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Potential L-Band Aquarius Radiometer and Scatterometer Soil Moisture Products from an Observing System Simulation Experiment

Luo, Y., Houser, P. R., Anantharaj, V. G., Fan, X., Dabbiru, L., Turlapaty, A.C., Aanstoos, J.V., & DeLannoy, G. J. (2008). Potential L-Band Aquarius Radiometer and Scatterometer Soil Moisture Products from an Observing System Simulation Experiment. 2008 Fall Meeting. San Francisco, California, USA: American Geophysical Union.


Research on the applications of remote sensing techniques has demonstrated the capabilities of microwave observations at L-band wavelength for measuring surface soil moisture. A new source of L-band sensor data, provided by instruments board on Aquarius satellite, is introduced and investigated. Planned for launching in 2010, though primarily dedicated to measuring sea surface salinity (SSS), Aquarius has the potential for providing global surface soil moisture measurements. Based on Aquarius frequencies and viewing characteristics, we are working on generation of the potential Aquarius soil moisture retrieval data, and evaluation and optimization of the impacts of the data products using the NASA's Land Information System (LIS), a powerful land modeling and assimilation system. This simulation of the Aquarius soil moisture retrieval process is being accomplished by means of an OSSE approach. Following the similar effort that resulted in the Hydros OSSE study, we investigate the capability of near feature Aquarius L-band passive and active sensor measurements for monitoring earth's soil moisture globally. Aquarius OSSE includes four key components for simulating soil moisture retrievals: a) land surface modeling (nature run) using LIS-based CLM; b) microwave emission and backscattering modeling; c) orbit and sensor modeling and d) soil moisture retrieval modeling. These components simulate major physical processes involved in data acquisition by the Aquarius radiometer and scatterometer measurements and data conversion to geophysical variables such as soil moisture fields. The first two modeling procedures are conducted at finer 0.125° grid spacing, and the rest of two procedures at coarser 1°, approximately 100 km satellite footprint scale. Linear aggregation is applied for the grid conversion. Aquarius OSSE is carried out over the central United States including the Red Arkansas river basin. One-year simulation period between October 2002 and September 2003 was selected to insure a fair test of the retrieval algorithm performance considering seasonal variations of diverse land surface conditions. We will present all kinds of possible soil moisture maps derived from coarse resolution Aquarius data depending on frequencies and incidence angles. We will make series of comparison of the synthetically derived soil moisture estimates against the CLM nature run to characterize the uncertainties due to land surface heterogeneity, instrument error, and parameter estimates. This comparison will provide new insights into the values of potential L-band Aquarius observations.

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