Analysis of Satellite-derived Soil Moisture and Previous-Time Precipitation

Global soil moisture datasets are currently available from several passive microwave

(PMW) radiometer systems, notably the Advanced Microwave Scanning Radiometer

(AMSR-E) onboard Aqua and the WindSat polarimetric radiometer onboard the Coriolis

satellite. Soil moisture varies spatially on scales from tens of centimeters to hundreds of

kilometers due to variations in soil properties, topography, land cover and precipitation.

Precipitation provides the largest influence to the short-term evolution of soil moisture

and the longer-time vegetation water content. Typically, the local morning overpass of

swath-limited sun-synchronous satellites is used for soil moisture processing, and does

not take full advantage of additional information between the infrequent and intermittent

satellite revisits. In particular, knowledge of the evolution of precipitation during a time

window prior to the satellite observation may be useful to dynamical soil moisture

estimation techniques from future satellite-based programs, such as the Soil Moisture

Active/Passive (SMAP) mission. Additionally, improved knowledge of the underlying

soil moisture and other geophysical properties are needed to improve over-land

precipitation estimation from space-based PMW-based radiometers/radar systems, such

as the Tropical Rainfall Measuring Mission (TRMM) and the future Global Precipitation

Mission (GPM).

In this presentation, we show the time evolution of soil moisture from a regions with

different land classifications, using data from a recently developed physically based

WindSat algorithm which retrieves soil moisture, vegetation water content and land

surface temperature using polarized 10, 18, and 37 GHz channel measurements. The

evolution is analyzed together with precipitation produced by a variety of recent

developed high resolution precipitation products (CMORPH, 3B42, and NRL-Blend),

which have the capability to produce 3-hourly maps of precipitation at similar spatial

scales of the WindSat land products. The analysis reveals details on how soil moisture

encompassing different land characteristics responds differently to the onset, frequency

and duration of precipitation, and how this response changes following extended periods

of no precipitation.