The 2012 event is what experts call a flash drought, meaning that it evolved quickly and unexpectedly. Low soil moisture was further depleted by the heat wave that started in May, and drought abruptly followed. By about May 5 the core regions of drought began to appear on the plant stress map earlier than the signs of drought appeared in other indicators, such as rainfall measurements.
"We think there's some early-warning potential with these plant stress maps, alerting us as the crops start to run out of water," Anderson says. Signals of plant stress may often appear first in satellite-derived maps of vegetation temperature before the crops have actually started to wilt and die. "The earlier we can learn things are turning south, presumably the more time we have to prepare for whatever actions might be taken."
For example, farmers may decide they need to buy supplemental feed from outside the drought-affected area to support their livestock, or they may need to adjust contract or insurance decisions.
The U.S. Drought Monitor already uses a combination of indices, such as rainfall, to describe drought conditions each week. The monitor currently does not include plant stress, but the potential is being explored. "Plant stress is one representation of drought impacts, and the drought monitoring community agrees that you can't do this with just one tool you need a lot of different tools," Anderson says.
Plant stress information has the potential to improve the skill of existing forecasts that predict drought out to weeks or months. Also, because the plant stress information is derived from satellites, it can describe drought conditions in areas where rain gauge and radar networks are sparse -- and it can do so at the scale of individual fields.
To produce th
|Contact: Kathryn Hansen|
NASA/Goddard Space Flight Center