A Holistic Perspective on the Calibration and Validation of Sentinel-2 L2A products: Contribution From the CCVS Project

In this presentation, we report on the preliminary findings of the H2020 project “Copernicus Cal/Val Solution” (CCVS), whose objective is to define a holistic solution to the cal/val of the Copernicus Sentinel missions. We focus more specifically on synergies of the Sentinel-2 mission with other Sentinel or third-party missions, in terms of cal/val requirements as well as reference data sources. Regarding the first aspect, CCVS will consolidate cal/val requirements for all missions with a unified approach. For instance, we compare validation requirements for Sentinel-2 L2A AOD and Water Vapour products to other optical missions like Sentinel-3 OLCI and SLSTR, as well as atmospheric composition missions. In addition, user-driven inter-operability requirements could lead to specific calibration or validation needs. A first example concerns the radiometric inter-calibration between Sentinel-2A and B, which could be ensured with better accuracy than the absolute calibration of either satellites. Geometric co-registration with other optical missions like Landsat could be also monitored. In terms of data sources, CCVS will first establish a survey of existing sources, including natural targets and in-situ data acquired in the frame of systematic measurement programs or ad-hoc campaigns. In a second step, we investigate potential data sources needed for calibration and validation, with a specific focus on directional surface reflectance and cloud mask

Copernicus Cal/Val Solution - D3.2 - Recommendations for R&D on Cal/Val Methods

This document presents a gap analysis of the methods used in the calibration and validation of Earth Observation satellites relevant to the Copernicus programme and suggests recommendations for the research and developments required to fulfil this gap when/where possible. The document identifies the gaps and limitations of the CalVal methods, used for calibration and validation (CalVal) activities for the current Copernicus missions. It will also address the development needs for future Copernicus missions. Four types of missions are covered based on the division used in the rest of the CCVS project: optical, altimetry, radar and microwave and atmospheric composition. Finally, it will give a prioritized list of recommendations for R&D activities on the CalVal methods. The information included is mainly collected from the deliverables of work packages 1 and 2 in the CCVS project and from the consortium experts in CalVal activities

Circulation générale océanique et variabilité à méso-échelle en Méditerranée Orientale: approche numérique

The circulation in the eastern Mediterranean basin has been studied using a general circulation model with very high horizontal resolution, climatologies, in-situ and remote sensed observations. A thorough validation of the model shows a good agreement of the various water masses. The surface circulation is also in good agreement with recent circulation schemes derived from observations. For instance, the main part of the Atlantic inflow follows the African coast and forms a permanent and intense coastal jet along the Libyan coasts, rather than the Mid Mediterranean Jet described few years ago by several authors. The well known mesoscale structures (Egyptian eddies, Ierapetra...) are also well reproduced. In good agreement with altimetric and SST observations, the model shows that energetic mesoscale eddies dominate the surface circulation in the south of the Levantine basin. Mesoscale eddies are more energetic in summer than in the whole of the basin. In addition, simulations allow a detailed analysis of the life cycle of these eddies and how they are able to control the mean circulation. Depending on the position and development of these eddies, different circulation regimes are observed. In particular, eddies in the Levantine basin (Egyptian eddies, Lattaquia, Ierapetra) can block and force offshore bifurcations of the coastal surface Atlantic inflow.L'étude de la circulation dans le bassin Est de la Mer Méditerranée a été abordée par une analyse conjointe de simulations numériques réalisées avec un modèle à très haute résolution horizontale, de climatologies et d'observations in-situ et satellitaires. Une validation approfondie du modèle montre un bon accord entre les différentes masses d'eau. La circulation de surface est, elle aussi, en bon accord avec les schémas de circulation récents. Ainsi, la majeure partie de l'eau atlantique suit la côte africaine et forme un jet côtier intense au niveau de la côte libyenne, plutôt que le Mid Mediterranean Jet décrit il y a quelques années par plusieurs auteurs. Les structures de mésoéchelle bien répertoriées (tourbillons d'Egypte, Ierapetra, ...)sont également correctement reproduites. En accord avec des observations par satellite, le modèle montre que des tourbillons de mésoéchelle très énergétiques dominent la circulation de surface dans le sud du bassin Levantin. Les tourbillons de mésoéchelle sont plus énergiques en été qu'en hiver dans l'ensemble du bassin. Les simulations permettent en outre une analyse détaillée du cycle de vie de ces tourbillons et comment ils sont susceptibles d'affecter la circulation moyenne. Selon la position et le développement des tourbillons, des différents régimes de la circulation peuvent être reproduits. Notamment, les tourbillons du bassin Levantin (Tourbillons egyptiens, Lattaquié, Ierapetra) peuvent entraîner des blocages et bifurcations vers le large de l'inflow côtier d'eau atlantique de surface

Circulation générale océanique et variabilité à méso-échelle en Méditerranée Orientale (Approche numérique)

L'étude de la circulation dans la Mer Méditerranée Est a été abordée par une analyse de simulations numériques d'un modèle à très haute résolution horizontale, de climatologies et d'observations in-situ et satellitaires. La validation du modèle montre un bon accord entre les différentes masses d'eau. La circulation de surface est en bon accord avec les schémas de circulation récents. L'eau atlantique forme un jet intense suivant la côte africaine. En accord avec des observations par satellite, le modèle montre que des tourbillons de mésoéchelle très énergétiques dominent la circulation de surface dans le sud du bassin. Les simulations permettent une analyse détaillée du cycle de vie de ces tourbillons et comment ils sont susceptibles d'affecter la circulation moyenne. Selon la position et le développement des tourbillons, des différents régimes de la circulation peuvent être reproduits. Les tourbillons du bassin Levantin peuvent entraîner des bifurcations vers le large de l'influx d'eau atlantique.The circulation in the eastern Mediterranean basin has been studied using a general circulation model with very high horizontal resolution, climatologies, in-situ and remote sensed observations. The model validation shows a good agreement of the various water masses. The surface circulation is also in good agreement with recent circulation schemes derived from observations. The Atlantic inflow forms a permanent and intense jet along the African coasts. In good agreement with altimetric and SST observations, the model shows that energetic mesoscale eddies dominate the surface circulation. In addition, simulations allow a detailed analysis of the life cycle of these eddies and how they are able to control the mean circulation. Depending on the position and development of these eddies, different circulation regimes are observed. In particular, eddies in the Levantine basin (Egyptian eddies, Lattakia, Ierapetra) can block and force offshore bifurcations of the coastal surface Atlantic inflow.AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Patterns of precipitation and convection occurrence over the mediterranean basin derived from a decade of microwave satellite observations

International audienceThe Mediterranean region is characterized by its vulnerability to changes in the water cycle, with the impact of global warming on the water resources being one of the major concerns in social, economical and scientific ambits. Even if precipitation is the best-known term of the Mediterranean water budget, large uncertainties remain due to the lack of suitable offshore observational data. In this study, we use the data provided by the Advanced Microwave Sounding Unit-B (AMSU-B) on board NOAA satellites to detect and analyze precipitating and convective events over the last decade at spatial resolution of 0.2° latitude × 0.2° longitude. AMSU-B observation shows that rain occurrence is widespread over the Mediterranean in wintertime while reduced in the eastern part of the basin in summer. Both precipitation and convection occurrences display a weak diurnal cycle over sea. In addition, convection occurrences, which are essentially located over land during summertime, shift to mostly over the sea during autumn with maxima in the Ionian sub-basin and the Adriatic Sea. Precipitation occurrence is also inferred over the sea from two other widely used climatological datasets, HOAPS (Hamburg Ocean AtmosphereParameters and Fluxes from Satellite Data) and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis interim (ERA-Interim). There is generally a rather fair agreement between these climatologies for describing the large-scale patterns such as the strong latitudinal gradient of rain and eastward rain signal propagation. Furthermore, the higher spatial resolution of AMSU-B measurements (16 km at nadir) gives access to mesoscale details in the region (e.g., coastal areas). AMSU-B measurements show less rain occurrences than HOAPS during wintertime, thereby suggesting that some of the thresholds used in our method might be too stringent during this season. We also observed that convection occurrences in ERA-Interim are systematically lower than those derived from AMSU-B. These results are potentially valuable to evaluate the rainfall parameterization in weather and climate models and to constrain ocean models. © 2014 by the authors

Preparation of the Calibration Baseline for Sentinel-2 Collection 1

The Sentinel-2 mission observes the Earth in 13 spectral bands in the visible and SWIR with a repeat cycle of 5 days for each satellite unit A and B. A complete reprocessing of the Sentinel-2 archive to generate the Collection-1 is currently under preparation. In this presentation we describe the activities performed by the Sentinel-2 Mission Performance Center to prepare the calibration baseline for Collection-1. The preparation activities involve a correction of some minor errors in the definition of the spectral response function at the beginning of the mission. A more significant change concerns the possible harmonization between the two sensors. Indeed, radiometric validation results reported by different teams confirm the presence of a small bias (around 1%) in the visible range between the satellites. Sentinel-2B is generally believed to be slightly too dark, while Sentinel-2A agrees better with other references. The presentation will describe the inter-satellite bias assessment as well as a study of the impact of a potential harmonization on Level-2 products

A high resolution climatology of precipitation and deep convection over the Mediterranean region from operational satellite microwave data: development and application to the evaluation of model uncertainties

International audienceA new precipitation and convection dataset for the Mediterranean Basin, derived from operational satellite microwave data is documented. The dataset is derived from diagnostics that rely on brightness temperatures measured since 1999 in the water vapour absorption line (183-191 GHz). The dataset consists of twice-daily (a.m. and p.m.) and monthly maps of precipitation and convection occurrences on a 0.2° lat × 0.2° long grid for the area 25°-60° N, 10° W-50° E. The instruments used so far are the AMSU-B sensor on the NOAA-15 to -17 satellites, and the MHS sensor on the NOAA-18 and -19 and METOP-2 satellites, with precipitation and convection available separately for the different sensors. The slightly different radiometric characteristics of MHS compared to AMSU-B do not affect significantly the continuity of the dataset. Precipitation and convection data from different sensors on different satellites are remarkably consistent, with generally small biases between the instruments. When larger biases appear, they can be explained either by the drifts in the satellite orbit, scan asymmetry, or temporal aliasing from insufficiently resolving the diurnal cycle of precipitation and convection. After a description of climatological aspects of rain and deep convection occurrence, the interest of this dataset to evaluate model uncertainties for simulating a high-impact weather event and for climatic regional runs over this area is illustrated