Estimation of Raindrop Size Distribution Parameters from Polarimetric Radar Measurements

Estimation of raindrop size distribution over large spatial and temporal scales has been a long-standing goal of polarimetric radar. Algorithms to estimate the parameters of a gamma raindrop size distribution model from polarimetric radar observations of reflectivity, differential reflectivity, and specific differential phase are developed. Differential reflectivity is the most closely related measurement to a parameter of the drop size distribution, namely, the drop median diameter (D0). The estimator for D0 as well as other parameters are evaluated in the presence of radar measurement errors. It is shown that the drop median diameter can be estimated to an accuracy of 10%, whereas the equivalent intercept parameter can be estimated to an accuracy of 6% in the logarithmic scale. The estimators for the raindrop size distribution parameters are also evaluated using disdrometer data based simulations. The disdrometer based evaluations confirm the accuracy of the algorithms developed herein.

[1]  V. Chandrasekar,et al.  Polarimetric Doppler Weather Radar: Principles and Applications , 2001 .

[2]  H. R. Pruppacher,et al.  A wind tunnel investigation of the internal circulation and shape of water drops falling at terminal velocity in air , 1970 .

[3]  Haldun Direskeneli,et al.  Dual-Polarzation Radar Estimation of Rainfall Parameters Compared with Ground-Based Disdrometer Measurements: October 29, 1982 Central Illinois Expenment , 1987, IEEE Transactions on Geoscience and Remote Sensing.

[4]  K. Beard,et al.  A New Model for the Equilibrium Shape of Raindrops , 1987 .

[5]  Karen Andsager,et al.  Laboratory Measurements of Axis Ratios for Large Raindrops , 1999 .

[6]  R. Gunn,et al.  THE TERMINAL VELOCITY OF FALL FOR WATER DROPLETS IN STAGNANT AIR , 1949 .

[7]  K. Beard,et al.  A field study of raindrop oscillations. Part I: Observation of size spectra and evaluation of oscillation causes , 1996 .

[8]  C. Ulbrich.  Natural Variations in the Analytical Form of the Raindrop Size Distribution , 1983 .

[9]  V. N. Bringi,et al.  Potential Use of Radar Differential Reflectivity Measurements at Orthogonal Polarizations for Measuring Precipitation , 1976 .

[10]  Eugenio Gorgucci,et al.  Measurement of Mean Raindrop Shape from Polarimetric Radar Observations , 2000 .

[11]  V. Chandrasekar,et al.  Raindrop axis ratios and size distributions in Florida rainshafts: an assessment of multiparameter radar algorithms , 1998, IEEE Trans. Geosci. Remote. Sens..

[12]  Eugenio Gorgucci,et al.  Specific Differential Phase Estimation in the Presence of Nonuniform Rainfall Medium along the Path , 1999 .

[13]  Y. Antar,et al.  On the relationship between the degree of preferred orientation in precipitation and dual‐polarization radar echo characteristics , 1987 .

[14]  R. C. Srivastava,et al.  Doppler Radar Observations of Drop-Size Distributions in a Thunderstorm , 1971 .

[15]  M. Sachidananda,et al.  Rain Rate Estimates from Differential Polarization Measurements , 1987 .

[16]  V. N. Bringi,et al.  Differential reflectivity and differential phase shift: Applications in radar meteorology , 1978 .

[17]  Jacques Testud,et al.  The Rain Profiling Algorithm Applied to Polarimetric Weather Radar , 2000 .

[18]  P. T. Willis,et al.  Functional fits to some observed drop size distributions and parameterization of rain , 1984 .

[19]  Carlton W. Ulbrich,et al.  Rainfall Microphysics and Radar Properties: Analysis Methods for Drop Size Spectra , 1998 .

[20]  A. R. Jameson.  Microphysical Interpretation of Multiparameter Radar Measurements in Rain. Part III: Interpretation and Measurement of Propagation Differential Phase Shift between Orthogonal Linear Polarizations , 1985 .

[21]  J. Joss,et al.  Ein Spektrograph für Niederschlagstropfen mit automatischer Auswertung , 1967 .