Luiz Carlos Baldicero Molion

Análise do comportamento das trovoadas no estado de alagoas, previsão à curto prazo

The thunderstorm frequency was studied using TRMM satellite and the DECEA data for the 10 year period (from 1998 to 2007). It was observed that the storms were more frequent in the summer months, with greater occurrence in March. The El Nino event inhibits the phenomenon (only 20% of cases of all), but in the La Nina and normal years, was observed an increase in days of storms up to 80% of the cases. The thunderstorms were associated with trade winds, with cyclonic curvature and in the high levels with ULCV, JSNEB and anticyclone. The thunderstorms were formed predominantly in northwestern ULCV in the entrance (warm side) and in the exit (cold side) of JSNEB. The observed vertical profiles of air and the dew point temperatures were similar to the forecasted profiles, constructed by the air parcels trajectories by HYSPLIT model, up to 48h and up to 24h antecedently, respectively. The index LI and CAPE+ predicted a very unstable atmosphere with 48 hours antecedence.

Tendências das classes de precipitação na região metropolitana de São Paulo

Trends of the annual and summer rainfall totals of 21 rain gauges located in the Metropolitan Region of Sao Paulo (MRSP) are analyzed using three rainfall classes: drizzle, moderate and intense. The rainfall data series are variable in time length within the period 1888 to 2004. Mann-Kendall tests are used to highlight the possible trends that are fitted by simple linear regression when they are statistically significant. Positive trends are found in the annual totals of 9 stations in the MRSP central area, but only 3 of them occurred in the summer period. Significant increasing (decreasing) trends in the frequency of drizzle events in the annual (summer) period are evident in 9 (8) of the gauges analyzed and, in 4 (6) of them, the drizzle frequency decreases. Regarding the moderate annual rainfall class, 3 gauges show increasing trend whereas one presents decreasing trend. However, considering only the summer season, 5 gauges show significant decreasing trend and only in one of them the trend is increasing. With respect to the severe annual rainfall events, 4 stations present significant increasing trend and only in one of them trend appears to be declining. When summer season is considered, only 2 gauges present significant decreasing trend.

ANÁLISES CLIMÁTICAS: O FILTRO HODRICK-PRESCOTT APLICADO AOS ÍNDICES ATMOSFÉRICOS DA OSCILAÇÃO SUL E DA OSCILAÇÃO DO ATLÂNTICO NORTE

The existence of apparent cycles or periodicities in long time series of meteorological variables helps understanding the physical processes that control the climate and the identified cycles may serve as tools for regional climate prognostics. With this insight, the Hodrick-Prescott (HP) filter was applied to the series of Southern Oscillation (SOI) and North Atlantic Oscillation (NAO) indices covering the 1900 to 2010 period. The application of the HP filter to a time series results into two new time series, one of the trend and other of the cyclic/random signal of the variable. Afterwards, the two series were submitted to the Morlet wavelet transform analysis for identifying the apparent cycles. The SOI trend presented cycles of 6, 9, 17 and 28 years, the first associated to the El Nino/La Nina Cycle and the next two possibly related to the 18 year Lunar Nodal Cycle (Saros Cycle), and the remainder, to the Pacific Decadal Oscillation (PDO) cycle. The NAO trend showed 6, 9 and 33 year cycles, the last two possibly related to the Saros Cycle. The linear correlation coefficients between the cyclic/ random SOI series, with 6 month lead, and the Brazilian rainfall totals presented high values, up to 0.72 and -0.67 for the countrys northern and southern regions, respectively, during the 1948-1999 (52 years) period, with a statistical significance level above 99%. This period covers the two recent PDO phases. Considering that climate models still do not have still adequate skill for regional forecasting in Brazil, it is suggested that the climate forecasting technique, using up to 6 month leading time of the cyclic/random SOI series, be exploited and, eventually, validated.