Changes of Cotton Climate Risk Degree in Henan Province

Basing on previous researches, this article established the cotton climate suitability model and the risk index to analyze the cotton climate risk degree in Henan Province. The result shows: in the last 40 years, the cotton climate risk degree presents a gradual increasing tendency in which the precipitation plays a very important role, and the climate suitability and its change have different performance to the risk change influence in different phases; the increase rate of risk degree is significantly regional and transitional. For example, from the eastern plain to the western mountainous area, the risk change rate becomes slower and slower, so the contrast of the central-southern Huang-Huai plain and Funiu highland is most remarkable; and in the north-south direction, the contrast between the fast increase belt from the central-southern Huang-Huai plain to the middle Yellow River and the slow increase belt from the northern side of the middle Yellow River to the lower Yellow River bank is especially remarkable, being possibly the results of topographic and climatic transitional belt; and the risk change process also has obvious regional differences. For instance, jumping change is an important characteristic in eastern Henan, while in the western mountainous area it is very rare. Although the 40 years changing tendency in this area is still increasing, the tendency has reduced gradually since the end of the 1980s, i.e. this sudden change type has obvious latitudinal difference.