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Coastal seas, shelf seas and marginal ice zones are dominated by small-scale ocean surface dynamic processes that play a vital role in the transport and exchange of climate-relevant properties like carbon, heat, water and nutrients between land, ocean, ice and atmosphere. Mounting evidence indicates that ocean scales below 10 km have far-ranging impacts on air-sea interactions, lateral ocean dispersion, vertical stratification, ocean carbon cycling, and marine productivity – governing exchanges across key interfaces of the Earth System, the global ocean and atmosphere circulation and climate. Yet, these processes remain poorly observed at the fine spatial and temporal scales necessary to resolve them. Ocean Surface Current Airborne Radar (OSCAR) is a new airborne instrument with the capacity to inform these questions by mapping vectorial fields of total ocean surface currents and winds at high resolution over a wide swath. Developed for the European Space Agency (ESA), OSCAR is the airborne demonstrator of the satellite mission concept ‘SeaSTAR’, which aims to map total surface current and ocean wind vectors with unprecedented accuracy, spatial resolution and temporal revisit across all coastal seas, shelf seas and marginal ice zones. Like SeaSTAR, OSCAR is an active microwave Synthetic Aperture Radar Along-Track Interferometer (SAR-ATI) with optimal three-azimuth sensing enabled by unique highly-squinted beams. In May 2022, OSCAR was flown over the Iroise Sea, France, in its first scientific campaign as part of the ESA-funded SEASTARex project. The campaign successfully demonstrated the capabilities of OSCAR to produce high-resolution 2D images of total surface current vectors and near-surface ocean vector winds, simultaneously, in a highly dynamic, macrotidal coastal environment. OSCAR current and wind vectors show excellent agreement against ground-based X-band radar derived surface currents, numerical model outputs and NovaSAR-1 satellite SAR imagery, with Root

Improvement of the current SMOS soil moisture products produced by the Barcelona Expert Centre (BEC) and development of new added-value products and/or applications over land.

The ERA* stress-equivalent wind (U10S) and stress vector product is a correction of the ECMWF ERA5 output by means of geo-located scatterometer-ERA5 differences over a few days temporal window. ERA* can correct for local, persistent NWP model output errors associated with physical processes that are absent or misrepresented by the model, e.g., strong current effects (such as WBCS, highly stationary), wind effects associated with the ocean mesoscales (SST), coastal effects (land see breezes, katabatic winds), PBL parameterization errors, and large-scale circulation effects, e.g., at the ITCZ

Improvement of the current SMOS soil moisture products produced by the Barcelona Expert Centre (BEC) and development of new added-value products and/or applications over land

Improvement of the current SMOS soil moisture products produced by the Barcelona Expert Centre (BEC) and development of new added-value products and/or applications over land

Improvement of the current SMOS soil moisture products produced by the Barcelona Expert Centre (BEC) and development of new added-value products and/or applications over land

For the first time, an accurate and complete picture of Mixed Layer (ML) water mass dynamics can be inferred at high spatio-temporal resolution via the material derivative derived from Sea Surface Salinity/Temperature (SSS/T) and Currents (SSC). The product between this satellite derived material derivative and in-situ derived Mixed Layer Depth (MLD) provides a satellite based kinematic approach to the water mass (trans)formation framework (WMT/F) above ML. We compare this approach to the standard thermodynamic approach based on air-sea fluxes provided by satellites, an ocean state estimate and in-situ observations. Southern Hemisphere surface density flux and water mass (trans)formation framework (WMT/F) were analysed in geographic and potential density space for the year 2014. Surface density flux differences between the satellite derived thermodynamic and kinematic approaches and ECCO (an ocean state estimate) underline: 1) air-sea heat fluxes dominate variability in the thermodynamic approach; and 2) fine scale structures from the satellite derived kinematic approach are most likely geophysical and not artefacts from noise in SSS/T or SSC—as suggested by a series of smoothing experiments. Additionally, ECCO revealed surface density flux integrated over ML are positively biased as compared to similar estimates assuming that surface conditions are homogeneous over ML—in part owing to the e-folding nature of shortwave solar radiation. Major differences between the satellite derived kinematic and thermodynamic approaches are associated to: 1) lateral mixing and mesoscale dynamics in the kinematic framework; 2) vertical excursions of, and vertical velocities through the ML base; and 3) interactions between ML horizontal velocities and ML base spatial gradients

[EN] Heat, moisture, gas, and momentum exchanges at the oceanic and atmospheric interface modulate, inter alia, the Earth’s heat and carbon budgets, global circulation, and dynamical modes. Sea surface winds are fundamental to these exchanges and, as such, play a major role in the evolution and dynamics of the Earth’s climate. For ocean and atmospheric modeling purposes, and for their coupling, accurate sea-surface winds are therefore crucial to properly estimate these turbulent fluxes. Over the last decades, as numerical models became more sophisticated, the requirements for higher temporal and spatial resolution ocean forcing products grew. Sea surface winds from numerical weather prediction (NWP) models provide a convenient temporal and spatial coverage to force ocean models, and for that they are extensively used, e.g., the European Centre for Medium-range Weather Forecasts (ECMWF) latest reanalysis, ERA5, with ubiquitous hourly estimates of sea-surface wind available globally on a 30-km spatial grid. However, local systematic errors have been reported in global NWP fields using collocated scatterometer observations as reference. These rather persistent errors are associated with physical processes that are absent or misrepresented by the NWP models, e.g., strong current effects like the Western Boundary Current Systems (highly stationary), wind effects associated with the oceanic mesoscale (sea surface temperature gradients), coastal effects (land see breezes, katabatic winds), Planetary Boundary Layer parameterization errors, and large-scale circulation effects, such as those associated with moist convection areas. In contrast, the ocean surface vector wind or wind stress derived from scatterometers, although intrinsically limited by temporal and spatial sampling, exhibits considerable spatial detail and accuracy. The latter has an effective resolution of 25 km while that of NWP models is of 150 km. Consequently, the biases between the two mostly represent the, [ES] Los vientos de la superficie del mar son fundamentales para estimar los flujos de calor y momento en la interfaz oceánica-atmosfera, ocupando un papel importante en la evolución y la dinámica del clima del planeta. Por tanto, en modelación (oceánica y atmosférica), vientos de calidad son cruciales para estimar adecuadamente estos flujos turbulentos. Vientos de la superficie del mar de salidas de modelos de predicción numérica del tiempo (NWP) proporcionan una cobertura temporal y espacial conveniente para forzar los modelos oceánicos, y todavía se utilizan ampliamente. Sin embargo, se han documentado errores sistemáticos locales en campos de NWP globales utilizando observaciones de dispersómetros co-ubicados como referencia (asociados con procesos físicos que ausentes o mal representados por los modelos). Al contrario, el viento de la superficie del mar derivado de los dispersómetros, aunque intrínsecamente limitado por el muestreo temporal y espacial, presenta una precisión y un detalle espacial considerables. Consecuentemente, los sesgos entre los dos representan principalmente los procesos físicos no resueltos por los modelos NWP. En esta tesis, se crea un producto de forzamiento del viento en la superficie del océano de alta resolución, el ERAú. ERAú se genera con una corrección media basada en diferencias geolocalizadas entre dispersometro y modelo, aplicadas por separado a dos reanálisis diferentes, el ERA-interim (ERAi) y el ERA5. Varias configuraciones de ERAú utilizando datos de dispersómetros complementarios acumulados en diferentes ventanas temporales (TW) se generan y validan frente a datos de viento independientes, a través de análisis estadísticos y espectrales de estructuras espaciales. El método corrige con éxito los sesgos del vector de viento local de la reanálisis. [...]

C-band scatterometer winds have been adjusted for extreme conditions and in this research extension to Ku-band scatterometers is investigated. With rain rates from the Global Precipitation Measurement mission collocated to the Ku-band scatterometer observations to identify and exclude rain contamination of winds, calibration of the Ku-band observations can be done. Using high-wind cases extracted from collocated C- and Ku-band observations, we develop a calibration model and extend the Ku-band winds to 35 m/s. Validation is obtained from the set not included in the model derivation, indicating a speed error less than 10% for wind speed larger than 30m/s. The modified speed is consistent with the Step Frequency Microwave Radiometer measurements, when collocated with another Ku-band scatterometer. A comparison for the Tropical Cyclone Manyi in 2018 shows the adjustedd wind fits better with the best-track information provided by the Chinese Meteorological Administration, while more details are revealed. Results can be improved after obtaining more collocations with the dual-frequency scatterometer "WindRad" onboard the FY-3E satellite. A method for wind direction enhancement in extreme conditions is also discussed

A modification of the Barcelona Expert Center (BEC) algorithm to downscale the Soil Moisture and Ocean Salinity (SMOS) soil moisture (SM) to 300 m spatial resolution is presented. It maintains the same functional relationship as the currently implemented version but employs the following inputs: SMOS brightness temperature (TB) and SM (25 km), European Center for Medium Weather Forecast (ECMWF) skin temperature (9 km), and Sentinel 3 Normalized Difference Vegetation Index (NDVI, 300 m).The performance of the downscaled SMOS SM at 300 m is analyzed by means of a temporal validation with in-situ observations from the Soil Moisture Measurements Stations Network of the University of Salamanca (REMEDHUS) and the Continuous Soil Moisture and Temperature Ground-based Observation Network (RSMN) during the year 2021. No significant differences in correlation, unbiased root mean square difference (ubRMSD) and bias are obtained over both networks compared to the 25 km and 1 km SM products, suggesting the BEC downscaling algorithm could work at hundreds of meters and result in a similar SM accuracy

This study is to present the lesson learned during the activities related to the Italian Space Agency (ASI) funded APPLICAVEMARS project which aims at estimating sea surface wind field from L-, C- and X-band Synthetic Aperture Radar (SAR) imagery. The paper focuses on the X-band results and it describes a new approach to estimate ancillary wind direction info from the SAR image itself using neural networks

Changes in the Earth’s water cycle can be estimated by analyzing sea surface salinity. This variable refects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere–ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensifcation of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ nearsurface salinity measurements. The largest positive diferences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratifcation of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean–atmosphere fuxes., This work was supported in part by the Spanish R&D project L-BAND (ESP2017-89463-C3-1-R), which is funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, and project INTERACT (PID2020-114623RB-C31), which is funded by MCIN/AEI/10.13039/501100011033. , and in part by the Euro-pean Space Agency by means of the Contract SMOS ESL L2OS. We also acknowledge funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). This work is a contribution to CSIC PTI Teledetect., Peer Reviewed, Postprint (published version)

Due to insufficient numerical resolution and inadequate parameterizations, Mesoscale Convective Systems (MCSs) and other forms of organized convection are absent from global numerical weather prediction (NWP) and global climate models (GCMs). Objective: Correlate (quantitatively) the ocean winds with precipitation in and near MCSs using ASCAT winds, and Meteosat Second Generation (MSG) Rain rates

Having a precise estimation of Tropical Cyclone (TC) center and intensity is of common concern to both physical oceanographers and weather. In this paper, an alternative approach to directly taking the maximum scatterometer-derived wind speed is proposed to assess the TC intensity. First, the TC center location is identified based on the unique characteristics of wind stress divergence/curl near the TC core. Then the radial extent of 17-m/s winds (i.e., R17) is calculated using the wind field data from the Haiyang-2B (HY-2B) scatterometer (HSCAT). The feasibility of HSCAT wind radii in determining TC intensity is evaluated using the maximum sustained wind speed in the best-track database

Surface wind observations from insitu and remote instruments (buoys and scatterometers) are characterized by different scales and measurement errors, which can be estimated with the triple collocation method (Stoffelen, 1998). In a previous study we assessed the errors of the different wind products using collocations of buoys, scatterometer and ECMWF model output (Cossu et al., 2021). In this study, we extend the triple collocation analysis to tropospheric winds (4D winds) using collocations of aircraft observations (Mode-S), vertical wind profiles from the Aeolus satellite mission (Fig. 1) and ECMWF model output

Monitoring ocean circulation at high resolution in both space and time is of paramount importance for under-standing and modelling the ocean-atmosphere climate system, especially in coastal areas. Spaceborne radar al-timeters have been used to successfully monitor ocean circulation on a global scale ( > 30km) in the deep ocean when the geostrophic approximation is generally valid. The ocean structures seen in high-resolution satellite measurements at meso (10-100km) and sub-mesoscale ( < 10km) are ubiquitous but little is known about their dynamics. During the last two decades, many studies have highlighted the key role played by the ocean sub-mesoscale in air-sea interactions, upper-ocean mixing and ocean vertical transport and the importance of ageo-strophic circulation in these processus. Understanding these smaller currents is critical to drive scientific under-standing of the exchanges of gas, heat, and momentum between the atmosphere and the ocean, and have im-portant implications for forecasting models and climate projections. SEASTAR is an Earth Explorer 11 candidate mission, which aims to observe ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas by providing simultaneous measurements of current and wind vectors at 1km resolution with accuracy of respectively 10cm/s and 2m/s. OSCAR (Ocean Surface Current Airborne Radar) is the demonstrator for this satellite concept, and is in development at the Euro-pean Space Agency (ESA) in the frame of its preparatory activities for ocean surface current retrieval with Meta-sensing as a prime contractor. OSCAR system will be representative of a satellite mission concept, observation parameters and accuracies directly relate to a potential satellite mission. OSCAR is a Ku-band (13.5 GHz) three-look direction SAR system with Along-track Interferometric (ATI) SAR and scatterometric capabilities. It is tailored to the measurement of 2D ocean surface motion and wind retrie

Important changes in the Earth’s water cycle can be assessed by analysing sea surface salinity, as this variable on average reflects the balance between precipitation and evaporation over ocean, being the upper layers the most sensitive to atmosphere-ocean interactions. In situ measurements of salinity are relatively scarce, reduced to a limited number of field campaigns, buoys, and drifters, and typically acquired some meters below the sea surface. Thus, they may not necessarily well represent ocean-atmosphere exchanges. Satellite measurements, on the contrary, are synoptic, repetitive and represent the uppermost surface of the ocean. In this work, we show that the dynamics captured by satellite-derived sea surface salinity (SSS) measurements differ from the dynamics shown by in situ near SSS (NSS) measurements. We compare a temporal series of 8 years of the Soil Moisture and Ocean Salinity (SMOS) SSS maps with the output of an ocean model that assimilates in situ salinity measurements, which includes salinity in the first meters of the surface (NSS), as well as the mixed layer depth (MLD) and the sea surface temperature (SST). On the one hand, the satellite SSS measurements present a clear intensification of the water cycle which is somewhat less evident in the NSS. The water cycle is expected to intensify in the context of global warming, according to the Clausius-Clapeyron (CC) relation, which states that the saturation of the water vapor pressure increases at a rate of 7% per degree Celsius of warming. During the analysed 8 years, we observe a positive SST trend ranging between 0.2ºC/year and 0.1ºC/year (depending on the region) and a SSS trend ranging between 0.008 psu/year and 0.015 psu/year, which is consistent with the CC law. On the other hand, we observe that the largest positive differences between the satellite SSS and the NSS trends are in regions that simultaneously present a large positive SST trend, and a negative MLD trend. This suggests that globa