Rainfall zoning of Bahia State, Brazil: an update proposal

Abstract The state of Bahia’s main climatic characteristic is the high spatial and chronological variability of precipitation. This heterogeneity may be used to determine of pluviometrically homogeneous areas that can define mesoregions in the state, since they allow better management of water resources and help in the elaboration of agricultural studies. The mesoregions already proposed by the scientific community for the state were based only on the annual precipitation in the proximity of the pluviometric stations. In this paper, besides these parameters, spatial and chronological rainfall distribution was considered, i.e., the Precipitation Concentration Degree (PCD) and Precipitation Concentration Period (PCP). The new zoning is based on an update of a study defined in 2000 that divided Bahia into eight mesoregions. Thus, 180 pluviometric stations were distributed throughout the state and grouped conforming to the division previously described. It was concluded that some stations of the same mesoregion had presented conflicting values for the analyzed parameters and, therefore, should not belong to the same area. Starting from an arrangement of the collection stations, considering their proximity, annual precipitation and statistical parameters, a new zoning for Bahia with 10 clusters was defined and validated through the statistical treatment of data.

摘要 巴伊亚州最显著的气候特征为降水的空间与时间变异性极强。这种降水异质性可用于划定雨量均质区域，以此划分该州的气候中分区，这类分区有助于优化水资源管理，并支撑农业相关研究的开展。此前学界为巴伊亚州提出的气候中分区方案，仅基于雨量观测站周边的年降水量数据。本文除采用上述参数外，还纳入了降水的时空分布特征，即降水集中程度（Precipitation Concentration Degree, PCD）与降水集中期（Precipitation Concentration Period, PCP）。本次全新的分区方案以2000年一项将巴伊亚州划分为8个气候中分区的研究为基础进行更新完善。据此，研究在全州范围内布设了180个雨量观测站，并按照前述分区方案对站点进行初步分组。研究结果表明，原属同一气候中分区的部分站点，其分析参数存在矛盾，因此不应划归至同一区域。本研究在对观测站点进行初步分组的基础上，结合站点的空间邻近性、年降水量及各类统计参数，最终划定了包含10个聚类簇的巴伊亚州全新气候分区方案，并通过数据统计处理完成了方案验证。