Relationship between Lower Positive Charge Center and Warm Cloud Depth in Thunderstorms over Qinghai-Xizang Plateau

Abstract

In order to make up for the limitation of thunderstorm processes observation， and to explain the relationship between the large lower positive charge region （LPCC） and the warm cloud depth （WCD） of thunderstorms from the close relationship between dynamics， microphysics and electrification process over Tibet Plateau， sensitivity test groups are set in this paper.The sounding initial field of a thunderstorm process with obvious LPCC and strong convection in Naqu area of Qinghai-Xizang Plateau is changed by three ways， and 10 groups of initial field examples with different WCD are obtained.The possible relationship between WCD and LPCC is simulated and analyzed by using a three-dimensional dynamics-electrification coupled model.The results show that WCD is not the only factor determining the strength of LPCC in the Tibet Plateau.The obvious LPCC requires a thin WCD with strong but not too strong rising speed.Even if the WCD is very thin， too strong updraft is only easy to form a normal type thunderstorm with very strong main positive and middle negative charge areas， and too weak updraft is only form normal type thunderstorms with weak main positive and middle negative charge regions.The two main sources of raindrops， namely， raindrops collision and collection with cloud water and graupel melting to form rainwater， and the main source of graupel， namely， graupel riming with cloud water mainly depend on the convective intensity.The inhibition effect of thin WCD on warm cloud precipitation process is less than the enhancement of strong updraft on warm cloud precipitation process.When the convective intensity changes little， WCD mainly dominate the distribution height of ice particles.The thinner the WCD， the smaller the size and the more the number of cloud droplets is transported above 0 ℃.It is more conducive to the growth of low-level ice particles， and the more obvious LPCC and middle negative charge region.When WCD is thicker， it is more conducive to the growth of higher ice particles， and LPCC tends to weaken， while the middle negative and main positive charge regions tend to be obvious.

Keywords

• qinghai-xizang plateau
• lower positive charge center
• warm cloud depth
• numerical model