Research on LowLevel Jet Identification and Automatic Drawing Method
Lowlevel jet is important for predicting severe convective weather. At present, the identification of lowlevel jet is conducted mainly by handwork, which brings the problem of low efficiency, easily influenced by subjective factors. So, based on the wind field data of the sounding stations in MICAPS, we propose an automatic lowlevel jet identification and drawing algorithm in this paper. The algorithm is based on the definition of the lowlevel jet axis, and detects the lowlevel jet axis from several aspects in terms of wind speed, wind direction, sounding station distribution, and the central axis position. Then after the steps of transitive closure clustering, key points extracting, lowlevel jet axis merging and the axis smooth ing, the automatic identification and drawing of lowlevel jet are achieved. The test result shows that the jet axis, which is automatically drawn, has the characteristics of accurate position and natural shape. Besides, it could reflect the transport path of water vapor in jet, and adapt to the complex environment of lowlevel jet. In the 291 test data, the identification rate reaches 94.96% and false alarm is not found.