Abstract-Soil Moisture and Ocean Salinity (SMOS) is an Earth Explorer Opportunity Mission from the European SpaceAgency with a launch date in 2007. Its goal is to produce global maps of soil moisture and ocean salinity variables for climatic studies using a new dual-polarization L-band (1400-1427 MHz) radiometer Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). SMOS will have multiangular observation capability and can be optionally operated in full-polarimetric mode. At this frequency the sensitivity of the brightness temperature ( ) to the sea surface salinity (SSS) is low: 0.5 K/psu for a sea surface temperature (SST) of 20 C, decreasing to 0.25 K/psu for a SST of 0 C. Since other variables than SSS influence the signal (sea surface temperature, surface roughness and foam), the accuracy of the SSS measurement will degrade unless these effects are properly accounted for. The main objective of the ESA-sponsored Wind and Salinity Experiment (WISE) field experiments has been the improvement of our understanding of the sea state effects on at different incidence angles and polarizations. This understanding will help to develop and improve sea surface emissivity models to be used in the SMOS SSS retrieval algorithms. This paper summarizes the main results of the WISE field experiments on sea surface emissivity at L-band and its application to a performance study of multiangular sea surface salinity retrieval algorithms. The processing of the data reveals a sensitivity of to wind speed extrapolated at nadir of 0.23-0.25 K/(m/s), increasing at ( ) is found to be correlated with the measured sea surface slope spectra. Peaks in ( ) are due to foam, which has allowed estimates of the foam brightness temperature and, taking into account the fractional foam coverage, the foam impact on the sea surface brightness temperature. It is suspected that a small azimuthal modulation 0.2-0.3 K exists for low to moderate wind speeds. However, much larger values (4-5 K peak-to-peak) were registered during a strong storm, which could be due to increased foam. These sensitivities are satisfactorily compared to numerical models, and multiangular data have been successfully used to retrieve sea surface salinity.
[1] Analysis of field observations of sea-surface elevation reveals the role of time-varying incident forcing and bound wave release mechanisms on the generation of infragravity waves on a barred beach. Observations of infragravity response were obtained during sea breeze and swell periods with wave height varying from 0.2 to 1.2 m and wave period from 3 to 16 s. The observations show a stronger infragravity response to longer period incident swell than to short period wind-sea. During the peak of the sea breeze, short period windsea is conducive to long wave generation by breakpoint forcing. Under swell-dominated conditions, the frequency and wave number of incoming bound waves associated with wave groups may satisfy the linear dispersion relationship, leading to resonant forcing of a free wave that appears to be released from the wave group. The transition between long wave generation due to bound wave release and time-varying breakpoint forcing agrees with the surf beat similarity parameter.Citation: Contardo, S., and G. Symonds (2013), Infragravity response to variable wave forcing in the nearshore,
Abstract-The results from two field experiments in the Mediterranean Sea are used to study the wind speed dependence of brightness temperature at L-band. During the EuroSTARRS airborne experiment, an L-band radiometer made measurements across a large wind speed gradient, enabling us to study this dependence at high wind speed. We compare our results with a two-scale emissivity model using several representations of the sea state spectrum. While the results are encouraging, unfortunately the accuracy of the measurements does not permit us to distinguish between the so-called twice Durden and Vesecky spectrum and the Elfouhaily spectrum above 7 m s 1 . The effect of foam is certainly small. During the WISE 2001 field experiment carried on an oil rig, we studied this dependence at low wind speed, finding an abrupt decrease of the wind speed effect on the brightness temperature below 3 m s 1 .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.