Title : ( On the impact of C-band in place of L-band radar for SMAP downscaling )
Authors: elaheh ghafari , Jeffrey P. Walker , Narendra N. Das , Kamran Davary , Alireza Faridhosseini , Xiaoling Wu , Liujun Zhu ,
Abstract
The National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) mission was launched on 31st January 2015, with the aim of providing global soil moisture maps at 9 km spatial resolution by combining L-band radar and radiometer observations. However, after the SMAP radar became inoperable, NASA decided to utilize the Sentinel 1A/1B C-band SAR data in its place. The new version of baseline brightness temperature (Tb) downscaling algorithm for SMAP is tested using L-band airborne data to evaluate the capabilities of the C-band Sentinel-1A SAR relative to L-band radar data in downscaling the SMAP Tb for achieving high resolution brightness temperature. In this study, the downscaling algorithm used L-band airborne Synthetic Aperture Radar (SAR) backscatter (σ) collected from the fifth Soil Moisture Active Passive Experiment (SMAPEx- 5) in south-eastern Australia to downscale 36 km L-band SMAP radiometer Tb pixels to 3 km and 9 km. The downscaling results were then compared with the published results using Sentinel-1A C-band backscatter, and evaluated against airborne 1 km resolution L-band passive microwave brightness temperature collected from SMAPEx-5. The results show that for vertical polarization the average Root Mean Square Error (RMSE) of downscaled Tb when compared with reference airborne Tb across 4 days at 9 km resolution were 4.9 K for Lband and 6.0 K for C-band, and increased to 9.3 K for L-band and 9.6 K for C-band at 3 km spatial resolution. Moreover, the correlation coefficient (R) of downscaled and reference Tb across the 4 days was 0.92 for L-band and 0.88 for C-band at 9 km, decreasing to 0.75 for L-band and 0.72 for C-band at 3 km spatial resolution. Accordingly, the RMSE increased and the correlation coefficient decreased when using C-band radar data in place of that at L-band. However, overall there is expected to be only a slight decrease in performance of the downscaling algorithm by using the Sentinel 1A data in place of the SMAP radar.
Keywords
, Downscaling Brightness temperature Backscatter L, band C, band SMAP Sentinel, 1A@article{paperid:1081376,
author = {Ghafari, Elaheh and Jeffrey P. Walker and Narendra N. Das and Davary, Kamran and Faridhosseini, Alireza and Xiaoling Wu and Liujun Zhu},
title = {On the impact of C-band in place of L-band radar for SMAP downscaling},
journal = {Remote Sensing of Environment},
year = {2020},
volume = {251},
number = {112},
month = {September},
issn = {0034-4257},
pages = {112111--14},
numpages = {-112097},
keywords = {Downscaling
Brightness temperature
Backscatter
L-band
C-band
SMAP
Sentinel-1A},
}
%0 Journal Article
%T On the impact of C-band in place of L-band radar for SMAP downscaling
%A Ghafari, Elaheh
%A Jeffrey P. Walker
%A Narendra N. Das
%A Davary, Kamran
%A Faridhosseini, Alireza
%A Xiaoling Wu
%A Liujun Zhu
%J Remote Sensing of Environment
%@ 0034-4257
%D 2020