Characteristics Of The Heavy Rainfall Vortex During Jianghuai Flood Season Based On Two Greenhouse Gas Emission Scenarios

The study is based on the simulated and projective outputs of the regional climate model RegCM4 with the horizontal resolution of 50 km. According to the model output, the analysis is done for the heavy rainfall vortex in JiangHuai during flood season to investigate its statistic structure and evolution characteristics. In addition, considering RCP4.5 and RCP8.5 scenarios of the new generation of scenario RCPs (Representative Concentration Pathways), the characteristics and evolution process of the low vortex during 2020 and 2030 is projected. The result shows that the simulation of RegCM4 model can reasonably capture both the environmental elements and characteristics of the vortex. The simulated outputs are similar to the reality in several ways including vertical developing height, lifetime and the relative rainstorm position of the vortex, but the simulated results are lower either on the number and warmest section height of vortex or the background temperature and humidity, while the intensity of vortex and velocity are higher. For the future from 2020 to 2030, the proportion of vortex with rainstorm is decreased, the vertical developing height of the vortex is mainly on 850 hPa; the mostly life cycle is 2 days; the distribution of heavy rainfall and the warmest zone height are close to those in historical period, but the intensity is weaken in the RCP4.5 scenario. Furthermore, in RCP8.5 scenario, the percentage of the vortex with rainstorm is greater than that in RCP4.5 scenario, the vertical developing height of the vortex is mainly on 700 hPa; the number of the vortex life cycle reached 3 days is increased; the vortex intensity is enhanced, and the thickness of the warmest zone is significantly extended. The moisture fronts in vortex are strengthen, but temperature fronts are weaken. In terms of the evolution characteristics, the vortex moving track mainly belongs to the two kinds of northeast and east of the two scenarios. While one of the important moving tracks is northward (18.2% of the total moving vortexes) in RCP8.5 scenario. In the aspect of vortex intensity changes with hours, the vortex in RCP4.5 is weaker than that in RCP8.5 comprhensively, and the trend of intensity is performed more stable. It illustrates that the enhancement of the vortex intensity and complexity of its trend in higher greenhouse gas emissions may influence the vortex heavyrainfall. It reveals that the more severe vortex precipitation may occur in the future with higher greenhouse gas emissions. So there should be further research on the development trend of low vortex with severe rainfall.