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Agricultural Drought Indices - US Department of Agriculture

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Figure 1. The February 8, 2011, <strong>US</strong> <strong>Drought</strong> Monitor.<br />

The North American <strong>Drought</strong> Monitor (NADM)<br />

Three years after the <strong>US</strong>DM was launched, the North American <strong>Drought</strong> Monitor (Lawrimore et al.<br />

2002) (Figure 2) debuted in 2002 as an “experimental” monthly product that is forged out <strong>of</strong> a<br />

partnership between several entities in Canada, Mexico, and the United States. Since that time,<br />

the experimental label has been shed. As with the U.S. <strong>Drought</strong> Monitor, the NADM blends<br />

science and art. There is no one “correct” way to measure drought. <strong>Drought</strong> indices are used to<br />

detect and measure droughts, but different indices measure drought in different ways, and no<br />

single index works under all circumstances (Heim 2002). The ranking percentile principal is the<br />

same, but the inputs vary slightly depending on which parameters are readily available to the<br />

respective agencies involved in each country. As the process stands now, each country follows<br />

the same basic methodology, utilizing their own indicators to depict drought conditions within their<br />

borders. The monthly author (which rotates between the three countries) is then responsible for<br />

working out the merging <strong>of</strong> the GIS shape files and reconciling any disputes along the borders.<br />

Impact and data information are exchanged in working out any differences in an iterative fashion<br />

until all issues are resolved. More information and details on the NADM can be found at<br />

http://www.ncdc.noaa.gov/temp-and-precip/drought/nadm/index.html.<br />

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