INFLUENCE UNDER-CLOUDY CONVECTIONS ON DEVELOPMENT OF A CLOUDY CONVECTION

Introduction: Cloud convection causes hazardous weather [23]. So heavy rains and subsequent floods are a direct consequence of convective storms. Storm phenomena are often highly localized, so predicting why, where and when a storm develops is one of the most difficult problems in weather forecasting [10]. Today, operational numerical models often cannot predict the location and time of the onset of cloud convection when it is initiated in the skid layer, since these processes are not well represented in the models. However, the influence of these processes on the initiation of cloud convection is often noted in studies [25, 39], so that to predict the beginning of cloud convection requires knowledge of the thermodynamics and dynamics of the sub-cloud layer. Materials and methods: To predict the parameters of cloud convection, radiosonde data is used, which are plotted on the upper-air diagram. As a rule, it is assumed that the rate of ascending flows and overheating at the level of condensation are zero. But it's not always the case. Therefore, it is important to determine how the parameters of the surface layer affect the values of the parameters of cloud convection at the level of condensation. Results: In the article the mathematical model of a convection moist under-cloud layer atmosphere is developed. The mathematical model represents system of the equations of movements, heat conductivity and the continuity, recorded in a two-dimensional vertical plane. The analytical solution of the indicated system is received. Expressions for level of convection, level of the maximum velocity, for vertical and horizontal components ofvelocity, vertical distribution of temperature are established. From the indicated expressions the criterion of development under cloudy convections is derived. The received expressions allow derived in turn expressions for convection parameters on a condensation level. And it in turn allows derived criterion of development of a cloudy convection. It is established that development of a cloudy convection depends, as from absolute values of deficit of dew point in a ground layer, and in a greater degree from a vertical gradient of a mass fraction of a water vapor. In particular at critical value of a vertical gradient of a mass fraction of water vapor «explosive growth» convections is observed. Discussion and conclusion: Analytical expressions are obtained for the dew point deficiencies in the surface layer, which determine the values of the overheating function and the ascending flow rate at the condensation level. It has been shown that the development of subliminal convection is significantly affected by the value of the mass fraction of water vapor. It has been established that with the values of the gradient of the mass fraction of water vapor approaching the critical value, there is an "explosive" growth of convective cells in the sublayer. It is also shown that there is a critical value of the gradient of the mass fraction of water, contributing to the development of cloud convection.

приземный слой атмосферы, подоблачная конвекция, уровень конденсации, облачная конвекция, двумерная модель конвекции, аналитическое решение, surface layer of atmosphere, under-cloudy convection, a condensation level, a cloudy convection, two-dimensional model of convection, the analytical solution

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