Soil moisture: The key to more accurate drought prediction?

Dr. Steven Quiring, Associate Professor in the Department of Geography at Texas A&M University

Drought is a major climatic hazard in the south central United States. The 2011 drought that affected the state of Texas and the southern United States was unprecedented in its intensity. Record dry conditions were present during much of the year, especially between March and August, and summer temperatures were the warmest ever recorded in Texas. Twelve-month rainfall was the lowest on record across much of western, central, and southern Texas, with many locations receiving less than 25% of normal precipitation. The record drought caused an estimated $7.62 billion in agricultural losses in Texas (~43% of mean annual agricultural receipts). Many rivers and reservoirs dried up and a number of towns in Texas ran out of drinking water. Wildfires ravaged the state destroying homes and lives. The drought also caused serious environmental damage and an estimated that 301 million trees died because of the drought. What caused this drought to occur? Why was this drought so severe? Myself and my team of students at Texas A&M University are studying what causes drought and developing seasonal climate forecasting tools that can be used to predict drought.

Building a Soil Moisture Database

Droughts are caused by a variety of factors including shifts in atmospheric circulation and sea-surface temperature. In addition, the characteristics of the land surface can also have an influence on the atmosphere and ultimately initiate or perpetuate drought conditions. One important land surface characteristic is soil moisture. When soils are drier than normal, less moisture is transferred to the atmosphere, triggering more heating of the surface and further exacerbating dry conditions. In other words, drought begets drought.

Soil moisture is a relatively slow varying component of the land-atmosphere system and therefore it is influences weather and climate on seasonal timescales. Because of this seasonal timescale, soil moisture can be effectively used to improve climate forecasts. However, our understanding of how soil moisture influences the climate is limited because of the relative lack of soil moisture measurements. My team at Texas A &M received funding from the National Science Foundation to build the North American Soil Moisture Database (soilmoisture.tamu.edu) to study what causes drought. To date, our team has collected more than 6 million soil moisture observations from nearly 2000 sites in Canada and the United States (map, left). We continue to search for additional stations, especially in Mexico, to increase the spatial density of the soil moisture observations. The Soil Moisture Database will provide us with the opportunity to systematically investigate how soil moisture varies in North America. The data being collected will also be used to help calibrate and validate estimates of soil-moisture content made from satellites and global climate models.

Regional Project, Global Implications

The ultimate goal of this project is help scientists better predict drought conditions and take steps to lessen its effects. The soil moisture data collection and resulting improvements in climate models will enhance our understanding of how soil moisture influences the climate on seasonal to inter-annual timescales. This knowledge is essential for developing more accurate climate forecasts.

Although the focus of this project is on North America, the soil moisture database will be available to the worldwide community, and the applications are innumerable in the agricultural, recreational, and land and water management spaces. This work in soil moisture and its application will be particularly useful to scientists in numerous disciplines as well as government agencies, farmers, and other stake holders around the world seeking to improve drought risk management through climate forecasting. This approach can be adapted to local and regional areas anywhere around the world and could drastically reduce the negative impacts seen by extreme drought conditions. Soil moisture has already been shown to play a major role in influencing the climate in many developing regions around the world including the Sahel, Brazil, India and China. Drought, through its impacts on agricultural production and water supply, is a global problem and improving our understanding of soil moisture will lead to improved drought prediction tools that can be used anywhere.

Further information about this project is available here:

• Conference presentations about the North American Soil Moisture Database
• Journal articles related to this research:
  • http://soilmoisture.tamu.edu/index.php/related-publications
  • http://soilmoisture.tamu.edu/index.php/project-publications