Drought And Its Impact On Wheat Yields In Chinese Wheat-growing Areas Based On Medium Resolution Remote Sensing Data

The climate change affects the atmospheric circulation, leading that the climate disasters happen frequently and it also increases the intensity. The climate change will directly affect the Spatial-temporal changes in food yields resources through various of ways, which will affect the food yields and the security of the national food and the rural economic development and the farmers’ income. The drought happens frequently and widely in our country. Many severe droughts have happened in recent years. This article studies the relationship between drought and food yields, pointing out that drought mitigation strategies have great practical significance when food yields can adapt to the climate change.This article is the Important National Basic Research Program of China (Program973), which is the subject (2010CB951503) of the Research of the Climate Change on the Spatial-temporal Evolution when Agricultural Disaster Happens. It is also the important part of the Research of the Climate Change on the Droughts in Major Grain Producing Areas and on the Food Yields Systems.This article is based on the subject. It studies the wheat-growing areas. It uses nearly thirty years of MODI S and AVHRR long time series of remote sensing data and the yields data of wheat in every province, and proper methods. This article has analyzed the drought and the changes in wheat growing season.. It also has analyzed the impact of drought on wheat. The main contents and results of the paper are as follows:(1) Analyze the adaptability of remote monitoring index in agricultural drought and improve the index. First, we analyze the adaptability of the remote sensing monitoring index VCI and TCI in the whole research area and every province. Then we improve the drought monitoring index according to the results of the analysis. And at last, we use the new index (VHI) to create the drought distribution data sets in wheat growing areas in the year2001to2010. The results show that:there is some complementary relationship between VCI and TCI in adaptability. The improved drought index VHI has concentrated the advantages of VCI and TCI, making the Remote monitoring of drought adaptation better. And it is much closer to the actual result of drought.(2) Analyze the change in drought and the wheat yields. On one hand, we classify the remote sensing monitoring results according to the classification principles in agricultural drought, using the classification results to analyze the prone time of drought and the change trends of drought. On the other hand, we use the wheat climate yields which is under the effect of the natural weather factors to analyze the change trends. The results show that the drought trends are bascially the same in winter wheat areas in northern provinces. The autumn drought tends to increase and the winter drought tends to be the same and the spring drought tend to decrease. And the drought trends are bascially the same in winter wheat areas in southern provinces as well. The autumn drought tends to decrease and the winter drought tends to increase and the spring drought tends to decrease. The wheat climate yields in every province in the south and north basically tends to increase.(3) Analyze the impact of drought on wheat yields. We first ignore the effect of the time of drought and the level of drought. We analyze the correlation between drought and the yields on the whole. And we further analyze the impact of drought in different seasons and different levels on wheat yields. The results show that the effect of drought on wheat yields in north is bigger than that in south. There is negative correlation between drought and wheat yields in different seasons in five northern provinces and four southern provinces. The impact of spring drought in northern areas is the most serious. There is negative correlation between drought and wheat yields in different levels in five northern provinces and four southern provinces. Both the severe and moderate droughts have serious effect on the yields and the light drought has a little effect on the yields in northern areas. In southern areas, the severe drought has the most serious effect on the yields and the moderate drought has a little effect on the yields. The light drought has no obvious effect on the yields. In contrast with the south and the north, the effect of three kinds of drought in north is bigger than that of south.