Velocity Dealiasing Scheme Study Of Cinrad And Analyse Of Its Effect

An operational challenge in using Doppler radar velocity field is velocity measurements are often aliased. The velocity dealiasing scheme using software is widely used in operation, because the technology implementation of velocity dealiasing using hardware is rather difficult. However, there are more or less some disadvantages because the velocity dealiasing scheme using software is based on the principle of continuity of wind fields. Moreover, there are many factors that affect and restrict the effect of velocity dealiasing, so the quality of different types of radar radial velocity data and the effects of signal to noise ratio on velocity aliasing and velocity dealiasing effect were analyzed in this paper. Besides, the experiments of velocity dealiasing were carried out by introducing the automated 2-D Multi-Pass Doppler Radar Velocity Dealiasing Scheme from NSSL of USA into the Typhoon and Severe Convective Storm data from Doppler Radar of China (SA and CB), and the characteristic of this new algorithm and the comparison with the current operational WSR-88D dealiasing scheme were analyzed. Furthermore, a new automated testing the effect of dealiasing scheme was also designed in order to further apply the new algorithm to operation. Some significant conclusions were gained as following.(1) The radar in Shanghai station is the WSR-88D radar of American next generational weather rader (NEXRAD) in operation system. We analyzed the observational radar data to the same weather process of Shanghai and Zhoushan stations, and found the values of the radial velocity of SA(SB) radar had a larger leaping in relative terms of the WSR-88D radar.(2) The signal to noise ratio has definite effects on local velocity change. We found the signal to noise ratio is bigger, the local velocity change is smaller, and vice versa.(3) The automated 2-D Multi-Pass Doppler Radar Velocity Dealiasing Scheme from Zhang et al. (2006) had a higher accuracy rating, especially when dealing with the dealiasing of radial velocity that had large amounts of data missing and discontinuity wind fields of distance folding. But there were some problems to deal with the velocity aliasing of isolated echoes.(4) Radial reading and processing method is also very important for the effect of velocity dealiasing. We did processing of radial normalization, filled radial deficiencies, and removed the echo scatters that had a weak strength and lied to the marginal zone of the large echo after reading the azimuth angle data. The effect of velocity dealiasing is improved to some extent. (5) AP (anomalous propagation) clutter had a certain impact on the effect of velocity dealiasing.(6) The method of automated testing the effect of dealiasing scheme could accurately identify the range bin of radial velocity that is not processed rightly in the basal data of volume scanning of Doppler radar and judge which data could being not also used through the processing of velocity dealiasing. Thereby,the effect of velocity dealiasing of the new algorithm is checked out for the data of radial velocity from China SA and CB radar and it provided the condition for business applications.(7) Inevitably, the 2-D Multi-Pass Doppler Radar Velocity Dealiasing Scheme has a certain drawbacks, and velocity aliasing of Doppler Radar is also an intractable problem that affect the information applications of wind fields, but the technology of velocity dealiasing has an importantly realistic significance. Thus, it is very necessary that further study on new algorithms, find out the causes that the new algorithm does not correctly handle some data and seek to solutions to better improve the algorithm.