USDA Forest Service

North Central Research Station

Precipitation

Daily precipitation data from the National Climate Data Center's (NCDC) TD-3200 file, as corrected by NCDC's Validated Historical Daily Data project, was used to develop maps of average monthly precipitation amounts and occurrences of "extreme" precipitation events.

Monthly precipitation averages were computed from observed daily precipitation data at each observation site across the North-central and Northeastern US over the period 1950-1993.  A kriging interpolation procedure was used to provide data at locations between observation sites.  Because the kriging process does not explicitly take into account small-scale factors that can influence measured precipitation at the surface, the precipitation maps should only be used to provide an indication of the broad, regional-scale variation.  The maps should not be used as tools to identify monthly average precipitation amounts at specific points on the maps.

 
Average Precipitation
 Jan  January Average Precipitation  May  May Average Precipitation  Sep  September Average Precipitation
 Feb  February Average Precipitation  Jun  June Average Precipitation  Oct  October Average Precipitation
 Mar  March Average Precipitation  Jul  July Average Precipitation  Nov  November Average Precipitation
 Apr  April Average Precipitation  Aug  August Average Precipitation  Dec  December Average Precipitation
Note:  The color scale for each image is set to increase the contrast for that image.  Because of this, one must take care to consider the individual color scales when comparing two images.
 

There are many ways to define "extreme" precipitation.  For this Disturbance Climatology system, an extreme precipitation event was defined as a daily episode that resulted in two or more inches of precipitation.  Observed daily precipitation data at each observation site across the North-central and Northeastern US over the period 1950-1993 were analyzed to determine the total number of these extreme events that occurred in each month over the 44-year period.  As with the monthly average precipitation maps, a kriging interpolation scheme was used to generate the maps of extreme precipitation occurrence over the entire North-central and Northeastern US.  The extreme precipitation maps should only be used to provide a broad, regional-scale indication of where extreme precipitation events tend to occur in each month.

 
Extreme Precipitation
 

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USDA Forest Service - North Central Research Station
Last Modified: January 26, 2005