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Comparison of Precipitation Estimation Using Single- and Dual-Frequency Wind Profilers: Simulations and Experimental Results

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  • 1 Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
  • | 2 Bureau of Meteorology Research Center, Melbourne, Victoria, Australia
  • | 3 JCET, University of Maryland, Baltimore, Maryland
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Abstract

The advantages and disadvantages of single-frequency (50 MHz) and dual-frequency (50 and 915 MHz) wind profiler drop size distribution retrievals are discussed by comparing retrievals of median volume drop diameter and rain rates. Simulated data, as well as observational data, show that the median volume diameter estimated from the single-frequency technique is biased higher than what is retrieved using the dual-frequency technique. This result is due to the strong 50-MHz Bragg scatter signal that masks the small drop (low fall velocity) part of the precipitation spectrum. The error in the estimation of the median volume diameter increases markedly with increasing vertical air motion spectral width. The error in the estimation of the median volume diameter is minimum for median volume diameters ranging from 0.5 to about 2.5 mm for the dual-frequency technique and 1.2 to about 2.5 mm for the single-frequency technique. The comparison of retrieved rain rates with rain gauge data shows a very good agreement for both techniques, but it was not always possible to retrieve precipitation information using the single-frequency technique.

Corresponding author address: Dr. Deepak Rajopadhyaya, CIRES, University of Colorado, Campus Box 216, Boulder, CO 80309.

Email: drajopad@numbat.colorado.edu

Abstract

The advantages and disadvantages of single-frequency (50 MHz) and dual-frequency (50 and 915 MHz) wind profiler drop size distribution retrievals are discussed by comparing retrievals of median volume drop diameter and rain rates. Simulated data, as well as observational data, show that the median volume diameter estimated from the single-frequency technique is biased higher than what is retrieved using the dual-frequency technique. This result is due to the strong 50-MHz Bragg scatter signal that masks the small drop (low fall velocity) part of the precipitation spectrum. The error in the estimation of the median volume diameter increases markedly with increasing vertical air motion spectral width. The error in the estimation of the median volume diameter is minimum for median volume diameters ranging from 0.5 to about 2.5 mm for the dual-frequency technique and 1.2 to about 2.5 mm for the single-frequency technique. The comparison of retrieved rain rates with rain gauge data shows a very good agreement for both techniques, but it was not always possible to retrieve precipitation information using the single-frequency technique.

Corresponding author address: Dr. Deepak Rajopadhyaya, CIRES, University of Colorado, Campus Box 216, Boulder, CO 80309.

Email: drajopad@numbat.colorado.edu

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