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The coastal boundary layer height (CBLH/Coastal‐BLH) is critical in determining the exchange of heat, momentum, and materials between the land and ocean, thereby regulating the local climate and weather change. However, due to the complexity of geographical characteristics and meteorological conditions, accurate estimation of the CBLH remains challenging. Herein, based on continuous high‐resolution measurements of CBL performed from November 2019 to April 2020 in coastal Ningbo city in eastern China, an optimal weighted ensemble model (OWEM) integrating multi‐meteorological variables of the ERA5 reanalysis data sets is constructed and validated to estimate the CBLH. The mean absolute percentage error of the derived CBLH by OWEM is as low as 3%–5%, significantly lower than that of 36%–65% of the ERA5 CBLH products. Furthermore, three categories of different weather scenarios, that is, sunny, cloudy, and rainy, are separately discussed, and OWEM shows greater performance and higher accuracies in comparison with the traditional Least Absolute Shrinkage and Selection Operator, Random Forest, Adaboost, LightGBM, and ensemble model, among which, OWEM under fair weather days behave best, with a robust R2 of 0.97 and a minimum mean absolute error (MAE) of 23 m. Further training results based on wind flow classification, that is, land breeze, sea breeze, and parallel wind, also indicate the outperformance of OWEM than other models, with a relatively large error in parallel wind of 50 m. Subsequent analysis of the Shapley Additive Explanations method strongly correlated with model feature importance, both reveal that thermodynamic factors such as temperature (T2m) and wind velocity (10 m U) are the major factors positively related to estimation accuracy during sunny days. Nevertheless, Relative Humidity dominates on rainy and cloudy days, TP on land breeze days, and dynamic variables like 10 m U and 10 m V on entire types of wind flow weather. In conclusion, the accurate estimation of CBLH from OWEM serves as a feasible and innovative approach, providing technical support for marine meteorology and related engineering applications, for example, onshore wind power, coastal ecological protection, etc. Plain Language Summary: The coastal boundary layer height (CBLH) is fast becoming a key parameter in atmosphere‐ocean interaction studies, and machine learning has been thought of as an effective way to accurate estimate it. In this work, we present a new model called optimal weighted ensemble model (OWEM), which integrates several meteorological variables from reanalysis data sets to estimate the CBLH and make a comparison with the ERA5 BLH under different weather conditions. We also analyze the feature importance that affects estimation accuracy using the Shapley Additive Explanations method and identify several variables as essential factors, to better understand the applicability and characterization of the OWEM for sunny, cloudy, rainy, and different wind flow days. [ABSTRACT FROM AUTHOR]

This article discusses the challenges faced by artisan fishers in southwestern India due to uncertain and extreme weather conditions, particularly during the monsoon season. Regular weather forecasts often do not provide enough information for fishers to make safe decisions about going out to fish. The article explores the use of a localized marine weather information service, using the Weather Research Forecasting (WRF) model, to improve the safety of artisan fishing. The study validates the effectiveness of the WRF model in predicting near-surface wind for small boat fishers in south India, based on local demand. [Extracted from the article]

The article titled "Brontophilia Carlos Castillejo Balsera" presents a series of photographs of storms and lightning captured by photographer Carlos Castillejo Balsera in different places in Spain, such as Barcelona, Lleida, and Zaragoza. The author expresses their passion for storms and the adrenaline they feel when chasing them. Over the course of two years, they have dedicated time to capturing these natural phenomena and share some of their best images in the article. [Extracted from the article]

The analysis of marine environmental parameters plays a significant role in various aspects, including sea surface target detection, the monitoring of the marine ecological environment, marine meteorology and disaster forecasting, and the monitoring of internal waves in the ocean. In particular, for sea surface target detection, the accurate and high-resolution input of marine environmental parameters is crucial for multi-scale sea surface modeling and the prediction of sea clutter characteristics. In this paper, based on the low-resolution wind speed, significant wave height, and wave period data provided by ECMWF for the surrounding seas of China (specified latitude and longitude range), a deep learning model based on a residual structure is proposed. By introducing an attention module, the model effectively addresses the poor modeling performance of traditional methods like nearest neighbor interpolation and linear interpolation at the edge positions in the image. Experimental results demonstrate that with the proposed approach, when the spatial resolution of wind speed increases from 0.5° to 0.25°, the results achieve a mean square error (MSE) of 0.713, a peak signal-to-noise ratio (PSNR) of 49.598, and a structural similarity index measure (SSIM) of 0.981. When the spatial resolution of the significant wave height increases from 1° to 0.5°, the results achieve a MSE of 1.319, a PSNR of 46.928, and an SSIM of 0.957. When the spatial resolution of the wave period increases from 1° to 0.5°, the results achieve a MSE of 2.299, a PSNR of 44.515, and an SSIM of 0.940. The proposed method can generate high-resolution marine environmental parameter data for the surrounding seas of China at any given moment, providing data support for subsequent sea surface modeling and for the prediction of sea clutter characteristics. [ABSTRACT FROM AUTHOR]

The mesoscale ensemble prediction system based on the Tropical Regional Atmosphere Model for the South China Sea (CMA-TRAMS (EPS)) has been pre-operational since April 2020 at South China Regional Meteorological Center (SCRMC), which was developed by the Guangzhou Institute of Tropical and Marine Meteorology (GITMM). To better understand the performance of the CMA-TRAMS (EPS) and provide guidance to forecasters, we assess the performance of this system on both deterministic and probabilistic forecasts from April to September 2020 in this study through objective verification. Compared with the control (deterministic) forecasts, the ensemble mean of the CMATRAMS (EPS) shows advantages in most non-precipitation variables. In addition, the threat score indicates that the CMA-TRAMS (EPS) obviously improves light and heavy rainfall forecasts in terms of the probability-matched mean. Compared with the European Center for Medium-range Weather Forecasts operational ensemble prediction system (ECMWF-EPS), the CMA-TRAMS (EPS) improves the probabilistic forecasts of light rainfall in terms of accuracy, reliability and discrimination, and this system also improves the heavy rainfall forecasts in terms of discrimination. Moreover, two typical heavy rainfall cases in south China during the pre-summer rainy season are investigated to visually demonstrate the deterministic and probabilistic forecasts, and the results of these two cases indicate the differences and advantages (deficiencies) of the two ensemble systems. [ABSTRACT FROM AUTHOR]

Aiming at the needs of mechanism analysis of rainstorms and development of numerical prediction models in south China, the Guangzhou Institute of Tropical and Marine Meteorology of China Meteorological Administration and the Chinese Academy of Meteorological Sciences jointly set up the Longmen Cloud Physics Field Experiment Base, China Meteorological Administration. This paper introduces the instruments and field experiments of this base, provides an overview of the recent advances in retrieval algorithms of microphysical parameters, improved understanding of microphysical characteristics, as well as the formation mechanisms and numerical prediction of heavy rainfalls in south China based on the field experiments dataset. [ABSTRACT FROM AUTHOR]

B I Part I of "U.S. Naval Oceanography: Pathfinders of the American Military" was published in the January/February 2023 issue of i Weatherwise Magazine. b Weather's Impact on Military Campaigns Historically, weather events have played key roles in outcomes of battles and entire campaigns. Naval Oceanography personnel provide highly-detailed environmental situational awareness information to members of all branches of the U.S. military, both conventional and special operations forces, including specific details of weather and ground conditions for specific areas of operations for both daytime and nighttime missions. A sister command to FNMOC, the Naval Oceanographic Office (NAVOCEANO) provides the U.S. military with detailed information vital to maritime operations throughout the globe, including underwater dynamics - oceanographic "weather." Crucially, their careful integration of a wide array of weather monitoring systems allowed them to forecast a lull in inclement weather, a break that German forecasters, utilizing a less sophisticated weather monitoring and processing system than that of the Allies, failed to predict. [Extracted from the article]

In the wake of a proposed installation of two-body floating heave buoy wave energy convertor (WEC) off coast of Vizhinjam in peninsular India, this paper analyses functional estimates of short duration mean power generation and associated variability at a site in deepwater vicinity of the port town. The work is motivated by two aspects that are of interest to project planners and academics. First, the recently proposed concept of capture width function allows a convenient, functional approach to estimate power output by a WEC unit, as well as the associated variability. However, the approach remains to be applied to WEC technologies that capture energy specifically through oscillatory dynamics of masses, given that the concept has no implicit representation for mechanical oscillations within a WEC. Second, power conversion by heave motion is often augmented by alternate dynamic modes in commercial makes of heave buoy WEC technology. Impact of multi-mode power capture, particularly on short duration output power variability, is of considerable interest in the context of network integration. Comparison to the well tested Pelamis WEC shows the latter to be a competitive alternative in terms of output power variability, and hence in some ways a better option than floating heave buoys. [ABSTRACT FROM AUTHOR]

Satellite remote sensing can measure large ocean surface areas, but the infrared-based sea surface temperature (SST) might not be correctly calculated for the pixels under clouds, resulting in missing values in satellite images. Early studies for the gap-free raster maps of satellite SST were based on spatial interpolation using in situ measurements. In this paper, however, an alternative spatial gap-filling method using regression residual kriging (RRK) for the Geostationary Korea Multi-Purpose Satellite-2A (GK2A) daily SST was examined for the seas around the Korean Peninsula. Extreme outliers were first removed from the in situ measurements and the GK2A daily SST images using multi-step statistical procedures. For the pixels on the in situ measurements after the quality control, a multiple linear regression (MLR) model was built using the selected meteorological variables such as daily SST climatology value, specific humidity, and maximum wind speed. The irregular point residuals from the MLR model were transformed into a residual grid by optimized kriging for the residual compensation for the MLR estimation of the null pixels. The RRK residual compensation method improved accuracy considerably compared with the in situ measurements. The gap-filled 18,876 pixels showed the mean bias error (MBE) of −0.001 °C, the mean absolute error (MAE) of 0.315 °C, the root mean square error (RMSE) of 0.550 °C, and the correlation coefficient (CC) of 0.994. The case studies made sure that the gap-filled SST with RRK had very similar values to the in situ measurements to those of the MLR-only method. This was more apparent in the typhoon case: our RRK result was also stable under the influence of typhoons because it can cope with the abrupt changes in marine meteorology. [ABSTRACT FROM AUTHOR]

As the demand for accurate weather forecasts continues to rise, there is an increasing need for specialized meteorological services. As a result, several private weather providers have emerged, offering customized meteorological solutions to meet the diverse needs of their clients. The present study introduces several meteorology-related applications from the point of view of WeatherNews Inc. (WNI), which is a private weather company. These applications are developed to primarily assist shipping- and energy-related companies, with greater emphasis being given to vessel weather routing.

As a high entropy energy (HEE), irregular seawater waves are a promising source of sustainable energy, and the development of matched harvesting technology is imperative to accommodate the new era. Here, a barycenter self‐adapting triboelectric nanogenerator (BSA‐TENG) that addresses these concerns and shows its applications as a distributed power source in isolated waters is reported. Benefitting from the physical gravity‐guided structure design, random vibrational water wave HEE can be effectively converted into rotational mechanical energy and then converted into electric energy. In a nonlinear seawater wave pool, a unit delivers a peak power of 0.1 mW under a load resistance of 500 MΩ when the working frequency is <1 Hz. On this basis, a self‐powered temperature sensor system and wireless signal transmitter have been developed and driven entirely by the BSA‐TENG. This work plays a key role in promoting ocean HEE harvesting and provides a workable way for a self‐powered service system in seawater wave and marine meteorology monitoring and forecasting. [ABSTRACT FROM AUTHOR]

Despite being a minor probability event, marine accidents can cause serious consequences such as casualties, environmental damage, and even massive economic losses. As an important part of the marine traffic safety system, the evaluation of navigation safety in coastal waters is of great significance to ensure the safety of ship navigation. In order to objectively evaluate the safety of navigation, this paper proposes an irregular grid division method that combines influencing factors including seabed topography, ship traffic flow, electronic charts, and marine meteorology. In this work, the navigable boundary was extracted by spatial analysis algorithms of the slope calculation. Based on the alpha-shape algorithm and the Voronoi diagram, the constrained Delaunay triangulation was used to extract the inner and outer boundaries of the ship′s navigation area, and the time-varying factors of marine hydrology and meteorology were integrated to form a dynamic irregular grid. The navigation safety evaluation indicators in coastal waters were divided into five risk levels, namely lower, low, medium, high, and higher. Then, the entropy weight theory was used to calculate the weight of the evaluation index. Finally, a safety evaluation model was constructed to evaluate the risk of navigation safety in coastal waters. Herein, taking the coastal waters of Lianyungang Port as a demonstration area, this paper divided the dynamic irregular grid and conducted the navigation safety analysis and evaluation based on the grid. The experimental results show that our method fully considers the influence of objective factors and the uncertainty of safety evaluation indicators and has favorable adaptability to the evaluation of navigation safety in coastal waters. [ABSTRACT FROM AUTHOR]

Sen Wang et al. present a detailed account of a coastal-fog event encountered during C-FOG campaign from the research vessel, and discuss the multi-layered fog-cloud structure and counter-gradient sensible heat fluxes during the event. Fog events are examined for the C-FOG main field site at Ferryland, Newfoundland as well as at other Atlantic Canadian airports. [Extracted from the article]

This paper proposes a simple and powerful optimal integration (OPI) method for improving hourly quantitative precipitation forecasts (QPFs, 0-24 h) of a single-model by integrating the benefits of different biascorrected methods using the high-resolution CMA-GD model from the Guangzhou Institute of Tropical and Marine Meteorology of China Meteorological Administration (CMA). Three techniques are used to generate multi-method calibrated members for OPI: deep neural network (DNN), frequency-matching (FM), and optimal threat score (OTS). The results are as follows: (1) The QPF using DNN follows the basic physical patterns of CMA-GD. Despite providing superior improvements for clear-rainy and weak precipitation, DNN cannot improve the predictions for severe precipitation, while OTS can significantly strengthen these predictions. As a result, DNN and OTS are the optimal members to be incorporated into OPI. (2) Our new approach achieves state-of-the-art performances on a single model for all magnitudes of precipitation. Compared with the CMA-GD, OPI improves the TS by 2.5%, 5.4%, 7.8%, 8.3%, and 6.1% for QPFs from clear-rainy to rainstorms in the verification dataset. Moreover, OPI shows good stability in the test dataset. (3) It is also noted that the rainstorm pattern of OPI relies heavily on the original model and that OPI cannot correct for deviations in the location of severe precipitation. Therefore, improvements in predicting severe precipitation using this method should be further realized by improving the numerical model's forecasting capability. [ABSTRACT FROM AUTHOR]

Although it was just a brief 3-day conference after a nearly 20-yr standstill, the Leipzig conference paved the way for international cooperation in the field of meteorology on land, thus opening the way for modern weather forecasting. On the 40th anniversary of the founding of the World Meteorological Organization in 1990, [4] acknowledged the importance of this conference: The achievements of the Leipzig Conference were twofold. All this year, I Monthly Weather Review i is celebrating its 150-yr history with a series of editorials showcasing its role in meteorological history. [Extracted from the article]

A common deficiency in coupled atmosphere‐ocean models is the lack of stratocumulus clouds near the west coasts of continents and shallow cumulus clouds over the trade wind regions. In this study, we examine changes of large‐scale trade wind environment associated with hydrometeors‐radiation‐circulation interactions, focusing over the south‐central Pacific, by carrying out experiments with falling ice (snow) radiative effects (FIREs) on or off using the CESM1‐CAM5 coupled model. Compared to observations/reanalysis data and an experiment with FIREs on (SON), an experiment with FIREs off (NOS) tends to have too‐high (0.3–0.9 K) sea surface temperature (SST) over the eastern half of the Pacific, and weaker surface wind stress over the northeast side but stronger stress over the southwest side of the study domain. The difference between NOS and SON shows lower‐tropospheric wind fields with a cyclonic‐like wind pattern, which is similar to surface wind stress, accompanied with weaker subsidence over the northeast side. The cyclonic‐like wind pattern causes stronger moisture convergence, accompanied with horizontal warm and moist advections, and stronger effective ascending motion over the northeast side of the study domain, building large‐scale environmental conditions to facilitate middle‐ and high‐clouds instead of shallow cumulus clouds in nature. This large‐scale environment in conjunction with the higher SSTs may be also responsible for the lack of the stratocumulus clouds near the coast of America. Remaining biases in SON such as the double intertropical convergence zone and parameterization deficiencies may also prevent a more realistic simulation of trade wind clouds and their associated large‐scale environments. Plain Language Summary: It has been reported that current coupled general circulation models (GCMs) show biases in large‐scale environments, for example, too‐weak subsidence, too‐warm SSTs and too‐weak surface wind stress and trade‐winds, along with too‐few low‐level clouds but with too‐frequent mid‐ and high‐level clouds over the Pacific trade‐wind regions in the Coupled Model Intercomparison Project Phase 5 (CMIP5). This study examined changes of the trade‐wind environment over South Pacific in CESM1‐CAM5 by turning on and off falling ice radiative effects (FIREs). We found that without falling ice radiative effects, that is the case for most CMIP5 models, ascent, warm and moist horizontal advections, and moisture convergence facilitate the occurrence of mid‐ and high‐clouds over trade‐wind regions relative to that with falling ice radiative effects. With falling ice radiative effects on, CESM1‐CAM5 reduced biases in sea surface temperature, winds, surface wind stress, temperature advection and moisture advection/convergence conduce to lower clouds. Key Points: Changes of the trade‐wind environment over South Pacific in CESM1‐CAM5 due to falling ice radiative effects (FIREs) on and off are examinedWith FIREs off, horizontal warm and moist horizontal advections, and moisture convergence facilitate the occurrence of mid and high cloudsWith FIREs, reduced biases in sea surface temperature (SST), winds, wind stress, temperature and moisture advections, and moisture convergence conduce to lower clouds [ABSTRACT FROM AUTHOR]

Often wave spectral models may be the only source of 2-dimensional wave spectra, but some concern exists that the wave spectral models may provide spectra which are too wide compared to those derived from wave measurements. The long history of the International Workshop on Wave Hindcasting and Forecasting has been previously described by Breivik et al. ([3], [4]) for the topical collections following the 13 SP th sp and 14 SP th sp Workshops. The workshop included the following session topics: Wave measurement Wave theory Wave modelling Wave forecasting Waves and sea ice Wave reanalysis Wave climatology Wave trend analysis Wave climate change Wave design criteria Wave extreme value analysis Rogue waves Storm surge modelling Storm surge operational forecasting Storm surge hindcast Storm surge climatology Coastal waves Coastal hazards Coastal modelling Coastal forecasting Air-sea interaction In addition to the topical sessions listed above, the workshop had four additional sessions. [Extracted from the article]

The present study aims to address a disconnect between science and the public in the form of a potential misalignment in the supply and demand of information known as the usability gap. In this case, we explore the salience of marine meteorological (metocean) information as perceived by users in two Southern Hemisphere countries: South Africa and New Zealand. Here, the focus is not only on the perceptions, usability and uptake of extreme event forecasts but rather focused on general, routine forecast engagement. The research was conducted by means of a survey, designed around three research questions. The research questions covered topics ranging from forecasting tool ergonomics, accuracy and consistency, usability, institutional reputation, and uncertainties related to climate change (to name but a few). The online questionnaire was widely distributed to include both recreational and commercial users. The study focused on identifying potential decision-making cultures that uniquely impact coastal ocean users' information needs. Cultural consensus analysis (CCA) was used to investigate shared understandings and variations in perceptions within the total group of respondents as well as in sectoral and country-based subgroups. We found varying degrees of consensus in the whole group (participants from both countries and all sectors combined) versus different subgroups of users. All participants taken together exhibited an overall moderate cultural consensus regarding the issues presented but with some variations in perspectives at the country-level, suggesting potential subcultures. Analysing national and sectoral subgroups separately, we found the most coherent cultural consensus in the South African users' cohort, with strong agreement regardless of sectoral affiliation. New Zealand's commercial users' cohort had the weakest agreement with all other subgroups. We discuss the implications from our findings on important factors in service uptake and therefore on the production of salient forecasts. Several priorities for science-based forecasts in the future are also reflected on, considering anticipated climate change impacts. We conclude by proposing a conceptual diagram to highlight the important interplay between forecast product co-development and scientific accuracy/consistency. [ABSTRACT FROM AUTHOR]

We simulated aerosol effects on cloud streets formed during continental cold‐air outbreaks over the Northwestern Pacific using an aerosol‐sensitive cloud microphysical scheme coupled with the Weather Research and Forecast model. The micro‐ and macro‐scale responses were examined under a wide range of aerosol concentrations. The cloud streets generally remain in a transient state, indicating that the aerosol particles may significantly affect the cloud system's development. The simulation results revealed a clear Twomey effect, but they were contrary to some of the Albrecht effect, especially under relatively clean conditions. Such reversed Albrecht effects stem mainly from dynamic response to changes in atmospheric stability associated with drizzle evaporation in the sub‐cloud layer. The dynamic response works against thermal forcing from the large air‐sea temperature gradient in a cold‐air outbreak. As the aerosol increases, the drizzle mechanisms weaken, and the boundary layer becomes more convective, leading to stronger dry‐air entrainment from the free troposphere. In individual clouds, the effect of entrainment on cloud water content may be compensated by more substantial vertical vapor flux. These mechanisms lead to a reduction in the cloud amount. Furthermore, the reduced moisture flux from drizzle evaporation in the sub‐cloud layer, as well as the reduced sedimentation speed of the smaller cloud drops, tend to lessen cloud thickness. The overall reduction in cloud dimensions may offset the Twomey effect by up to 20% in cloud albedo. Plain Language Summary: Cloud streets formed during continental cold‐air outbreaks over the Northwestern Pacific are susceptible to aerosol effects. Our simulations revealed a clear Twomey effect, but they were contrary to some of the Albrecht effect, especially under relatively clean conditions. The key mechanism is that the suppression of drizzle under more numerous aerosols may destabilize the boundary layer and alter the dynamics as well as energy and moisture fluxes. These influences lead to significant cloud cover changes and thus offset the Twomey effect by up to 20% in cloud albedo. Key Points: Twomey effect (cloud albedo increases with increasing aerosol concentration) is substantial in cloud streetsCloud thickness decreases in response to increasing aerosol, which is contrary to the Albrecht effectIncreasing aerosol concentration generally reduces cloud cover, but the trend reverses when substantial drizzle develops [ABSTRACT FROM AUTHOR]

After successful launch in November 2018 and successful commissioning of Metop-C, all three satellites of the EUMETSAT Polar System (EPS) are in orbit together and operational. EPS is part of the Initial Joint Polar System (IJPS) with the United States (NOAA) and provides the service in the midmorning orbit. The Metop satellites carry a mission payload of sounding and imaging instruments, which allow provision of support to operational meteorology and climate monitoring, which are the main mission objectives for EPS. Applications include numerical weather prediction, atmospheric composition monitoring, and marine meteorology. Climate monitoring is supported through the generation of long time series through the program duration of 20+ years. The payload was developed and contributed by partners, including NOAA, CNES, and ESA. EUMETSAT and ESA developed the space segment in cooperation. The system has proven its value since the first satellite Metop-A, with enhanced products at high reliability for atmospheric sounding, delivered a very strong positive impact on NWP and results beyond expectations for atmospheric composition and chemistry applications. Having multiple satellites in orbit—now three—has enabled enhanced and additional products with increased impact, like atmospheric motion vector products at latitudes not accessible to geostationary observations or increased probability of radio occultations and hence atmospheric soundings with the Global Navigation Satellite System (GNSS) Radio-Occultation Atmospheric Sounder (GRAS) instruments. The paper gives an overview of the system and the embarked payload and discusses the benefits of generated products for applications and services. The conclusions point to the follow-on system, currently under development and assuring continuity for another 20+ years. [ABSTRACT FROM AUTHOR]

'It is planning, it is science, it is management, and it is a huge change of human relations with the ocean.' As introduced by Dr Vladimir Ryabinin, the Intergovernmental Oceanographic Commission (IOC) Executive Secretary and Assistant Director-General of the United Nations Educational, Scientific and Cultural Organization (UNESCO), the UN Decade of Ocean Science for Sustainable Development (the Decade, 2021–2030) got underway this January. To echo that, on 14 January 2021, a Special Forum on the Decade was held in hybrid mode as part of the Fifth Xiamen Symposium on Marine Environmental Science (XMAS-V) in Xiamen University, China. The Forum was organized to promote the Decade through insightful talks and in-depth discussions with international and regional representatives who have been actively involved in the planning of the Decade. In addition to Dr Ryabinin, Zhanhai Zhang, Chief Engineer of the Ministry of Natural Resources of China, gave an inspiring opening speech. What followed were presentations by invited speakers. They then joined a panel discussion chaired by Dr Minhan Dai from Xiamen University. This article is edited and re-organized from the record of this Special Forum. Brandon Justin Bethel PhD Student of Marine Meteorology at Nanjing University of Information Science and Technology, China Fei Chai Professor at University of Maine, USA Karen Evans Principal Research Scientist of the Commonwealth Scientific and Industrial Research Organization (CSIRO) Oceans and Atmosphere, Australia Fangli Qiao Senior Scientist at the First Institute of Oceanography, Ministry of Natural Resources, China Martin Visbeck Professor and Head of Research Unit, Physical Oceanography at GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany Wenxi Zhu Head and Programme Specialist of IOC Sub-Commission for the Western Pacific (WESTPAC) Minhan Dai (Chair) Professor and Director of the State Key Laboratory of Marine Environmental Science, Xiamen University, China [ABSTRACT FROM AUTHOR]

Intensive air‐sea interaction and the formation of the salinity barrier layer (BL) in the Pacific has fundamental importance to the El Niño evolution. The structure and formation of the BL in the equatorial Pacific Ocean during moderate and extreme El Niños over the past 30 years are investigated using in situ temperature and salinity data measured by the TAO/TRITON array and the data‐assimilating ECCO2 product. In the western and central Pacific Ocean, the BL is thicker during moderate El Niños compared to extreme El Niños due to a deeper isothermal layer depth compared to the density defined mixed layer depth. Moreover, in the western and central Pacific Ocean, the anomalous zonal eastward current related to the westerly wind event that initiates El Niños is found to be stronger during extreme El Niños, advecting the thicker BLs from west to east. A salinity budget suggests that during both moderate and extreme El Niño events, surface freshwater flux dominates at the equator. During extreme El Niños, the change in the freshwater flux drives a strong surface jet in the far western Pacific at 1°S, 156°E. North of the equator, the surface freshwater flux largely dampens this advective impact. Thus during the different El Niño strengths, the BL distribution, evolution and impact are also different. This suggests that climate models need to better distinguish different types of El Niño events in order to simulate the ENSO dynamics correctly. Plain Language Summary: During the different El Niño scenarios, the barrier layer (BL) distribution, evolution and impact are different. Observations from TAO/TRITON array shows that the BL is thicker during moderate El Niños than during extreme El Niños in the western and central Pacific Ocean. Less heat input leads to a thinner isothermal layer depth during extreme El Niños. Stronger anomalous zonal eastward current during extreme El Niños advects the thicker BLs from west to east, dampens thick BL maintaining in the western and central Pacific Ocean. During extreme El Niños, the diagnosis shows that the change in the freshwater flux further drives a strong eastward surface jet mainly through salinity effect in the far western Pacific, further advect the thick BL to the east. Climate models need to better distinguish the evolution of BL during different types of El Niño events. Key Points: Salinity stratified barrier layers (BLs) are thicker in the western Pacific Ocean during moderate El Niños compared to extreme El NiñosDifferences in the freshwater flux and advection are the main reasons for the discrepancies during the two types of El Niño eventsDuring extreme El Niños, the freshwater flux results in a salinity‐dominated zonal current anomaly advecting BLs eastward [ABSTRACT FROM AUTHOR]

The constant flux layer assumption simplifies the problem of atmospheric surface layer (ASL) dynamics and is an underlying assumption of Monin‐Obukhov similarity theory (MOST), which is ubiquitously applied to model interfacial exchange and atmospheric turbulence. Within the marine environment, the measurements necessary to confirm the local ASL as a constant flux layer are rarely available, namely: direct observations of the near‐surface flux gradients. Recently, the Research Platform FLIP was deployed with a meteorological mast that resolved the momentum and heat flux gradients from 3 to 16 m above the ocean surface. Here, we present an assessment of the prevalence of the constant flux layer within the ASL, using an approach that accounted for the role of wave‐coherent motion in air and evaluated each observed flux gradien. Our analysis revealed that only 30%–40% of momentum flux gradients were approximately constant; for the heat fluxes, this increased to 50%–60%. For low winds, the stationarity of local turbulence was critical to the constant flux layer's validity, but resulted in excising a large proportion of the observed profiles. Under moderate wind speeds, swell‐wind alignment was associated with momentum flux divergence. Our findings suggest that the constant flux layer, as it is conventionally defined, is not generally valid over the ocean. This holds significant implications for measuring air‐sea fluxes from single point sources and marine applications of MOST. Plain Language Summary: Our ability to quantify the exchange of energy and material (e.g., gas) between the atmosphere and ocean has greatly improved over the second half 20th and into the beginning of the 21st centuries. While there have been significant technological and methodological advancements within the community of researchers studying this problem, a central theory to the physical framework we use to conduct the majority of studies has not been adequately validated or assessed using observations over the ocean. The constant flux layer model (or assumption) greatly simplifies the physical problem of studying the atmosphere near the ocean surface, but the data necessary to validate this theory are rarely collected. A recent field campaign deployed a unique ocean‐going platform that enabled us to conduct this much needed evaluation. We found strong evidence suggesting that the constant flux layer model is only valid within the general marine environment at most 50%–60% of the time. We also found that the prevalence of this theory's validity differed between the exchange (i.e., flux) of kinetic energy and heat, two critical parameters controlling the atmosphere‐ocean system. Our findings suggest that the simplified physics we rely on to study air‐sea exchange needs to be critically re‐evaluated. Key Points: Profiles of eddy covariance fluxes were used to evaluate the prevalence of the constant flux layer above ocean wavesOnly one third of momentum flux gradients were deemed "constant"; non‐divergence was substatially higher for the heat fluxesFlux divergence was strongly linked with turbulence non‐stationarity, swell‐wind alignment, and moderate‐strong stability conditions [ABSTRACT FROM AUTHOR]

Modeling air‐sea interactions during cold air outbreaks poses a major challenge because of the vast range of scales and physical processes involved. Using the Polar WRF model, we investigate the sensitivity of downstream air mass properties to (a) model resolution, (b) the sharpness of the marginal‐ice zone (MIZ), and (c) the geometry of the sea ice edge. The resolved sharpness of the MIZ strongly affects peak heat fluxes and the atmospheric water cycle. For sharper MIZs, roll convection is initiated closer to the sea ice edge, increasing both evaporation and precipitation. This yields an increased heat transfer into the atmosphere while the net effect on the atmospheric moisture budget is small. Overall, higher atmospheric resolution increases both the peak and net heat extracted from the ocean. The geometry of the sea ice edge can induce convergence or divergence zones that affect the air‐sea exchange. Plain Language Summary: In the Arctic, sea‐ice insulates a relatively warm ocean from a rather cold atmosphere. From time to time, very cold air masses spill out from the sea ice over the open ocean. When this happens, large amounts of heat and moisture are released from the ocean into the atmosphere, heating and moistening the air above while cooling the ocean. In this study, we investigate how the modeled heat and moisture exchange depends on the resolution of the atmospheric model and on properties of the marginal ice zone between the pack ice and the open ocean. The higher the resolution of the atmospheric model and the sharper the transition from the pack ice to the open ocean, the more heat and moisture is released from the ocean into the atmosphere. This dependence of the heating on model resolution is particularly pronounced close to the sea‐ice edge. Key Points: Evaporation and precipitation increase in tandem with increasing resolutionSharper resolved marginal ice zones yield higher peak and overall heat uptakeOverall sensible heat uptake and moisture balance is consistent across resolutions [ABSTRACT FROM AUTHOR]

University of Latvia (UL) has acquired experience in the development of operational oceanographic data visualisation software FiMar for search and rescue purposes since 2004. Free operational object drift forecast service developed by UL is available on: www.water.lv/fimarweb since 2018. Developments benefit from oceanographic model data from Copernicus Marine Environment Monitoring service and operational oceanography Hiromb-BOOS model at UL and marine meteorology data from the Danish Meteorological Institute driven HARMONIE model. Recent experience has shaped the numerical drift experiment: floating particles have been daily released on the surface of the virtual Baltic Sea model and their paths have been analysed. Results show that the coastline of Latvia, which accounts 3.5% of the coastline in the model, receives 9.3% of the released particles - illustrating the dominant winds in the region. Seasonality of number of particles washed ashore in Baltic Sea shoreline of Latvia is analysed in the study. [ABSTRACT FROM AUTHOR]

Four basic types of synoptic-scale conditions describe the atmospheric structure and variability observed over the Japan Sea during the 1999/2000 winter season: (1) flow of cold Asian air from the northwest, (2) an outbreak of very cold Siberian air from the north and northeast, (3) passage of a weak cyclone over the southern Japan Sea with a cold air outbreak on the backside of the low, and (4) passage of a moderate cyclone along the northwestern side of the Japan Sea. In winter, the Russian coastal mountains and a surface-air temperature inversion typically block cold surface continental air from the Japan Sea. Instead, the adiabatic warming of coastal mountain lee-side air results in small air-sea temperature differences. Occasional outbreaks of very cold Siberian air eliminate the continental surface-based inversion and stability, allowing very cold air to push out over the Japan Sea for 1-3 days. During these outbreaks, the 0degreesC surface air isotherm extends well southward of 40degreesN, the surface heat losses in the center of the Japan Sea can exceed 600 W m(-2), and sheet clouds cover most of the Japan Sea, with individual roll clouds extending from near the Russian coast to Honshu. During December through February, 1991-2002, these strong cold-air outbreak conditions occur 39% of the time and contribute 43% of the net heat loss from the Japan Sea. The average number of strong cold-air events per winter (November-March) season is 13 (ranging from 5 to 19); the 1999/2000 winter season covered in our measurements was normal.

The International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is a collection and archive of in situ marine observations, which has been developed over several decades as an international project and recently guided by formal international partnerships and the ICOADS Steering Committee. ICOADS contains observations from many different observing systems encompassing the evolution of measurement technology since the 18th century. ICOADS provides an integrated source of observations for a range of applications including research and climate monitoring, and forms the main marine in situ surface data source, e.g., near-surface ocean observations and lower atmospheric marine-meteorological observations from buoys, ships, coastal stations, and oceanographic sensors, for oceanic and atmospheric research and reanalysis. ICOADS has developed ways to incorporate user and reanalyses feedback information associated with permanent unique identifiers and is also the main repository for data that have been rescued from ships’ logbooks and other marine data digitization activities. ICOADS has been adopted widely because it provides convenient access to a range of observation types, globally, and through the entire marine instrumental record. ICOADS has provided a secure home for such observations for decades. Because of the increased volume of observations, particularly those available in near-real-time, and an expansion of their diversity, the ICOADS processing system now requires extensive modernization. Based on user feedback, we will outline the improvements that are required, the challenges to their implementation, and the benefits of upgrading this important and diverse marine archive and distribution activity.

The IMOS HF-Radar array in South Australia provides observations of the ocean waters south of Spencer Gulf. In addition to ocean surface currents, the data from this array can be processed to provide near real-time observations of wave statistics and wind direction. The Australian Bureau of Meteorology requires access to these observations for forecast modelling but currently only have a single Waverider buoy operating in South Australian waters at Cape du Couedic, south of Kangaroo Island, which provides no directional information. The HF-Radar array could potentially be used to augment the current operational observation systems used by the Bureau. In this paper, we evaluate the performance of the HF-Radar system against observations from the Waverider buoy and an automatic weather station at Neptune Island and also compare the HF-Radar observations to a wave model based on the eSA-Marine forecast grid. The results suggest that upgrading the HF-Radar to provide near real-time wave and wind data would provide a new, independent source of environmental observations for the Bureau. [ABSTRACT FROM AUTHOR]

In the South China Sea, sea fog brings severe disasters every year, but forecasters have yet to implement an effective sea-fog forecast. To address this issue, we test a liquid-water-content-only (LWC-only) operational sea-fog prediction method based on a regional mesoscale numerical model with a horizontal resolution of about 3 km, the Global and Regional Assimilation and Prediction System (GRAPES), hereafter GRAPES-3km. GRAPES-3km models the LWC over the sea, from which we infer the visibility that is then used to identify fog. We test the GRAPES-3km here against measurements in 2016 and 2017 from coastal-station observations, as well as from buoy data, data from the Integrated Observation Platform for Marine Meteorology, and retrieved fog and cloud patterns from Himawari-8 satellite data. For two cases that we examine in detail, the forecast region of sea fog overlaps well with the multi-observational data within 72 h. Considering forecasting for 0–24 h, GRAPES-3km has a 2-year-average equitable threat score (ETS) of 0.20 and a Heidke skill score (HSS) of 0.335, which is about 5.6% (ETS) and 6.4% (HSS) better than our previous method (GRAPES-MOS). Moreover, the stations near the particularly foggy region around the Leizhou Peninsula have relatively high forecast scores compared to other sea areas. Overall, the results show that GRAPES-3km can roughly predict the formation, evolution, and dissipation of sea fog on the southern China coast. [ABSTRACT FROM AUTHOR]

The paper presents an overview of the current marine observational systems which provide primary information for operational monitoring and predicting the variability of the main hydrophysical fields on the scales from several tens to several thousand kilometers (of the order of the Rossby baroclinic deformation radius and higher). Such systems provide the regular implementation of oceanographic and marine meteorological observations, their rapid interpretation and delivery to users; this is a subject of a relatively new discipline, operational oceanology. The active development of this discipline during the recent two decades suggests that the forecasting of the marine environment state will eventually reach the same level of accuracy and reliability as in operational meteorology, a more successful and older discipline. [ABSTRACT FROM AUTHOR]

The structure of a melting layer associated with a mesoconvective system is examined using a combination of in situ aircraft measurements and a unique Doppler radar operated by the U.S. Navy that has a range resolution as fine as 0.5 m. Interest in this case was motivated by ground-based all-sky camera images that captured the transient development of midlevel billow cloud structures within a precipitating trailing stratiform cloud shield associated with a passing deep convective system. A sequence of high-fidelity time–height radar measurements taken of this storm system reveal that the movement of the billow cloud structure over the radar site corresponded with abrupt transitions in the observed low-level precipitation structure. Of particular note is an observed transition from stratiform to more periodic and vertically slanted rain shaft structures that both radar and aircraft measurements indicate have the same temporal periodicity determined to arise visually between successive billow cloud bands. Doppler, balloon, and aircraft measurements reveal these transient bands are associated with a shallow circulation field that resides just above the melting level in a layer of moist neutral stability and strong negative vertical wind shear. The nature of these circulations and their impact on the evolving precipitation field are described in the context of known nimbostratus cloud types. [ABSTRACT FROM AUTHOR]