plain Language Summary: State‐of‐the‐art climate models have been plagued by biases in the Inter‐Tropical Convergence Zone (ITCZ), where the trade winds converge and the world's most intense rainfall occurs. Climate models often produce one ITCZ in each hemisphere, a double ITCZ, when there is nearly always one ITCZ observed in the northern hemisphere. In this study, we investigate why the northern hemisphere ITCZ dominates over the east Pacific Ocean using an idealized model driven by observed southern and northern hemisphere contrasts in: (a) sea surface temperature (SST) only and (b) both SST and atmospheric temperature. Experiments driven by only SST contrasts produce a double ITCZ‐like structure that is reminiscent of climate model double ITCZ biases. In observations, a cold tongue of ocean water on the equator induces relatively weak high surface pressure and a double ITCZ‐like wind convergence. At the same time, relatively strong high surface pressure spreads out in the southern hemisphere due to stratocumulus clouds and the ocean surface. Together, the equatorial cold tongue and stratocumulus clouds enable a more northern hemisphere dominant ITCZ. This study provides a dynamical link between the equatorial cold tongue, low clouds, and double ITCZs, which continue to be problematic in models. Key Points: East Pacific ITCZ surface wind convergence is strongly controlled by SST and boundary layer (BL) horizontal temperature gradientsSST gradients overemphasize the equatorial cold tongue leading to excessive equatorial divergence and latitudinally confined double ITCZsBL temperature gradients show a shallow cold tongue and deep cold air below the trade wind inversion are key to maintaining a northern ITCZ [ABSTRACT FROM AUTHOR]