Seasonal Rainfall Variability in Ethiopia and Its Long-Term Link to Global Sea Surface Temperatures
Seasonal Rainfall Variability in Ethiopia and Its Long-Term Link to Global Sea Surface Temperatures
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DOI：
10.3390/w12010055
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发表时间：
2020-01-01
期刊：
影响因子：
3.4
通讯作者：
Shimizu, Katsuyuki
中科院分区：
文献类型：
--
作者：
Alhamshry, Asmaa;Fenta, Ayele Almaw;Shimizu, Katsuyuki
调查海面温度对季节性降雨的影响是管理埃塞俄比亚水资源的一个关键因素。为此，SST和降雨量数据被用来研究埃塞俄比亚夏季（1951-2015）和春季（1951-2000）降雨分布不均匀的大范围不均匀地区。首先，根据降雨的空间均匀性和季节性，将降雨网格点初步细分为区域。这引入了新的集群，包括9个夏季降雨高峰区（7月/8月）和5个春季降雨高峰区（4月/5月）。然后，通过计算区域内网格点的平均降雨量，得出每个区域的时间序列。其次，显着相关的海洋区域，埃塞俄比亚降雨确定通过交叉相关平均在每个均匀区和月平均SST之间。对于夏季降水为主要雨季的情况，几内亚湾和南太平洋对降水带有明显的影响，滞后时间分别为5-6个月和6-7个月。此外，对于滞后时间为5-6个月的第8和第9夏季降水区，南太平洋共同海温区表现出相反的正相关和负相关。因此，这两个地区之间的海温差异与夏季降水的相关性更强（r >= 0.46）。结果表明，北方大西洋海温对春季降水区（3、5）的影响滞后6-7个月，相关系数r >= -0.40。因此，这项研究表明，南太平洋和北方大西洋的海温可以作为埃塞俄比亚夏季和春季暴雨预测模型的有效输入，分别。
Investigating the influence of sea surface temperatures (SSTs) on seasonal rainfall is a crucial factor for managing Ethiopian water resources. For this purpose, SST and rainfall data were used to study a wide range of inhomogeneous areas in Ethiopia with uneven distribution of rainfall for both summer (1951-2015) and spring (1951-2000) seasons. Firstly, a preliminary subdivision of rainfall grid points into zones was applied depending on spatial homogeneity and seasonality of rainfall. This introduced new clusters, including nine zones for summer rainfall peak (July/August) and five zones for spring rainfall peak (April/May). Afterward, the time series for each zone was derived by calculating the rainfall averaged over grid points within the zone. Secondly, the oceanic regions that significantly correlated with the Ethiopian rainfall were identified through cross-correlations between rainfalls averaged over every homogeneous zone and the monthly averaged SST. For summer rainfall as a main rainy season, the results indicated that the Gulf of Guinea and southern Pacific Ocean had a significant influence on rainfall zones at a lag time of 5-6 and 6-7 months. Besides, for summer rainfall zones 8 and 9 at lag time 5-6 months, the common SST regions of the southern Pacific Ocean showed the opposite sense of positive and negative correlations. Thus, the difference in SSTs between the two regions was more strongly correlated (r >= 0.46) with summer rainfall in both zones than others. For the spring season, the results indicated that SST of the northern Atlantic Ocean had a strong influence on spring rainfall zones (3 and 5) at a lag time 6-7 months, as indicated by a significant correlation (r >= -0.40). Therefore, this study suggests that SSTs of southern Pacific and northern Atlantic oceans can be used as effective inputs for prediction models of Ethiopian summer and spring rainfalls, respectively.