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Your
query was:
an="H21D-1380"
HR: 0800h
AN: H21D-1380
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
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