Interpolation is essential in radar data coordinate transformation and radar network process due to the polar coordinate storage of radar data. In order to improve the effect and observation ability of radar network, an interpolation method based on Fourier spectrum analysis ("Fourier interpolation method" for short) has been developed for weather radar echo imagery data. The principle of this method is based on fitting discrete radar-sampling points with Fourier spectrum analysis and then re-sampling for the purpose of interpolation. The algorithm is introduced by steps and cases like typhoon and heavy rain radar images detected by Fuzhou radar and Nanjing SA radar have been studied by comparing Fourier interpolation with bilinear interpolation method in processing radar echo image at low angle. Bilinear interpolation method could narrow the strong echo area because of its "average" process, but Fourier interpolation method can avoid this problem in a certain extent with spectral analysis and sampling properties. Fourier interpolation method can highlight the structural characteristics of strong echo area when processing cumuliform cloud echo derived from convective precipitation in a proper distance, and in the far distance it can interpolate the strong echo centers that low resolution radar cannot detect. Due to the fitting equation, in the strong echo area, the results of Fourier interpolation have a better consistency with true value (fitting degree R2 is more than 0.98; slope is 0.98; intercept is only 0.31 dBZ, closed to 0 dBZ), but the consistency between the bilinear interpolation and the true value is worse (fitting degree R2 is 0.94, the slope is only 0.79, intercept is more than 8.04 dBZ). Fourier interpolation method performs better than the commonly-used bilinear interpolation method in highlighting the structure characteristics of strong echoes in severe convective area and is conducive to showing some severe convective centers which cannot be detected because of the lower spatial resolution at long distance. Due to the large amount of calculation, further research is needed to shorten the calculation time.
[1]Askelson M A, Aubagnac J P, Straka J M, 2000. An adaptation of the Barnes filter applied to the objective analysis of radar data[J]. Mon Wea Rev, 128:3050-3082.
[2]Fulton R. 1998. WSR-88D polar to HRAP mapping[Z]. Tech Memo, Hydrology Research Laboratory, Office of Hydrology, National Weather Service, Silver Spring, MD, 33.
[3]Jorgensen D P, Hildebrand P H, Frush C L. 1983. Feasibility test of an airborne pulse-Doppler meteorological radar[J]. J Appl Meteor, 22:744-757.
[4]Miller L J, Mohr C G, Weinheimer A J. 1986. The simple rectification to Cartesian space of folded radial velocities from Doppler radar sampling[J]. J Atmos Oceanic Tech, 3:162-174.
[5]Mohr C G, Vaughn R L. 1979. An economical procedure for Cartesian interpolation and display of reflectivity factor data in three-dimensional space[J]. J Appl Meteor, 18:661-670.
[6]Serafin R J, Wilson J W. 2000. Operational weather radar in the United States:Progress and opportunity[J]. Bull Amer Meteor Soc, 81:501-518.
[7]Shapiro A, Robinson P, Wurman J, et al. 2003. Single-Doppler velocity retrieval with rapid-scan radar data[J]. J Atmos Oceanic Tech, 20:1758-1775.
[8]Weygandt S S, Shapiro A, Droegemeier K K. 2002. Retrieval of model initial fields from single-Doppler observations of a supercell thunderstorm. Part I:Single-Doppler velocity retrieval[J]. Mon Wea Rev, 130:433-453.
[9]Duan Yiping, Liu Shoudong, Liu Liping, et al. 2014. Application of CINRAD mosaic products on artificial hail suppression[J]. Plateau Meteor, 33(5):1426-1439. DOI:10.7522/j. issn. 1000-0534.2013.00139.<br/>段艺萍, 刘寿东, 刘黎平, 等. 2014. 新一代天气雷达三维组网产品在人工防雹的应用[J]. 高原气象, 33(5):1426-1439.
[10]Huang Jiayou. 2000. Meteorological statistical analysis and prediction method[M]. Beijing:Meteorological Press, 309-343.<br/>黄嘉佑. 2000. 气象统计分析与预报方法[M]. 北京:气象出版社, 309-343.
[11]Huang Yunxian, Zhang Ying. 2008. Comparison of interpolation schemes for the Doppler Weather Radar data[J]. Remote Sensing Informatin, 23(2):39-45.<br/>黄云仙, 张英. 2008. 多普勒天气雷达数据插值方法比较研究[J]. 遥感信息, 23(2):39-45.
[12]Li Bai, Gu Qingdong, Li Ruiyi, et al. 2013. Analyses on disastrous weather monitoring capability of CINRAD and future development[J]. Meteor Mon, 39(3):265-280.<br/>李柏, 古庆同, 李瑞义, 等. 2013. 新一代天气雷达灾害性天气监测能力分析及未来发展[J]. 气象, 39(3):265-280.
[13]Liu Jie, Xu Xiao Feng, Luo Hui. 2012. An empirical research on the impacts of extreme weather and climate events on agricultural economic output in China[J]. Sci Sin Terrae, 42(7):1076-1082.<br/>刘杰, 许小峰, 罗慧. 2012. 极端天气气候事件影响我国农业经济产出的实证研究[J]. 中国科学:地球科学, 42(7):1076-1082.
[14]Wang Qingdong, Yan Wei, Ma Ning. 2002. Algorithm for digital weather radar networking and composite image[J]. Journal of PLA University of Science and Technology:Natural Science Edition, 3(2):90-93.<br/>王庆东, 严卫, 马宁. 2002. 数字化天气雷达组网拼图算法[J]. 解放军理工大学学报:自然科学版, 3(2):90-93.
[15]Wang Zhenhui, Zhang Peichang. 2001. A study on the algorithm making attenuation correction to observations of radar reflectivity factor (II):Numerical simulations and a case study[J]. Plateau Meteor, 20(2):115-120.<br/>王振会, 张培昌. 2001. 天气雷达回波衰减订正算法的研究(Ⅱ):数值模拟与个例实验[J]. 高原气象, 20(2):115-120.
[16]Wen Ying, Zhao Yang, Zhao Guo, et al. 2015. Characteristics of lightning activity and radar reflectivity during typhoon ‘Morakot’ landfall[J]. Plateau Meteor, 34(3):832-841. DOI:10.7522/j. issn. 1000-0534.2015.0036.<br/>温颖, 赵阳, 赵果, 等. 2015. 台风"莫拉克"登陆过程的闪电活动与雷达回波特征[J]. 高原气象, 34(3):832-841.
[17]Xiao Xian, Xiao Hui, Wang Zhenhui, et al. 2008. Applications of Fourier phase analysis technique to computation of radar cloud echo motion vectors[J]. J Nanjing Insti Meteor, 30(4):473-482.<br/>肖现, 肖辉, 王振会, 等. 2008. 傅立叶相位技术在雷达回波移动矢量特征分析中的应用[J]. 南京气象学院学报, 30(4):473-482.
[18]Xiao Yanjiao, Liu Liping. 2006. Study of methods for interpolating data from weather radar network to 3-D grid and mosaics[J]. Acta Meteor Sinica, 64(5):647-657.<br/>肖艳姣, 刘黎平. 2006. 新一代天气雷达网资料的三维格点化及拼图方法研究[J]. 气象学报, 64(5):647-657.
[19]Yang Ji, Liu Liping, Li Guoping, et al. 2012. A new techniques for storm cell and mesoscale convective systems identification, tracking and nowcasting based on the radar mosaic data[J]. Acta Meteor Sinica, 70(6):1347-1355.<br/>杨吉, 刘黎平, 李国平, 等. 2012. 基于雷达回波拼图资料的风暴单体和中尺度对流系统识别、跟踪及预报技术[J]. 气象学报, 70(6):1347-1355.
[20]Zhai Panmao, Liu Jing. 2012. Extreme weather/climate events and disaster prevention and mitigation under global warming background[J]. Engineering Sciences, 14(9):55-63+84.<br/>翟盘茂, 刘静. 2012. 气候变暖背景下的极端天气气候事件与防灾减灾[J]. 中国工程科学, 14(9):55-63+84.
[21]Zhang Hong, Wang Zhenhui, Xu Jianming. 2006. An experiment to derive cloud motion vectors from satellite images with 2-D Fourier phase analysis technique[J]. Plateau Meteor, 25(1):105-109.<br/>张红, 王振会, 许建明. 2006. 利用静止卫星云图进行二维傅里叶相位导风试验[J]. 高原气象, 25(1):105-109.
[22]Zhang Lei, Wang Zhenhui, Yang Yanrong. 2011. Application test of Doppler radar data in numerical model ARPS[J]. J Meteor Sci, 31(5):567-575.<br/>张蕾, 王振会, 杨艳蓉. 2011. 多普勒天气雷达资料在数值模式ARPS中的试验[J]. 气象科学, 31(5):567-575.
[23]Zhang Peichang, Wang Zhenhui. 2001. A study on algorithm to make attenuation correction to radar observations of radar reflectivity factor(Ⅰ):Theoretical analysis[J]. Plateau Meteor, 20(1):1-5.<br/>张培昌, 王振会. 2001. 天气雷达回波衰减订正算法的研究(Ⅰ):理论分析[J]. 高原气象, 20(1):1-5.
[24]Zhang Peichang. 1989.4-D assimilation method of weather radar network[J]. J Nanjing Insti Meteor, 12(3):22-28.<br/>张培昌. 1989. 天气雷达组网拼图的四维同化方法[J]. 南京气象学院学报, 12(3):22-28.
[25]Zhang Peiyuan, Yang Hongping, Hu Shaoping. 2008. Applications of new generation weather radar to nowcastingand warning of severe weather[J]. Meteor Mon, 34(1):3-11.<br/>张沛源, 杨洪平, 胡绍萍. 2008. 新一代天气雷达在临近预报和灾害性天气警报中的应用[J]. 气象, 34(1):3-11.
[26]Zhang Yiping, Yu Xiaoding, Sun Jinglan, et al. 2014. Formation mechanism and analysis of radar observation of a heavy rainstorm accompanied by hail that back of trough[J]. Plateau Meteor, 33(4):1093-1104. DOI:10.7522/j. issn.1000-0534.2012.00200.<br/>张一平, 俞小鼎, 孙景兰, 等. 2014. 一次槽后型大暴雨伴冰雹的形成机制和雷达观测分析[J]. 高原气象, 33(4):1093-1104.
[27]Zhang Zhixian, Zhang Qiang, Zhao Qingyun, et al. 2014. Analysis on radar echo and precipitation retrieve of short-duration heavy precipitation in Southeast Gansu[J]. Plateau Meteor, 33(2):530-538. DOI:10.7522/j. issn. 1000-0534.2013.00001.<br/>张之贤, 张强, 赵庆云, 等. 2014. 陇东南地区短时强降水的雷达回波特征及其降水反演[J]. 高原气象, 33(2):530-538.
[28]Zou Haibo, Shan Jiusheng, Deng Shiru. 2014. Study of the Doppler radar data gridding[J]. Meteor Disaster Reduction Research, 35(2):23-30.<br/>邹海波, 单九生, 邓诗茹. 2014. 多普勒雷达资料的网格化研究[J]. 气象与减灾研究, 35(2):23-30.
