環境汚染と気候変動

抽象的な

Climate Characterization and Variability in Agro-Ecological Zones of Anger Sub-Basin, Nile Basin of Ethiopia

Geremew Fekadu Boru, Zelalem Biru Gonfa, Girma Mamo Diga

The study was carried out to characterize and analyze the variability of the local climate in the agro-ecological zones of the Anger sub-basin for agricultural purpose. The results show that the mean annual rainfall ranges between 1246.8 mm to 2067.9 mm for all agro-ecological zones with the CV of varying from 14.5 to 28.6 in the subbasin. Rainfall concentration index ranges from (14.5% to 15.1%) indicating irregular rainfall distribution and standardized rainfall anomaly shows that dry condition is higher in warm sub-humid lowland and warm moist lowland agro-ecological zones than in tepid sub-humid mid highland zones of the sub-basin. The variability in the average onset date of rainfall in varies from125 ± 7 DOY (May 04 to 128 ± 6 DOY (May 07) with CV varies from 8.4% to 13.5 % in all AEZ. Also, the average cessation dates rainy season varies from 304 ± 1 (27 Oct) to 308 ± 5 (Nov 03) with CV varies from 3.3% to 4.3% in all zones. The rainfall trend is not statistically significant (P>0.05) for all the agroecological zones. An increasing trend also is seen in temperature which is highly related with a dry spell of the subbasin. The degree of dry spell probability descends down to zero from half of April to end of September and curves converge to their minimum only during the peak rain period (June to August or DOY 153-244) in all agro-ecological zones.