Open AccessAbsolute Calibration of Jason-1 and Envisat Altimeter Ku-Band Radar Cross Sections from Cross Comparison with TRMM Precipitation Radar Measurements
Author(s) -
N. Tran,
O. Z. Zanifé,
Bertrand Chapron,
D. Vandemark,
Patrick Vincent
Publication year - 2005
Publication title -
journal of atmospheric and oceanic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.774
H-Index - 124
eISSN - 1520-0426
pISSN - 0739-0572
DOI - 10.1175/jtech1791.1
Subject(s) - remote sensing , ku band , radar altimeter , radar , nadir , altimeter , offset (computer science) , c band , space based radar , backscatter (email) , geology , calibration , radar cross section , precipitation , environmental science , geodesy , meteorology , radar imaging , radar engineering details , satellite , physics , computer science , telecommunications , wireless , astronomy , quantum mechanics , programming language , optics
One year of collocated, rain-free nadir Ku-band backscatter cross-section measurements from the Tropical Rainfall Mapping Mission (TRMM) precipitation radar (PR) and both Jason-1 and Envisat RA-2 altimeter measurements have been compiled to compare these three sources of Ku-band radar cross section. With the exception of a +1.46 dB relative offset between Jason-1 and PR measurements and a −1.40 dB offset between Envisat and PR ones, all three Ku-band measurements compare very well in terms of dependencies upon model wind speed estimates and significant wave height measurements. The altimeter radars and the rain radar thus provide consistent measurements, and observed biases can be rationalized as differences in the radar calibration. The precipitation radar, which also covers off-nadir measurements, has been absolutely calibrated using an active radar calibrator. Consequently, the observed relative offsets can be used to indirectly calibrate both Jason-1 and Envisat altimeter Ku-band radar cross sections in an absolute sense.