Abstract: The northeast Brazil rainfall index is calculated from data for Fortaleza (3.7S, 38.5W) and Quixeramobim (5.3S, 39.3W) Brazil obtained from the NCAR World Monthly Surface Station Climatology (http://rda.ucar.edu/datasets/ds570.0/).

Fortaleza and Quixeramobim (indicated as "F" and "Q" on the map of annual total rainfall, respectively) are located on the southern margin of the land monsoon and ... oceanic ITCZ rainfall region. Fortaleza is on the coast and Quixeramobim is located several 100 kilometers inland.

To calculate the index, both the Fortaleza and Quixeramobim time series are standardized by calendar month with respect to the period 1950-79. This calculation removes the seasonal cycle of the mean and standard deviation for each series. The standardized series are then averaged together, and standardized again. This series is called the Fortaleza Quixeramobim index (FQI). Northeast Brazil rainfall is most commonly discussed in terms of the average conditions during the wet season, February through May. February through May (FMAM) averages are employed in the following figures, and the FMAM-averages are standardized with respect to the period 1950-79.

credit: Joint Institute for the Study of the Atmosphere and Ocean (JISAO), Department of Atmospheric Sciences, University of Washington