Pedometrics

Global soil moisture map

http://www.nature.com/news/2010/100630/full/news.2010.325.html

The first satellite-derived map of global soil moisture has been unveiled today at the Living Planet Symposium, an Earth-observation conference being held this week in Bergen, Norway.

The Soil Moisture and Ocean Salinity (SMOS) mission — part of the European Space Agency’s (ESA) extended ‘living planet’ programme on Earth observation — was launched in November 2009. After a six-month commissioning and calibration period, the instrument became operational on 21 May.

Data from SMOS have now enabled researchers to assemble a comprehensive map of global soil moisture that covers all land areas of the world, except for frozen soils at high latitudes and in some mountain regions.

The map, generated on 24 June, depicts features such as the unusual current soil dryness in the southern United Kingdom, and the relative soil wetness in parts of western Africa caused by recent abundant convective rainfall.

The most surprising features on the map, however, are the relatively high soil-moisture values throughout the central United States, where scientists would have expected much drier soil at this time of year.

The SMOS satellite carries an interferometric radiometer that captures images of ‘brightness temperature’, a measure of the microwave radiation emitted from Earth’s surface. Complex algorithms are used to process the raw data and turn them into global soil-moisture maps every three days. Maps of ocean salinity, not yet released, will be produced every 30 days.

This comprehensive satellite map of soil moisture covers most land areas of the world, and was produced from data gathered by the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) mission. Its most surprising finding is the unusual wetness in western African and central US soils. (Dryness is indicated by blue, wetness by red.)