Niu Shengjie

Non-linear dynamic model retrieval of subtropical high based on empirical orthogonal function and genetic algorithm

Aiming at the difficulty of accurately constructing the dynamic model of subtropical high, based on the potential height field time series over 500 hPa layer of T106 numerical forecast products, by using EOF (empirical orthogonal function) temporal-spatial separation technique, the disassembled EOF time coefficients series were regarded as dynamical model variables, and dynamic system retrieval idea as well as genetic algorithm were introduced to make dynamical model parameters optimization search, then, a reasonable non-linear dynamic model of EOF time-coefficients was established. By dynamic model integral and EOF temporal-spatial components assembly, a mid-/long-term forecast of subtropical high was carried out. The experimental results show that the forecast results of dynamic model are superior to that of general numerical model forecast results. A new modeling idea and forecast technique is presented for diagnosing and forecasting such complicated weathers as subtropical high.

Z-R Relationship from the Particle Size and Velocity (Parsivel) Optical Disdrometer and its Application in Estimating Areal Rainfall

In order to improve the precision of Radar rainfall estimates, the Parsivel was used for observation of rain drop spectra over Leizhou Peninsula from July to August, 2007. A total of 18070 size distributions were analyzed and the Z-R relationship of convective precipitation and mixtures of convective and stratocumulus cumulogenitus precipitation were obtained. These Z-R values were used for estimating areal rainfall and then compared with observations from automatic weather station. Cases with convective and mixtures of convective and stratocumulus cumulogenitus precipitation were selected for the evaluation. The precipitation studies were also used to evaluate the precision of the PARSIVEL measurements as compared to the rainfall data of automatic weather station.

Comparison of the Cloud Water Content Retrieved by Radar and from Numerical Model

The fully elastic three-dimensional convective storm model (IAP-CSM3D) established by the Institute of Atmospheric Physics (IAP), Chinese Academy of Science was used to simulate a strong convective storm that occurred in Hunan province on Apr.23th, 2004. The reflectivity observed by the Doppler weather radar was used to retrieve the water content, and established two display modes, which are CAPPI and VCS. Calculation field is defined as the square grid area with the radar station as center, with the horizontal side length of 150 km, with the height of 30 km, and with the distinguish ability of 1 km*1 km*1 km. To retrieve the cases water content in comparison with the water content from the numerical modeling. The result as the follow is indicated: the constant value line distribution of the retrieved water content is parallel to the simulated output as a whole no matter in the development stage or in the strong stage of the storm, and the strength in the storm center as well as the height position is consistent well, that reflect the storm structure on the whole and the retrieve effect is rather perfect.