This paper reports the development of a soil moisture retrieval algorithm for spaceborne passive microwave radiometers. The algorithm is based on a modified radiative transfer model, so-called DMRT-AIEM model. The implementation of this algorithm consists of three steps: 1) forward model parameters optimization; 2) lookup table generation and 3) lookup table reversion and soil moisture estimation. The algorithm was tested at a CEOP (coordinate enhanced observing period) reference site on the Mongolia Gobi. The retrieved soil moisture data was compared with the in situ observations. The comparison results show that the performance of the new algorithm is good, giving a standard error of the estimate (SEE) of 3.8% and R-square of 0.4. Moreover, a successful TB validation on SSM/I low frequencies was achieved by the RTM used in this algorithm. It means this algorithm provides a possibility to retrieval around 20 years' soil moisture data from SSM/I observations.
['Hui Lu', 'Toshio Koike', 'Tetsu Ohta', 'David Kuria', 'Hiroyuki Tsutsui', 'Tobias Graf', 'Hideyuki Fuji', 'Katsunori Tamagawa']
Development of a soil moisture retrieval algorithm for spaceborne passive microwave radiometers and its application to AMSR-E and SSM/I