National Climatic Data Center, 16 August 2004

Several climate indicators are used to monitor drought in the United States. These indicators include:

• the Palmer Z Index, Palmer Drought Severity Index, and Palmer Hydrological Drought Index

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• the one-month, two-month, three-month, six-month, nine-month, 12-month, and 24-month Standardized Precipitation Index

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• maps showing the percent of normal precipitation for airport stations for the current month, last three months, and year-to-date

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• the statewide precipitation ranks for current month (short-term) and 3-months, 6-months, and 12 months (longer-term)

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• the percent of normal precipitation maps, based on Cooperative Network and other station reports, provided by the NOAA Regional Climate Centers (HPRCC)

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• the precipitation amount and percent of normal precipitation maps, based on an algorithm that incorporates the effects of topography, provided by the Spatial Climate Analysis Service of the Oregon Climate Service

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• NOAA satellite observations of vegetation health are most effective during the warm season months. The beginning of August VHI (Vegetation Health Index) map showed pockets of vegetative stress across parts of the West and northern High Plains in the contiguous U.S., and across much of eastern Alaska into adjoining Yukon Territory in Canada:
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• the short-term surface wetness anomaly map computed by NOAA's National Climatic Data Center from the Special Sensor Microwave Imager (SSMI), a polar orbiting satellite with global coverage. (During the cold season, the presence of snow cover complicates the SSMI analyses. SSMI-based temperature anomalies cannot be computed over a snow-covered area.) The wetness anomaly product shows surface wetness conditions, which may reflect the presence (or absence) of rainfall as well as meltwater from snowpack.

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• modeled runoff, evaporation, and soil moisture conditions as calculated by the National Weather Service

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• modeled soil moisture conditions in the top and deeper soil layers as calculated by the Midwest Regional Climate Center

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• the percent of average precipitation map for the water year to date for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center

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• the USGS July daily streamflow and monthly mean streamflow maps

Climate Services Division
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4876
phone: 828-271-4800
email: ncdc.info@noaa.gov

Richard Heim
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Richard.Heim@noaa.gov