Open AccessA satellite altimeter model for ocean slick detection
Author(s) -
Tournadre J.,
Chapron B.,
Reul N.,
Vandemark D. C.
Publication year - 2006
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jc003109
Subject(s) - altimeter , remote sensing , radar altimeter , geology , waveform , significant wave height , scatterometer , environmental science , backscatter (email) , footprint , nadir , satellite , sea surface height , wave height , meteorology , wind speed , radar , wind wave , oceanography , computer science , physics , telecommunications , paleontology , astronomy , wireless
About 5% of Ku‐band altimeter ocean data are degraded by the occurrence of high radar return cross sections (σ 0 ), usually called σ 0 blooms. During blooms, which occur during no or low wind conditions, the mean altimeter waveform can significantly depart from the expected shape. In about 60% of the cases the waveforms are distorted to such an extent that either the range tracker loses lock or the off‐nadir angle estimate becomes unrealistic. The analysis of high data rate altimeter waveforms during bloom events reveals the presence of V‐shaped patterns similar to the ones observed during rain events. These patterns trace small‐scale (i.e., smaller than the altimeter footprint) changes in surface backscatter. Such variations of surface roughness are commonly observed in SAR images under low wind conditions. On the basis of the experience gained through the analysis of high‐resolution altimeter waveforms in the presence of rain cell, a model is developed to analyze the altimeter response to phenomena whose length scale is smaller than the altimeter footprint. The model is applied to simple patterns (linear slicks and circular patches) as well as to realistic surface σ 0 estimated by SAR. It is also used to analyze bloom events in terms of surface slicks. The model results shows that the small‐scale σ 0 variations explain the behavior of altimeter waveforms in bloom events. The results also show that a good proportion of data during bloom events are still valid for estimating geophysical parameters as the Brown model remains valid. Use of high‐resolution altimeter waveforms may also offer an interesting mean to study marine slick occurrence rates and type.