Changes in precipitation patterns significantly affect flood and drought hazard management and water resources at local to regional scales. Therefore, the main motivation behind this paper is to examine the spatial and temporal rainfall variability over Sri Lanka by Standardized Rainfall Anomaly Index (SRAI) and Precipitation Concentration Index (PCI) from 1990 to 2019. The Mann–Kendall (MK) trend test and Sen’s slope (SS) were utilized to assess the trend in the precipitation concentration based on PCI. The Inverse Distance Weighting (IDW) interpolation method was incorporated to measure spatial distribution. Precipitation variability analysis showed that seasonal variations are more than those of annual variations. In addition, wet, normal, and dry years were identified over Sri Lanka using SRAI. The maximum SRAI (2.27) was observed for the year 2014 for the last 30 years (1990–2019), which shows the extremely wet year of Sri Lanka. The annual and seasonal PCI analysis showed moderate to irregular rainfall distribution except for the Jaffna and Ratnapura areas (annual scale-positive changes in Katugastota for 21.39% and Wellawaya for 17.6%; seasonal scale-Vavuniya for 33.64%, Trincomalee for 31.26%, and Batticaloa for 18.79% in SWMS). The MK test, SS-test, and percent change analyses reveal that rainfall distribution and concentration change do not show a significant positive or negative change in rainfall pattern in Sri Lanka, despite a few areas which experienced significant positive changes. Therefore, this study suggests that the rainfall in Sri Lanka follows the normal trend of precipitation with variations observed both annually and seasonally.

中文翻译：

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斯里兰卡的时空降雨变化和浓度

降水模式的变化显着影响地方到区域范围内的洪水和干旱灾害管理和水资源。因此，本文的主要动机是通过 1990 年至 2019 年的标准化降雨异常指数 (SRAI) 和降水浓度指数 (PCI) 来检验斯里兰卡的时空降雨变化。曼肯德尔 (MK) 趋势检验和Sen斜率（SS）用于评估基于PCI的降水浓度趋势。结合逆距离加权（IDW）插值方法来测量空间分布。降水变率分析表明，季节变化大于年变化。此外，使用 SRAI 确定了斯里兰卡的潮湿、正常和干燥年份。最大 SRAI (2. 27）在过去 30 年（1990-2019 年）中观察到 2014 年，这表明斯里兰卡极端潮湿的一年。年度和季节性 PCI 分析显示，除了 Jaffna 和 Ratnapura 地区外，降雨量分布适中至不规则（Katugastota 为 21.39%，Wellawaya 为 17.6%；季节性规模-Vavuniya 为 33.64%，亭可马里为 31.26%，以及Batticaloa 在 SWMS 中为 18.79%）。MK 检验、SS 检验和百分比变化分析表明，尽管少数地区经历了显着的正变化，但降雨分布和浓度变化并未显示出斯里兰卡降雨模式的显着正或负变化。因此，本研究表明，斯里兰卡的降雨量遵循降水的正常趋势，具有年和季节的变化。