The Simulation of L-Band Microwave Emission of Frozen Soil during the Thawing Period with the Community Microwave Emission Model(CMEM)  

作　　者：Shaoning Lv Clemens Simmer Yijian Zeng Jun Wen and Zhongbo Su 

机构地区：[1]Institute for Geosciences and Meteorology at the University of Bonn,Auf dem Huegel 20,53121 Bonn,Germany [2]Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences,Fudan University,200438 Shanghai,China [3]Cloud and Precipitation Exploration Laboratory(CPEX-Lab)of Geoverbund ABC/J,Jülich,Germany [4]Department of Water Resources,Faculty of Geo-Information Science and Earth Observation(ITC),University of Twente,P.O.Box 217,7500AE,Enschede,Netherlands [5]The Plateau Atmosphere and Environment Key Laboratory of Sichuan Province,Chengdu University of Information Technology,Chengdu,610225 Sichuan,China

出　　处：《Journal of Remote Sensing》2022年第1期46-64,共19页国际遥感学报（英文）

基　　金：This research was funded by the Deutsche Forschungsgemeinschaft(DFG)via the research group FOR2131 on“Data Assimilation for Improved Characterization of Fluxes across Compartmental Interfaces”,subproject P2,the National Natural Science Foundation of China(Grant 42075150);the Natural Science Foundation of Shanghai(No.21ZR1405500).

摘　　要：One-third of the Earth’s land surface experiences seasonal freezing and thawing.Freezing-thawing transitions strongly impact land-atmosphere interactions and,thus,also the lower atmosphere above such areas.Observations of two L-band satellites,the Soil Moisture Active Passive(SMAP)and Soil Moisture and Ocean Salinity(SMOS)missions,provide flags that characterize surfaces as either frozen or not frozen.However,both state transitions—freezing and thawing(FT)—are continuous and complex processes in space and time.Especially in the L-band,which has penetration depths of up to tens of centimeters,the brightness temperature(T_(B))may be generated by a vertically-mixed profile of different FT states,which cannot be described by the current version of the Community Microwave Emission Model(CMEM).To model such complex state transitions,we extended CMEM in Fresnel mode with an FT component by allowing for(1)a varying fraction of an open water surface on top of the soil,and(2)by implementing a temporal FT phase transition delay based on the difference between the soil surface temperature and the soil temperature at 2.5 cm depth.The extended CMEM(CMEM-FT)can capture the T_(B)progression from a completely frozen to a thawed state of the contributing layer as observed by the L-band microwave radiometer ELBARA-III installed at the Maqu station at the northeastern margin of the Tibetan Plateau.The extended model improves the correlation between the observations and CMEM simulations from 0.53/0.45 to 0.85/0.85 and its root-mean-square-error from 32/25 K to 20/15 K for H/V-polarization during thawing conditions.Yet,CMEM-FT does still not simulate the freezing transition sufficiently.

关 键 词：SOIL FREEZING MICROWAVE 

分 类 号：S15[农业科学—土壤学]