The Canvass Of Low-lever Jet Identification Based On The Single Doppler Radar

With the establishing of the new generation Doppler weather radar (NEXTRAD) network, the weather radar data is applied widely. The images of real-timereflectivity, radial velocity and base spectrum width received from the observation provide plentiful information about cyclones, storms, halls, fronts, shears, jets, and so on. They are useful for improvement of researches about strong weathers and great scale weathers. Now this article is Wing to identify the low-level jet automatically by analyzing the images of Doppler weather radar, simulating the characters of radial velocities, basing on the radial velocity data of Doppler weather radar.In chapter one, the development of weather radar at home and abroad, the purposes of this research and structures of this research are given.In chapter two, we withdraw the information for radar identification from the weather characteristics of the low-level jet. Based on the low-level jet wind characteristics, and by the software Matlab, we simulate its velocity expression and average horizontal velocity distribution to find and verify the algorithm.Then in chapter three, choose the height whose mean velocity which comes from the VAD wind profiles at each height based on the velocity-azimuth display algorithm increased continuously at first and then started to decrease as the height needed. At the decided height, insert velocity for all involved azimuths, get the distribution of radial velocity at the same height, and then evolve the horizontal velocity at all positions. Calculate the velocity gradient at the azimuth of the vertical lines to the mean wind direction. Imitate the dots having big gradient and large horizontal velocity to a line for accomplishing the identification of the low-level jet.In chapter four, the Doppler weather radar system which the exploitation of low-level jet algorithm in this paper is based on is introduced. The tool follows the secondary system software, use Visual C++6.0, and be tied to the system.After finishing the design of the algorithm, in chapter 5, we tested the module and compared with the result of experience by using the Doppler weather radar data of a strong fall accompanied by low level jet in Anhui province in 10 July 2003. Then, we found that this module is good to identify low-level jet, not useful for the situation while the characters are not distinct.At last, in chapter 6, the quality of the algorithm is discussed and summarized. So does the further research of this algorithm.