| Mesoscale model simulations have been performed of a severe thunderstorm that occurred on 22-23 August 2001 in Huabei area in china. Combing with satellite, Doppler radar images and general weather observations, the evolution mechanism of the severe thunderstorm is analysed with emphasis on the orographic effect of Taihang mountain. The model simulations indicate that the severe storm is occurred in the pattern high-level of northwest flow, the waterjumping downhill flow form Taihang mountain is the key mechanism to initiate the convective, on the other hand, the terrain can induce unbalanced low-level flow, which play an importance role in generating the mesoscale gravity waves(MGWs) by convergence and divergence in low-level troposphere.The explosive Convective can initiate MGWs in high-level troposphere and enhanced the low-level MGWs. Convective and shear instability can provide the wave energy. During the initial and merger stages, the convective and MGWs interact with each other constructively. Specifically, the line of deep convective seems to provide the waves energy through enhancing mass convergence/divergence, the waves tend to help organize convective elements into a line structure, the wave-CISK is an crucial mechanism, and the wave/convection interaction fit certain theories of gravity wave propagation and the vertical structure conceptual model. After the storm move in Shandong area, the moist downdrafts appears, the MGWs apart from the thunderstorm and move faster, the MGWs weaken gradually because absence of wave duct and energy supply. |
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