Sea surface emissivity observations at L-band: first results of the Wind and Salinity Experiment WISE 2000

Abstract

Abstract-Sea surface salinity can be measured by passive microwave remote sensing at L-band. In May 1999, the European Space Agency (ESA) selected the Soil Moisture and Ocean Salinity (SMOS) Earth Explorer Opportunity Mission to provide global coverage of soil moisture and ocean salinity. To determine the effect of wind on the sea surface emissivity, ESA sponsored the Wind and Salinity Experiment (WISE 2000). This paper describes the field campaign, the measurements acquired with emphasis in the radiometric measurements at L-band, their comparison with numerical models, and the implications for the remote sensing of sea salinity.

The WISE 2000 and 2001 field experiments in support of the SMOS mission: sea surface L-band brightness temperature observations and their application to sea surface salinity retrieval

“…Results shown in Fig. 13 from [16] are in reasonable agreement with Hollinger [17] and Swift [18] measurements, with reduced error bars, and give an extrapolated sensitivity at nadir of 0.22 K/(m/s). The sensitivity to with incidence angle increases at horizontal polarization, while it decreases at vertical polarization, and around , the brightness temperature at vertical polarization becomes insensitive to wind speed.…”

“…The sea surface temperature showed the start of the cooling from the warm summer value 22 C down to 16 C. At the beginning of the field experiment, the atmosphere was stable, but quickly changed to unstable conditions ( 6 C to 12 C). Since wind speed measurements have to be referred from 2.6 or 69 m ( only wind data from November [15][16][17][18][19][20][21][22]2001) to 10-m height, and the atmospheric conditions were quite unstable, atmospheric instability corrections were applied [19]. 5 The derivation of the brightness temperature sensitivity to wind speed follows the same steps as for WISE 2000, but the number of data points is much larger (Table II), since incidence angles at 30 , 40 , 50 , and 60 , corresponding to the afternoon-evening measurements pointing to the northeast, are also available.…”

Sea state effect on the sea surface emissivity at l-band

“…However, until recently, experimental data were very scarce. The main goal of the ESA-sponsored Wind and Salinity Experiment (WISE) 2000 and 2001 campaigns was to determine the TB sensitivity to wind speed (or sea state) [1], [2]. The campaigns took place at Repsol's Casablanca oil rig, located at 40 43.02 N 21.50 E, 40 km away from the Ebro River mouth on the coast of Tarragona, Spain.…”

Wind speed effect on L-band brightness temperature inferred from EuroSTARRS and WISE 2001 field experiments

“…As a result, the Soil Moisture and Ocean Salinity mission (SMOS) (http://www.cesbio.ups-tlse.fr/fr/indexsmos.html) was selected to be launched in 2007 by the European Space Agency (ESA) in 1999. In preparing for the SMOS mission, ESA sponsored several field experiments in order to improve sea surface emissivity models in L-band: EuroSTARRS [5], WISE 2000 [6], and WISE 2001 [7]. In this paper, we address the issue of the effects of sea surface roughness and foam on emissivity.…”

“…This disagreement between model and data might come from a modification of part of the wave spectrum due to the presence of the platform, especially by creating reflected waves. In addition, it was observed during WISE 2000 that waves reflected by the platform affect the amount of foam: the foam coverage observed north of the platform was lower than the one observed west by one order of magnitude [6].…”