Abstract
Northeast Ethiopia is a semi-arid region that exhibits high rainfall and temperature variability. The impact of climate change has received a great deal of attention worldwide. This study focused on detecting trends in in rainfall (1983-2013) and temperature (1981-2010) at annual, seasonal and monthly time scales for six weather stations in semi-arid north eastern Ethiopia. The study also aimed to determine dry spell length, number of rainy days, onset and cessation dates, and length of growing period. The non-parametric tests such as Mann-Kendall and Sen’s Slope were used to determine climatic trends. The results indicated that both the annual maximum and minimum temperature in the study region showed an increasing trend, but only the trend for maximum temperature was significant. In the same manner, both the Belg and Kiremt seasons maximum and minimum temperature also showed an increasing trend but only trend of maximum temperature during Belg season and trend of minimum and maximum temperature during Kiremt seasons was significant. The annual and Belg season rainfall in the region showed a decreasing trend and its trend was significant. The coefficient of rainfall variability for annual and Belg season was very high which could affect agricultural production in the region. In the contrary, the trend for Kiremt season rainfall was increasing without significant trend. On the other hand, the average length of dry spell during the Kiremt season in the region was generally long that ranged from 27 days to 39 days and showed both decreasing and increasing but with no significant trend in most stations. The number of annual rainy days also showed both increasing and decreasing trends but its trend was not significant. The length of growing period in the region was relatively stable at all stations during the last 30 years period without non-significant trend. In general, from the analysis of annual, seasonal and monthly rainfall and temperature data series it can be concluded that rainfall and temperature characteristics of the study area is changing, even though some of the trends on both parameters were not statistically significant.
Highlights
Agriculture is very sensitive to climatic and, more generally, environmental conditions [36]
The contribution to the annual total from the main season, varies across weather stations that range from 64% to 77% depending on the site of the location
Previous studies in the Amhara regional state of Ethiopia indicated that the main season (Kiremt) and the short rainy season (Belg) had contributed 55-85% and 824%, respectively to the annual rainfall totals [2, 3]. [18] reported that the main rainy season (Kiremt) contributes largely to the annual rainfall totals in all stations in northern Ethiopia that ranges from 50-90% depending on the site of the location and the Belg rainfall makes a considerable contribution to the annual rainfall totals in some areas such as Adigrat (29%), Edagahamus (31%) and Alamata (36%)
Summary
Agriculture is very sensitive to climatic and, more generally, environmental conditions [36]. In Ethiopia, agriculture remains the most important sector of the economy. The contribution of agriculture to the national economies through food supply, employment creation, export earnings, etc. The sector plays a dominant role in the economy of Ethiopia, contributing 41% GDP, 80% of the employment and the majority of foreign exchange earnings [16]. Global average surface temperature is expected to increase by 1.4 to 5.8°c over the period 1990 to 2100 [21]. This warming is expected to have a significant impact on the precipitation regime and water availability. These changes in precipitation are likely to be accompanied by an increase in its variability [21] and along with the projected
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