Air-sea Interaction Research Articles

Bubbles spray aerosols: Certitudes and mysteries.

Ocean spray aerosol formed by bubble bursting are at the core of a broad range of atmospheric processes: they are efficient cloud condensation nuclei and carry a variety of chemical, biological, and biomass material from the surface of the ocean to the atmosphere. The origin and composition of these aerosols is sensibly controlled by the detailed fluid mechanics of bubble bursting. This perspective summarizes our present-day knowledge on how bursting bubbles at the surface of a liquid pool contribute to its fragmentation, namely to the formation of droplets stripped from the pool, and associated mechanisms. In particular, we describe bounds and yields for each distinct mechanism, and the way they are sensitive to the bubble production and environmental conditions. We also underline the consequences of each mechanism on some of the many air-sea interactions phenomena identified to date. Attention is specifically payed at delimiting the known from the unknown and the certitudes from the speculations.

Two Approaches of the Spring North Atlantic Sea Surface Temperature Affecting the Following July Precipitation over Central China: The Tropical and Extratropical Pathways

Abstract The spring tripole sea surface temperature (SST) anomalies in North Atlantic are an outstanding regional mode of interannual variability. Based on the observed and reanalyzed datasets during 1979–2019, this study reveals the relationship and linking mechanism between the spring tripole North Atlantic SST anomalies and the central China July precipitation (CCJP). Results show that the tripole SST anomalies, especially the warm SST anomalies in the tropical North Atlantic (TNA) and the subpolar North Atlantic (SNA), often cause surplus CCJP through the tropical and extratropical pathways. On the one hand, the spring TNA SST warming induces a pan-tropical climate response with the cooling in the central equatorial Pacific and the warming in the Indo-western Pacific until the following July through a series of air–sea interactions, helping maintain an anomalous anticyclone over the northwest Pacific and transport more warm humid flows to central China. On the other hand, the spring TNA and SNA SST warming persist into the following July and then emanate a wave train extending from the SNA throughout the Eurasian continent to East Asia, which induces an anomalous anticyclone over North China with its southeast flank transporting more cold air to central China. The warm humid flows from the south against the cold air from the north are conductive to the local ascending motion, favoring the increased CCJP. Our results highlight both the tropical and extratropical teleconnection pathways of the North Atlantic SST anomalies affecting the CCJP. This suggests an important seasonal predictor of the regional climate. Significance Statement July is the peak rainy month of central China, with heavy precipitation occurring frequently and often causing serious impacts on the local production and livelihood of millions of people. This study finds that the spring tripole sea surface temperature anomalies in North Atlantic induced by the North Atlantic Oscillation can exert significant impacts on the following July precipitation over central China through both the tropical and extratropical pathways. This improves our understanding of the causes of the surplus July precipitation over central China and has important implications for the seasonal predictability of the regional climate.

Diversity of MJO Initiation Regions and Processes

Abstract The diversity of the Madden–Julian oscillation (MJO) initiation (i.e., initial onset of active convection before moving eastward) regions was explored using a clustering method. Regions favorable for MJO initiations are grouped into four longitude zones: the Atlantic and Africa (AA), the Indian Ocean (IO), the Maritime Continent (MC), and the western Pacific (WP). The region-dependent dominant initiation mechanisms are explored using a composite procedure. The AA initiation is attributed to a circumnavigating process associated with a preceding MJO. As upper-tropospheric westerly anomalies move into the AA region, the associated descending motion leads to suppressed convection over the IO, which further triggers convection onset to its west through anomalous westward moisture advection. The IO initiation arises from the downstream forcing of a preceding suppressed phase of MJO. A delayed air–sea interaction process also plays a role. The MC initiation is triggered by a westward-propagating dry equatorial Rossby wave in the Pacific. The low-level poleward flows associated with the anticyclonic Rossby wave gyres advect high mean moisture, promoting the convection onset over the MC. The WP initiation is triggered by a preceding suppressed phase of MJO that moves eastward, in a way similar to the downstream scenario in the IO. The AA initiation is usually associated with a La Niña–like background sea surface temperature pattern, which favors the decoupling of upper-tropospheric westerly anomalies from the preceding MJO. The MC and WP initiations are more frequent during El Niño, as the relevant meridional moisture gradient is sharper and the eastern Pacific is moister.

On the dynamics of the eradication of a warm core mesoscale eddy after the passage of Hurricane Irma (2017)

Mesoscale oceanic eddies are known to influence air-sea interactions during tropical cyclone (TC) passage by either hindering or sustaining air-sea fluxes into the TC core. However, little is known as to how TCs alter the dynamical structure of such eddies during and after TC passage. Through simulations of Hurricane Irma (2017) using the Navy’s Coupled Ocean Atmospheric Mesoscale Prediction Scheme for Tropical Cyclones, it is found that a simulated mesoscale warm core eddy (WCE) located to the right of the model track disappeared shortly after the TC had passed over it. To further explore this phenomena, time series of ocean kinetic energy, available potential energy (APE), a vorticity budget, and a potential vorticity (PV) budget are examined to understand how TC-induced upper ocean currents influenced the eddy disappearance. Time series of APE within the model-simulated eddy show APE reaching a minimum as the circulation of the eddy disappeared in the model field and positive vorticity, dominated by vertical vorticity advection, became a maximum approximately 6 h after TC passage. These results were confirmed by the PV budget. The succession of subsurface vorticity changes suggest that the WCE was eradicated by a near-inertial wave wake that occurred earlier than expected. As found in a prior study, the early-onset of a near-inertial wake occurs when the model simulated TC with a small radius of maximum winds interacts with the subsurface ocean current field. The findings are important with regards to TC forecasting because the accurate representation and placement of eddies in the model field is necessary to correctly predict the coupled air-sea response during TC passage and for subsequent TCs with similar tracks. Such feedbacks from TCs can also have near-term and long-term influence on the prediction of air-sea interaction in the local and regional marine environment.

The mechanisms of the subseasonal zonal oscillation of the western Pacific subtropical high in 10–25-day period and 25–50-day period

This study investigates the evolution characteristics and the mechanism, including the convection–circulation interaction and the air–sea interaction, of the subseasonal zonal oscillation of the western Pacific subtropical high (WPSH) in 10–25-day period and 25–50-day period. Accompanied with the westward extension of the WPSH, a suppressed convection propagates northwestward over the western Pacific with an anticyclonic circulation anomaly at its northwest. A warm sea surface temperature anomaly (SSTA) lags the anomalous convection, showing near-quadrature phase relationship in temporal, and the magnitude of SSTA in 25–50-day period is greater than that in 10–25-day period. Further analysis shows that in both two periods the westward extension of the WPSH is mainly attributed to the convection–circulation interaction. The suppressed convection-induced cooling stimulates the divergence anomaly at the northwest of the suppressed convection, causing anticyclonic anomaly through the horizontal divergence effect. In turn, the anticyclonic anomaly motivates the downward dry advection in planetary boundary layer (PBL) preceding the suppressed convection, and thus favors the propagation of the suppressed convection. Through such interaction processes, the convection and circulation anomalies are combined and propagate together, leading to the zonal oscillation of the WPSH. Moreover, it is also found that the significance of air–sea interaction in two periods is distinct due to different magnitudes of the SSTA. In 10–25-day period, the ocean has no obvious feedback on the atmospheric circulation, while in 25–50-day period, the oceanic anomaly can fully develop and impact on the atmosphere more effectively.

Simulations of sea fog case impacted by air–sea interaction over South China Sea

A sea fog event in the South China Sea was simulated using a coupled ocean–atmosphere model (WRF for the atmosphere and ROMS for the ocean). Offshore and onshore visibility, liquid water content, air temperature, humidity, and wind speed observations and MICAPS data were utilized to validate the model results. The results of the coupled model were also compared with those of the uncoupled atmosphere model. Sea fog duration in the coupled model was closer to offshore and onshore observations, but the uncoupled model emptily forecasted offshore fog, and underreported onshore fog. Air–sea temperature difference played an important role in regulating the formation and dissipation of sea fog. The decrease of sea surface temperature in the coupled model cooled the low-level atmosphere, promoted the condensation of low-level water vapor, and increased the low-level water vapor. The decrease of air–sea temperature difference strengthened the low-level stable stratification, which weakened the horizontal wind speed and favored the formation and development of sea fog. Rising wind speed was the major driver of fog dissipation.

2022: An Unprecedentedly Rainy Early Summer in Northeast China

In the early summer (June) of 2022, the spatial mean precipitation in northeast China (NEC) was 62% higher than normal and broke the historical record since 1951. Based on the precipitation data of 245 meteorological stations in NEC and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, this paper analyzes the role of large-scale circulation and sea-surface temperature (SST) associated with anomalous precipitation over NEC in June using singular value decomposition (SVD), correlation analysis, regression analysis, and composite analysis methods, and further investigates the possible cause of the abnormal precipitation in June 2022. Results show that the northeast China cold vortex (NCCV) accompanying the blocking high in the Okhotsk Sea (BHOS) has been the primary mid-to-high latitude atmospheric circulation pattern affecting NEC precipitation in June since 2001. This circulation pattern is closely related to the tripole SST pattern over the North Atlantic (NAT) in March. In June 2022, the NAT SST anomaly in March stimulates eastward-propagating wave energy, resulting in the downstream anomalous circulation pattern in which the NCCV cooperates with the BHOS in the mid-high latitudes of East Asia. Under this background atmospheric circulation favorable for precipitation, the Kuroshio region SST anomaly in June led to a more northward and stronger anomalous anticyclone in the northwestern Pacific through local air–sea interaction, which provides more sufficient water vapor for NEC, resulting in unprecedented precipitation in June 2022.

The Moist Quasi-Geostrophic Coupled Model: MQ-GCM 2.0

Abstract. This paper contains a description of recent changes to the formulation and numerical implementation of the Quasi-Geostrophic Coupled Model (Q-GCM), which constitute a major update of the previous version of the model (Hogg et al., 2014). The Q-GCM model has been designed to provide an efficient numerical tool to study the dynamics of multi-scale midlatitude air–sea interactions and their climatic impacts. The present additions/alterations were motivated by an inquiry into the dynamics of mesoscale ocean–atmosphere coupling and, in particular, by an apparent lack of the Q-GCM atmosphere's sensitivity to mesoscale sea-surface temperature (SST) anomalies, even at high (mesoscale) atmospheric resolutions, contrary to ample theoretical and observational evidence otherwise. Major modifications aimed at alleviating this problem include an improved radiative-convective scheme resulting in a more realistic model mean state and associated model parameters; a new formulation of entrainment in the atmosphere, which prompts more efficient communication between the atmospheric mixed layer and free troposphere; and an addition of a temperature-dependent wind component in the atmospheric mixed layer and the resulting mesoscale feedbacks. The most drastic change is, however, the inclusion of moist dynamics in the model, which may be key to midlatitude ocean–atmosphere coupling. Accordingly, this version of the model is to be referred to as the MQ-GCM model. Overall, the MQ-GCM model is shown to exhibit a rich spectrum of behaviors reminiscent of many of the observed properties of the Earth's climate system. It remains to be seen whether the added processes are able to affect in fundamental ways the simulated dynamics of the midlatitude ocean–atmosphere system's coupled decadal variability.

Sensitivity of ECMWF coupled forecasts to improved initialization of the ocean mesoscale

AbstractIt has been hypothesized that initial conditions derived from eddy‐resolving ocean models could benefit eddy‐permitting forecast systems at subseasonal lead times (2 weeks to 2 months) by providing improved ocean initial conditions and reduced sea‐surface temperature (SST) errors associated with a more realistic representation of mesoscale features and ocean fronts such as the Gulf Stream. Here, we test this hypothesis by running a series of coupled 32‐day reforecasts with ocean initial conditions derived from native resolution (i.e., eddy‐permitting) and higher resolution (i.e., eddy‐resolving) ocean reanalyses. Initial conditions derived from the eddy‐resolving reanalysis reproduce observed temperature and sea‐level variability associated with mesoscale ocean eddies more accurately. Furthermore, forecasts of ocean variables are significantly improved in the extratropics, particularly in regions of observed intense mesoscale variability. This result is relevant for the marine forecasting community and demonstrates the potential for improved probabilistic forecasts of ocean variables in affordable ensemble forecast systems. However, the impacts on the mean state and forecast skill in the atmosphere are more limited. Based on an evaluation of model biases as a function of lead time, we conclude that there is room for further improvements to the initialization of the Gulf Stream that could lead to more significant impacts on atmospheric skill. Furthermore, we demonstrate that our reforecasts underestimate the strength of mesoscale air–sea interaction in the vicinity of strong SST fronts by 20–40%. We speculate that the impacts of improved ocean eddy initialization on atmospheric forecast skill may be larger in coupled models with higher ocean and atmosphere resolutions that can simulate air–sea interaction in the midlatitudes more realistically.

Air–Sea Interactions on Titan: Effect of Radiative Transfer on the Lake Evaporation and Atmospheric Circulation

Titan’s northern high latitudes host many large hydrocarbon lakes. Like water lakes on Earth, Titan’s lakes are constantly subject to evaporation. This process strongly affects the atmospheric methane abundance, the atmospheric temperature, the lake mixed layer temperature, and the local wind circulation. In this work we use a 2D atmospheric mesoscale model coupled to a slab lake model to investigate the effect of solar and infrared radiation on the exchange of energy and methane between Titan’s lakes and atmosphere. The magnitude of solar radiation reaching the surface of Titan through its thick atmosphere is only a few watts per square meter. However, we find that this small energy input is important and is comparable in absolute magnitude to the latent and sensible heat fluxes, as suggested in a study by Rafkin & Soto (2020). The implementation of a gray radiative scheme in the model confirms the importance of radiation when studying lakes at the surface of Titan. Solar and infrared radiation change the energy balance of the system leading to an enhancement of the methane evaporation rate, an increase of the equilibrium lake temperature almost completely determined by its environment (humidity, insolation, and background wind), and a strengthening of the local sea breeze, which undergoes diurnal variations. The sea breeze efficiently transports methane vapor horizontally, from the lake to the land, and vertically due to rising motion along the sea breeze front and due to radiation-induced turbulence over the land.

Evaluating the impact of intermediate and deep sound speed uncertainty in the Irminger Sea on acoustic situational awareness

High-resolution observations from moorings and transect data can provide new insights into ocean structures, their variability, and the downstream effects on acoustic operations. Previously, we established a framework to maintain optimal communication and navigation for small-scale, under-ice operations that focused on spatio-temporal variability in the upper water column and around an autonomous underwater vehicle. However, mid- and deep-water sound speed fidelity are crucial for larger operations that exploit convergence zone ranging. The Irminger Sea is a useful case study for understanding how sound speed uncertainty, whether from partial data or models, obscures the informational content from acoustics. Generally, the density gradient dominates the sound speed at depth. In the Irminger Sea, hydrographic variability comes from the advection of different water masses through the region at all depths and also from water mass modification by local air-sea interaction. Instead of a uniform gradient as a result of hydrostatic loading, a shifted gradient in the mid-water column and a negative gradient near the bottom are often observed in mooring and transect data. This talk presents initial results for understanding the impacts of the environment through the lens of impact on acoustic propagation. [Work supported by the Office of Naval Research]

The atmospheric hinder for intraseasonal sea-air interaction over the Bay of Bengal during Indian summer monsoon in CMIP6

The atmospheric hinder for intraseasonal sea-air interaction over the Bay of Bengal during Indian summer monsoon in CMIP6

Developing an Observing Air–Sea Interactions Strategy (OASIS) for the global ocean

AbstractThe Observing Air–Sea Interactions Strategy (OASIS) is a new United Nations Decade of Ocean Science for Sustainable Development programme working to develop a practical, integrated approach for observing air–sea interactions globally for improved Earth system (including ecosystem) forecasts, CO2 uptake assessments called for by the Paris Agreement, and invaluable surface ocean information for decision makers. Our “Theory of Change” relies upon leveraged multi-disciplinary activities, partnerships, and capacity strengthening. Recommendations from >40 OceanObs’19 community papers and a series of workshops have been consolidated into three interlinked Grand Ideas for creating #1: a globally distributed network of mobile air–sea observing platforms built around an expanded array of long-term time-series stations; #2: a satellite network, with high spatial and temporal resolution, optimized for measuring air–sea fluxes; and #3: improved representation of air–sea coupling in a hierarchy of Earth system models. OASIS activities are organized across five Theme Teams: (1) Observing Network Design & Model Improvement; (2) Partnership & Capacity Strengthening; (3) UN Decade OASIS Actions; (4) Best Practices & Interoperability Experiments; and (5) Findable–Accessible–Interoperable–Reusable (FAIR) models, data, and OASIS products. Stakeholders, including researchers, are actively recruited to participate in Theme Teams to help promote a predicted, safe, clean, healthy, resilient, and productive ocean.

Physical–empirical prediction model for the dominant mode of extreme high temperature events in eastern China during summer

The dominant mode of extreme high temperature events in eastern China during summer shows a dipole pattern with opposite anomalies over southern and northeastern China, which explains 25% of the variance. We document the limited prediction skill of the National Centers for Environmental Prediction Climate Forecast System, version 2 (CFSv2) for the dominant mode of these events. Based on the mechanisms related to the dominant mode, a physical–empirical model was established that improved the prediction of extreme high temperature events in eastern China, which will help in disaster prediction and mitigation. The physical connection between the dominant mode and the summer sea surface temperature (SST) over the western tropical and subtropical Pacific Ocean was predicted well by the CFSv2 hindcasts, and thus the areal mean CFSv2-hindcast SSTs over the western tropical and subtropical Pacific Ocean served as a predictor in the physical–empirical model. In the observations, the soil moisture over southern China in the preceding December (soil_Dec) combined the signal of the air–sea interactions over the tropical and northern extratropical Pacific Ocean, which induced anomalous SSTs in the Indian and western tropical Pacific oceans in the following summer and contributed to the dominant mode. Soil_Dec was therefore closely correlated with the dominant mode and was used as a predictor. The results of the one-year-leave cross-validation and independent hindcast showed that the time series of the dominant mode was better predicted by the physical–empirical model than by the CFSv2 hindcasts, with an improved correlation coefficient from insignificant to about 0.8, a root-mean-square error reduced by about 50% and an increased rate of same signs. The physical–empirical model showed advantages in the prediction of the dominant mode of summer extreme high temperature events over eastern China, which may be used in the prediction of other climate variables.

Variability of the Mindanao Dome upwelling system during ENSO event from 2010 to 2015

The Mindanao Dome (MD) upwelling system has important implications for the local and even the global air-sea interaction, but its changing process in hydroecological conditions and response mechanism influenced by ENSO cycle are still unclear. The evolution of MD upwelling process and the changes in hydro-climatic environments in MD region in three typical El Niño, La Niña, and normal years during ENSO event from 2010 to 2015 are analyzed. Results reveal that migration of surface water is the main factor controlling the changes in the intensity of the MD upwelling during this ENSO cycle but not the variations in wind stress curl. Massive westward accumulation (eastward movement) of surface warm water and strengthened (weakened) upwelling Rossby waves together induce the enhancement (weakness) of the MD upwelling during mature phase of 2015/2016 El Niño (2010/2011 La Niña) year. In addition, NECC and MD upwelling together control the biological activities in surface waters in MD region during this ENSO cycle. The meandering NECC and MD upwelling both strengthen (weaken) when 2015/2016 El Niño (2010/2011 La Niña) occur, which transport more (less) nutrients to surface sea from horizontal and vertical levels, respectively, leading to an increase (decrease) in surface Chl-a. Two synopsis mechanisms are proposed to illustrate the response mechanism of the MD upwelling evolution and eco-hydro-climatic variations in the MD region to 2015/2016 El Niño (2010/2011 La Niña) event, respectively. This paper highlights the prospect for the role played by ENSO cycle in local ecological effects and hydro-climatic evolution, which further has profound implications for understanding the influence of the global climate change on the ocean carbon cycle.

Coastal Upwelling in the Western Bay of Bengal: Role of Local and Remote Windstress

Monsoon winds drive upwelling along the eastern coast of India. This study examined the role of coastally trapped Kelvin waves in modulating the seasonal variability of local alongshore windstress (AWS)-driven coastal upwelling along the western Bay of Bengal. The winds generated AWS resulting in a positive cross-shore Ekman transport (ET) from March to the end of September, which forced coastal upwelling along the eastern coast of India. However, coastally trapped Kelvin waves could also modulate this process by raising or lowering the thermocline. Remotely sensed windstress, sea surface temperature (SST), and sea surface height anomaly (SSHA) were used to compute the AWS (the wind-based proxy upwelling index) and an SST-based proxy upwelling index (UISST). A new parametric method of the estimation of coastal angles was developed to estimate the AWS and ET. Coastal upwelling and the Kelvin waves were identified based on the climatology of SSHA, AWS, and UISST, in addition to a complex principal component (CEOF) analysis of the SSHA. The UISST and AWS were found to be closely correlated along the southern section of the east coast of India (between Kavali and Point Calimere), where the coastal upwelling was largely local AWS-driven. However, along the northern section of the coast (between Kashinagara and Kakinada), coastal upwelling was triggered by the first upwelling Kelvin wave, sustained by the local AWS, and then terminated by the first downwelling Kelvin wave. This analysis illustrated that remote equatorial windstress caused coastal upwelling along the northern part of the Indian east coast, while it was primarily locally driven in the southern coast. The findings are helpful in better understanding the mechanisms modulating coastal upwelling along the western Bay of Bengal. These would provide useful insights into the primary productivity and the air–sea interactions in the region.

The Atmospheric Response to Meridional Shifts of the Gulf Stream SST Front and Its Dependence on Model Resolution

Abstract The Gulf Stream (GS) plays a key role in shaping the North Atlantic climate. Moreover, the associated sea surface temperature (SST) front undergoes interannual-to-decadal variability that is thought to force significant atmospheric circulation anomalies. However, general circulation models do not accurately reproduce the atmospheric response to SST front variability as estimated from observations. In this work we analyze the atmospheric response to the GS SST front (GSF) shifts in a multimodel ensemble of atmosphere-only simulations forced with observed SSTs (1950–2014). The atmospheric response is found to be resolution dependent. Only the high-resolution simulations produce a wintertime response similar to observed anomalies. More specifically, (i) analysis of the atmospheric thermodynamic balance close to the GSF showed that the anomalous diabatic heating associated to the GSF displacement is mainly balanced by vertical motion and by meridional transient eddy heat transport (not the case for low-resolution models), while (ii) the large-scale response includes a meridional shift of the North Atlantic eddy-driven jet and storm track homodirectional to the GSF displacement. This atmospheric response is accompanied by changes in low-level baroclinicity close to and north of the GSF, resulting from the oceanic forcing and the zonal atmospheric circulation anomalies respectively. The low-level baroclinicity anomalies lead to changes in baroclinic eddy activity and, ultimately, in the jet via eddy–mean flow interaction. Considering the two-way nature of air–sea interactions, using historical atmosphere-only simulations is a powerful way to isolate the impact of realistic oceanic variability on the atmosphere. Our results suggest that interannual-to-decadal predictability may be higher than what low-resolution models currently indicate.

Intense atmospheric frontogenesis by air–sea coupling processes during the passage of Typhoon Lingling captured at Ieodo Ocean Research Station

The Ieodo Ocean Research Station (Ieodo ORS) is a fixed marine observation platform at the boundary of the Yellow and East China Seas. In 2019, a Category 4 Typhoon Lingling passed by the Ieodo ORS very closely. At that time, the Ieodo ORS observed Sea Surface Temperature (SST) cooling of 4.5 °C by vertical mixing and negative turbulent heat flux (i.e., the sum of sensible and latent heat fluxes) due to the SST cooling. In this study, uncoupled and coupled simulations were conducted to examine the role of air-sea interactions in changes in atmospheric frontogenesis around the typhoon passage. In the coupled simulation, SST cooling up to 6 °C occurred over the dangerous semicircle due to vertical mixing induced by wind stress. Strong wind stress also enhanced the SST gradient and, therefore, contributed to the formation of a steeper atmospheric frontal zone. Moreover, the comparison with reliable datasets supports the physical linkage between SST cooling and atmospheric frontogenesis by utilizing the meridional theta-e gradient and moisture convergence zone. Therefore, from the simulation results, we hope to improve our understanding of atmospheric frontogenesis by air–sea coupling processes in the future development of a coupled atmosphere–ocean modeling system.

The Influence of Solar Activity on Snow Cover over the Qinghai–Tibet Plateau and Its Mechanism Analysis

Using global ocean vertical temperature anomaly data, we identified that a significant response of the sea temperature anomaly (STA) to the solar radio flux (SRF) exists. We found that the STA exhibited a significant correlation with Asian summer and winter precipitation, among which the response from the Qinghai–Tibet Plateau (the QTP) was particularly noticeable. Based on NCEP/NCAR reanalysis data, the latent heat flux (LHF) anomaly, which plays a key role in winter precipitation in China, especially over the QTP, showed a significant response to the SRF in the Pacific. The results demonstrated the bottom-up mechanism of impact of solar activity (SA) on the plateau snow through sea–air interaction. Meanwhile, a top-down mechanism was also present. When the SRF was high, the stratospheric temperature in the low and mid-latitudes increased and the temperature gradient pointed to the pole to strengthen the westerly wind in the mid-latitudes. The EP flux showed that atmospheric long waves in the high altitudes propagated downward from the stratosphere to the troposphere. A westerly (easterly) wind anomaly occurred in the south (north) of the QTP at 500 hPa and the snowfall rate over the QTP tended to increase. When the SRF was low, the situation was the opposite, and the snowfall rate tended to decrease. The model results confirmed that when total solar irradiance (TSI) became stronger (weaker), both of the solar radiation fluxes at the top of the atmosphere and the surface temperature over the QTP increased (decreased), the vertical updraft intensified (weakened), and the snowfall rate tended to increase (decrease) accordingly. These conclusions are helpful to deepen the understanding of SA’s influence on the snow cover over the QTP.

Spatiotemporal variability and climate teleconnections of global ocean wave power

Climate change impacts have driven a transformation of the global energy system. The utilization of renewable energies is required to meet energy demands while protecting the environment. Wind-generated waves, carrying energy from the atmosphere, are a possible energy supply. However, global and long-term variability in wave resources due to the effects of climate change remain uncertain. This study quantified the spatiotemporal patterns and availability of global wave power (GWP) based on the ERA5 hourly and monthly reanalysis products, spanning from 1979 to 2020. The most promising wave resources appeared centralized in the westerlies of both hemispheres, and the wave power exhibited a “rich-get-richer” trend in the Southern Ocean, dominating the overall distribution and variability of GWP. Significant seasonal and interannual oscillation trends in GWP were observed, but with little variations on daily and hourly time scales. We found the average GWP in ERA5 products increased by 12.89% suddenly in 1991, mainly caused by the beginning of altimeter assimilation. This also implies the potential underestimation of wave fields in the modeling results before the advent of altimeter. In the altimeter era, annual GWP exhibits (quasi-) decadal oscillation (variation near ±4%), which differed from the monotonous increases previously reported. An analysis and source tracing based on the climate teleconnections indexes revealed that the primary climate driver of the variability was the Southern Annual Mode (r = 0.84). This study provides scientific guidance for wave power utilization and helps deepen our understanding of air-sea interactions.