Abstract:
In order to explore the variation of water requirement of crops with climate change in different seasons in the North China Plain, seasonal response of reference crop evapotranspiration (ET
o) to key climatic variables in the North China Plain was analyzed. First, the FAO56 Penman-Monteith equation was used to calculate ET
o at 48 weather stations over the study area from 1960 to 2012. Second, the interannual changing trend of ET
o and its key climatic influential factors, i.e. air temperature (
T), sunshine hours (
n), wind speed (
u) and relative humidity (RH), were analyzed for different seasons. Sensitivity analysis had been done on ET
o sensitivity to the four climatic variables respectively. Finally, contributions of these climatic factors to the change in ET
o were analyzed based on the sensitivity of ET
o to these climatic factors and relative interannual changes in these climate factors. It was revealed that ET
o from 1960 to 2012 showed a downward changing trend in all the seasons.
T increased while
n,
u, and RH decreased. ET
o was found to have a positive sensitivity to
T,
n, and
u and a negative sensitivity to RH. The maximum sensitivity of ET
o to T and the maximum sensitivity of ET
o to
n appeared in the summer, while the maximum sensitivity of ET
o to
u and the maximum sensitivity of ET
o to RH appeared in the winter. It was found that the decline of ET
o in the spring, autumn and winter was mainly affected by the decrease in
u, and the decrease of ET
o in the summer was mainly attributed to the decrease of
n.