多普勒天气雷达组网拼图有效数据区域分析

引用本文

杨洪平, 张沛源, 程明虎, 李柏, 熊毅, 高玉春, 陈大任. 多普勒天气雷达组网拼图有效数据区域分析[J]. 应用气象学报, 2009, 20(1): 47-55. 复制到剪切板

Yang Hongping, Zhang Peiyuan, Cheng Minghu, Li Bai, Xiong Yi, Gao Yuchun, Chen Daren. The Valid Mosaic Data Region of the CINRAD Network[J]. Journal of Applied Meteorological Science, 2009, 20(1): 47-55 复制到剪切板

多普勒天气雷达组网拼图有效数据区域分析

杨洪平^1,2, 张沛源¹, 程明虎¹, 李柏², 熊毅³, 高玉春², 陈大任²

1. 中国气象科学研究院灾害天气国家重点实验室, 北京 100081;
2. 中国气象局气象探测中心, 北京 100081;
3. 中国气象局监测网络司, 北京 100081

2007-12-07 收到, 2008-07-25 收到修改稿.

资助项目: 国家自然科学基金项目 (40375006) 和武汉暴雨研究所开放基金课题 (IHR20053) 共同资助

摘要: 在正常情况下, 由于天线仰角和地球曲率原因, 雷达波束位置在远距离处要比近距离处高。当雷达电磁波能量被部分阻挡时, 回波强度观测值低估; 被完全挡住时, 探测不到地物后的目标。该文利用高分辨率地形高程数据计算波束阻挡率, 确定组网拼图有效数据区域以及波束部分阻挡时的回波强度订正方法。根据业务观测模式VCP11及VCP12的14个仰角值, 在标准大气假定下, 对湖南、江西、浙江、福建、广东、广西和海南已建多普勒天气雷达组网的数据有效区域进行计算, 绘制出海拔1500 m, 3000 m和6000 m高度上有效区域图。分析结果表明:CAPPI数据有效范围比等射束高度图更能反映出多普勒天气雷达业务观测范围; 若采用VCP12模式观测, 与采用VCP11或VCP21模式观测相比, 不仅增加低层探测密度, 而且可扩大雷达实际探测距离, 其回波数据更适合于组网拼图。

关键词: 多普勒天气雷达组网拼图有效数据区域

The Valid Mosaic Data Region of the CINRAD Network

Yang Hongping^1,2, Zhang Peiyuan¹, Cheng Minghu¹, Li Bai², Xiong Yi³, Gao Yuchun², Chen Daren²

1. State Key Laboratory Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081;
2. Atmospheric Observation Technical Center of CMA, Beijing 100081;
3. Department of Observation and Telecommunication, China Meteorological Administration, Beijing 100081

Abstract: Along the normal propagation path, the radar ray becomes higher and higher due to effects of the earth curvature and positive elevation angle of transmitter. Actually, radar waves are often blocked as they propagate through mountain areas. When radar beam has occultation, its real sample volume will be smaller than that of zero occultation, echo intensity of targets will be underestimated if it is partial occultation, and targets will be totally missed if complete occultation occurs. It is common practice now to use occultation rate for beam occultation correction. Assuming that radar waves propagate in standard atmosphere, occultation rates of radar beam herein are calculated with the high resolution digital elevation map data, and are utilized to analyze the valid mosaic data region of netted radars and to assess the beam occultation correction. Test shows that echo will be severely underestimated and waves can be considered to be completely blocked when the occultation rate is larger than 55 %. Based on that, in terms of the 14 elevation angles of two Volume Coverage Pattern modes, VCP11 and VCP12, the real detecting ranges of netted radars are obtained. The netted radars include the local CINRAD in Hunan, Jiangxi, Zhejiang, Fujian, Guangdong, Guangxi and Hainan provinces. Compared with the equivalent beam range at the same height, the valid data range of CAPPI is more suitable to represent the real detection range. Among the valid mosaic date regions at the height of 1500 m, 3000 m and 6000 m above the sea level, the largest blank area can be seen in the graph of 1500 m height, but can hardly be seen in that of 6000 m height. In the overlapping area of 6000 m height, most common grids can be detected by three radars or more, some by the maximum of six. Observations in VCP12, compared with that in VCP11 or in VCP21, are more useful to construct mosaic data not only because of its dense vertical sample in low elevation but also its larger valid data range in mountain areas. According to the definition formula of echo intensity, correction of intensities sampled in partial occultation range gates is obtained from its occultation rate. For instance, the correction value is 1.0 dB, 1.5 dB, 2.2 dB, 3.0 dB and 3.5 dB while the occultation rate is 20 %, 30 %, 40 %, 50 % and 55 % respectively. In the experiment of correction, base data are observed in the common latitude longitude grid at the same time by the two weather radars in Wenzhou and Ningbo. The common grids are separated into two groups. The group Ⅰ consists of the grids where Wenzhou radar has partial occultation and Ningbo radar has none. And the group Ⅱ consists of the grids where both two has no occultation. Therefore, the observations of Wenzhou radar are corrected in group Ⅰ, and correction is assessed by the observations of Ningbo radar. The results indicate that the correlative coefficient of corrected data is larger than that of uncorrected in group Ⅰ, and the values are close to that of group Ⅱ, the corrections are effective.

Key words: Doppler radar radar mosaic valid data region

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图 1. 雷达波束的地物遮挡示意图 (阴影部分为地形) Fig 1. An example of radar beams obscured by ground obstacles (shaded areas denote topograph)


图 4. 赣州雷达6000 m等射束高度图 (虚线) 与CAPPI数据有效区域 (细实线为VCP11, 粗实线为VCP12, 距离圈间距150 km) Fig 4. Coverage of equivalent beam range (dashed line) and CAPPI valid data region (thin line denotes CP 11 and thick line denotes VCP12) at 6000 m above the sea level (distance between range ring is 150 km)