Caracterização física e dinâmica de episódios de chuvas intensas nas regiões sul e sudeste do Brasil / Physical and dynamical characteristics of heavy rainfall episodes in southern and southeastern Brazil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The heavy rainfall events occurred in Southern and Southeastern Brazil between 1960 and 2004 are investigated. It is observed positive trends in the annual frequency of these events in both regions in this period of 45 years. The trend in Southern Brazil is more significant. The atmospheric environments associated with these events also are investigated, but within the 1979-2004 period, which is covered by Reanalysis 2 data. Five synoptic-scale patterns are identified in both regions. The heavy rainfall events are classified into two classes, according to its rolationship with tho patterns: positives and negatives. The composite fields for the positively correlated events in Southeastern show configuration similar to those associated with SACZ, while negatively correlated events suggest the influence of cold fronts. The composite fields for Southern events show more commons characteristics: a low-pressure center located over northern Argentina and strong northwesterly winds over Paraguay that transport warm and moist air to Southern Brazil. One of the patterns presents unique conditions like a southwest-northeast oriented trough over northern Argentina and a high-pressure center located south of Southern Brazil. Comparisons between the events in Southern Brazil with those in Southeastern Brazil reveal that the former are associated with stronger synoptic forcing. In the regional scale, the simulations performed with MM5 model are used to obtain field composites as well as to analyze the moisture, vorticity and heat budgets. MM5 has a weak performance in simulate rainfall quantities. However, the synoptic-scale environment is well captured. Regional composite fields show little differences in function of the synoptic-scale patterns. This shows that the conditioning of the atmosphere to heavy rainfall occurrence by synoptic-scale does not produce, necessarily, important differences in the regional scale configurations.

ASSUNTO(S)

precipitação extrema meteorologia dinâmica meteorologia sinótica modelagem numérica compostos extreme precipitation dynamic meteorology numerical modeling composites

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