Weather-climate Characteristics Of East Asian Summer Monsoon Interdecadal Variations And Its Correlation With Solar Activity

The sun is the nearest star to the Earth, but also the most basic energy source in the Earth’s climate system.The variations of solar activity has a very important influence on the global weather and climate system. Monsoon as a large-scale atmospheric circulation system, its formation is due to the solar heating of land and ocean diffiences caused. 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 weather and clmate characteristics has always been am important issue in the meterological research. This paper is mainly for the weather and clmate characteristics of interdecadal variation of EASM and its correlation with solar activity. From the SST, temperature, circulation, wind field and the other aspects, the ways of solar activity impact on the interdecadal of EASM is analysed. 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, summer climate of China and the interdecadal variation of EASM is significantly related. In eastern China has the obvious difference with the western region. With the abrupt change of EASM, China climate change occurred between the1960s and1970s. The distribution of precipitation is completely diffirent in abnormally strong EASM year and abnormally weak EASM year. The temperature distribution has significant regional characteristics.(2) The relationship between interdecadal variation of EASM and sunspot activity is discussed by using Morlet wavelet analysis method. Meanwhile, the variation of solar magnetic index is analysed and the same cycle of interdecadal variation of EASM and solar activity is also identified. Further, the deeply research is based on their common cycle and the solar magnetic field affects the Earth’s atmosphere is also elaborated. Results indicate that the solar activity is an important factor affecting interdecadal variation of EASM.(3) Study on the sea temperature, temperature of East Asia continent, the West Pacific subtropical high (WPSH) response to solar activity and the interdecadal variation of atmospheric circulation. Meanwhile, the possible ways of solar activity affects EASM is also discussed. The results show that solar activity affects the interdecadal variation of global SST anomalies.and also plays an important role of the Pacific Decadal Oscillation (PDO). The most obvious influence is reflected in its cycle of about22years for PDO.In the eastern region of China, variation of solar activity and temperature is consistent with the strength of EASM.(4) According to analyzing the interdecadal variation of geopotential height field, West Pacific subtropical high, sea level pressure (SLP) field and850hPa wind field, the results show that WPSH is northerly and westerly in strong EASM year; it is southerly and easterly in weak EASM year. SLP and850hPa wind field are weakened in mid-1960s and abrupt in the late1970s. It is better reflected the influence of land-sea thermal difference on the interdecadal variation of EASM. Solar radiations are absorbed by sea and continent at different levels, and then make changes in land and sea temperature. It will lead to land-sea thermal anomaly, further affecting EASM.(5) By analysis of the major space weather events before the abnormal heavy rainfall, it is tentatively that linked the variation of solar activity to the heavy rainfall events. It is initially explored the relationship between solar activity and abnormal weather events. The results show that variations of solar radiation and geomagnetic index correspond to the abnormal precipitation events in troposphere. Meanwhile, in the analysis and diagnosis of the two typical abnormal precipitation events, based on atmospheric energetics theory and WPD method, we have derived a new energy parameter E and the characteristic of atmospheric energy conversion during heavy rainfall was discussed. It is also provided a new way of thinking for the future severe weather forecasting and diagnosising.