Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

Physics o f Auroral Phenomena”, Proc. XXXVI Annual Seminar, Apatity, pp. 189 - 192, 2013 © Kola Science Centre, Russian Academy of Science, 2013 Polar Geophysical Institute NUMERICAL SIMULATION OF THE INITIAL STAGE OF THE FORMATION OF LARGE-SCALE CYCLONIC VORTICES IN THE VICINITY OF THE INTERTROPICAL CONVERGENCE ZONE I.V. M in g a lev 1, N .M . A stafieva2, K.G. O rlov1, V.S. M ingalev1, O.V. M ingalev1, V.M. Chechetkin3 A b s tra c t. A regional non-hydrostatic mathematical model of the wind system of the lower atmosphere, developed recently in the Polar Geophysical Institute, is utilized to investigate the initial stage of the origin of large-scale vortices at tropical latitudes. The model produces three-dimensional distributions of the atmospheric parameters in the height range from 0 to 15 km over a limited region of the Earth's surface. Simulations are performed for the case when this region is intersected by an intertropical convergence zone, with the horizontal velocity field being asymmetric relatively the centerline of the intertropical convergence zone inside and beyond it. The results of modeling indicate that the origin of a convexity of the intertropical convergence zone, having the specific forms, can lead to the formation of a pair of cyclonic vortices. In tro d u c tio n It is known that severe tropical cyclonic storms and hurricanes can cause tremendous damage and numerous fatalities. Therefore, prediction o f tropical cyclone formation is very important problem. Many of the details of the initial stage of the formation of tropical large-scale vortexes, however, are still unresolved. Mathematical models have the potential to make significant contributions to our knowledge of the processes responsible for the formation o f tropical large-scale vortices. Recently, a regional mathematical model o f the wind system of the lower atmosphere has been developed in the Polar Geophysical Institute (PGI) [Belotserkovskii et al., 2006]. This mathematical model has been applied to verify the hypothesis of the influence o f the shape o f the intertropical convergence zone (ITCZ) on the process of the formation o f tropical cyclones. It was shown that the origin of a convexity in the configuration of the intertropical convergence zone can lead to the formation of a cyclonic vortex during the period for about one day. Its center is close to the southern edge o f the initial intertropical convergence zone [Mingalev et al., 2011]. The results of mathematical modeling have indicated that the origin of a convexity of the intertropical convergence zone, having the specific forms, can lead to the formation o f not only a single cyclonic vortex but also a cyclonic-anticyclonic pair [Mingalev et al., 2012]. The purpose of the present work is to continue these studies and to investigate numerically, applying the regional mathematical model of the wind system o f the lower atmosphere developed in the PGI, the initial stage of the origin of large-scale vortices in the vicinity o f the intertropical convergence zone. M a th em a tic a l model In this study, the regional non-hydrostatic mathematical model of the wind system of the lower atmosphere, developed not long ago at the Polar Geophysical Institute, is applied. In the model, the atmospheric gas is considered as a mixture of air and water vapor, in which two types of precipitating water (namely, water microdrops and ice microparticles) can exist. The model is based on the numerical solution of the system of transport equations containing the equations of continuity for air and for the total water content in all phase states, momentum equations for the zonal, meridional, and vertical components of the air velocity, and energy equation. The characteristic feature of the model is that the vertical component o f the air velocity is calculated without using the hydrostatic equation. Instead, the vertical component of the air velocity is obtained by means of a numerical solution of the appropriate momentum equation, with whatever simplifications of this equation being absent. In the momentum equations for all components o f the air velocity, the effect o f the turbulence on the mean flow is taken into account by using an empirical subgrid-scale parameterization similarly to the global circulation model of the Earth’s atmosphere developed earlier in the PGI [Mingalev I. and Mingalev V , 2005; Mingalev et al., 2007]. In essence, the applied regional mathematical model is based on numerical solving of non-simplified gas dynamic equations and produces three-dimensional distributions of the wind components, temperature, air density, water vapor density, concentration of micro drops of water, and concentration of ice particles in the height range from 0 to 15 km over a limited region of the Earth's surface. The dimensions of this region in longitudinal and latitudinal directions are 40° and 25°, respectively. The model takes into account heating / cooling of the air due to Po la r G eophysical Institute, Apatity, Russia Space Reseach Institute, Moscow , Russia 3 K eldysh Institute o f A p p lied Mathematics, Moscow, Russia 189