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by Adirosi, E., Gorgucci, E., Baldini, L. and Tokay, A.
Abstract:
To date, one of the most widely used parametric forms for modelling raindrop size distribution (DSD) is the three-parameter gamma. The aim of this paper is to analyse the error of assuming such parametric form to model the natural DSDs. To achieve this goal, a methodology is set up to compare the rain rate obtained from a disdrometer-measured drop size distribution with the rain rate of a gamma drop size distribution that produces the same triplets of dual-polarization radar measurements, namely reflectivity factor, differential reflectivity, and specific differential phase shift. In such a way, any differences between the values of the two rain rates will provide information about how well the gamma distribution fits the measured precipitation. The difference between rain rates is analysed in terms of normalized standard error and normalized bias using different radar frequency, drop shape-size relations, and disdrometer integration time. The study is performed using four datasets of DSDs collected by two-dimensional video disdrometers deployed in Huntsville (Alabama), in three different pre-launch campaigns of the NASA/JAXA GPM ground validation programme including the HyMeX SOP 1 field campaign in Rome. The results show that differences in rain rates of the disdrometer DSD and the gamma DSD determining the same dual polarization radar measurements exist and exceed those related to the methodology itself and disdrometer error sampling, supporting the finding that there is an error associated to gamma DSD assumption.
Reference:
Adirosi, E., Gorgucci, E., Baldini, L. and Tokay, A., 2014: Evaluation of Gamma Raindrop Size Distribution assumption through comparison of rain rates of measured and radar-equivalent gamma DSDJournal of Applied Meteorology and Climatology, 53, 1618-1635.
Bibtex Entry:
@Article{Adirosi2014,
  Title                    = {Evaluation of Gamma Raindrop Size Distribution assumption through comparison of rain rates of measured and radar-equivalent gamma DSD},
  Author                   = {Adirosi, E. and Gorgucci, E. and Baldini, L. and Tokay, A.},
  Journal                  = {Journal of Applied Meteorology and Climatology},
  Year                     = {2014},
  Pages                    = {1618-1635},
  Volume                   = {53},

  Abstract                 = {To date, one of the most widely used parametric forms for modelling raindrop size distribution (DSD) is the three-parameter gamma. The aim of this paper is to analyse the error of assuming such parametric form to model the natural DSDs. To achieve this goal, a methodology is set up to compare the rain rate obtained from a disdrometer-measured drop size distribution with the rain rate of a gamma drop size distribution that produces the same triplets of dual-polarization radar measurements, namely reflectivity factor, differential reflectivity, and specific differential phase shift. In such a way, any differences between the values of the two rain rates will provide information about how well the gamma distribution fits the measured precipitation. The difference between rain rates is analysed in terms of normalized standard error and normalized bias using different radar frequency, drop shape-size relations, and disdrometer integration time. The study is performed using four datasets of DSDs collected by two-dimensional video disdrometers deployed in Huntsville (Alabama), in three different pre-launch campaigns of the NASA/JAXA GPM ground validation programme including the HyMeX SOP 1 field campaign in Rome. The results show that differences in rain rates of the disdrometer DSD and the gamma DSD determining the same dual polarization radar measurements exist and exceed those related to the methodology itself and disdrometer error sampling, supporting the finding that there is an error associated to gamma DSD assumption.},
  Copublication            = {4: 3 It, 1 USA},
  Doi                      = {10.1175/JAMC-D-13-0150.1},
  Keywords                 = {Precipitation, Drop size distribution, Radars/Radar observations},
  Owner                    = {hymexw},
  Timestamp                = {2014.04.01},
  Url                      = {http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-13-0150.1}
}