V. N. Bringi

Publications (4)0.63 Total impact

• Article: The differential reflectivity dual polarization method of rainfall measurements

  T. A. Seliga, V. N. Bringi
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  ABSTRACT: Several methods used to estimate rainfall rate-R were surveyed. The distribution N(D) of dropsizes is of central importance in determining the reflectivity factor-Z, attenuation rate-K, and R. With single parameter measurement techniques either of the remotely sensed parameters Z or K can be used to estimate R when gross assumptions on N(D) can be made. If N(D) can be described by a two parameter distribution, dual measurement techniques can better estimate R without invoking these coarse assumptions. Three techniques whereby two variables might be measured are reviewed: (1) dual wavelength in which Z and K are remotely measured; (2) dual polarization in which reflectivity is measured with two orthogonal polarizations; and (3) rain gage-radar combinations whereby in situ point measurements of R and radar measurement of Z or R are combined to obtain a better assessment of rain over areas between gages.
  11/1981;
• Article: Ground-truth measurement systems

  R. Serafin, T. A. Seliga, R. M. Lhermitte, J. A. Nystuen, S. Cherry, V. N. Bringi, R. Blackmer, G. M. Heymsfield
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  ABSTRACT: Ground-truth measurements of precipitation and related weather events are an essential component of any satellite system designed for monitoring rainfall from space. Such measurements are required for testing, evaluation, and operations; they provide detailed information on the actual weather events, which can then be compared with satellite observations intended to provide both quantitative and qualitative information about them. Also, very comprehensive ground-truth observations should lead to a better understanding of precipitation fields and their relationships to satellite data. This process serves two very important functions: (a) aiding in the development and interpretation of schemes of analyzing satellite data, and (b) providing a continuing method for verifying satellite measurements.
  11/1981;
• Article: Differential Reflectivity Measurements in Rain: First Experiments

  T.A. Seliga, V.N. Bringi, H.H. Al-Khatib
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  ABSTRACT: Results of the first measurements of differential reflectivity (ZDR) in rain are reported. ZDR = 10 log (ZH/ZV) dB involves copolar measurements of ZH and ZV, the radar reflectivity factors at horizontal and vertical polarizations, respectively. The data were obtained with the University of Chicago-Illinois State Water Survey (CHILL) radar facility in Oklahoma during Spring 1977 and confirmed theoretical expectations that ZDR should be positive, ranging between around 0-4 dB. By combining ZDR measurements with ZH, it is shown how estimates of N0 and D0, the parameters of an exponential raindrop size distribution, can be obtained. These estimates were subsequently used to compute rainfall rates as a function of range along a radar ray. These results illustrate that ZDR can have important applications in the quantitative, remote measurement of drop-size distributions and rainfall.
  Geoscience Electronics, IEEE Transactions on 11/1979;
• Article: Scattering from non-spherical hydrometeors

  V. N. Bringi, T. A. Seliga
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  ABSTRACT: A new theoretical formulation for scattering from a wide class of non-spherical hydrometeors has been developed recently using Waterman’s extended integral equation technique. The transition or T-matrix formulation is an exact solution to the scattering problem and computer programs have been developed to handle both homogeneous and imbedded bodies (e.g., a dielectric imbedded within another dielectric body). This theory will be briefly reviewed followed by sample computations of backscattering calculations of (a)oblate spheroidal icestones of varying sizes and eccentricities, (b)ice-stones with surface perturbations to model roughness, and (c)rough ice-stones covered with a thin coating of water. The method is realistically applicable for sizes up to D ≈3 λand for a wide range of dielectric constants. Comparisons with measurements of backscattering from a non-concentric dielectric-clad spherical perfect conductor is included. Récemment, en utilisant la technique de l’équation intégrale étendue de Waterman, on a développé une nouvelle formulation théorique de la diffusion par une classe d’hydrométéore non sphérique. La formulation de la transition ou matrice en T est une solution exacte des problèmes de la diffusion, aussi a- t- il été possible d’élaborer des programmes pour calculateurs s’appliquant à la fois aux corps homogènes et aux corps inhomogènes (par exemple un diélectrique enrobé dans un autre). Cette théorie sera brièvement exposée et suivie d’un exemple de calcul de rétrodiffusion de grêlons (a)en forme de sphéroïde aplati de différentes dimensions et excentricités, (b)avec perturbations de surface par rapport à la rugosité du modèle, (c)recouverts d’une fine pellicule d’eau. La méthode est parfaitement applicable à des grêlons dont le diamètre atteint 3 λet pour une gamme étendue de valeur de la constante de diélectrique. On établit des comparaisons avec des mesures de rétrodiffusion provoquée par une sphère parfaitement conductrice revêtue d’une couche non concentrique de diélectrique.
  annals of telecommunications - annales des télécommunications 04/1977; 32(11):392-397. · 0.63 Impact Factor