Standardized Precipitation Index (SPI) is used to determine dry and humid periods according to the cumulative probability method at different time scales. . In this study, the rainfall data between the years of 1980-2018 belonging to of Kayseri Meteorology Station was simulated by CLIGEN stochastic climatic data generator. SPI indices calculated by using observed and simulated precipitation were evaluated with the statistical methods at the time scales of 3-, 6-, 9- and 12- months. The SPI values of 3-, 6-, 9- and 12- month which are observed and simulated with CLIGEN are close to each other and the performance of the model is very high in calculating the SPI values of these time series. However, as the time period increased, the model's representative ability decreased.

Ethiopian agriculture is a vulnerable sector from effects of climate variability. This study identified how strong is the effect of climate variability on smallholders’ crop income in Central highlands and Arssi grain plough farming systems of the country. The unbalanced panel data (1994-2014) of the study collected for eight rounds analysed through fixed effect regression. The model result shows that successive increment of crop season rainfall keeping the temperature constant has negative and significant effect on households’ crop income in the study area. The crop income responds similarly for temperature increment if the rainfall remains constant. Given this, simultaneous increment of the two climate related inputs has positive and significant effect on crop income. Other variables like flood, frost, storm, and rainfall inconsistency in the onset and cessation time affected households’ crop income negatively and significantly. Similarly, draught power and human labour, which are critical inputs in the crop production of Ethiopian smallholders, have positive and significant effect on crop income as to the model result. Thus, this study recommended that there should be supplementing the rainfall through irrigation, check dam and other activities to have consistent water supply for the crop production that enable smallholders to collect better income. Additionally, negative effect of temperature increment should be curved through adopting long lasting strategies like afforestation.