[en] Climate change will have important implications in the agriculture of water-short regions, such as Huang-Huai-Hai Plain (3H Plain), where expected warmer and drier conditions might augment crop water requirement (ETc). To evaluate the effect of climate change, a data set consisting of observed daily values of air temperature, relative humidity, sunshine duration and wind speed from five selected weather stations in the 3H Plain and covering the period 1981-2009 was used for estimating reference evapotranspiration (ET0). ET0 was calculated using FAO-56 Penman-Monteith equation; then sensitivity coefficient of ETc of major climatic variables and regional responses of precipitation deficit to climate change were conducted in the 3H Plain. The results showed that a clear drop in solar radiation (SR) was detected and temperatures increased, especially the minimum temperature. Wind speed (WS) decreased significantly in most of the stations, especially from seeding to jointing stages for wheat. No significant change was detected for relative humidity (RH) in 1981-2009. Temperature was the most sensitive variable in general for the plain, followed by SR, WS and RH. The decrease of sensitivity coefficient of solar radiation (SSR) mainly occurred in seeding to jointing stages and heading to maturity stages of winter wheat. Sensitivity coefficient of temperatures (ST) increased in Beijing, Xinxiang, Xuzhou and Yanzhou stations, which means that an increase in temperatures may lead to a larger increase of ETc in these four stations. However, ST decreased in the Shijiazhuang station. With the decrease of WS, ETc will decrease due to the positive coefficient in Beijing and Xinxiang stations. Trends of SRH showed no significant changes in the time series analysis. A positive relationship was detected between precipitation deficit and relative humidity, and the latter was considered the most correlative factor for precipitation deficit.
