Precipitation variations of Longxi, northeast margin of Tibetan plateau since AD 960 and its relationship with solar activity

The precipitation variations of Longxi area, northeast margin of Tibetan plateau since AD 960 are reconstructed from Chinese historical documentary records. It shows that since AD 960, the precipitation of Longxi fluctuantly decreased to the lowest in the end stage of 17th century and 18th century. After this period, the precipitation gradually increased. Three short wet periods of Longxi in the last millennium were: from the end of 10th century to the early of 11th century, from the end of 12th century to the early of 13th century and the first half of 20th century. The precipitation variations of Longxi coincide well with variations of the Northern Hemisphere temperature and the atmospheric 14C concentration, the modeled solar output, the reconstructed total solar irradiance, which shows that solar activity may be the main driving force of precipitation variations of Longxi on multi-decadal to centennial scales in the last millennium. Synchronous variations of Longxi precipitation and Northern Hemisphere temperature may be ascribed to the same control of solar activity. Solar activity controls remotion of the north edge of Asian summer monsoon by affecting Asia summer monsoon intensity, East Asian winter monsoon intensity and the locations of westerlies, thus further dominates precipitation variations of Longxi.