Interannual Variability of Precipitation for the Centro de Lançamento de Alcântara in ENSO-Neutral Years

Abstract

The interannual variability of precipitation in El Niño/Southern Oscillation-neutral years was studied for the Centro de Lançamento de Alcântara region. Monthly precipitation, sea surface temperature, wind at 925 hPa and outgoing longwave radiation data from various gridded datasets for the 1951-2010 period (60 years) were used. The data grouping was based on terciles. For the Centro de Lançamento de Alcântara in El Niño/Southern Oscillationneutral years, March is the month of the rainy quarter (March to May) when the interhemispheric gradient of the sea surface temperature anomalies over the Atlantic (GRAD) and the atmospheric circulation at 925 hPa over the Centro de Lançamento de Alcântara were able to best explain the variability of precipitation. In this month, the wind direction at 925 hPa was the factor that explained the highest fraction of precipitation variance (40%), followed by GRAD (30%) and the wind magnitude (20%). For the Centro de Lançamento de Alcântara, in general, above-average precipitation was related to weak north-northeasterly low-level winds and southward GRAD, while below-average precipitation was related to strong east-northeasterly low-level winds and northward GRAD. These features were related to an eastward expansion of the Amazon convection towards the northern Northeast Brazil and might be related to a slight southward displacement of the Intertropical Convergence Zone in above-average precipitation years.

Wet Days in the Dry Quarter of the Alcântara Launch Center Region: Observational Features

“…Above-mean (below-mean) values of PWET and NWET are significantly related to southward (northward) GRAD, i.e., South Atlantic Ocean with positive (negative) SST anomalies and/or North Atlantic Ocean with negative (positive) SST anomalies, and weak (strong) low-level wind over the CLA region. These relationships agree with the results of Marques and Oyama (2015) for the rainy quarter in the CLA region. Although the linear correlations with GRAD and MAG are significant, the fraction of explained variance (measured by the coefficient of determination, r 2 ) is rather limited: 9% to 10% for PWET and 15% to 27% for NWET.…”

“…These factors affect the interannual variability of precipitation for the CLA in the rainiest months (Marques and Fortes 2012; Marques and Correa 2014; Pereira and Marques 2014). Their monthly values are computed using the same datasets and methodologies described in Marques and Oyama (2015). The degree of association between the time series of the quarterly (SON) mean of a given factor and the time series of PWET or NWET is assessed by the Pearson coefficient of correlation.…”