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While it is known that sea surface temperature (SST) variability in the subtropical northeastern Pacific (SNEP) can be forced by wintertime atmospheric variability, the region over which atmospheric variability plays the significant driving role remains to be elucidated. Based on observational data during 1900–2014 and a first-order autoregressive model, we show that SNEP SST variability is dominantly forced by wintertime atmospheric variability over the North Pacific, slightly north of the SNEP. Atmospheric variability south of the SNEP, however, does not play the dominant driving role because of atmospheric barotropic response that partially offsets baroclinic Gill response over the ocean surface. Further, by decomposing North Pacific atmospheric variability into tropical Pacific (TP)-forced and non-TP-forced components using a tropical Pacific pacemaker experiment, we find that the leading modes in the two components comparably contribute to forcing SNEP SST in the historical record. Further analyses show that their contribution is unstable on decadal timescales, with stronger forcing effect from TP-forced Aleutian Low (AL) variability before the 1930s and after the 1980s. Such non-stationary forcing effect is primarily attributed to the relative amplitude between TP-forced AL and non-TP-forced atmospheric variability, which would affect the predictability of SNEP SST variability. [ABSTRACT FROM AUTHOR]

The dependence of the large-scale structure of oceanographic fields on short-term variations in atmospheric forcing (AF) at the ocean surface has been studied. Estimates of this dependence were obtained by comparing the results of two numerical experiments with the NEMO model in the ORCA1 configuration used as a computational core in the data assimilation system at the Hydrometeorological Center of Russia. The experiments similar in all other respects differed only in the discreteness of the AF data: 3–24 hours in the main experiment and 1 month in the experiment with time-averaged AF. Large-scale characteristics were compared: kinetic energy averaged over large regions, Atlantic Meridional Overturning Circulation, meridional heat transport, mixed layer depth, and sea ice volume. It has been shown that neglecting high-frequency AF variability can significantly distort the long-term evolution of oceanographic fields reproduced by ocean models and thereby affect the quality of model forecasts. [ABSTRACT FROM AUTHOR]

The bidirectional mass exchange between the Marmara Sea and the Aegean Sea provides one part of the critical hydrodynamic links between the Black Sea and the Mediterranean Sea. In this study, we examined exchange in the Dardanelles based on a 3-D numerical model simulation covering an 11-year period under realistic atmospheric forcing. The model includes the Black Sea, the Marmara Sea, and a part of the Aegean Sea to include the remote effects of basin dynamics. The main features as one-, two-, and three-layered flow structures are successfully reproduced by the model in comparison to earlier observations. It is found that the strait is subject to submaximal exchange by only one control near the Nara Pass. According to long-term modeling results, most variability occurs on synoptic time scales, and wind stress has a dominant role in those variations. The seasonal and interannual variability of exchange flow is relatively low and displays a close relationship with freshwater input to the Black Sea. [ABSTRACT FROM AUTHOR]

Sub-hourly heavy precipitation events (SHHPs) associated with regional low-pressure (RegL) systems in Portugal are a natural hazard that may have significant socioeconomic implications, namely in agriculture. Therefore, in this paper, their dynamic and thermodynamic drivers are analysed. Three weather stations were used to isolate SHHPs from 2000 to 2022. Higher precipitation variability is found in southern Portugal, with a higher ratio of extreme events on fewer rainy days. This study shows that these SHHP events are associated with low-pressure systems located just to the west of the Iberian Peninsula. These systems exhibit a cold core, particularly strong at mid-levels, and a positive vorticity anomaly, which is stronger in the upper troposphere, extending downward to low levels. These conditions drive differential positive vorticity advection and, therefore, rising motion to the east of the low-pressure systems. Moreover, at low levels, these systems promote moisture advection over western Iberia, also generating instability conditions, which are assessed by instability indices (Convective available potential energy, the Total-Totals index, and the K-index). The combination of these conditions drives heavy precipitation events. Lastly, the total column cloud ice water revealed higher values for the heavier precipitation events, suggesting that it may be a useful predictor of such events. [ABSTRACT FROM AUTHOR]

The unprecedented North Pacific marine heatwave (known as the Blob) in 2013/14 winter has attracted many research interests, considering its dramatic impacts on the ecosystem and regional climate. Meanwhile, the summertime Blob events have also emerged in recent decades. In this study, we identified four Blob events in the summer of 2014, 2015, 2019, and 2020 during the Satellite Era. Here we show diversity existed in the formation of summer Blob events. The atmospheric forcing responsible for the Blob is the weakened North Pacific subtropical high (NPSH), which contributes significantly to the Blob in 2019 via anomalous shortwave radiation. However, the atmospheric forcing alone cannot fully explain all the Blob events, especially the one in 2020 when the weakened NPSH is absent. Other than the weakened NPSH, the preceding spring sea surface temperature (SST) warm anomalies in the northeast Pacific can persist into the following summer due to anomalous mixed layer heat content and significantly contribute to the Blob. A binary linear regression model considering both the SST persistence and the NPSH is constructed, successfully reproducing the observed Blob variation for the period 1982–2020 (r = 0.76, p < 0.001). The model improves the ability to capture the warm peaks in all four summer Blob events, which either single factor cannot fully depict. [ABSTRACT FROM AUTHOR]

Introduction. For the effective use of unmanned aerial vehicles (UAV), it is required to take into account the impact of atmospheric environmental factors. Based on the existing level of development of the research and methodological apparatus, it is impossible to determine the probability of damage to the UAV under the conditions of complex exposure to atmospheric environmental factors and to assess the feasibility of further performance of the flight task. Violation of the UAV operation process is caused by the influence of atmospheric precipitation, wind and temperature conditions of the environment. The work aims at the development of a methodology for determining the probability of damage to UAV as a result of exposure to atmospheric environmental factors, as well as to evaluate the performance of the software package implementing the developed algorithm using triangular, trapezoidal, pentagonal, and Gaussian membership functions.Materials and Methods. A technique is proposed that makes it possible, using the theory of fuzzy logic, to determine the probability of damage to the UAV with inaccuracies and uncertainties in the description of atmospheric effects of the environment. It takes into account possible atmospheric forcing and enables to determine the probability of damage to the UAV under various atmospheric influences. The computational complexity of the algorithm implementing the technique depends significantly on the number of qualitative assessments of atmospheric impacts on UAV.Results. A method for determining the probability of damage to UAV as a result of exposure to atmospheric environmental factors based on fuzzy sets (triangular, trapezoidal, pentagonal, Gaussian) was proposed and tested. The use of fuzzy sets for estimating the conditions of the UAV application environment was described. An algorithm was developed to determine the probability of damage to the UAV as a result of exposure to atmospheric environmental factors. A computational experiment was carried out to determine the complexity of calculating the probability of UAV damage as a result of atmospheric forcing under various environmental conditions: «moderate conditions» at a wind speed of 3 m/s, precipitation intensity of 0.8 mm/h, and air temperature of 5 °C; «very heavy conditions» of the external environment at a wind speed of 12 m/s, precipitation intensity 3.5 mm/h, and air temperature of –6 ºС. It was established that the use of triangular membership functions to calculate the probability of damage to the UAV as a result of atmospheric forcing provided higher performance compared to the rest ones (trapezoidal, pentagonal, Gaussian).Discussion and Conclusions. The values of the UAV damage probabilities obtained during the implementation of the methodology under atmospheric environmental influences can be used at the pre-flight preparation stage and during the flight to assess the feasibility of further performance of the flight task. Based on the analysis of the application of the considered forms of membership functions, recommendations for their application are given. The use of algorithms with triangular membership functions will provide high performance of UAV control systems (UAV CS).

A comparison of simulations of the global ocean circulation with the NEMO/SI3 model with two types of atmospheric forcing (DFS5.2 and CFSR/CDAS), as well as with two grid resolutions (1° and 0.25°) is presented. The objective of such comparison is to substantiate a choice of a source of data on atmospheric forcing and a grid resolution for use in an operational system for the ocean state diagnosing and forecasting. It is shown that all considered simulations reproduce main large-scale ocean characteristics. The CFSR/CDAS merged meteorological dataset, which provides better agreement with actual data, is quite suitable for specifying atmospheric forcing in retrospective and operational applications of the NEMO/SI3 model, including its use as a computational core in the data assimilation system within the framework of the analysis–forecast–analysis sequential assimilation scheme. [ABSTRACT FROM AUTHOR]

To mitigate temporal aliasing effects in monthly mean global gravity fields from the GRACE and GRACE‐FO satellite tandem missions, both tidal and non‐tidal background models describing high‐frequency mass variability in atmosphere and oceans are needed. To quantify tides in the atmosphere, we exploit the higher spatial (31 km) and temporal (1 hr) resolution provided by the latest atmospheric ECMWF reanalysis, ERA5. The oceanic response to atmospheric tides is subsequently modeled with the general ocean circulation model MPIOM (in a recently revised TP10L40 configuration that includes the feedback of self‐attraction and loading to the momentum equations and has an improved bathymetry around Antarctica) as well as the shallow water model TiME (employing a much higher spatial resolution and more elaborate tidal dissipation than MPIOM). Both ocean models consider jointly the effects of atmospheric pressure variations and surface wind stress. We present the characteristics of 16 waves beating at frequencies in the 1–6 cpd band and find that TiME typically outperforms the corresponding results from MPIOM and also FES2014b as measured from comparisons with tide gauge data. Moreover, we note improvements in GRACE‐FO laser ranging interferometer range‐acceleration pre‐fit residuals when employing the ocean tide solutions from TiME, in particular, for the S1 spectral line with most notable improvements around Australia, India, and the northern part of South America. Plain Language Summary: In addition to many rather slow processes such as the melting of glaciers, rapid mass redistribution related to the weather also measurably affect the Earth's gravity field. The ability of monitoring liquid freshwater changes within the Earth system from the satellite gravity missions GRACE (2002–2017) and GRACE‐FO (since 2018) relies on accurate background models of mass variability in atmosphere and oceans for both tidal and non‐tidal processes. Atmospheric tides are primarily excited in the middle atmosphere by solar energy absorption at periods of 24 hr and its overtones. We find additional tidal signatures in the atmosphere excited by periodic deformations of both crust and sea‐surface of the Earth. We thus introduce here a new data set for the atmospheric tides and their corresponding oceanic response that features both more waves and higher accuracy than other background models previously used for the processing of GRACE and GRACE‐FO satellite gravimetry data. Key Points: Sixteen relevant tidal lines identified in hourly data from ERA5 atmospheric reanalysisDedicated simulations with a high‐resolution global hydrodynamic model to simulate ocean tides with atmospheric influenceNew tidal models reduce pre‐fit residuals in GRACE‐FO Laser Ranging Interferometer data [ABSTRACT FROM AUTHOR]

Abstract To mitigate temporal aliasing effects in monthly mean global gravity fields from the GRACE and GRACE‐FO satellite tandem missions, both tidal and non‐tidal background models describing high‐frequency mass variability in atmosphere and oceans are needed. To quantify tides in the atmosphere, we exploit the higher spatial (31 km) and temporal (1 hr) resolution provided by the latest atmospheric ECMWF reanalysis, ERA5. The oceanic response to atmospheric tides is subsequently modeled with the general ocean circulation model MPIOM (in a recently revised TP10L40 configuration that includes the feedback of self‐attraction and loading to the momentum equations and has an improved bathymetry around Antarctica) as well as the shallow water model TiME (employing a much higher spatial resolution and more elaborate tidal dissipation than MPIOM). Both ocean models consider jointly the effects of atmospheric pressure variations and surface wind stress. We present the characteristics of 16 waves beating at frequencies in the 1–6 cpd band and find that TiME typically outperforms the corresponding results from MPIOM and also FES2014b as measured from comparisons with tide gauge data. Moreover, we note improvements in GRACE‐FO laser ranging interferometer range‐acceleration pre‐fit residuals when employing the ocean tide solutions from TiME, in particular, for the S1 spectral line with most notable improvements around Australia, India, and the northern part of South America.

A regional, high-resolution reanalysis was analyzed to explore extreme heat loss events in the Northern Red Sea (NRS) and their links to specific regional atmospheric circulation patterns. Such events are determinant for the overturning circulation of the Red Sea and occur frequently between November and March, with maximum frequency during December and January. During these events, the most intense heat loss, often with daily-averaged values lower than -1000 W/m2, is found over the southern half of the Gulf of Aqaba and along the western coastline of the open NRS. Analyses of the spatial modes of variability of these events suggest that the majority of them extend over the entire NRS in an almost uniform way; however, secondary, nonuniform patterns related to regional adjustment in the wind field are also identified. The uniform cold outbursts are associated with distinct atmospheric circulation patterns, which favor the transfer of cold air masses from higher latitudes over the eastern Mediterranean Sea via a strong northwest wind field. Nonuniform events affect considerable parts of the NRS and occur when cold and dry air masses reach the NRS through the Middle East and the northern part of the Arabian Peninsula. The regional sea level pressure drives a clockwise rotation of the wind field that ultimately blows from the northeast/east direction. This rotation of the wind field favors local intensification and lee areas defined by the complex topography and characteristic gaps in the mountain chain along the eastern coastline of the NRS, reflecting the differentiations in the spatial distribution of the heat flux minima.

Sub-hourly heavy precipitation events (SHHPs) associated with regional low-pressure (RegL) systems in Portugal are a natural hazard that may have significant socioeconomic implications, namely in agriculture. Therefore, in this paper, their dynamic and thermodynamic drivers are analysed. Three weather stations were used to isolate SHHPs from 2000 to 2022. Higher precipitation variability is found in southern Portugal, with a higher ratio of extreme events on fewer rainy days. This study shows that these SHHP events are associated with low-pressure systems located just to the west of the Iberian Peninsula. These systems exhibit a cold core, particularly strong at mid-levels, and a positive vorticity anomaly, which is stronger in the upper troposphere, extending downward to low levels. These conditions drive differential positive vorticity advection and, therefore, rising motion to the east of the low-pressure systems. Moreover, at low levels, these systems promote moisture advection over western Iberia, also generating instability conditions, which are assessed by instability indices (Convective available potential energy, the Total-Totals index, and the K-index). The combination of these conditions drives heavy precipitation events. Lastly, the total column cloud ice water revealed higher values for the heavier precipitation events, suggesting that it may be a useful predictor of such events.

Characteristics of marine heatwaves (MHWs) in the East Asian Marginal Seas (EAMS) were investigated using the daily Optimum Interpolation Sea Surface Temperature for 37 years (1982–2018), focusing on seasonal changes and regional differences. The summer MHWs occur 54% more frequently (2.7 events/decade) in a relatively wide area than in other seasons. The strong (up to 3.7 °C) and long-lasting (up to 38 days/event) winter MHWs are concentrated along the subpolar front (SPF) in the East/Japan Sea (EJS) where the MHWs are 20% longer (2.2 days/event) than in the Yellow and East China Seas (YECS). The summer MHWs are primarily driven by increased shortwave radiation associated with reduced cloud cover and latent cooling from the weakened wind over the western flank of developing subtropical highs. Driving mechanisms of the winter MHWs differ by region. The YECS MHWs occur mainly due to the atmospheric processes associated with weakening continental highs, while the EJS MHWs are largely driven by the northward shift of the SPF. Although large-scale atmospheric processes primarily drive the summer MHWs occurring in a wide area in the EAMS, our findings suggest that ocean processes can be major contributors to intensified MHW generation in limited areas, especially in winter. [ABSTRACT FROM AUTHOR]

Here we isolate groundwater responses to atmospheric forcing of surface water levels by relating anomalies in coastal aquifer hydraulic head time‐series to weather events. Our results demonstrate that atmospheric forcing has a greater effect on groundwater exchange and extended residence time over astronomical tidal pumping at times. During winter, atmospheric groundwater forcing was associated with winter storm passage and had a recurrence interval of approximately 7 days. During summer, atmospheric groundwater forcing was limited to weak diurnal atmospheric convection and infrequent tropical cyclone activity. Because winter storms and tropical cyclones commonly produce precipitation, atmospheric groundwater forcing can synergize with the timing of meteoric recharge producing periods of intense submarine groundwater discharge. Plain Language Summary: Groundwater discharges from the seafloor into coastal waters through a process known as submarine groundwater discharge. Submarine groundwater discharge is composed of fresh water from the land and recirculated seawater drawn into the seafloor by ocean processes. In this manuscript, we document the effect of shifting winds brought about by winter storms, tropical cyclones, and land/sea breezes on seawater recirculation through seafloor sediments. Strong onshore winds cause regional mounding of seawater against the shoreline and infiltration into coastal aquifers while offshore winds allow groundwater to drain from the seafloor back into coastal waters. This effect we term, atmospheric groundwater forcing, leads to periods of intense submarine groundwater discharge following tropical cyclones and winter storms. Key Points: Atmospheric groundwater forcing is a seawater recirculation process driven by wind forcing of coastal surface water levelsAtmospheric groundwater forcing is seasonally associated with winter storms, tropical cyclones, and atmospheric convection cyclesThe timing of atmospheric groundwater forcing can synergize with meteoric recharge leading to subterranean estuary flushing [ABSTRACT FROM AUTHOR]

Water level measurements at four sub-basins of a highly dissipative coastal lagoon were used to study variability at tidal and subtidal scales and to determine whether atmospheric forcing influenced variations in water level at tidal scales. The amplitude of the main astronomic constituents, which were diurnal, attenuated quickly to <5% by the second sub-basin. The attenuation was represented well by an analytical solution that described a damped wave. The semidiurnal constituent with a period of 12 h (S2), however, decreased to 50% of the lagoon's entrance amplitude and then increased to 60% by the fourth sub-basin. Reproduction of this S2 behavior by the analytical model required unrealistically low signal attenuation, much lower than for the other semidiurnal constituent (12.42 h, M2). This behavior suggested that the S2 amplification was non-gravitational and related to semidiurnal atmospheric forcing, which was dominated by barometric pressure. Such suggestion was confirmed by coherence and wavelet coherence analysis and by the fact that the largest overtide was related to the interaction between S2, instead of M2, and the diurnal constituent. This study documents that a highly dissipative coastal lagoon becomes forced semidiurnally by barometric pressure toward its head. Subtidal water levels were studied with empirical orthogonal functions, revealing 2 modes that explained ~85% of the variance. Mode 1 was related to northerly winds ('Nortes') and mode 2 was linked to the Trade winds that dominate the region. [ABSTRACT FROM AUTHOR]

Characteristics of marine heatwaves (MHWs) in the East Asian Marginal Seas (EAMS) were investigated using the daily Optimum Interpolation Sea Surface Temperature for 37 years (1982–2018), focusing on seasonal changes and regional differences. The summer MHWs occur 54% more frequently (2.7 events/decade) in a relatively wide area than in other seasons. The strong (up to 3.7 °C) and long-lasting (up to 38 days/event) winter MHWs are concentrated along the subpolar front (SPF) in the East/Japan Sea (EJS) where the MHWs are 20% longer (2.2 days/event) than in the Yellow and East China Seas (YECS). The summer MHWs are primarily driven by increased shortwave radiation associated with reduced cloud cover and latent cooling from the weakened wind over the western flank of developing subtropical highs. Driving mechanisms of the winter MHWs differ by region. The YECS MHWs occur mainly due to the atmospheric processes associated with weakening continental highs, while the EJS MHWs are largely driven by the northward shift of the SPF. Although large-scale atmospheric processes primarily drive the summer MHWs occurring in a wide area in the EAMS, our findings suggest that ocean processes can be major contributors to intensified MHW generation in limited areas, especially in winter.

• Regularity and amplitude of solitons show a clear fortnightly cycle • Observed arrival times oscillated between 14 (spring tides) and 20 h (neap tides) • Atmospheric forcing modulates important aspects of soliton propagation Internal waves are commonly observed in oceans and lakes where high stratification exists. In the present study in the Strait of Gibraltar, we analyse internal soliton signals recorded in different locations in their eastward propagation from their release point (Camarinal Sill) to the continental slope of the northwestern Alboran Sea. Moreover, the effect of subinertial forcing on the release of solitons is also explored. The internal soliton activity was assessed from different approaches: (i) in-situ data (i.e., current and temperature measurements or High-Frequency Radar), (ii) numerical modelling, and (iii) an analytical approach. The arrival of solitons over the continental slope of the north-western Alboran Sea showed fortnightly variability in both number (occurrence) and amplitude during spring tides when compared with during neap tides. The observed arrival times of the solitons oscillated between 14 (spring tides) and 20 h (neap tides). Nevertheless, to provide a comprehensive explanation for the fluctuations in travel times, it is necessary to consider the subinertial variability driven by atmospheric forcing, which impacts both the flow in the Strait of Gibraltar and the mesoscale patterns in the Alboran Sea (e.g., the Coastal Cyclonic Gyre). [ABSTRACT FROM AUTHOR]

The Hatteras coastal ocean is centrally located along the east coast of the 48 contiguous United States, offshore of Cape Hatteras in a complex land/ocean/atmosphere region where major ocean currents of differing temperatures and salinities meet and interact, where the atmosphere fluctuates on a wide range of time scales, and where atmosphere-ocean interactions vary both spatially and temporally. The Gulf Stream current typically leaves its contact with the continental margin here. Continental shelf currents from the north and from the south converge here, resulting in a net shelf-to-ocean transport of shelf waters that carry important water properties and constituents. The two major drivers of these shelf currents and exchanges are the atmosphere and the oceanic Gulf Stream. Atmospheric driving of the Hatteras coastal ocean is through surface wind stress and heat flux across the air-sea interface. The complexity and importance of this region motivated the NSF-sponsored PEACH research program during 2017–2018 (PEACH: Processes driving Exchange At Cape Hatteras). In this paper, we utilize the substantial number of observations available during PEACH to describe the atmospheric forcing of the ocean then. Atmospheric conditions are described in terms of two seasons: the warm season (May to mid-September), with predominantly mild northeastward winds punctuated by occasional tropical cyclones (TCs); and the cool season (mid-September through April), with a nearly continuous, northeastward progression of energetic extratropical cyclones (ETCs) through the region. Cool season ETCs force the region with strong wind stress and ocean-to-atmosphere heat flux episodes, each with a time-scale of several days. Wind stress fluctuation magnitudes typically exceed mean stress magnitudes in each season by a factor of 3–5. These stresses account for just over 40% of the total current variability in the region, showing the wind to be a major driver of the ocean here. Atmosphere-ocean heat flux is typically into the ocean throughout the warm season (~100 W m-2); it is essentially always out of the ocean during the cool season (~500 W m-2 or more). New results herein include: southward intraseasonal oscillations of the jet stream's position drove the strongest ETCs (including one "bomb" cyclone); and during the 41 years leading up to and including PEACH, the season-averaged number and strength of atmospheric cyclones passing over the Hatteras coastal ocean have shown little long-term change. Looking ahead, the NSF Pioneer Array is scheduled to be relocated to the northern portion of the Hatteras coastal ocean in 2024, and the NASA SWOT satellite has begun its ocean topography mission, which has a ground-track cross-over here. • Wind stress and air-sea heat fluxes drive the Hatteras coastal ocean variability. • These forcing vary between the warm season and the cool season. • Cool season extratropical cyclones (ETCs) drive the strongest stresses and fluxes. • Newly discovered cascading events are a cool season shelf water export process. • Little change in ETC numbers & strength has been found in the past 40 years. [ABSTRACT FROM AUTHOR]