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New Research on a Remotely Sensed Drought Severity Index

UM scientists, including CFC Professor Steve Running, just published the cover story in the Bulletin of the American Meteorological Society on satellite-based drought monitoring. The group, including Qiaozhen Mu, Maosheng Zhao, John Kimball and Running 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 asses global-scale drought. These indices measure precipitation, snowpack, streamflow, and other water supply indicators and are used by organizations such as the US Department of Agriculture. Many of these existing indices have some limitations -- they might only cover the United States or can't monitor 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 vegetation greenness and productivity -- a key indicator of drought conditions.

Their new drought severity index captures all of the major regional droughts from the past decade (the timeframe of data they used). This new drought severity index (DSI) showed drought conditions globally at 8-day, monthly, and annual intervals. They tested its performance first in the Asia and Pacific regions where some 23 million hectares are drought-prone -- 1/5 of the total rice production area in the region. Their annual interval DSI accurately documented the high frequency and very 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. This DSI does have some limitations, such as false drought detection in areas where vegetation was damaged by something other than drought.

With some further studies and evaluation of this new DSI, it will be 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. These are especially needed in parts of the world not covered well by current drought measurement technologies.

In 2012, Montana was impacted by drought; September was the driest in Montana history. Agricultural fields and topsoils were dry, rivers and streams ran low, and wildfires burned more than 1,000,000 acres of the state.  Right now, 34% of Montana is experiencing drought conditions and nearly 7% 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.