East Asian Summer Monsoon Variations And Its Influence On NDVI In The Mid-lower Yangtze River Valley Of China

China is located in the typical region of East Asian monsoon; the East Asian monsoon strength plays an important role in climate distributions and changes of China, especially the East Asian summer monsoon (EASM). Its long-term variation of climate characteristics has always been an important issue in the meterological research. As an important factor of ecology, vegetation is not only enduring the climate change but also has feedback on climate change positively. It is a sensitive indicator for environment change. This paper is mainly for the climate characteristics of interdecadal variation of EASM and its influence on NDVI in the mid-lower Yangtze River valley of China. Based on the long term data of NCEP/NCAR, HadSLP2and NOAA/AVHRR GIMMS NDVI, the interdecadal of EASM impact on NDVI in the mid-lower Yangtze River valley is analyzed, by the methods of trend analysis, correlation analysis and Morlet wavelet analysis. Further, the work also has certain innovation. The main conclusions are as follows:(1) A162years longer time series of EASM index has been established. Analysis shows that in mid-1960s, the strength of EASM weakened, and then weakened again in mid-1970s.Meanwhile, the conversion from strong summer monsoon years to the weak summer monsoon years is completed. It is also found that, the change of the West Pacific subtropical high can also cause the change of the east Asian summer monsoon. The subtropical high has an obvious trend of weakening, west ridge point moving eastward and west ridge line moving northward, so EASM is stronger; on the contrary, the subtropical high has an obvious trend of strengthening, west ridge point moving westward and west ridge line moving southward, so EASM is weaker.(2) The relationship between EASM and climate of China is discussed. It shows that summer climate of China and the interdecadal variation of EASM is significantly related. In eastern China has obvious difference with the western region. the EASM and the precipitation in mid-lower Yangtze River valley shows negative, but the temperature shows positive.(3) The vegetation index of NDVI had trend of increasing in the mid-lower Yangtze River valley. The year border fluctuation change was obvious and yearly average rate of change reached2.6%. In the entire district vegetation year change in the whole presented the very strong seasonal characteristic. From the view of spatial, the vegetation in the mid-lower Yangtze River was better, spring presented an enhancing tendency and summer also presented an enhancing tendency except Jiangsu province, the vegetation in autumn was best, the winter is worst and it had a reduced tendency. From the whole, the NDVI change between the southeast and northwest is difference, the vegetation NDVI in northwest is significantly higher than southeast.(4) According to analyzing the correlation among the EASM, precipitation and NDVI, the results show that the summer precipitation in mid-lower Yangtze River valley changed not obviously, and the precipitation in southeast is significantly higher than northwest. It is same with distribution of NDVI, so the precipitation is an important factor to influence the growth of vegetation. The correlation between EASM and NDVI is negative, the EASM is strong, the NDVI in mid-lower Yangtze River valley is low, the EASM is weak, the NDVI in mid-lower Yangtze River valley is high. At the same time, both the EASM and NDVI exhibits oscillation periods of4-6years, so the change of NDVI in mid-lower Yangtze River valley may be due to the change of EASM.