6 research outputs found
Nonlinear instability of baroclinic atmosphere with reference to planetary scale disturbances
In this paper we investigate the stability of zonal flow in a baroclinic atmosphere with respect to finiteamplitude planetary-scale disturbances by applying Arnolds method. Specifically, we examine the sign of the second variation of a conserved functional for the case of a polytropic atmosphere (i.e. one with a linear lapse rate) and with a linear profile of zonal wind. Sufficient stability conditions for an infinite atmosphere (i.e. with a temperature lapse rate equal to zero) are satisfied only for an atmosphere in solid body rotation. For a polytropic atmosphere of finite extent (a lapse rate is not equal zero) the sufficient conditions of stability can be satisfied if a lid is placed below min(Zmax, polytropic atmospheric height). The dependence of height Zmax on values of the vertical gradient of the zonal wind and the zonal temperature distribution is calculated.Pages: 363-37
Application of the modified ertel's potential vorticity to investigation of south hemisphere circulation
A arbitrariedade que existe em definição geral da vorticidade potencial de Ertel (EPV) é usada para conseguir vorticidade potencial (PV) modificada " optimal ", no sentido de minimizar a rapidez de mudança da PV com tempo devido ao atrito e a aquecimento diabatico. Foi obtido que novo PV modificado e alguns dos seus funcionais são quasi-conservadores em processos climáticos, e podem ser usados com alguma vantagem em investigações de regimes climaticos. Aplicando funcionais tais como a carga do vorticidade, e entropia informativa da distribuição da massa de ar sob vorticidade potencial modificado de Ertel ao estudo de comportamento temporal das estatisticas da circulação para os meses de janeiro e de julho detectamos um crescimento progressivo da diferença da temperatura do ar entre equador e pólo na superfície do Hemisfério Sul durante os 1980s
The Instability of Ultra-long Waves during the Formation of Long- term Weather Anomalies
The ultra-long waves of the main meteorological fields (geopotential, velocity, temperature, ozone) play a very important role in the formation of weather and climate regimes of the atmospheric circulation. There is a obvious correlation between the eyents of the blocking formation and the values of the amplitude of the first mode of geopotential. In this work we have investigated the relationship between the vortex formation in the Eastern Pacificand a blocking episode during 19/12-26/12/1996 near 180W. We have found that this blocking is associated with large amplitude of the wave with zonal number 4, and the formation the vortex is associated with this blockirig. Arriving South' America and interacting with the South Convergence Zone (SACZ) this vortex is converting,into blocking vortex pair over South of Brazil. Very strong precipitation was generated over Southern Brazil at that time. In order to determine the role the baroclinic instability for the increasing of ultra-long waves we have used geostroph!c equation type II and investigated stability of zonal flow in more common nonlinear formulation. We found that the growing of the amplitude of planetary waves in our case was not associated with this type of instability.Pages: 1415-141
Implementacao de uma nova parametrizacao de radiacao solar no modelo ETACLIM
Neste trabalho um novo esquema de parametrização da radiação solar é implementado no modelo ETACLIM, desenvolvido no CPTEC para estudos de mudanças climáticas regionais. Comparações entre as versões original e modificada do modelo e observações para o mês de janeiro de 2003, mostram uma melhoria na simulação dos fluxos de radiação solar à superfície e uma diminuição do viés positivo na temperatura do ar à superfície sobre grande parte do continente sul americano. Na região da ZCAS observa-se um incremento do fluxo de radiação solar, o qual é associado ao aumento da cobertura de nuvens baixas. Estes resultados preliminares indicam que é necessário um ajuste nos esquemas de convecção e microfísica com a nova parametrização de radiação solar para melhorar o desempenho do modelo
Relacoes entre os processos ENOS em grande escala e peculiaridades climaticas regionais no Norte do Brasil
The correlation between the precipitation over Northern Brazil and some parameters caracterizing a large-scaled circulation over this region was investigated. It is found that interannual oscilation of the precipitation in this region is connected with alternation of different monthlymean circulation patterns
Relacoes entre os processos ENOS de grande escala e pecualiaridade do clima regional no Sul do Brasil
The correlation between precipitation in the southern Brazil and parameters caracterizing the regional and global circulation is studied. It is found that anomalously large precipitation in this region during november for El Niño years is connected with South Atlantic cyclones that can reach the states of Paraná and São Paulo states. The recurence of this synoptic situation is evinced in the EOF pattern