Impact of climate on grain yield per unit area in China during the years of 1949-1992

The grain yield per unit area in China has been increasing from 1949 to 1992 with annual fluctuations, which was caused by both policies and monsoon climate. The total grain yield is divided into trend yield, which reflects the influence of economic factors, and climate yield, which reflects the impact of climate factors. The results of grain and climate yield by EOF (empirical orthogonal function) method show that the grain yield in the eastern China is higher and more fluctuating than that in the western region. The spatial and temporal distributions of climate yield were divided into four patterns. Regional unaminity of climate-yield variations is the first and main spatial pattern, and then there are the spatial patterns of north-south difference and east-west difference in some years. Generally, climate conditions are good for grain yield during the 1950s and 1980s all over the country.