Monitoring Earth's Water Cycle From Space To Improve Weather Forecasting

By Don Comis
March 1, 2004

Tom Jackson, a hydrologist with the Agricultural Research Service's Hydrology and Remote Sensing Laboratory in Beltsville, Md., is the lead scientist for validation of the data to be collected by Hydros, a new satellite being developed by the National Aeronautics and Space Administration (NASA). By 2010, Hydros should be orbiting the Earth daily and providing an unprecedented monitoring of the planet's water cycle.

Data from Hydros will feed into weather and climate models that currently predict soil moisture for daily forecasts based on precipitation and other, indirect measurements. In the future, these models will have real-time, direct measurements of soil moisture from satellite sensors.

Soil moisture is among the top terrestrial environment measurements needed by the U.S. Departments of Agriculture, Commerce, Defense and Transportation. Changes in soil moisture drive the atmospheric circulation that spawns storms that bring rain to farmers--and hazards to military and civilian aircraft and to land vehicles--along with more general hazards, like flooding.

For more than a decade, ARS, NASA and other agencies have been testing soil moisture sensors in Oklahoma for use on Hydros. They started in Oklahoma partly because it has the easiest land to monitor from space: mostly bare in spring and summer, and covered with only grass or wheat in winter.

In 2002, Jackson and colleagues began a series of annual Soil Moisture Experiments (SMEX), starting with Iowa corn and soybean fields, where plant cover is a little harder to see through.

SMEX03 focused on the most difficult land of all--forests--in Alabama, Georgia, Oklahoma and Brazil. That campaign was typical of those conducted over the years. The scientists tested sensors on satellites and airplanes and compared sensor data to ground-level readings of moisture in plant leaves and soil, as well as to readings from a permanent network of monitoring towers.

Read more about the SMEX03 campaign in the March issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.