Synergistic Evaluation of Passive Microwave and Optical/IR Data for Modelling Vegetation Transmissivity towards Improved Soil Moisture Retrieval.

Mina Moradizadeh,George P Petropoulos,Prashant K Srivastava

doi:10.3390/s22041354

Abstract

Vegetation cover and soil surface roughness are vital parameters in the soil moisture retrieval algorithms. Due to the high sensitivity of passive microwave and optical observations to Vegetation Water Content (VWC), this study assesses the integration of these two types of data to approximate the effect of vegetation on passive microwave Brightness Temperature (BT) to obtain the vegetation transmissivity parameter. For this purpose, a newly introduced index named Passive microwave and Optical Vegetation Index (POVI) was developed to improve the representativeness of VWC and converted into vegetation transmissivity through linear and nonlinear modelling approaches. The modified vegetation transmissivity is then applied in the Simultaneous Land Parameters Retrieval Model (SLPRM), which is an error minimization method for better retrieval of BT. Afterwards, the Volumetric Soil Moisture (VSM), Land Surface Temperature (LST) as well as canopy temperature (TC) were retrieved through this method in a central region of Iran (300 × 130 km2) from November 2015 to August 2016. The algorithm validation returned promising results, with a 20% improvement in soil moisture retrieval.

Highlights

Received: 28 October 2021Volumetric Soil Moisture (VSM) content is the volume of water accumulated in soil pores, usually recorded as a percent or volumetric ratio for different depths.The knowledge of soil moisture content is essential in several applications in the field of ecological, hydrological and meteorological processes [1]
Since the Qp method is used in the Simultaneous Land Parameters Retrieval Model (SLPRM) algorithm to model the roughness effects, the main purpose of this study is to minimize the effect of vegetation on the Advanced Microwave Scanning Radiometer-2 (AMSR2) microwave Brightness Temperature (BT), by applying appropriate modelling for the retrieval of VSM content along with
Soil moisture, canopy temperature and land surface temperature were obtained by applying the SLPRM model at different levels of vegetation density, validated by using ground sensor data like soil moisture and soil temperature

Summary

Introduction

Volumetric Soil Moisture (VSM) content is the volume of water accumulated in soil pores, usually recorded as a percent or volumetric ratio (i.e., cm3 /cm3 ) for different depths. The knowledge of soil moisture content is essential in several applications in the field of ecological, hydrological and meteorological processes [1]. Due to high temporal and spatial variability of soil moisture and temperature, remote sensing is the only rational instrument to measure and monitor them in an efficient manner, in a wide range of areas [3,4]. Microwave (MW) remote sensing has great potential for measuring and monitoring of soil characteristics. Different methodologies are found in the literature to explain the rationale behind the estimation of surface soil characteristics accurately [5]

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