ABSTRACT Rainfall analyses are essential to evaluate the risk of soil erosion by water. Seasonality and concentration of precipitation need to be considered in the assessment of erosive potential of the rainfall. Spatial variations and trends in annual rainfall, seasonality and rainfall erosivity, have been studied in this work for the Western region of Andalusia in order to improve the analysis of soil degradation associated with erosivity and to determine potential alterations related to climate change. The present study is based on data from monthly rainfall recorded in the period 1945 to 2005 in a total of 225 rain-gauge stations spread all over region. Rainfall seasonality has been obtained by means of the use of two seasonality indices: (i) the Walsh and Lawler index (SI) and (ii) the precipitation concentration index (PCI). Soil erosion risk has been determined estimating the erosivity by the Modified Fournier Index (MFI). For each year, the SI, PCI, MFI, and precipitation values for different seasons (fall, winter, spring, summer, fall-winter, and spring-summer) were calculated. The time-series trend of the annual and seasonal precipitation and the annual values of the SI, PCI, and MFI indices have been examined by using the nonparametric Mann-Kendall test. The results show a marked seasonality in the rainfall. A small, although relevant, fraction of the area has a high erosivity index. Finally, a decreasing trend in the spring-summer rainfall has been detected in 72% of the rain gauges considered.

中文翻译：

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安达卢西亚西部降雨季节性和侵蚀性的空间和趋势分析（1945-2005 年）

摘要 降雨分析对于评估水土流失的风险至关重要。在评估降雨的侵蚀潜力时需要考虑降水的季节性和浓度。在这项工作中，研究了安达卢西亚西部地区年降雨量、季节性和降雨侵蚀力的空间变化和趋势，以改进与侵蚀力相关的土壤退化的分析，并确定与气候变化相关的潜在变化。本研究基于 1945 年至 2005 年期间记录的月降雨数据，这些数据分布在整个地区的 225 个雨量站中。降雨季节性是通过使用两个季节性指数获得的：（i）沃尔什和劳勒指数（SI）和（ii）降水集中指数（PCI）。土壤侵蚀风险已通过修正的傅尼叶指数 (MFI) 估算侵蚀性来确定。对于每一年，计算了不同季节（秋季、冬季、春季、夏季、秋季-冬季和春季-夏季）的 SI、PCI、MFI 和降水值。年和季节性降水的时间序列趋势以及 SI、PCI 和 MFI 指数的年值已使用非参数 Mann-Kendall 检验进行检验。结果显示降雨具有明显的季节性。该区域的一小部分虽然相关，但具有较高的侵蚀性指数。最后，在 72% 的雨量计中检测到春夏季降雨量呈下降趋势。计算冬季、春季、夏季、秋季-冬季和春季-夏季）。年和季节性降水的时间序列趋势以及 SI、PCI 和 MFI 指数的年值已使用非参数 Mann-Kendall 检验进行检验。结果显示降雨具有明显的季节性。该区域的一小部分虽然相关，但具有较高的侵蚀性指数。最后，在 72% 的雨量计中检测到春夏季降雨量呈下降趋势。计算冬季、春季、夏季、秋季-冬季和春季-夏季）。年和季节性降水的时间序列趋势以及 SI、PCI 和 MFI 指数的年值已使用非参数 Mann-Kendall 检验进行检验。结果显示降雨具有明显的季节性。该区域的一小部分虽然相关，但具有较高的侵蚀性指数。最后，在 72% 的雨量计中检测到春夏季降雨量呈下降趋势。部分区域具有高侵蚀指数。最后，在 72% 的雨量计中检测到春夏季降雨量呈下降趋势。部分区域具有高侵蚀指数。最后，在 72% 的雨量计中检测到春夏季降雨量呈下降趋势。