Advances in Geosciences
www.adv-geosci.net
1680-7340
1680-7359
16
Observation, Prediction and Verification of Precipitation (EGU Session 2007)
2008
10.5194/adgeo-16-27-2008
http://www.adv-geosci.net/16/27/2008/
http://www.adv-geosci.net/16/27/2008/adgeo-16-27-2008.html
http://www.adv-geosci.net/16/27/2008/adgeo-16-27-2008.pdf
27
32
2008-04-09
Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths
F. Teschl
franz.teschl@tugraz.at
W. L. Randeu
M. Schönhuber
R. Teschl
Department of Broadband Communications, Graz University of Technology, Graz, Austria
Institute of Applied Systems Technology, Joanneum Research, Graz, Austria
Polarimetric radar variables of rainfall events, like differential
reflectivity <i>Z</i><sub>DR</sub>, or specific differential phase <i>K</i><sub>DP</sub>, are better
suited for estimating rain rate <i>R</i> than just the reflectivity factor for
horizontally polarized waves, <i>Z</i><sub>H</sub>. A variety of physical and empirical
approaches exist to estimate the rain rate from polarimetric radar
observables. The relationships vary over a wide range with the location and
the weather conditions.
In this study, the polarimetric radar variables were simulated for S-, C-
and X-band wavelengths in order to establish radar rainfall estimators for
the alpine region of the form <i>R</i>(<i>K</i><sub>DP</sub>), <i>R</i>(<i>Z</i><sub>H</sub>, <i>Z</i><sub>DR</sub>), and
<i>R</i>(<i>K</i><sub>DP</sub>), <i>Z</i><sub>DR</sub>. For the simulation drop size distributions of hundreds
of 1-minute-rain episodes were obtained from 2D-Video-Distrometer
measurements in the mountains of Styria, Austria. The sensitivity of the
polarimetric variables to temperature is investigated, as well as the
influence of different rain drop shape models – including recently
published ones – on radar rainfall estimators. Finally it is shown how the
polarimetric radar variables change with the elevation angle of the
radar antenna.
Andsager, K. K, Beard, V., and Laird, N. L.: Laboratory Measurements of axis ratios for large raindrops, J. Atmos. Sci., 56, 2673–2683, 1999.
Aydin, K. and Giridhar, V.: C-band Dual Polarization Radar Observables in Rain, Journal of Atmospheric and. Oceanic Technology, 9, 383–390, 1992.
Brandes, E., Zhang, G., and Vivekanandan, J.: Experiments in rainfall estimation with a polarimetric radar in a subtropical environment, J. Appl. Meteor., 41, 674–685, 2002.
Bringi, V. N. and Chandrasekhar, V.: Polarimetric Doppler Weather Radar, Principles and Applications, Cambridge University Press, 636 pp., 2001.
Doviak, R. J. and Zrni\'c, D. S.: Doppler Radar and Weather Observations – 2nd edition, Academic Press, San Diego, 1993.
Keenan, T. D., Carey, L. D., Zrni\'c, D. S., and May, P. T.: Sensitivity of 5 cm wavelength polarmetric radar variables to raindrop axial ratio and dropsize distribution, J. Appl. Meteor., 40, 526–545, 2001.
Matrosov, S. Y., Clark, K. A., Martner, B. E., and Tokay, A.: X-band polarimetric radar measurements of rainfall, J. Appl. Meteor., 41, 941–952, 2002.
May, P. T., Keenan, T. D., Zrni\'c, D. S., Carey, L. D., and Rutledge, S. A.: Polarimetric radar measurements of tropical rain at a 5-cm wavelength, J. Appl. Meteor., 38, 750–765, 1999.
Morrison, J. A. and Cross, M. J.: Scattering of a plane electromagnetic wave by axisymmetric raindrops, Bell Syst. Tech. J., 53, 955–1019, 1974.
Oguchi, T.: Attenuation and phase rotation of radio waves due to rain: Calculations at 19.3 and 34.8 GHz, Radio Sci., 8, 31–38, 1973.
Poiares Baptista, J. P. V.: OPEX reference book on radar – Second Workshop of the OLYMPUS propagation Experimenters, 8–10~November~1994, ESA ESTEC, Noordwijk, The Netherlands, ESA WPP publications, WPP-083, ISSN 1022–6656, 1994.
Pruppacher, H. R., and Beard, K. V.: A wind tunnel investigation of the internal circulation and shape of water drops falling at terminal velocity in air, Quart. J. Roy. Meteor. Soc., 96, 247–256, 1970.
Pruppacher, H. R. and Pitter, R. L.: A semi-empirical determination of the shape of cloud and rain drops, J. Atmos. Sci., 28, 86–94, 1971.
Ray, P. S.: Broadband complex refractive indices of ice and water, Appl. Opt. 11, 1836–1844, 1972.
Schönhuber, M., Urban, H., Poiares Baptista, J. P. V., Randeu, W. L., and Riedler, W.: Measurements of Precipitation Characteristics by a New Distrometer. Proceedings of Atmospheric Physics and Dynamics in the Analysis and Prognosis of Precipitation Fields, 15–18~November~1994, Rome, Italy, 1994.
Schönhuber, M.: About Interaction of Precipitation and Electromagnetic Waves, Doctoral thesis, Institute of Communications and Wave Propagation, Graz University of Technology, Austria, 1998.
Thurai, M., Huang, G. J., Bringi, V. N., Randeu, W. L., and Schönhuber, M.: Drop Shapes, Model Comparisons, and Calculations of Polarimetric Radar Parameters in Rain, J. Atmos. Ocean. Tech., 24, 1019–1032, 2007.
Thurai, M. and Bringi, V. N.: Drop Axis Ratios, from a 2D-Video Disdrometer, J. Atmos. Ocean. Technol., 22, 963–975, 2005.
Zrni\'c, D. S., Keenan, T. D., Carey, L. D., and May, P.: Sensitivity analysis of polarimetric variables at a 5-cm wavelength in rain, J. Appl. Meteor., 39, 1514-1526, 2000.