The removal of noise and velocity ambiguity and retrieval and verification of horizontal wind field is a prerequisite to make the best and fullest use of Doppler radar measurements. This approach was applied to the Doppler radar data collected during August 2005 for a landing typhoon Matsa (0509) in Yantai, Shangdong Province, and the verified result shows that the quality control for this dataset was successful. The horizontal wind field was retrieved and then verified by studying the characteristics of the radar radial velocity and large-scale wind field and the vertical cross section of the radial velocity determined with the typhoon center as the circle center and comparing it with satellite imagery. The results show that the meso- and small-scale systems in Matsa and its horizontal and vertical structure could be clearly retrieved using the dataset collected by single Doppler radar, and a shear or a convergence was corresponding with a band of severe storm around Matsa. At the same time, the retrieved wind field from single Doppler radar is proved to be a reliable and high-resolution dataset in analyzing the inner meso-scale structure of Matsa. It is also proved that the method for removing the velocity ambiguity could be an effective approach for preliminary quality control of the Doppler radar data, and the VAP method could also be a reasonable solution for the analysis of mesoscale wind field.
A new Planetary Boundary Layer (PBL) model (namely MY-4 in this paper) was developed with reference to Mellor-Yamada’s Level 4 turbulent closure concept. Having been coupled with a meso-scale model MM5, MY-4 was util-ized to simulate a heavy-rain process, which took place over South China during June 8-9, 1998. Its model outputs indi-cated that the rainfall process was well captured in terms of its intensity and geographical distribution. More importantly, in comparison with MM5’s original boundary layer models, MY-4 made the following improvements: (1) MY-4 not only simulated the major weather systems like low vortexes and low-level jets more accurately, thus improving the general weather pattern of the rainfall process, but it was also capa-ble of restraining the occurrence of false rainfall centers with maximum precipitation amounts exceeding 160 mm. (2) Having been compared with the wind profile observed at Hong Kong, it revealed that MY-4 could reproduce the wind speed fluctuations in a short time scale reasonably well, which was not yet achieved in the original PBL models in MM5. Furthermore, a more detailed comparative study was made on the results simulated by MY-4 and a PBL model (which is based on Mellor-Yamada’s Level 2.5 concept) re-spectively. It showed that the contributions of turbulences generated by the two categories of PBL models to the wind fields at a lower atmosphere were increasingly different even in the first 1-2 hours of integrations. As the analysis dem-onstrated, under the nonlinear interactions within the meso-scale MM5 model, it was the turbulences in the boundary layer that had the most important impacts on the final model outputs and MY-4 seemed to better reflect this turbulent process, hence leading to the aforementioned im-provements.
