|Houser, P - UNIV. OF ARIZ.|
|Shuttleworth, W - UNIV. OF ARIZ|
|Famiglietti, J - UNIV. OF TEXAS|
|Gupta, H - UNIV. OF ARIZ|
|Syed, K - UNIV. OF ARIZ.|
Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1998
Publication Date: N/A
Interpretive Summary: Soil moisture is very important in semiarid regions. It is important for the survival of plants and has a significant influence on watershed runoff, evaporation and water use by plants. Remote sensing of soil moisture is possible in semiarid regions but such data is typically available infrequently. A model was developed to track the evolution of soil moisture over a basin. Various methods were tested to assimilate or bring in the remotely sensed soil moisture estimates to improve the model. It was found that an assimilation technique that is not too complex but utilizes all the observed remotely sensed data was the best.
Technical Abstract: The feasibility of synthesizing distributed fields of soil moisture by the novel application of four-dimensional data assimilation (4DDA) applied in a hydrological model is explored. Six, 160 square kilometers Push Broom Microwave Radiometer (PBMR) images gathered over the USDA-ARS Walnut Gulch experimental watershed in southeast Arizona were assimilated into the TOPLATS hydrologic model using several alternative assimilation procedures Modification of traditional assimilation methods was required to use these high-density PBMR observations. The images were found to contain horizontal correlations with length scales of several tens of kilometers, thus allowing information to be advected beyond the area of the image. Information on surface soil moisture also was assimilated into the subsurface using knowledge of the surface-subsurface correlation. Newtonian nudging assimilation procedures are preferable to other techniques because they nearly preserve the observed patterns within the sampled region, but also yield plausible patterns in unmeasured regions and allow information to be advected in time.