1 Spatial Modelling of the Terrestrial Environment - Georeferencial

4
Using Coupled Land Surface and
Microwave Emission Models to
Address Issues in Satellite-Based
Estimates of Soil Moisture
Eleanor J. Burke, R. Chawn Harlow and W. James Shuttleworth
4.1 Introduction
Atmospheric models would benefit from improved initialization and description of the
evolution of soil-moisture status, the main impact being through the local and regional
availability of the soil moisture that can reach the atmosphere by evaporation from the soil
or by transpiration from plants (Beljaars et al., 1996; Betts et al., 1996; Liu and Avissar,
1999; Koster et al., 2000). At present, the most practical method of improving the accuracy
of soil moisture in models is via the use of land data assimilation systems (LDAS).
LDAS are two-dimensional arrays of the land-surface scheme used in the relevant weatheror
climate-forecast model forced, to the maximum extent possible, by observations. The
resulting modelled soil moisture status is less biased by poor simulation of the near-surface
atmospheric forcing, especially precipitation. An example of an LDAS running in near
real-time can be found at (http://ldas.gsfc.nasa.gov): it consists of several physically based
land-surface models running on a common 0.125 ◦ -resolution grid covering the contiguous
United States. It is driven by common surface forcing fields, which include observed hourly
gauge-radar precipitation, and observed GOES-based satellite-derived surface solar insolation
(Mitchell et al., 2000). In coming years, such LDAS may well become the routine
mechanism by which many predictive weather and climate models will be initiated. If this
is so, it will be via assimilation into LDAS that other data relevant to the current status of the
Spatial Modelling of the Terrestrial Environment. Edited by R. Kelly, N. Drake, S. Barr.
C○ 2004 John Wiley & Sons, Ltd. ISBN: 0-470-84348-9.