Ciclo diário e eventos intensos de precipitação no planalto Costeiro do Estado da Bahia.

Abstract

The objective in this study is to analyze the precipitation variability in four municipalities of the coastal high plains of Bahia State: Salvador, Ilhéus, Eunapólis e Teixeira de Freitas. Hourly precipitation time series obtained by processing the raw data of automatic weather stations operated by the Institute for Environment and Water Resources (INEMA) is the main dataset used in the research. The period of study is from April 2000 to February 2009. The diurnal precipitation cycle was analyzed by means of the rainfall totals and frequencies (in days) considering the 24 one-hour intervals that constitute one day. Intense rainfall events were identified by applying the percentile technique to the daily 24-hour precipitation totals time series. It rains all year long in the four municipalities. In general, the number of intense events and raindays is higher in years with larger precipitation totals. The diurnal cycle of rainfall frequency for Salvador and Ilhéus has similar characteristics: an afternoon minimum and a maximum at dawn (Ilhéus) and morning (Ilhéus and Salvador). The daily cycle for Eunapólis and Teixeira de Freitas show two periods of maximum (early morning and early afternoon), and two minima, one short, in mid-morning, and a long-lasting one, in nighttime. A selected case study was performed focusing on a cloud cluster that developed in a trough area in the easterlies over Bahia State in October 2006, in the night of the 14th and dawn of the 15th.