Improvement and Application Test of TREC Algorithm for Convective Storm Nowcast

Chen Mingxuan; Wang Yingchun; Yu Xiaoding

Vol.18, NO.5, 2007

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Chen Mingxuan, Wang Yingchun, Yu Xiaoding. Improvement and application test of TREC algorithm for convective storm nowcast. J Appl Meteor Sci, 2007, 18(5): 690-701.

Citation:

Chen Mingxuan, Wang Yingchun, Yu Xiaoding. Improvement and application test of TREC algorithm for convective storm nowcast. J Appl Meteor Sci, 2007, 18(5): 690-701.

Chen Mingxuan, Wang Yingchun, Yu Xiaoding. Improvement and application test of TREC algorithm for convective storm nowcast. J Appl Meteor Sci, 2007, 18(5): 690-701.

Citation:

Chen Mingxuan, Wang Yingchun, Yu Xiaoding. Improvement and application test of TREC algorithm for convective storm nowcast. J Appl Meteor Sci, 2007, 18(5): 690-701.

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Improvement and Application Test of TREC Algorithm for Convective Storm Nowcast

1.
Institute of Urban Meteorology, CMA, Beijing 100089
2.
China Meteorological Administration Training Center, Beijing 100081

Received Date: 2006-02-15
Rev Recd Date: 2007-03-01
Publish Date: 2007-10-31

Abstract

Abstract

At present, cross-correlation extrapolation is one of the main algorithms for convective storm now cast. Motion vectors of convective storm for every divided equal-sized two-dimensional arrays of radar echo or other data measured at two times several minutes apart by calculating optimal spatial cross-correlation are obtained in the algorithm. The obtained motion vectors are customarily called TREC (tracking radar echoes by correlation) vectors or TREC winds. And then, storm now cast can be achieved by extrapolating radar echoes or other data based on the obtained TREC vectors. The algorithm results involve not only the changing characteristics of magnitude and direction of the motion vectors, but also shape varieties of the whole echoes in the course of their movement. So the result of storm now cast based on the algorithm is assuredly reasonable and significant in meteorology. The basic principle of TREC is introduced firstly. And a number of methods to improve the algorithm result are presented, including noisy vector restriction and clutter contamination removal, discarded or missing motion vector supplement, vector smoothing, and so on. Analysis results of two cases indicate that the tracked motion vectors can be markedly improved after quality control and optimization processes to TREC algorithm. Finally, based on the optimized TREC algorithm and Tianjin radar data, storm nowcast tests and verifications of four intense convective storms that occur in Beijing-Tianjin-Hebei areas during 2004 and 2005 summertime, including two squall line cases, a hailstorm case and a strong thunderstorm case, are described in detail. The results indicate that the improved algorithm is available for convective storm nowcast.The algorithm can automatically produce 30-minute or 60-minute forecast of location and shape of radar echoes or storm characteristics based on the extrapolated vectors. The forecast results are close to what is actually happening. Because the algorithm can automatically produce forecast results in real time mode, it is helpful for convective storm now cast and warning.The forecast results are also clear at a glance, so abilities of forecasters for strong convective storm identification and forecast can be enhanced by the algorithm. An expectation is that the improved algorithm can be used for operational storm now cast in the near future.
- cross-correlation;
- TREC;
- now cast;
- radar echo

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References(23)

Figures and Tables

图 1 2005年8月8日19:44天津雷达PPI强度回波与由交叉相关算法追踪得到回波移动矢量 (仰角:0.4°)(a) 质量控制前, (b) 质量控制后

Fig. 1 Coloured plan position indicator (PPI) of Tianjin radar reflectivity with elevation angle of 0.4° at 19:44 on August 8, 2005 and overlaid TREC vectors without quality control (a) and with quality control (b)

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图 2 交叉相关外推预报算法对2004年7月29日飑线过程大于等于35dBz的反射率因子09:38(a) 和09:50(c) 的30min外推预报，以及相应的30min后10:08(b) 和10:20(d) 的强雷达回波 (仰角:0.4°)

Fig. 2 30-min forecast of reflectivity echo (≥35 dBz) at 09:38(a) and 09:50(c) on July 29, 2004 based on TREC vectors, and reflectivity observation (≥35 dBz)30-min later from Tianjin radar with elevation angle of 0.4 at 10:08(b) and 10:20(d)

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图 3 交叉相关外推预报算法对2004年7月29日飑线过程的35 dBz以上反射率因子峰值可能出现范围在09:19(a) 和09:44 (b) 的30 min外推预报 (黑色线范围), 以及30 min后的实况分析 (彩色阴影区)

Fig. 3 30-min forecast of extension of reflectivity maximum (≥35 dBz) at 09:19(a) and 09:44(b) on July 29, 2004(black contour) based on TREC vectors, and actual extension of reflectivity maximum (≥35 dBz)30-min later (shaded color)

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图 4 交叉相关外推预报算法对2005年5月31日雹暴过程35 dBz以上反射率因子在11:18的30 min外推预报 (a) 以及相应的30 min后强雷达回波的实况 (b)(仰角:0.4°)

Fig. 4 30-min forecast of reflectivity echo (≥35 dBz) at 11:18(a) on May 31, 2005 based on TREC vectors, and reflectivity observation (≥35 dBz)30-min later from Tianjin radar with elevation angle of 0.4° at 11:18(b)

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图 5 交叉相关外推预报算法对2005年6月13日雹暴过程35 dBz以上反射率因子在08:47的30 min外推预报 (a) 以及相应的30 min后强雷达回波的实况 (b)(仰角:0.5°)

Fig. 5 30-min forecast of reflectivity echo (≥35 dBz) at 08:47(a) on June 13, 2005 based on TREC vectors, and reflectivity observation (≥35 dBz)30-min later from Tianjin radar with elevation angle of 0.5° at 09:18(b)

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图 6 交叉相关外推预报算法对2005年6月13日飑线过程的35 dBz以上反射率因子峰值可能出现范围在08:47的30 min外推预报 (黑色线范围), 以及30 min后的实况分析 (彩色阴影区)

Fig. 6 30-min forecast of extension of reflectivity maximum (≥35 dBz) at 08:47on June 13, 2005(black contour) based on TREC vectors, and actual extension of reflectivity maximum (≥35 dBz)30-min later (shaded color)

DownLoad: Full-Size Img PowerPoint

图 7 交叉相关外推预报算法对2005年6月13日飑线过程的反射率因子在08:41的60 min外推预报 (a) 以及60 min后的实况 (b)

Fig. 7 60-min forecast of reflectivity echo at 08:41(a) on June 13, 2005 based on TREC vectors, and reflectivity observation with elevation angle of 0.5° at 09:36(b)

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图 8 交叉相关外推预报算法对2005年7月14日强对流过程35 dBz以上反射率因子在20:36(a) 和20:47(c) 的30 min外推预报以及相应的21:03(b) 和21:15(d) 强雷达回波实况 (仰角:0.5°)

Fig. 8 30-min forecast of reflectivity echo (≥35 dBz) at 20:36(a) and 20:47(c) on July 14, 2005 based on TREC vectors, and reflectivity observation (≥35 dBz) 30-min later from Tianjin radar with elevation angle of 0.5° at 21:03(b) and 21:15(d)

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