University of Montana scientists, including Regents Professor of Ecology Steve Running, recently published the cover story for the Bulletin of the American Meteorological Society on satellite-based drought monitoring.
The group, including Qiaozhen Mu, Maosheng Zhao, John Kimball and Running, all from UM, and Nathan McDowell from the Los Alamos National Laboratory, developed a satellite-sensed global drought severity index. Accurate mapping and monitoring of drought severity worldwide is needed as water becomes a more valuable and scarce resource.
The scientists first reviewed strengths and weaknesses of common indices already used to monitor and assess global-scale drought. These indices measure precipitation, snowpack, stream flow and other water-supply indicators and are used by the U.S. Department of Agriculture and other similar organizations. Many existing indices also have some limitations, such as only covering the United States or not monitoring long-term droughts well.
The authors propose a new framework for measuring global drought severity that uses remotely sensed data from NASA’s Terra and Aqua satellites. Those satellites collect data from vegetated surfaces to measure changes in greenness and productivity, key indicators of drought conditions.
Their new drought severity index (DSI) includes data from all of the major regional droughts from the past decade. The DSI showed conditions globally at eight-day, monthly and annual intervals. They tested its performance first in the Asia and Pacific regions, where some 23 million hectares – one-fifth of the total rice production area in the region – are drought-prone. Their annual interval DSI accurately documented the high-frequency, intense droughts of this region.
The annual DSI also successfully reported other extreme droughts, such as the 2003 heat wave in Europe and the Great Russian Heat Wave in 2010. The DSI does have some limitations, such as false drought detection in areas where vegetation was damaged by something other than drought.
With further studies and evaluation, the new DSI will become a valuable tool to detect and monitor drought globally. This DSI and similar global products derived from satellite data could be useful for regional drought assessment and mitigation efforts, especially in parts of the world not covered well by current drought-measurement technologies.
In 2012, drought hit Montana, with September being the driest month in state history. Agricultural fields and topsoils were dry, rivers and streams ran low, and wildfires burned more than 1 million acres. Right now, 34 percent of Montana is experiencing drought conditions and nearly 7 percent of the state is in extreme drought. The drought outlook summary released by the National Weather Service on Jan. 17 also states that range and pasture feed conditions in December were rated poor to very poor. The Montana Climate Office intends to produce a weekly version of this DSI covering the entire state beginning in April.