Analysis On The Features Of Ground Atmospheric Electric Field And Studies On The Lightning Forecasting Based On Multi-source Observations

In this paper, firstly, the data of atmospheric electric field in Nanjing, Zhenjiang, Yangzhou and Changzhou have been quality controlled, uniformed calibrated and network organized, then the spatial variations of atmospheric electric field and charge structures have been analyzed by combining with the data of radar, lightning location and sounding data. Finally, the lightning forecasting methods are proposed and the results have been analyzed by using the above multivariate observations separately and synthetically.According to the characteristcs of atmospheric electric field observations, quality controlling method for the data of atmosphere electric field has been proposed in order to improve the quality of atmospheric electric field data. After quality controlling, uniformed calibration and network organization, we ananlyed the data and found that the distribution characteristics of atmospheric electric field consistent with radar echo and lightning positionning data. The lightnings occur in the area where the electric field gradient is large.The characteristics of electric field under different weather conditions (especially thunderstorm) were analyzed. The results showed that the isolated thunderstorms’electric field had a clear evolution process while the multi-units thunderstorms’were complicated. The evolutions of thunderstorms’s electric field can be divided into three types:positive increasing, negative increasing and up-down jitter. In the meantime, the evolution of electric field closely realted with lighting occurrence and the lighting process was agreed well with three types of the evolution of thunderstorms’s electric field. The slow change, jumpiness and polarity inversion are the features of electric field used for distinguishing thunderstorm and can be used for lightning forecasting.As for the charge structure of thunderstorm, first, the electric field evolution was simulated under different charge structures, and then the charge structure of thunderstorm was analyzed by comparing the electric field observation data with simulation electric field with the help of radar data. It is found that the charge structures of thunderstorms are complicated and diversified. The charge structure of thunderstorms is mainly dipole and the tripole charge structure is also existed. The relation of radar reflectivity and thunderstorm initial feature, the characteristics of environmental temperature and charge distribution were implemented in the inversion of charge distribution parameters in this paper, and then a quasi-normal charge distribution model was proposed. The method was used to analyze three isolated thunderstorms and a MCS that passed through the experiment site in2009. The evolution of charge density with time and the space distribution of these thunderstorms can be abtained. The simulated space electric field and charge density space distribution were compared with other observation and networked electric field with interpolation method. It is found that the distribution of atmospheric electric field agrees well with radar echo and lightning location data. The lightning occurred in the place where the electric field gradient is large. In addition, it illustrate that the model and obtained parameters are reasonable to some extent, and the method for networking electrostatic field using radar and sounding data is feasible. There existed some deviation between networked electric field with interpolation method and the location of lightning and radar echo. Therefore, it also showed that the site deploy of electric field mill is very important.The methods and the effect of lightning forecasting based on atmospheric electrostatic field, radar and lightning location data separately were analyzed and found that:the lightning forecasting made use of lightning location data is feasible; the proportion of EF absolute amplitude which exceed1kV/m reach1/3is considered the best electrostatic field amplitude index, while the best electrostatic field differential index is defined as the times of difference absolute amplitude which exceed0.15kV/m reach2times in two radar scan times, which are more suitable indexes for the region in this study.Based on the lightning forecasting with atmospheric electrostatic field, radar and lightning location data separately, a method of cloud-ground (CG) lightning nowcasting based on electric field observations, radar data was proposed. The experimental (2009) and independent test (2010) results shows that POD (Probability of Detection, POD) is82.7%, FAR (False Alarm Rate, FAR) is14.6%, CSI (Critical Success Index, CSI) is72.4%and average lead time is20.8min. Besiades, on the basis of the temporal relationship of electric field mills, radar and lightning location mill observation when thunderstorms move toward, a lightning nowcasting method based on a combination of lightning location system, electric field and radar data was proposed and the results show that POD, FAR and CSI values were87.1%,16.5%and74.4%respectively and average lead time was24.4min. Finally, a classical thunderstorm example of regional lightning warning in the region is analyzed. Results show that this method can present a visual development of thunderclouds and lightning; it can provide some useful information about the region’s lightning characteristics.