A two-layer, global, primitive equation zonally averaged model with diurnal cycle of radiation is used for studying the seasonal variations of the Inter-Tropical Convergence Zone (ITCZ). In order to investigate the mechanism that affects the displacement of the ITCZ over different types of surfaces three numerical experiments were made, considering: a)the earth's surface covered by the actual fractions of land, ocean, ice and snow; b) the earth's surface covered only by ocean ("aqua-planet"); and c) the earth's surface covered only by land ("continental planet"). The results showed that in the case of the "aqua-planet"the seasonal variation of the ITCZ was around 15\ub0, like in the case considering the earth's surface covered by the fractions of the different types of surface; in the case of the "continental planet", the seasonal variationof the ITCZ was larger than in the other cases (around 25\ub0). It was also that in the case of the earth's surface covered by land there was a strong seasonal inversion of the wind from the winter to the summer hemisphere. In the case of the erath's surface covered by ocean the seasonal inversion of the wind was moderate. RESUMO: Um modelo estatistico-dinamico de media zonal, de duas camadas, global, de equacoes primitivas, incluindo uma representacao do ciclo diurno da radiacao solar e utilizado para o estudo das variacoes sazonais da Zona de Convergencia Intertropical (ZCIT). Para investigar os mecanismos que afetam seu deslocamento sobre diferentes tipos de superficie foram realizados tres experimentos, que consideraram a superficie do globo coberta: a)pelas fracoes reais de terra, oceano, gelo e neve; b?somente por oceano ("planeta aquatico"); e c)somente por terra ("planeta continental"). Os resultados mostraram que, no caso do "planeta aquatico", a ZCIT teve um deslocamento sazonal de 15\ub0 de latitude, como no caso de se considerar as fracoes reais dos diferentes tipos de superficie dentro dos cinturoes de latitude; no caso do "planeta continental", a ZCIT teve um deslocamento sazonal maior, cerca de 25\ub0 de latitude. Foi notado, no caso do experimento com a superficie coberta por continente, uma forte inversao sazonal do vento, do hemisferio de inverno para o verao. No caso do experimento com a superficie coberta por oceano, a inversao sazonal do vento foi moderada.Pages: 75-8
