HR: 0800h
AN: H21D-1380    [Abstracts]
TI: Snow Water Equivalence Retrieval Using Dual-frequency and Polarization Radar
AU: * Shi, J
EM: shi@icess.ucsb.edu
AF: Institute for Computational Earth System Science, University of California, Santa Barbara, CA 93106 United States
AU: Cline, D
EM: Donald.Cline@noaa.gov
AF: National Operational Hydrologic Remote Sensing Center National Weather Service NOAA, 1735 Lake Drive West, Chanhassen, MN 55317 United States
AB: The study of snow has become an important area of research in the natural sciences, particularly in hydrology and climatology. Snow water equivalence is the most important parameter. Active microwave sensors are highly sensitive to the snowpack parameters of greatest interest to hydrologists. However, the studies have found that in general the sensitivities of radar measurements to dry snow water equivalence are very weak at C-band. Higher-frequency radar is needed to provide the reliable measurements for quantitative retrieval of snow water equivalence. In this study, we evaluated the feasibility of using the dual frequency (X-band 9.6 GHz and Ku-band 17GHz) and dual polarization (VV and VH) radar to estimate snow water equivalence. The components in this study include: 1. Using a model to establish a database for algorithm development: The simulation model is a second-order radiative transfer model where 1) the surface scattering components s are simulated by AIEM model for the co-polarized signals and the semi-empirical model of VH/VV for the cross-polarization signals, 2) the volume scattering component are calculated by the dense medium model with ellipsoid grain shape in order to simulate the cross-polarization signals, and 3) the bi-static IEM model is used for the boundary condition so that the interaction components between snow volume scattering and the surface scatterings can be correctly simulated. 2. Decomposition technique: we found that the depolarization factor VH/VV is proportional to the volume scattering and surface-volume scattering contributions and inversely relates the surface scattering contribution. Using this phenomenon, we developed a technique the estimate the snow volume and the ground surface scattering components. 3. Estimation of SWE using the volume scattering components: We found that the ratio of the volume scattering components from two frequencies can be written as a function of snow optical thickness at corresponding frequencies. In this way, the effects of snow volume scattering albedo can be minimized so that the optical thickness of snow pack at each frequency can be estimated. Then, the albedo and SWE can be estimated. 4. Estimation of the snowpack optical thickness using the ground surface scattering components, it is found that the surface scattering components of VV polarization at two Ku-band frequencies can also be used to estimate the snowpack optical thickness. This is due to the surface backscattering at snow-ground interface being almost identical since the surface is rough at 9.6 and 17 GHz. The difference in the surface scattering components (after passing snowpack) results from the difference in optical thickness of snowpack at these two frequencies. However, the other snow extinction properties are still required for estimation of SWE. It is found that the both the volume and surface scattering components are required for SWE estimation in order to cover a wide range snow properties.
DE: 0758 Remote sensing
DE: 0794 Instruments and techniques
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
SC: Hydrology [H]
MN: Fall Meeting 2005