SPATIAL, SEASONAL, AND TEMPORAL VARIATIONS IN RAINFALL AGGRESSIVENESS IN THE SOUTH OF BRAZIL

ABSTRACT The objective of this study is to evaluate spatial and temporal variations in rainfall aggressiveness in southern Brazil. A total of 181 rain gauge stations located in southern Brazil with rainfall time series from 1976 to 2015 were used. Seasonal and annual rainfall aggressiveness values measured according to the Modified Fournier Index (MFI) were analyzed. The trends in the data series were evaluated using the Mann-Kendall test at a level of significance of 5%. Maps on spatial and seasonal variations in rainfall aggressiveness were prepared. The percentage of rain gauge stations with significant decreasing trends, significant increasing trends, and no significant trends in rainfall aggressiveness between years was 3.3%, 7.7%, and 89.0%, respectively. Moreover, 90% of stations had no significant trends between seasons. There were seasonal differences in rainfall aggressiveness between the three southern states in Brazil caused by rainfall factors. Rainfall aggressiveness was comparatively higher in the west of Santa Catarina and southwest of Paraná due to the rains originating from the mesoscale convective systems predominant in autumn, and in the north coast of Santa Catarina and east coast of Paraná due to convective and orographic precipitations predominant in the summer.

摘要 本研究旨在评估巴西南部地区降雨侵蚀力的时空变化特征。本研究共使用巴西南部181个雨量站1976年至2015年的降雨时间序列数据。分析了基于修正傅里埃指数（Modified Fournier Index, MFI）计算得到的季尺度与年尺度降雨侵蚀力值。采用显著性水平为5%的曼-肯德尔（Mann-Kendall）检验对数据序列的趋势进行了评估，并绘制了降雨侵蚀力时空及季节变化的空间分布图。各雨量站的年际降雨侵蚀力呈显著下降、显著上升及无显著趋势的站点占比分别为3.3%、7.7%和89.0%。此外，90%的站点其季际降雨侵蚀力无显著趋势。受降雨影响因素差异，巴西南部三个州的降雨侵蚀力存在季节差异。圣卡塔琳娜州西部与巴拉那州西南部的降雨侵蚀力相对更高，这源于秋季占主导的中尺度对流系统（mesoscale convective systems）带来的降雨；而圣卡塔琳娜州北海岸及巴拉那州东海岸的降雨侵蚀力较高，则归因于夏季占主导的对流性与地形性降水。