Soil Moisture:
Science Motivation

Satellite Validation

Walnut Gulch PBMR data

• General: Satellite microwave sensors that might be used to study global soil moisture are just now being launched and are still being flight tested (Canada's RADARSAT, ERS-2). Aircraft microwave sensors, like NASA's Push-Broom Microwave Radiometer (PBMR), illustrate the kind of data we might get from space. Note the large contrast between DRY and WET conditions and how the WET pattern follows the underlying contours of Anticedent Precipitation Index (API) contours indicating mm of residual rainfall. Microwave sensors are only sensitive to near-surface (0-5 cm) soil moisture in open or sparsely covered areas and this is why we would like students to collect their data in these types of locations.

• Specific: The PBMR made about seven 15 km long passes over the ARS Walnut Gulch Experimental Watershed (in AZ) on two dates in 1990. Day-of-Year 212 was hot and dry (except in the town of Tombstone, lower left); while DOY 216 was cool and wet after two rainfall events, indicated qualitatively by the API contours.

Agricultural and Vegetation Needs

Russian Soil Moisture Data

• General: Student-derived near-surface soil moisture can be contoured and used to produce maps, like this one, that will be valuable for studying seasonal variations in soil moisture and could be used to initialize GCM's. Maps of soil moisture like this one are very rare, particularly in today's world as all major governments are cutting funding of base-line environmental data collection.

• Specific: An extensive network of agricultural soil moisture stations over the Former Soviet Union have been interpolated to illustrate the major seasonal and regional differences in soil moisture observed over many years. This illustration is derived from depth-profile measurements that estimate the amount of water in a 2 meter column that would be available for plant growth.

Spring soil moisture map

• General: by Winnipeg Climate Center, Canadian Dept. of Environment
• Specific:

Improving Global Climate Models

Earth System Science

• General:
• Specific:
  The Importance of Soil Moisture in Weather & Climate Prediction

Global Hydrologic Cycle

• General: Water is transported by a variety of processes. Try to identify the fluxes (movements) and reservoirs (storages) in this diagram.

• Specific:

Hydrologic Scales

• General:
• Specific:

Bretherton Diagram

• General: Soil Moisture data is useful to initialize and validate general circulation models (GCM's). Even if our data is not wide-spread, we can compare local concentrations of measurements with model output at that location.

• Specific: This schematic diagram illustrates the processes scientists try to model at the land-surface and couple to atmospheric transfers of energy and mass. What GLOBE observations will you be making and where do they fit in to the big picture?