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Analysis of Video Disdrometer and Polarimetric Radar Data to Characterize Rain Microphysics in Oklahoma

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  • 1 School of Meteorology, University of Oklahoma, Norman, Oklohoma
  • | 2 National Center for Atmospheric Research,* Boulder, Colorado
  • | 3 Cooperative Institute for Mesoscale Meteorological Studies, Norman, Oklahoma
  • | 4 National Center for Atmospheric Research, Boulder, Colorado
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Abstract

In this paper, data from three 2-dimensional video disdrometers (2DVDs) and an S-band polarimetric radar are used to characterize rain microphysics in Oklahoma. Sampling errors from the 2DVD measurements are quantified through side-by-side comparisons. In an attempt to minimize the sampling errors, a method of sorting and averaging based on two parameters (SATP) is proposed. The shape–slope (μ–Λ) relation of a constrained gamma (C-G) model is then refined for the retrieval of drop size distributions (DSDs) from polarimetric radar measurements. An adjustable term that is based on observed radar reflectivity and differential reflectivity is introduced to make the C-G DSD model more applicable. Radar retrievals using this improved DSD model are shown to provide good agreement with disdrometer observations and to give reasonable results, including in locations near the leading edge of convection where poorly sampled large drops are often observed.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation

Corresponding author address: Qing Cao, School of Meteorology, University of Oklahoma, NWC Suite 5200, David L. Boren Blvd., Norman, OK 73072. Email: qingcao@ou.edu

Abstract

In this paper, data from three 2-dimensional video disdrometers (2DVDs) and an S-band polarimetric radar are used to characterize rain microphysics in Oklahoma. Sampling errors from the 2DVD measurements are quantified through side-by-side comparisons. In an attempt to minimize the sampling errors, a method of sorting and averaging based on two parameters (SATP) is proposed. The shape–slope (μ–Λ) relation of a constrained gamma (C-G) model is then refined for the retrieval of drop size distributions (DSDs) from polarimetric radar measurements. An adjustable term that is based on observed radar reflectivity and differential reflectivity is introduced to make the C-G DSD model more applicable. Radar retrievals using this improved DSD model are shown to provide good agreement with disdrometer observations and to give reasonable results, including in locations near the leading edge of convection where poorly sampled large drops are often observed.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation

Corresponding author address: Qing Cao, School of Meteorology, University of Oklahoma, NWC Suite 5200, David L. Boren Blvd., Norman, OK 73072. Email: qingcao@ou.edu

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