Variation of agro-climatic indices in Kurdistan province of Iran within 1962–2012

Abstract

The purpose of this study was to evaluate the observed changes of agro-climatic indices over Kurdistan Province in the west of Iran. To prepare of climatic data were used the station based diurnal maximum, minimum and mean air temperature together with the total precipitation data within 1962–2012 over the Kurdistan Province region. Using geospatial Kriging method, climatic data were interpolated to grids of 6 × 6 km for each day. Agro-climatic indices were estimated and were mapped based on the gridded data. The results showed that the observed changes in the indices were significant but not uniform. Statistical analysis revealed the positive trend for the indices of last spring frost (LSF), LSF-2, FFP, FFP-2, FFF, FFF-2, NDor-15, NDor-5, start growing season (SGS), EGS, GSL, GDD, GDD10, PD1 and PD10 over the western and eastern lowland areas. While, the negative trends the aforementioned indices were observed over the central and northern highlands. These results are in agreement with significant increase in summer temperature (Tmin, Tmax and Tmean) for western and eastern parts, but significant decrease for high altitudes located in central and north parts of study area. At high altitudes, especially over central and northern parts, the date of LSF and SGS have been gradually delayed with statistically significant at 95 % confidence level.