?K要
本文的目的在建立中央大學雙偏極化雷達資料(C-Band)的處理流程以及對降雨估計法的研究。 在資料處理方面，本研究對總差異相位差( )做了去折疊以及平滑的動作，也修正了水平回波( )、差異反射率( )的能量衰減問題，並針對 系統偏移部分提出一新修正方法，利用小雨滴區域的 平均值應為零當約束關係來修正 ，接著再使用 、 、比差異相位差( )三參數的相依關係式反求一理想之 ，和觀測的 比較來修正 系統偏移，使用本研究修正過的 、 能大幅改善降雨率的估計。
在降雨估計法方面，除了使用以往的經驗公式求降雨率外，並嘗試了先反演雨滴粒徑分佈再推估降雨率的方法。 在假設Gamma雨滴粒徑分佈的情形下，μ、Λ兩參數會有一約束關係存在，本研究即利用此約束關係，搭配雙偏極化雷達的 、 、 三參數中的兩參數來估算雨滴粒徑分佈，進而推算降雨率，藉此來改善定量降水估計的精確度，各降水估計法的比較結果顯示，有使用 此參數的降水估計法在強降水時表現最佳，而且使用 組合的雨滴粒徑分佈反演法在反演降雨率的定量上表現最好。 在雨滴粒徑分佈的反演方面，本文所使用的組合方法能掌握到雨滴粒徑的變化情形，但整體表現的比較，則有待日後作更多個案的分析。

Abstract
High time resolution C-Band polarimetric Doppler radar data from the measurements of NANMADOL typhoon rain were analyzed to study the algorithms for retrieving rain rate. Before using the radar data, corrections such as: unfolding of differential phase shift( )、correction of energy attenuation、correction of system bias were done. When compared with the raingauges, it showed that a better rain rate estimate result with the corrected polarimetric radar parameters.
A constrained relation between the shape( ) and slope( ) parameters will appear when the drop size distribution(DSD) is assumed to be a gamma distribution. In this study, the constrained relation and two of the three radar parameters: reflectivity( )、differential reflectivity( ) and specific differential phase shift ( ) were used to retrieve the DSD and rain rate. The result showed that , the use of is much better than in heavy rain, and the retrieved accumulative rain agree with the measurements of raingauges very well.

參考文獻：
張偉裕, 2002: 利用雨滴譜儀分析雨滴粒徑分佈(納莉颱風個案), 國立中央大學碩士論文, 95頁。
劉慈先, 2002： SCSMEX期間利用C-Pol偏極化雷達氣象參數觀測降水系統之分析, 國立中央大學碩士論文, 67頁。
鳳 雷, 2002: 熱帶降水系統之雙偏振雷達觀測研究。 台灣大學大氣科學博士論文，161頁。
林位總, 2004: 利用二維雨滴譜儀研究雨滴譜特性, 國立中央大學碩士論文, 89頁。
Battan, L.J., 1973: Radar Observations of the Atmosphere. University of Chicago Press, 324 pp.
Brandes, E. A., G. Zhang, and J. Vivekanandan, 2003: An evaluation of a drop distributionbased rainfall estimator. J. Appl. Meteor., 42, 652–660.
Brandes, E. A., G. Zhang, and J. Vivekanandan, 2004: Comparison of Polarimetric Radar Drop Size Distribution Retrieval Algorithms. J. Atmos. Oceanic Technol., 21, 584–598.
Bringi , V. N., V.Chandrasekar, N. Balakrishnan, and D.S. Zrnic, 1990: An Examination of propagation effects in rainfall on radar measurements at microwave frequencies. J. Atmos. Oceanic Technol., 7, 829-840.
Bringi , V. N., K.Knupp, A. Detwiler, L. Liu, I. J. Caylor, and R. A. Black, 1997:
Evolution of a Florida Thunderstorm during the Convection and Precipitation / Electrification Experimenrt:The Case of 9 August 1991. Mon. Wea Rev., 125, 2131-2160.
Bringi, V. N., and V. Chandrasekar 2001: Polarimetric Doppler Weather Radar: Principles and Applications, Cambridge Univ. Press, 636 pp.
Bringi , V. N., G. Huang, and V. Chandrasekar,2002: A Methodology for Estimating the Parameters of a Gamma Raindrop Size Distribution Model from Polarimetric Radar Data: Application to a Squall-Line Event from the TRMM/Brazil Campaign. J. Atmos. Oceanic Technol., 19, 633-645.
Doviak, R. J., and D. S. Zrnic 1993: Doppler Radar and Weather Observations, 2nd ed. San Diego, CA: Academic, 562 pp.
Gorgucci, E., G. Scarchilli, and V. Chandrasekar,1999: A procedure to calibrate multiparameter weather radar using properties of the rain medium, IEEE Trans. Geosci. Remote Sens., 37, 269–276.
Jameson, A. R., and E. A. Mueller,1985: Estimation of propagation-Differential Phase Shift from Sequential Orthogonal Linear polarization Radar Measurements. J. Atmos. Oceanic Technol., 2, 133-137.
Keenan T. D., D. S. Zrnic, L. D. Carey and P. May, 2000: Sensitivity Analysis of Polarimetric Variables at a 5-cm Wavelength in Rain. Amer. Meteo. Soci. 39,1514-1526.
Pruppacher, H.R., and R.L. Pitter, 1971: A semi-empirical determination of the shape of cloud and raindrops. J. atmos. Sci., 28, 86-94.
Ray, P. S., 1972: Broad-band complex refractive indices of ice and water. Appl. Opt., 11, 1836-1844.
Scarchilli G., E. Gorgucci, V. Chandrasekar, and T. A. Seliga, 1993: Rainfall Estimation using polarimetric Techniques at C-Band Frequencies. J. Appl. Meteorol., vol. 32, 1150-1160.
Scarchilli G., E. Gorgucci, V. Chandrasekar, Member,IEEE, and A.Dobaie, 1996:Self-Consistency of Polarization Diversity Measurement of Rainfall. IEEE Trans., vol. 34, 22-26.
Sachidananda, M., and D. S. Zrnic, 1987: Rain rate estimates from differential polarization measurements. J. Atmos. Oceanic Technol., 4, 588-598.
Seliga T. A.，and V. N. Bringi, 1976: Potential use of radar differential reflectivity measurements at orthogonal polarizations for measuring precipitation. J. Appl. Meteorol., vol. 15, pp. 69–76.
Seliga T. A.，and V. N. Bringi, 1978: Differential reflectivity and differential phase shift: Applications in radar meteorology. Radio Sci. 13, 271-275.
Smyth T.J., and A.J. Illingworth, 1998: Correction for attenuation of radar reflectivity using polarization data. Q. J. R. Meteorol. Soc., 124, 2393-2415.
Ulbrich, C.W., 1983: National variations in the analytical form of the raindrop size distribution. J. Climate Appl. Meteor., 22, 1764-1775.
Vivekanandan, J., G. Zhang, S. M. Ellis, D. Rajopadhyaya, and S. K. Avery, 2003: Radar reflectivity calibration using differential propagation phase measurement, Radio Sci, 38(3), 8049, doi:10.1029/2002RS002676.
Wakimomoto, R.M., and V.N. Bringi, 1988: Dual-polarization observationsof microbursts associated with intense convection: the 20 July storm during MIST project. Mon. Wea. Rev., 116, 1521-1539.
Zeng Z., 1998: Polarimetric Radar Studies of Convective Storm Development, Master Thesis, Department of Atmo. Sci. University of Washington, 146pp.
Zhang, G., J. Vivekanandan, and E. A. Brandes, 2001: A method for estimating rainrate and drop size distribution from polarimetric radar measurements. IEEE Trans. Geosci. Remote Sens., 39, 830-841.
Zrnic D.S., T.D. Keenan, L.D. Carey, and P. May, 2000: Sensitivity analysis of polarimetric variables at a 5-cm wavelength in rain. J. Appl. Meteorol., vol. 39, 1514-1526.