Areal estimation of intensity and frequency of summertime precipitation over a midlatitude region

Abstract

Spatially averaged precipitation characteristics derived from observations are needed to evaluate climate model generated precipitation intensity and frequency. In this study, observations from gauges and radar datasets are used to address three issues that are related to the areal estimation of intensity and frequency of summertime precipitation over the state of Ohio, USA. First, spatial averages of intensity and frequency from point precipitation are found to be very sensitive to the averaging method (i.e., spatial averaging followed by temporal averaging versus temporal followed by spatial averaging), particularly at lower precipitation thresholds. Second, approximately 30 gauges are found to be necessary to construct average intensity for a typical climate model grid, which is much higher than the gauge number required for average precipitation amount. Finally, the fractional area receiving rainfall is found to have a fairly linear relation with the precipitation amount averaged over the grid, but the slope differs between the gauge and radar data. Copyright 2006 by the American Geophysical Union.