Growth-Season Precipitation Variations in the Joint Area between the Asian Westerly Jet Area and the Climate Transition Zone over the Past Two Centuries

Abstract

The uneven water resource distribution between different areas across the globe has been worsening. The area where the eastern margin of the Asian westerly jet area meets the low-altitude area of the transition zone (which has a temperate continental monsoon climate) is delicate and sensitive to climate change. An urgent issue is to determine the climate change pattern of this area in the past. On the basis of core samples of four tree species in four typical regions of this joint area, we built a standardized chronological table according to tree-ring width and reconstructed the cumulative precipitation from March to August series in the above area in the past 203–343 years. Since the reconstructed results corresponded well to climate events and drought and flooding periods in historical records, the reconstructed model was stable and reliable. The results were as follows: The precipitation in the study area from east to the west in the growth season has changed dramatically, and the period has gradually shortened. In the 19th century, there was a wet period in the high-latitude area. From the 19th century to the 1950s, the entire study area experienced a significant dry period that lasted for 20–45 years; the starting time of the dry period was gradually delayed from the west to the middle, and the wet period gradually grew shorter at an increasing rate. In the past half-century, this area experienced a significant drought period, and the drying rate was higher in the west and east regions than in the central region. In the past two centuries, the precipitation varied significantly in the study area, and the wet period played a dominant role, growing gradually shorter. The middle and west regions of the Asian westerly jet area and the high-latitude regions of the transition zone all experienced significant wetting or drying processes in the first half of the 19th century, and since then, all areas experienced significant drying processes under the influence of global warming, which may be intensified by the westerly circulation.