局地积云降水过程对云结构的影响

THE INFLUENCE OF THE PROCESS OF PRECIPITATION ON THE STRUCTURE OF LOCAL CUMULUS

  • 摘要: 本文考虑了降水过程中水滴对空气的拖带作用和降温作用,并考虑到含水量变化时,由于水滴对空气拖带力的变化,而对垂直运动产生的反馈影响,导出了局地积云的运动方程、热力方程和含水量方程,并由此研究在降水过程中云中空气垂直运动、云内外温差和含水量结构的变化。计算结果指出,局地积云在降水过程的影响下,云中空气的垂直运动、云内外温差和含水量都要明显变小,并且很快地由下向上逐渐出现下沉运动,云也由下向上逐渐消散。计算结果与实际观测现象是基本相似的。本文共做了五个不同条件的个例数值计算,并由此分析比较了不同降水强度、不同稳定度、不同云中初始条件和不同云外环境所起的不同作用。

     

    Abstract: Taking consideration of the feedback on the vertical motion due to the drag force and the cooling effect acted on the air by raindrops, a system of differecitial equations for the vertical velocity, temperature difference between cloud and environment and the water.content is introduced. The solutions are analysed numerically for five sets of different parameters. From the analysis the effect of different intensity of precipitation, stratification, initial condition and environment are studied, and it is further found that under the influence of precipitation process, the vertical velocity, temperature difference and water content in cloud are reduced very quickly, and the descending motion appeas rapidly first at the cloud base, then spreads upward. Thus, starting from the cloud base, the cloud dissipates rapidly. This resembles the observed process of the dissipation of a precipitating cloud.

     

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