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

摘要

The precipitation variations of Longxi area, northeastmargin of the Tibetan Plateau since AD 960 are reconstructed from Chinesehistorical documentary records. These records show that since AD 960, theprecipitation of Longxi decreased and reached the lowest level at the end ofthe 17th and the 18th centuries. After this period, the precipitationgradually increased. The three short wet periods of Longxi in the lastmillennium were: from the end of the 10th century to the early years of the11th century, from the end of the 12th century to the early years of the13th century and during the first half of the 20th century. Theprecipitation variations coincide well with variations of the NorthernHemisphere temperature and the atmospheric 14C concentration, as wellas the averaged 10Be concentration and the reconstructed solarmodulation record which show that solar activity may be an important drivingforce of the precipitation variations of Longxi on multi-decadal tocentennial scales during the last millennium. Solar activity controls themotion of the north edge of the Asian summer monsoon by affecting the Asiasummer monsoon intensity, the East Asian winter monsoon intensity and thelocations of westerlies, thus further dominating precipitation variations ofLongxi. Synchronous variations of Longxi precipitation and NorthernHemisphere temperature may also be ascribed to the same control of solaractivity.