13th Conference on Applied Climatology and the 10th Conference on Aviation, Range, and Aerospace Meteorology

Monday, 13 May 2002: 5:15 PM
Re-evaluation of extreme rainfall areal reduction factors
Robert J. Allen, Northeast Regional Climate Center, Cornell Univ., Ithaca, NY; and A. T. DeGaetano
Poster PDF (606.1 kB)
The 24-hour areal reduction factor (ARF) is re-evaluated using 47 years (1949-1995) of rainfall data from the Cooperative Observer (COOP) network for two diverse locations in the Northeast, northern New Jersey and West Virginia, with basin sizes ranging from 100 to 3000 km 2 . The variation of ARF, defined as the ratio of mean areal precipitation (MAP) to average point precipitation, using different spatial averaging techniques is investigated. These methods include Thiessen polygons, inverse distance weighting and kriging, as well as standard averaging. The functional dependence of ARF on return period is also explored. Using the Beta-P distribution, point and areal rainfall for several return periods are estimated. Preliminary analysis shows that as return period increases, ARF generally decreases. To quantify the accuracy of our calculated ARF, various supplemental data sets, including the Integrated Flood Observing and Warning System (IFLOWS) network and the New Jersey Home Network, are used in conjunction with the COOP stations to calculate ARF based on the last 6 years (1996-2001). In addition to increasing the spatial density of point estimates, radar estimates of MAP are also used during the period 1996-2001.

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