Precipitation Reconstruction And Multi-scale Variations Of Northern China Over The Past 400 Years

Based on the yearly precipitation data from meteorological stations in northern China(North and Northwest China), precipitation variability of the recent 60 years was analyzed, and North and Northwest China can be further divided into six sub-regions by using REOF analysis method. Using the dryness/wetness indices from historical documents and paleoclimate data from tree-ring, the annual precipitation series was reconstructed for period from 1600 to present in North and Northwest China and the characteristics of precipitation variations were analyzed by using the statistical methods. Furthermore, by comparing the different regions’ precipitation series, the spatial patterns of precipitation variations in the westerly-dominated western region and the Asian monsoon dominated eastern region was studied for the last centuries.The main results are given as follows:(1) The precipitation increased in Northwest China and decreased in North China, showing an anti-of-phase(opposite tendency) variation. The whole area (North and Northwest China) was divided into six sub-regions related to different terrain, geographical position and circulation systems.(2) The precipitation in northern has not a significant tendency during the last hundred years. The aunual precipitation was relatively less before 1950’s. It was relatively more during the earlier stage of the second half of the 20th century and relatively less again in the later period of the 20th century in North China. The precipitation became more in Northwest China since 1980’s.(3) The reconstructed precipitation since 1600 showed that, the whole area was much drier during 1700-1730 and much wetter during 1880～1900; In the other periods, the climatic conditions were different; The anti-of-phase variations between the west and the east like that of, the recent 60 years also existed in the far past. There were significant ～70-year,～110-year and ～10-year periodic oscillations in the variations of precipitation in the whole area. Multi-decade and century-scale periodic oscillations were significant in Northwest China, and, decade and multi-decade periodic oscillations were significant in North China. The abrupt shifts in precipitation took place more frequently in Northwest than in North China.(4) The cumulative percentage anomalies of precipitation showed that, the anti-of-phase variations existed during most time periods of the recent 400 years. The westerly-dominated region was relatively dry, and the Asian monsoon region was relatively wet during the "Little Ice Age", vice versa during the "Medieval Warm Period". This indicated that precipitation in the west and the east also showed anti-of-phase variations during the last centuries to millennium.(5) The solar activities might have significantly affected precipitation variability of the whole area on decadal scale; the solar effect was also evident on centurial scale in Northwest China and, multi-decadal scale in North China. Strong (weak) solar activity was generally related to arelatively drier (wetter) climate in westerly-dominated regionand a wetter (drier) condition in the Asian monsoon region. The solar activity on multi-decadal to centurial scale might be one of the reasons for the anti-of-phase variation of precipitation between the west and the east. Therefore, the different response of precipitation (moisture) in the westerly-dominated region and the Asian monsoon region to the external forcings, particularly solar forcing, probably result in the anti-of-phase variations on the multi-time scale. The precipitation (moisture) in Asian arid and semi-arid region is increasing due to the increasing Indian Monsoon index; the precipitation (moisture) in East Asian monsoon-dominated region is decreasing due to the decreasing East Asian Monsoon index. The anthropogenic activity also affects the precipitation (moisture) change.