Air Sea Research Articles

Impact of southern annular mode on the Indian Ocean surface waves

AbstractInterannual climate modes, especially the southern annular mode (SAM), significantly influence the wave climate modulation of the Indian Ocean (IO). The present study, aligned with previous research, identifies two crucial swell generation regions in the IO: the extratropical southern Indian Ocean (ETSI) and the tropical southern Indian Ocean (TSIO). The SAM, governing Southern Ocean surface winds, significantly shapes wave generation in these zones, thereby dominantly regulating IO wave conditions. Positive SAM phases shifts the westerlies poleward creating significant negative anomalies in the northern ETSI, reducing wave generation and swell propagation into the northern IO (NIO) basins, while the positive wind anomalies in the western TSIO creates a new swell generation area that directs swells towards the Arabian Sea, elevating wave heights there during monsoons. Conversely, negative SAM phases enhance TSIO easterlies, making it the primary IO swell source, increasing swell activity in the Bay of Bengal, notably during premonsoon and monsoon seasons. SAM impact expands beyond swells, influencing NIO wave climate by altering wind seas through Hadley cell (HC) circulation shifts. Positive SAM phases trigger NIO and midlatitude anomalous warming, intensifying HC and NIO surface winds in the next season, thereby affecting convection and subsequent sea surface temperature (SST) anomaly changes. The “SAM positive anomaly wind‐SST oscillations (SPAWSO)” pattern emerges, where warm SST anomalies in DJF and JJA precede increased surface winds in MAM and SON, thus increasing the wind‐sea conditions in the NIO. SPAWSO, hence, acts as a delayed mode, season‐dependent positive air–sea interaction cycle linked to positive SAM phases, significantly impacting NIO's wind‐sea dynamics. Thus the present study provides better insights into the long‐term wave prediction accuracy in the IO by considering the direct swell influence and SPAWSO‐driven wind‐sea changes, aiding preparations for changing wave dynamics and their impacts.

Effect of land–sea air mass transport on spatiotemporal distributions of atmospheric CO2 and CH4 mixing ratios over the southern Yellow Sea

Abstract. To reveal the spatiotemporal distributions of atmospheric CO2 and CH4 mixing ratios and regulation mechanisms over the China shelf sea, two field surveys were conducted in the southern Yellow Sea in China in November 2012 and June 2013, respectively. The results observed showed that mean background atmospheric CO2 and CH4 mixing ratios were 403.94 (±13.77) ppm and 1924.8 (±27.8) ppb in November 2012 and 395.90 (±3.53) ppm and 1918.0 (±25.7) ppb in June 2013, respectively. An improved data-filtering method was optimised and established to flag atmospheric CO2 and CH4 emission from different sources in the survey area. We found that the spatiotemporal distributions of atmospheric CO2 and CH4 mixing ratios over the southern Yellow Sea were dominated by land–sea air mass transport, which was mainly driven by seasonal monsoon, while the influence of air–sea exchange was negligible. In addition, atmospheric CO2 and CH4 mixing ratios over the southern Yellow Sea could be elevated remarkably at a distance of approximately 20 km offshore by land-to-sea air mass transportation from the Asian continent during the early-winter monsoon.

Interdecadal Variability in the Interface Between the Indian Summer Monsoon and the East Asian Summer Monsoon

AbstractThis study investigates the interdecadal variability (IDV) of the interface between the Indian summer monsoon and the East Asian summer monsoon (IIE). Results suggest that the IDV of the IIE is characterized by a uniform zonal movement associated with seesaw variations between the Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM). The IDV of the IIE is closely linked to two air–sea coupled modes: one resembles the Asian–Pacific Oscillation (APO) and the other resembles the North Atlantic tripole (NAT) pattern. Both the APO‐like and NAT‐like patterns facilitate an eastward shift of the IIE during their positive phase. The APO‐like mode strengthens the western North Pacific subtropical high (WNPSH), which further enhances the climatological southwesterly wind over East Asia and leads to an intensification of the EASM. The simultaneous anticyclonic anomaly over the India and Bay of Bengal (BOB) region weakens the ISM. The NAT‐like mode forces a wave train of alternating cyclonic and anticyclonic anomalies across Eurasia, causing southwesterly anomalies over East Asia that favors a stronger EASM. The atmospheric response is reversed during the negative phases of the APO‐like and NAT‐like patterns. Recent decades have seen a weakening influence of the APO‐like mode, but a growing impact of the NAT‐like mode on the IIE‐IDV. The interdecadal transition of the IIE–APO and IIE–NAT relationships has a smaller influence on the IIE than that of the phase change of the APO‐like and NAT‐like patterns. Modeling results confirm the influence of the APO‐like and NAT‐like patterns on the IIE‐IDV.

Quantified effect of seawater biogeochemistry on the temperature dependence of sea spray aerosol fluxes

Abstract. Future change in sea surface temperature may influence climate via various air–sea feedbacks and pathways. In this study, we investigate the influence of surface seawater biogeochemical composition on the temperature dependence of number-based sea spray emission fluxes. The dependence of sea spray fluxes was investigated in different water masses (i.e., subantarctic, subtropical and frontal bloom) with contrasting biogeochemical properties across a temperature range from ambient (13–18 ∘C) to 2 ∘C using seawater circulating in a plunging jet sea spray generator. We observed a significant increase in the sea spray total concentration at temperatures below 8 ∘C. Specifically, at 2 ∘C, there was an average 4-fold increase compared to the initial concentration at ambient temperatures. This temperature dependence was more pronounced for smaller-sized sea spray particles (i.e., nucleation and Aitken modes). Moreover, the temperature dependence varied based on the seawater type and its biogeochemical properties. While the sea spray flux at moderate temperatures (8–11 ∘C) was highest in frontal-bloom waters, the effect of low temperature on the sea spray flux was highest in subtropical seawaters. The temperature dependence of the sea spray flux was found to be inversely proportional to the abundance of the cyanobacterium Synechococcus in seawater. This relationship allows for parameterizing the temperature dependence of sea spray emission fluxes based on Synechococcus, which may be utilized in future modeling exercises.

Mechanisms for Abrupt Summertime Circumpolar Surface Warming in the Southern Ocean

Abstract In recent years, the Southern Ocean has experienced unprecedented surface warming and sea ice loss—a stark reversal of the sea ice expansion and surface cooling that prevailed over the preceding decades. Here, we examine the mechanisms that led to the abrupt circumpolar surface warming events that occurred in late 2016 and 2019 and assess the role of internal climate variability. A mixed layer heat budget analysis reveals that these recent circumpolar surface warming events were triggered by a weakening of the circumpolar westerlies, which decreased northward Ekman transport and accelerated the seasonal shoaling of the mixed layer. We emphasize the underappreciated effect of the latter mechanism, which played a dominant role and amplified the warming effect of air–sea heat fluxes during months of peak solar insolation. An examination of the CESM1 large ensemble demonstrates that these recent circumpolar warming events are consistent with the internal variability associated with the Southern Annular Mode (SAM), whereby negative SAM in austral spring favors shallower mixed layers and anomalously high summertime SST. A key insight from this analysis is that the seasonal phasing of springtime mixed layer depth shoaling is an important contributor to summertime SST variability in the Southern Ocean. Thus, future Southern Ocean summertime SST extremes will depend on the coevolution of mixed layer depth and surface wind variability. Significance Statement This study examines how reductions in the strength of the circumpolar westerlies can produce abrupt and extreme surface warming across the Southern Ocean. A key insight is that the mixed layer temperature is most sensitive to surface wind perturbations in late austral spring, when the regional mixed layer depth and solar insolation approach their respective seasonal minimum and maximum. This heightened surface temperature response to surface wind variability was realized during the austral spring of 2016 and 2019, when a dramatic weakening of the circumpolar westerlies triggered unprecedented warming across the Southern Ocean. In both cases, the anomalously weak circumpolar winds reduced the northward Ekman transport of cool subpolar waters and caused the mixed layer to shoal more rapidly in the spring, with the latter mechanism being more dominant. Using results from an ensemble of coupled climate simulations, we demonstrate that the 2016 and 2019 Southern Ocean warming events are consistent with the internal variability associated with the Southern Annular Mode (SAM). These results suggest that future Southern Ocean surface warming extremes will depend on both the evolution of regional mixed layer depths and interannual wind variability.

Research on Visual Perception for Coordinated Air–Sea through a Cooperative USV-UAV System

The identification and classification of obstacles in navigable and non-navigable regions, as well as the measurement of distances, are crucial topics of investigation in the field of autonomous navigation for unmanned surface vehicles (USVs). Currently, USVs mostly rely on LiDAR and ultrasound technology for the purpose of detecting impediments that exist on water surfaces. However, it is worth noting that these approaches lack the capability to accurately discern the precise nature or classification of those obstacles. Nevertheless, the limited optical range of unmanned vessels hinders their ability to comprehensively perceive the entirety of the surrounding information. A cooperative USV-UAV system is proposed to ensure the visual perception ability of USVs. The multi-object recognition, semantic segmentation, and obstacle ranging through USV and unmanned aerial vehicle (UAV) perspectives are selected to validate the performance of a cooperative USV-UAV system. The you only look once-X (YOLOX) model, the proportional–integral–derivative-NET (PIDNet) model, and distance measurements based on a monocular camera are utilized to realize these problems. The results indicate that by integrating the viewpoints of USVs and UAVs, a collaborative USV-UAV system, employing the aforementioned methods, can successfully detect and classify different objects surrounding the USV. Additionally, it can differentiate between navigable and non-navigable regions for unmanned vessels through visual recognition, while accurately determining the distance between the USV and obstacles.

Changes in El Niño characteristics and air–sea feedback mechanisms under progressive global warming

In this study, we investigate the potential changes of El Niño characteristics, including intensity, frequency and CP/EP El Niño ratio, under progressive global warming based on the 140-year CMIP6 model simulation outputs with the 1pctCO2 experiment. Major air-sea feedback mechanisms attributing to the changes are also examined. The CMIP6 ensemble means project a slight enhancement of El Niño intensity by about 2% and a modest increase of El Niño frequency by about 4% from the first to the second 70-year periods. It is found that these small changes result from the opposite response to global warming between CP and EP El Niño, i.e., the intensity of EP El Niño is projected to weaken by nearly 4.6% while the intensity of CP El Niño is projected to increase by about 4.5%. Since CP El Niño occurs more frequently than EP El Niño in CMIP6 simulations, this leads to a slight enhancement of the total El Niño intensity if these two types of El Niño were not separated. A similar situation occurs in projecting the future change of El Niño frequency, i.e., the frequency of EP El Niño is projected to decrease by about 1.4% while the frequency of CP El Niño is projected to increase by about 2%, thereby leading to a modest increase of the total El Niño frequency. By comparing the variance explained by key air-sea feedback mechanism between the two 70-year periods, we also note that the increased CP/EP ratio can be explained by the enhanced role played by the SF (seasonal footprinting) mechanism in a warmer atmosphere. Our study also points out that, as long as a climate model can correctly produce the intensity (variance) of major air-sea feedback mechanisms, the relationship between changes in El Niño characteristics and changes in feedback mechanisms can be physically robust.

Evaluation of Electromagnetic Fields of Extremely Low-Frequency Horizontal Electric Dipoles at Sea–Air Boundaries

The technologies of undersea detection and communication, seabed sensor networks, and geophysical detection using electromagnetic waves have emerged as research focal points within the field of marine science and engineering. However, most studies have focused on the propagation of electromagnetic fields over long distances within the shallow “sea-seabed” environment. This paper introduces a quasi-static approximation method to address the Sommerfeld numerical integration challenge within the near-field region, employing the horizontal electric dipole (HED) as a model. It derives the Sommerfeld numerical integral expressions under conditions where the wave-number ratio at the “seawater-air” boundary does not adhere to the requirement of |k0/k1| << 1 (where subscripts 0 and 1 denote seawater and air media, respectively). Building upon this, the paper simplifies the Bessel-Fourier infinite integral term within the integral expression to obtain Sommerfeld numerical integral approximations for the propagation of electromagnetic fields in the near region of extremely low frequency (ELF) within seawater. The study further conducts simulations and calculations to determine amplitude variations in electromagnetic field intensity generated by an ELF HED at different frequencies, dipole heights, and observation point depths. It concludes with an analysis of electromagnetic field propagation characteristics at the seawater-air boundary. Experimental findings highlight the lateral wave as the primary mode of electromagnetic wave propagation at this interface.

GOBAI-O2: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly 2 decades

Abstract. For about 2 decades, oceanographers have been installing oxygen sensors on Argo profiling floats to be deployed throughout the world ocean, with the stated objective of better constraining trends and variability in the ocean's inventory of oxygen. Until now, measurements from these Argo-float-mounted oxygen sensors have been mainly used for localized process studies on air–sea oxygen exchange, upper-ocean primary production, biological pump efficiency, and oxygen minimum zone dynamics. Here, we present a new four-dimensional gridded product of ocean interior oxygen, derived via machine learning algorithms trained on dissolved oxygen observations from Argo-float-mounted sensors and discrete measurements from ship-based surveys and applied to temperature and salinity fields constructed from the global Argo array. The data product is called GOBAI-O2, which stands for Gridded Ocean Biogeochemistry from Artificial Intelligence – Oxygen (Sharp et al., 2022; https://doi.org/10.25921/z72m-yz67); it covers 86 % of the global ocean area on a 1∘ × 1∘ (latitude × longitude) grid, spans the years 2004–2022 with a monthly resolution, and extends from the ocean surface to a depth of 2 km on 58 levels. Two types of machine learning algorithms – random forest regressions and feed-forward neural networks – are used in the development of GOBAI-O2, and the performance of those algorithms is assessed using real observations and simulated observations from Earth system model output. Machine learning represents a relatively new method for gap filling ocean interior biogeochemical observations and should be explored along with statistical and interpolation-based techniques. GOBAI-O2 is evaluated through comparisons to the oxygen climatology from the World Ocean Atlas, the mapped oxygen product from the Global Ocean Data Analysis Project and to direct observations from large-scale hydrographic research cruises. Finally, potential uses for GOBAI-O2 are demonstrated by presenting average oxygen fields on isobaric and isopycnal surfaces, average oxygen fields across vertical–meridional sections, climatological seasonal cycles of oxygen averaged over different pressure layers, and globally integrated time series of oxygen. GOBAI-O2 indicates a declining trend in the oxygen inventory in the upper 2 km of the global ocean of 0.79 ± 0.04 % per decade between 2004 and 2022.

The role of in situ ocean data assimilation in ECMWF subseasonal forecasts of sea‐surface temperature and mixed‐layer depth over the tropical Pacific ocean

AbstractThe tropical Pacific plays an important role in modulating the global climate through its prevailing sea‐surface temperature spatial structure and dominant climate modes like El Niño–Southern Oscillation (ENSO), the Madden–Julian Oscillation (MJO), and their teleconnections. These modes of variability, including their oceanic anomalies, are considered to provide sources of prediction skill on subseasonal timescales in the Tropics. Therefore, this study aims to examine how assimilating in situ ocean observations influences the initial ocean sea‐surface temperature (SST) and mixed‐layer depth (MLD) and their subseasonal forecasts. We analyze two subseasonal forecast systems generated with the European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS), where the ocean states were initialized using two Observing‐System Experiment (OSE) reanalyses. We find that the SST differences between forecasts with and without ocean data assimilation grow with time, resulting in a reduced cold‐tongue bias when assimilating ocean observations. Two mechanisms related to air–sea coupling are considered to contribute to this growth of SST differences. One is a positive feedback between the zonal SST gradient, pressure gradient, and surface wind. The other is the difference in Ekman suction and mixing at the Equator due to surface wind‐speed differences. While the initial mixed‐layer depth (MLD) can be improved through ocean data assimilation, this improvement is not maintained in the forecasts. Instead, the MLD in both experiments shoals rapidly at the beginning of the forecast. These results emphasize how initialization and model biases influence air–sea interaction and the accuracy of subseasonal forecasts in the tropical Pacific.

Analysis of high waves and coastal flooding event in Manado in mid-January 2021 (meteotsunami perspective)

Meteotsunami is atmospheric-induced ocean waves at the frequency of tsunami waves (2 minutes-2 hours). On January 17, 2021, the high waves tsunami-like due to lousy weather superimposed with the high tide were reported hitting the coastal area of Manado City, North of Sulawesi. This research examined the characteristic of that tsunami wave-like phenomenon. The sea level, atmospheric data (i.e., wind and air pressure), and weather satellite imagery were used in this study. The sea level, air pressure, and wind data were filtered to remove the low-frequency signal to obtain the amplitude of the high-frequency signal. The results showed that a high-frequency sea level signal’s maximum wave height (peak to trough) is up to 0.4 m. This condition responded to the increase in high-frequency maximum wind speed reaching 11 m/s associated with the convective system, such as the Cumulonimbus cloud system, detected 10 hours before the maximum high-frequency sea-level event. These circumstances meet the meteotsunami criteria, but the other parameter, such as air pressure, is not.

Internal Solitary Waves within the Cold Tongue of the Equatorial Pacific Generated by Buoyant Gravity Currents

Abstract The equatorial cold tongue in the Pacific Ocean has been intensely studied during the last decades as it plays an important role in air–sea interactions and climate issues. Recently, Warner et al. revealed gravity currents apparently originating in tropical instability waves. Both phenomena have strong dissipation rates and were considered to play a significant role in cascading energy from the mesoscale to smaller horizontal scales, as well as to vertical scales less than 1 m. Here, we present Sentinel-3 satellite observations of internal solitary waves (ISWs) in the Pacific cold tongue near the equator, in a zonal band stretching from 210° to 265°E, away from any steep bottom topography. Within this band these waves propagate in multiple directions. Some of the waves’ characteristics, such as the distance between wave crests, crest lengths, and time scales, are estimated from satellite observations. In total we identify 116 ISW trains during one full year (2020), with typical distances between crests of 1500 m and crest lengths of hundreds of kilometers. These ISW trains appear to be generated by buoyant gravity currents having sharp fronts detectable in thermal infrared satellite images. A 2D numerical model confirms that resonantly generated nonlinear internal waves with amplitudes of O(10) m may be continuously initiated at the fronts of advancing gravity currents. Significance Statement Satellite imagery reveals the repeated occurrence of internal solitary waves in the near-equatorial region of the east Pacific, despite the absence of topography. These waves appear to be resonantly generated over the sheared Equatorial Undercurrent by gravity currents that propagate as frontal zones of 1000-km scale tropical instability waves, providing a physical link with viscous mixing scales.

Acoustical effects of extreme weather events

The transfer of water from evaporating regions to precipitating regions drives the global water cycle, and understanding its dynamics is essential in determining how weather patterns will respond to changes in global climate. An intensification of the global water cycle has been reported using 50-year sea surface salinity data (Durack and Wijffels, 2010, J. Climate) with the consequence of more frequent extreme weather events. However, data under extreme weather conditions over the ocean are rare and a lot of physics remains to be investigated. As part of the Ocean Climate Stations that NOAA is maintaining, the 1-year data presented here are from Ocean Station Papa (50°N, 145°W), including measurements of wind speed, rain rate, currents, wave height and direction, bubble plume spatial structure and dynamics, and ambient noise for wind speeds up to 25 m/s. This full suite of data enables the study of the statistical properties of bubble plumes, their relation to meteorological parameters, and how to take them into account in ambient noise prediction, especially under severe weather conditions. Knowledge gained through this unique dataset can be critical for understanding air–sea interaction, validating satellite rain products, and predicting the ambient noise field under extreme weather conditions.

Evaluation of Ocean Currents Observed from Autonomous Surface Vehicles

Abstract The development of autonomous surface vehicles, such as the Boeing Liquid Robotics Wave Glider, has revolutionized our ability to collect surface ocean–lower atmosphere observations, a crucial step toward developing better physical understanding of upper-ocean and air–sea interaction processes. However, due to the wave-following nature of these vehicles, they experience rapid shifting, rolling, and pitching under the action of surface waves, making motion compensation of observations of ocean currents particularly challenging. We present an evaluation of the accuracy of Wave Glider–based ADCP measurements by comparing them with coincident and collocated observations collected from a bottom-mounted ADCP over the course of a week-long experiment. A novel motion compensation method, tailored to wave-following surface vehicles, is presented and compared with standard approaches. We show that the use of an additional position and attitude sensor (GPS/IMU) significantly improves the accuracy of the observed currents.

The Potential Role of Bering Strait in the Dynamics of Multidecadal Variability in the North Atlantic: An Idealized Model Study

Abstract Multidecadal variability on time scales between 20 and 70 years have been observed in the time series of North Atlantic SST. Many mechanisms have been proposed to explain multidecadal variabilities in the Atlantic. Generally, it is the interaction between the meridional overturning circulation (MOC) and North Atlantic surface buoyancy distribution that sustains this variability, with buoyancy anomalies either due to ocean-only processes or to air–sea interactions. In this context, the role of the Arctic Ocean, especially its freshwater flux into the North Atlantic, has been underappreciated. Bering Strait, the only oceanic pathway between the Pacific Ocean and the Arctic Ocean, has been found important in Arctic Ocean freshwater budget and in modulating the time-averaged state and long-term response of the MOC to high-latitude buoyancy forcing anomalies, via freshwater transport between the Pacific and Atlantic Oceans. In this paper, we use idealized configurations that include a Pacific-like wide basin and an Atlantic-like narrow basin. The two basins are connected both in the south and north to longitudinally periodic channels, representing the Southern Ocean and the Arctic Ocean, respectively. The Pacific-like basin is opened to the north only through a shallow and narrow strait, while the Atlantic-like basin is fully open to the north. With the goal of studying the role of Bering Strait in the multidecadal variability, we find that the freshwater transport from the Bering Strait forms a tongue structure along the western boundary of the narrow basin, which enhances the local horizontal density gradient. The western boundary region becomes unstable to large-scale baroclinic anomalies, giving rise to multidecadal variability.

Statistical Characteristics of Droplets Formed due to the “Bag Breakup” Fragmentation Event at the Interface between Water and High-Speed Air Flow

Abstract Recent studies indicate that the dominant mechanism for generating sprays in hurricane winds is a “bag breakup” fragmentation. This fragmentation process is typically characterized by inflation and consequent bursting of short-lived objects, referred to as “bags” (sail-like pieces of water film surrounded by a rim). Both the number of spray droplets and their size distribution substantially affect the air–sea heat and momentum exchange. Due to a lack of experimental data, the early spray generation function (SGF) for the bag breakup mechanism was based on the assumed similarity with resembling processes. Here we present experimental results for the case with a single isolated bag breakup fragmentation event. These experiments revealed several differences from similar fragmentation events that control the droplet sizes, such as secondary disintegration of droplets in gaseous flows and bursting of bubbles. In contrast to the bubble bursting, the film thickness of the bag canopy is not constant but is random with lognormal distribution. Additionally, its average value does not depend on the canopy radius but is determined by the wind speed. The lognormal size distribution of the canopy droplets is observed in conjunction with the established mechanism of liquid film fragmentation. The rim fragmentation results in two types of droplets, and their size distribution has been found to be lognormal distribution. The constructed SGF is verified by comparing it with experimental data from the literature. The perspectives of transferring the results from laboratory to field environment have also been discussed. Significance Statement The “bag breakup” fragmentation is the dominant mechanism for generating spray in hurricane winds. The number and the sizes of the spray droplets substantially affect the heat transport from the ocean to the atmosphere and, thereby, the development of hurricanes. This paper presents experimental data and analysis that demonstrate how droplet formation occurs during bag breakup fragmentation. It also shows analysis of the quantity and size of droplets formed during a single fragmentation event. This work demonstrates how obtained experimental results can be applied to real field conditions in the context of hurricane prediction models.

Reducing the use of cement with marble waste for seaside concrete construction through the Graphite Carbon Particles system

This research aims to save the environment by reducing the dredging of natural resources and air pollution in cement factories which produce a lot of CO2 emissions through the use of marble industrial waste. By reducing the amount of cement by 25% and replacing it with Carbon Graphite Particle Marble Powder for concrete construction work with a design quality of K-250 or fc' 20.75 MPa by using it in buildings by the sea under the influence of sea air, the concrete quality is obtained higher than the quality design concrete is 22.76 MPa > 20.75 MPa. The compressive strength testing process was carried out based on ASTM C 39/C 39M - 05. Meanwhile, for workability, based on the slump test results, a 12 cm slump value was obtained with the testing process referring to SNI 1972: 2008 and ASTM C143/C143M-12. Refining marble waste using a grinder with a capacity of 5.5 HP equipped with a 200-micron filter. The combustion process uses a high-pressure combustion engine with combustion capabilities of up to 20000 C. Carbon particles are obtained at temperatures between 8500 C and 9000 C for 120 minutes. Temperature measurement using an Infrared Thermometer with a capacity of up to 15000 C.

The Impact of Surface Waves and Spray Injection Velocities on Air–Sea Momentum and Heat Fluxes

Surface waves and sea spray play a significant role in air–sea fluxes in high winds. The present study used a marine atmosphere surface layer (MASL), which couples the traditional Monin–Obukhov similarity theory, sea spray generation function, the balance of turbulent kinetic budget, and momentum/enthalpy conservation equations. Based on this model, the effects of wave states and spray injection velocities on air–sea momentum/enthalpy fluxes and near-surface wind/temperature profiles were theoretically investigated. Based on the assumption that the velocity of injected spray is the same as that of the ambient airflow, it was found that spray could increase the near-surface air turbulence intensity and inhibit air–sea fluxes at 10 m above the sea surface. Correspondingly, near-surface wind speeds and temperature increase in high winds. This phenomenon becomes prominent in cases of large wave ages or surface waves supporting a minority of air–sea fluxes. Based on the assumption that the velocity of the edges of breaking water bags is used to estimate that of spray injection, the opposite results were found: spray could weaken the near-surface air turbulence and increase total air–sea fluxes at 10 m above the sea surface. In this case, the near-surface wind speeds and temperature decreased. This reduction becomes remarkable when surface waves are full-developed or the majority of air–sea momentum fluxes are supported by waves.

Sources of the predictability of month‐to‐month variation of precipitation anomalies in East Asia during summer

AbstractDuring boreal summer, the patterns of precipitation anomalies in East Asia have notable month‐to‐month variations, which may induce alternated wet and dry conditions in different regions of East Asia during summer. In this study, based on observation and reanalysis data, the dynamic processes of monthly precipitation anomalies in three sub‐regions of East Asia (South China, the Yangtze River valley and northern–northeastern China) are investigated, which are associated with different combined effects of tropical air–sea interaction and mid‐to‐high latitude Rossby waves during different months. These dynamic processes dominate the leading modes of month‐to‐month variation of precipitation anomalies in East Asia during summer. To understand what dynamic processes are the key sources of the predictability of month‐to‐month variation of precipitation anomalies in East Asia during summer, a method of spatially running pattern correlation coefficient (SR_PCC) is applied to examine the differences in prediction skill of geopotential height anomalies, sea‐level pressure anomalies and sea surface temperature anomalies between the years of well and poorly predicted precipitation anomalies. Based on the results of CFSv2 hindcast and CMIP6‐AMIP experiments, both the air–sea interaction over tropical Indo–Pacific region and the mid‐to‐high latitude Rossby waves over the Eurasian continent are key sources of predictability of month‐to‐month variation of precipitation anomalies in East Asia during boreal summer.

Stochastic analysis of air–sea heat fluxes variability in the North Atlantic in 1979–2022 based on reanalysis data

A dynamic stochastic model based on the Langevin stochastic differential equation is introduced for the reanalysis data of the ERA5 database to model and analyze the behavior of latent and sensible air–sea heat fluxes in the North Atlantic for the period 1979–2022. The point estimates of the random coefficients (the drift vector and the diffusion matrix) of this type of equation for the entire period under consideration are presented. The numerical methods and software tools for statistical analysis of time evolution of the coefficients as well as determination their relationships and the behavior of their maxima, averages and minima at various time intervals (days, months, years), are developed. A strong seasonality for the coefficients of the equation is demonstrated. The spatiotemporal variability of the dynamic and stochastic components of the coefficients of the Langevin equation and their relationship with jet streams of different regions of the North Atlantic is analyzed. The presence of non-trivial positive trends in the drift and diffusion coefficients, especially for the latent fluxes, within the interannual variability is demonstrated. One indicates a quantitative increase in the air–sea interaction on the interannual scale. Numerical estimation was carried out using high-performance computing cluster with software implementation in the Python programming language. The tools for dynamic visualization of various quantities on geographical maps of the region under consideration are also presented.