TMI/TRMM surface soil moisture (LPRM) L3 1 day 25 km x 25 km nighttime V001 (LPRM_TMI_NT_SOILM3) at GES DISC

TMI/TRMM surface soil moisture (LPRM) L3 1 day 25 km x 25 km nighttime V001 is Level 3 (gridded) data set. Its land surface parameters, surface soil moisture, land surface (skin) temperature, and vegetation water content, are derived from passive microwave remote sensing data from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), using the Land Parameter Retrieval Model (LPRM). There are two files per day, one daytime and one nighttime, archived as two different products. This document is for the nighttime product. The data set covers the period from December 1997 to April 2015 (when the instruments on the TRMM satellite were shut down in preparation for its reentry into the earth's atmosphere).

The LPRM is based on a forward radiative transfer model to retrieve surface soil moisture and vegetation optical depth. The land surface temperature is derived separately from TMI's Ka-band (37 GHz). A unique feature of this method is that it can be applied at any microwave frequency, making it very suitable to exploit all the available passive microwave data from various satellites.

Input data are from the TMI Brightness Temperatures (1B-11) product, nighttime passes, as processed using LPRM (i.e., LPRM/TMI/TRMM Level 2 product, LPRM_TMI_SOILM2_V001).

TMI/TRMM 地表土壤水分（LPRM）L3级1日25km×25km夜间产品V001是一套三级（网格化）数据集。其包含的地表参数、地表土壤水分、地表（皮肤）温度以及植被含水量，均源自热带降雨测量任务（Tropical Rainfall Measuring Mission, TRMM）微波成像仪（TMI）的被动微波遥感数据，并通过土地参数反演模型（Land Parameter Retrieval Model, LPRM）反演得到。每日存在两个文件，分别对应日间与夜间观测，作为两款独立产品存档，本文档针对其中的夜间产品。本数据集的时间覆盖范围为1997年12月至2015年4月（TRMM卫星上的仪器在准备重返地球大气层时被关停）。

LPRM基于正向辐射传输模型，用于反演地表土壤水分与植被光学厚度。地表温度则单独通过TMI的Ka波段（37GHz）数据反演得到。该方法的独特特性在于可适配任意微波频率，因此能够充分利用各类卫星获取的所有可用被动微波数据。

输入数据来源于TMI亮温（1B-11）产品的夜间过境数据，经LPRM处理后生成（即LPRM/TMI/TRMM二级产品LPRM_TMI_SOILM2_V001）。