Research On Interdecadal Variability Of Summer Precipitation And Its Causes In China In Recent 30 Years

By using 160-stations monthly precipitation date in China and NCEP/NCAR reanalysis data and NOAA sea surface temperature data for nearly 30 years, using a variety of statistical methods study interdecadal variability of summer precipitation. The main results are as follows:(1) The analysis on interdecadal variability of summer precipitation and its causes in China indicate:1) Precipitation have experienced two turning points from interdecadal components in nearly 30 years in China. The first one took place in the early 1990s of the 20th century and the second was occurrence of the early 21st century.In the 1990s, the South China region as a whole is into a rainy period. After the 21st century, China summer rainfall region JAC is more, to the south of the Yangtze River and north of the Yellow River, significantly less than normal rainfall.2) When abnormal anticyclone circulation controls northern China, and abnormal cyclone circulation controls southern China at 850hPa, and position of the westerly jet is southward at 200hPa, and height field type at 500hPa presents EAP type and the EU type negative phase, and the South Asian High principal is west at 100hPa, Such circulation area causes more precipitation in south of the Yangtze River.3) In the past 30 years, The subtropical high and the precipitation in Southern China area showed a significant positive correlation. SST interdecadal variations largely affect the interdecadal variations of precipitation, but this influence on the precipitation there is instability (in time and space domain).(2) The analysis on summer rainfall interannual interdecadal variability and its possible mechanism in China indicate:1) The past 30 years China summer rainfall interannual variability of the overall experience of the weak-strong-weak in three stages.2) Southwest, South China Sea and the South East of the three channels of water vapor flux and near the Sea of Okhotsk and the cold air from the Arctic polar activities interannual variability directly affects the strength to change the frequency of occurrence of summer droughts.3) The past 30 years, the Indian Ocean and Pacific SST and central North Pacific region interannual variability experienced weak-strong-weak in three stages. In the equatorial Pacific and China summer rainfall interannual variability is closely related to interdecadal transition area located nino3 area. During the 1993-2003 Indian Ocean SST interannual variability dominates the summer drought, and links the eastern Pacific Ocean during 2004-2013 SST interannual variability of rainfall more closely.4) Summer rainfall in China interannual variability interdecadal anomaly a possible mechanism:Winter eastern Pacific/Indian Ocean and interannual variability of strong (weak), the Walker circulation interannual variability enhanced (weak), resulting in the warm pool for fleeting interannual variability of change, but change the warm pool convection also affect the East Asian summer atmospheric circulation, resulting in Summer rainfall in China interannual variability interdecadal anomaly.(3) The analysis on abnormal summer rainfall interdecadal variability in China and its relationship to interannual variability indicate:1) the interdecadal anomaly provides the background for the interannual variability, under different background decadal and interannual variability of summer rainfall also occur decadal variations. 2) South, North interdecadal components and interannual variability of precipitation first mutation time is more consistent, while the first mutation of interdecadal components slightly earlier than the second mutation of interannual variability in JAC.3) In the south, JAC, North China, when rainfall was increased by reducing the mutation, the corresponding oscillator strength from weak to strong, and vice versa.