Aspectos sinóticos associados à ocorrência do jato em baixos níveis na América do Sul - reanálise NCEP/NCAR e simulação com o MCGA CPTEC/COLA / Synoptics aspects associated to the occurrence of the low levels jet in the south America - reanalyses of the NCEP/NCAR and simulation with the MCGA CPTEC/COLA

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Cases of LLJ occurrence to the east of Andes were identified in NCEP/NCAR reanalyses data and in daily results of a climate simulation with the CPTEC/COLA AGCM, to identify the associated atmospheric patterns. weather forecasting of a case when there was occurrence of LLJ was also evaluated. Analysis performed in different seasons indicated similar synoptic characteristics. Then, the atmospheric features were analysed considering the occurrence or not of MCSs. Composites of LLJ cases showed synoptic situations that occur in cases when there is MCS over northern Argentina or convective activity in funnel shape associated with a frontal system, or not related to convection. The characteristics of low pressure over Argentina, vorticity centers at low and high levels and moisture advection, present different intensities in different groups, as well as different intensities and extension of the LLJ. In the EOF analysis the main patterns and variability of zonal and meridional wind field at 850 hPa and 200 hPa, SLP and OLR in cases of LLJ were established. The lag correlation indicated the pressure reduction in days with LLJ and also a trough and ridge displacement associated with a wavetrain over pacific and South America. A cluster analysis applied in LLJ cases obtained from the model results showed different intensity and orientation of the northerly flow associated with the LLJ, as well as the location of the frontal system to the south, that act as a channel for the low level flow. The low level flow, pressure field and vertical wind structure were well represented in the 24 and 48 hours forecasting using the CPTE/COLA AGCM.

ASSUNTO(S)

jato em baixos níveis jbn variability synoptic measurements padrões de correlação modos de variabilidade de jbn climatic simulation simulação climática características de escala sinótica low level jets correlation

ACESSO AO ARTIGO

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