Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

Time-dependent modeling o fthe initial stage o f theformation o fcyclones in the intratropical convergence zone o fthe northern hemisphere Simulation results CD V-D a -J 20 Г 15 10 ’ / . / / / 7 / / / / V / / / / -■' • / / у . . ' / / / / ’* ; / У/ s S / • / / / , , / , • / / / , . / / / , / r-y / / 6/J/ a >* ^ я* / /•-*•_ - SSV4S4 44 4 4 N S 4 4 S 4 V 4 V. Ч V X «.• » ч 4 . V ‘ n > » v; >. S; \.\.:V;VV \ V . ч s' \ ~ s ч-V\ \ у . . VNv’V ' si s.4 v > r‘\ \ ' V VV\ \ ЧV» • 4 \ s 'j V■\' ' \ \ ' \ \ \ Г:- .*;iy&i"<K.Sr;*г-< V S N \ ' \ V 4 \ \ N 4 4 4 \ % \ \ \ \ V, \ \ The important parameters of the utilized regional mathematical model are the boundary conditions and initial distributions of the calculated quantities. To assign the initial and boundary conditions for the present paper, we have studied many results of satellite microwave monitoring of the Earth’s atmosphere, obtained in Space Research Institute and included in the electronic collection “GLOBAL-Field” ( 'http://www.iki.rssi.ru/asp) . As a consequence of these studies, we have advanced a hypothesis of the important role of the shape of the intratropical convergence zone on the process of the formation of tropical cyclones. It is known that the intratropical convergence zone is similar to a band, in which zonal westward flow of air predominates, with the air velocity being abnormally high. The width of the intratropical convergence zone can achieve a value of some hundreds of kilometers. To verify the advanced hypothesis, we disposed the south boundary of the simulation domain in the vicinity of the equator. It was supposed that, at the initial moment, distributions of zonal, meridional and vertical components of the wind were consistent with the situation when the intratropical convergence zone intersects the simulation domain in the west-east direction. Calculations were made for various cases in which the initial forms of the intratropical convergence zone were different and contained convexities with distinct shapes. Initially, let us consider the first case when, at the initial moment, the intratropical convergence zone contains a convexity in the north direction, with the deviation achieving a value of a few hundreds of kilometers. The initial form o f the intratropical convergence zone may be easy seen from the top panel of the Fig.l, where it is like a light curved band. It is essential to note that, in the considered first case, the left crook of the convexity is sharp while the right crook o f the convexity is gently sloping, with the left and right ends of the convexity being at the same latitudes. The time evolution of model parameters was numerically simulated using the mathematical model during the period for about one day. The results of time-dependent modeling are partly shown in Fig. 1. As can be seen from this figure, in the course of time, the initial distribution o f horizontal component of the air velocity was considerably transformed. A cyclonic vortex flow arose whose center is close to the southern edge of the initial intratropical convergence zone. The horizontal wind velocity in this cyclone achieved a value o f 20 m/s during the period of twenty seven hours. The radius of this large-scale cyclonic vortex is about 600 km. In addition, we made simulations for second and third cases when, at the initial moment, the intratropical convergence zone has different configurations. For both cases, the initial forms o f the intratropical convergence zone contained the convexities analogous to the convexity o f the first case. However, for the second case, the right end of the convexity is situated at more northern latitudes than the left end of the convexity (see top panel of Fig. 2). On the contrary, for the third case, the right end of the convexity is situated at more southern latitudes than the left end o f the convexity (see top panel of Fig. 3). The results of time-dependent modeling for second and third cases of the initial configurations of the intratropical convergence zone are partly shown in Figs. 2 and 3. As can be seen from this figures, in the course of time, cyclonic vortex flows arose whose centers are close to the southern edge o f the initial intratropical convergence zone. These vortices are analogous to that obtained for the first case. 15 : № 43 V-O =3 a -J Cft v -o aT 3 '' ^ /У v\. T*- ' '• ■ 4 . - •. .. .. • - к V. v X - C v V s . . . 4 A V V..< ' S 4 S 4 K « V *v-V V '. V S s N N 4 ,S V Ч V ■“! 4 V \ К N 4 \ \ \ \ N \ \ \ V \ \ \ \ Л \ V ч т и Т и п n 7 u и и и '. / / / / / / / / / / / I I I I п г •- , ' S S / / / / / / / U Li ......... i s p i ' t e / 20 I 15 10 20 Fig. 1. The distributions of horizontal component of the air velocity (m/s) at the altitude of 600 m, assigned at the initial moment (top panel), computed 12 hours after the beginning of calculations (middle panel), and computed 27 hours after the beginning o f calculations (bottom panel). The results are obtained for the first initial configuration of the intratropical convergence zone. 183