ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
A New Detection Algorithm of Mesoscale Vortex During Meiyu Period
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Abstract:
The occurrence and development of mesoscale vortices directly influence heavy rainfalls during Meiyu period. Identifying mesoscale vortices accurately helps to improve the prediction of heavy precipitation. An objective method is proposed to automatically detect the centers of mesoscale vortices from gridded wind field in this study. Using global analysis from National Centers for Environmental Prediction (NCEP), USA, two cases during the 2013-2014 Meiyu periods were selected to compare the existing two algorithms which are based on vorticity or height distribution and the new one. The results indicate that since smallscale systems do not obey geostrophic wind relationship, the centers of wind, vortex and low pressure scarcely overlap Meiyu fronts, thus decreasing the accuracy of detection on the basis of vorticity or pressure. However, the new method is based on winds and can precisely identify most vortex centers with a higher precision than the other two algorithms. Then the new method is used to analyze the vertical structure and time evolution of different vortices in the two cases. The analysis shows that the new method does not need any manual intervention, specific level or time restriction. It can identify the position, 3D structure and time evolution of any mesoscale vortex falling in the domain in a very short time. Also, it can be used to detect mesoscale vortices on stationary fronts during Meiyu periods, very helpful for forecasters to do realtime analysis and forecast severe precipitation.
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