Estimation of Areal Distribution of Rain Intensities by Radar & Rain Gauges

Project Number:

95R-01

Project Duration:

24 months

Dates:

May 1, 1995 to April 30, 1997

Institution of Principle Investigator while on this project:

Hebrew University of Jerusalem

Investigators (most current known information)

Rosenfeld, Daniel (PI)

Associate Professor, Hebrew University of Jerusalem, The Institute of Earth Sciences, Jerusalem 91904, ISRAEL

TEL: +972-2-658-5821, FAX: +972-8-651-2372, Email: daniel@vms.huji.ac.il

Morin, Joseph

Soil Conservation Department, Rupin Institute Post, Soil Erosion Research Station, Emek Hefer 60960, ISRAEL

Proposal Abstract

The objectives of the work were to provide the most accurate possible radar rainfall measurements for an area of 2000 km2 located in the southern part of Israel. Transforming the radar reflectivity to rain intensity was done by the classic method of power-law Z-R, with periodical correction by the cumulative rainfall as measured by 56 integrating rain gauges. This method was preferred over the WPPM method because the radar internal calibration was found to be unstable and shifted between rain periods. Therefore a Z-R had to be established for each individual rainstorm. The calibration which was done separately for two periods gave reasonable results. The ratio R/G (Radar/Gauge) daily cumulative rainfall, for the different stations averaged unity by the definition of the method, with about St. error of 20%. Radar's storm intensity analysis, for a few case studies, also shows close agreement with the ground recorder gauges. The frequency distribution as well as the intensity segment sequences were quite similar.

The temporally and spatially detailed rainfall data provided by radar enables good analysis of rainfall-runoff events in watershed hydrology. In using radar data for hydrological purposes the scale at which the data is represented should be considered, since watershed size dominates the outlet runoff characteristics.

Outcome

Articles in Journals

Rosenfeld, D. and C. W. Ulbrich. 2003. "Cloud microphysical properties, processes and rainfall estimation opportunities." In Radar and Atmospheric Science: A Collection of Essays in Honor of David Atlas, eds. Roger M. Wakimoto and Ramesh Srivastava, Chapter 10. Meteorological Monographs 52:237-258 AMS.

Rosenfeld, D. and E. Amitai. 1998. "Comparison of WPMM vs. regression for evaluating Z-R relationships." Journal of Applied Meteorology 37:1241-1249.

Books

Atlas, D., D. Rosenfeld and A.R. Jameson. 1997. "Evolution of radar rainfall measurement: Steps and Mis-steps." In Weather Radar Technology for Water Resources Management. eds. B. Braga and O. Massambani, Chapter 1:1-60. UNESCO Press, Montevideo.

Rosenfeld, D. and C. G. Collier. 1999. "Estimating surface precipitation." In Global Energy and Water Cycles. eds. K. A. Browning and R. J. Gurney, Chapter 4.1:124-133. Cambridge University Press.