Papel dos fluxos de calor latente e sensível em superfície associado a um caso de ciclogênese na Costa Leste da América do Sul

Abstract

RESUMONeste estudo foram realizados experimentos numéricos com um modelo meteorológico regional a fim de verificar o impacto dos Fluxos de Calor Latente (FCL) e Calor Sensível (FCS) em superfície no desenvolvimento de um ciclone intenso ocorrido sobre a costa leste da região sudeste da América do Sul, entre os dias 24 e 26 de julho de 1998. A taxa de intensificação do ciclone foi reduzida em 6 hPa/24 h no experimento em que os FCL e FCS estavam ausentes. Verificou-se que a ausência do FCL apresentou maior impacto do que a ausência do FCS, fazendo com que a taxa de intensificação fosse reduzida em 6 hPa/24 h para o experimento sem FCL e permanecesse inalterada sem FCS, mas neste último a isóbara de menor valor no centro do ciclone ocupou uma área menor. A ausência dos FCL e FCS em superfície gerou uma camada mais seca e mais fria próxima à superfície oceânica, reduzindo a instabilidade potencial do ambiente e diminuindo a intensificação do ciclone. Concluiu-se, portanto que os FCL e FCS em superfície foram importantes antes da fase de mais rápido desenvolvimento do ciclone, agindo no sentido de preparar o ambiente para uma ciclogênese mais intensa, através do fornecimento de energia e umidade para a baixa troposfera. Na fase de mais rápido desenvolvimento, a energia e a umidade disponíveis nas camadas mais baixas da atmosfera (inseridos na fase anterior) também foram importantes, permitindo ao ciclone se desenvolver mais intensamente do que ocorreria em um ambiente mais seco e menos instável termicamente. Palavras-Chave: ciclogênese, fluxos de calor em superfície, modelo regional. ABSTRACT: ROLE OF SURFACE LATENT AND SENSIBLE HEAT FLUXES ASSOCIATED TO A SOUTH AMERICA EAST COAST CYCLOGENESIS CASENumeric experiments were run with meteorological regional model with the purpose to verify the impact of both latent and sensible surface heat fluxes (FCL and FCS, respectively) during the development of an intense east cost cyclone over southeastern region of South America from 24 to 26 July, 1998. The intensification rate of the cyclone was reduced by 6 hPa/24 h in the experiment where the FCL and FCS were absents. It was also verified that the absence of FCL presented more impact than without FCS. The intensification rate was reduced by 6 hPa/24h in the experiment without FCL and became unaltered in the experiment without FCS, but in the later the isobar with minimum value around the cyclone center occupied a smaller area. The absence of the FCL and FCS generated a drier and colder layer near the oceanic surface, reducing the environmental potential instability and decreasing the cyclone intensification. With these results it is possible to conclude that the FCL and FCS were important before the phase of most rapid cyclone development, preparing the environment to a more intense cyclogenesis, supplying both energy and moisture to the lower troposphere. In the phase of the most rapid development, the available energy and moisture (inserted in the previous phase) in the lower levels were also important, allowing the cyclo...

On precursors of South American cyclogenesis

“…Finally, to avoid taking into the cyclone statistics weak events with little impact on local weather, only centres lasting a minimum of 24 hr, and with a minimum pressure, taken throughout the whole lifecycle, below 1010 hPa (e.g. Gan and Rao, 1991; Dal‐Piva, 2001; Trigo 2005) are considered hereafter to be extratropical cyclones.…”

Synoptic and dynamical analysis of subtropical cyclone Anita (2010) and its potential for tropical transition over the South Atlantic Ocean

“…The fast and strong deepening of some observed cyclones in this area of the Atlantic was pointed out by Dal Piva et al . [] and Gozzo and da Rocha [] as a result of the intense latent and sensible turbulent heat fluxes provided by the warm waters of the Brazilian Current. In the absence of such heating, Reboita et al .…”

Forecast Structure Development for Modelling the Southern Brazilian Continental Shelf Hydrodynamic

“…The South Atlantic High-Pressure Center and the Polar Mobile Anticyclone are high-pressure zones, and the region comprised between both is a depression where winds from both systems converge (Gan, 1992). Such convergence creates the cold front cyclonic circulation, generally associated with the Subtropical Convergence Zone and the Brazil-Malvinas confluence (dal Piva et al, 2008).…”