A Microwave Scattering Model of Vegetated Surfaces Based on Bor/dda and Nmm3d for Smap Mission

1. ABSTRACT In this paper, we present forward model of the microwave backscattering from a vegetated terrain at L band for application in the upcoming SMAP (Snow Moisture Active and Passive) mission. The objective of the SMAP mission is to provide global measurements of soil moisture and its freeze/thaw state [1]. These measurements will be used to enhance understanding of processes that link the water, energy and carbon cycles, and to extend the capabilities of weather and climate prediction models. One of the baseline retrieval algorithms of SMAP is snapshot algorithm which uses each radar acquisition independently to invert for soil moisture. The scattering properties of vegetation layer above the soil surface have a significant effect on the backscattering cross section in microwave remote sensing at L band [2]. The vegetated surface model includes a layer of cylinders and disks to represent the vegetation layer on top of the rough surface. The radar acquisition is sensitive to the vegetation water content (VWC) and physical structure of the vegetation. The physical-based forward scattering model is essential to understand the relationship between the vegetated surface and radar responses. The microwave scattering model in this paper is based on numerical solution of Maxwell equations using BOR and DDA for volume scattering and NMM3D (Numerical solution of Maxwell equations of 3D simulations) for rough surface scattering [3] [4].