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Multi-Channel Regression Inversion Method for Passive Remote Sensing of Ice Water Path in the Terahertz Band

1
College of Meteorology and Oceanography, National University of Defense Technology, Nanjing 211101, China
2
National Key Laboratory on Electromagnetic Environmental Effects and Electro-Optical Engineering, Army Engineering University, Nanjing 210007, China
3
National Satellite Meteorological Center, Beijing 100081, China
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(8), 437; https://doi.org/10.3390/atmos10080437
Received: 5 July 2019 / Revised: 18 July 2019 / Accepted: 26 July 2019 / Published: 28 July 2019
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Abstract

Retrieval of ice cloud properties using passive terahertz wave radiometer from space has gained increasing attention currently. A multi-channel regression inversion method for passive remote sensing of ice water path (IWP) in the terahertz band is presented. The characteristics of the upward terahertz radiation in the clear-sky and cloudy-sky are first analyzed using the Atmospheric Radiative Transfer Simulator (ARTS). Nine representative center frequencies with different offsets are selected to study the changes of terahertz radiation caused by microphysical parameters of ice clouds. Then, multiple linear regression method is applied to the inversion of IWP. Combinations of different channels are selected for regression to eliminate the influence of other factors (i.e., particle size and cloud height). The optimal fitting equation are obtained by the stepwise regression method using two oxygen absorption channels (118.75 ± 1.1 GHz, 118.75 ± 3.0 GHz), two water vapor absorption channels (183.31 ± 1.0 GHz, 183.31 ± 7.0 GHz), and two window channels (243.20 ± 2.5 GHz, 874.4 ± 6.0 GHz). Finally, the errors of the proposed inversion method are evaluated. The simulation results show that the absolute errors of this method for the low IWP cases are below 7 g/m2, and the relative errors for the high IWP cases are generally ranging from 10 to 30%, indicating that the multi-channel regression inversion method can achieve satisfactory accuracy. View Full-Text
Keywords: terahertz wave; passive remote sensing; ice water path; multi-channel regression terahertz wave; passive remote sensing; ice water path; multi-channel regression
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Weng, C.; Liu, L.; Gao, T.; Hu, S.; Li, S.; Dou, F.; Shang, J. Multi-Channel Regression Inversion Method for Passive Remote Sensing of Ice Water Path in the Terahertz Band. Atmosphere 2019, 10, 437.

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