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A New Climatology of Sea Surface Wind Speed Under Cloud-Free Conditions for the Estimation of the Impact of Sunglint in GMES Sentinel-3

Mounir Lekouara(1), Bernardo Carnicero Dominguez(2) and Miguel Aguirre(2)

(1) National Oceanography Centre (NOCS), European Way, SO14 3ZH Southampton, United Kingdom
(2) ESA (ESTEC), Keplerlaan 1, 2200 AG Noordwijk, Netherlands

Abstract

Ocean Colour Instruments and missions are affected by sun glint. Knowledge of the effect of sun glint is key at the very early design of such missions both for coverage degradation knowledge and proper payload sizing. Sun glint depends on sun-spacecraft geometry but also on wind speed at sea surface level. Traditionally a constant global wind speed is assumed to calculate sun glint during the early phases of satellite design. However wind speed has yearly and geographical variations. Geographical and yearly sea surface wind speed statistics under cloud free conditions should be used in order to properly estimate sun glint affecting Ocean Colour Instruments

The ESA Grid Processing On Demand (G-POD) architecture has allowed the processing of 5 years of MERIS Reduced Resolution Level-2 products in order to build 1) a new climatology of global ocean wind speed under cloud and ice-haze free conditions, 2) a new climatology of cloud and ice-haze coverage at the time of MERIS passes. The wind speed information was provided by the ECMWF model and attached to the MERIS products, the cloud and ice-haze coverage was extracted from the MERIS RR L2 flags.

The above-cited climatologies were used to compute the impact of sun glint during the Phase A of Sentinel-3 and compared with constant wind speed regimes. Sun glint was calculated based on the on the Cox and Munk model of the surface of the ocean for the sun glint estimation. The wind parameter for the Cox Munk model was extracted from the climatology of wind speed under cloud and ice-haze free conditions.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry