The Relationship Between Anomaly Of Soil Moisture Over Qinghai-tibet Plateau In Spring And Summer Precipitation In Eastern China

The feedback effect of soil moisture on precipitation has been one of the hot spots in the mechanism of precipitation. Due to the special location and topography of the Qinghai Tibet Plateau, the influence of the surface non adiabatic change of the surface of the spring on the summer rainfall in eastern China is an important scientific issue. Based on a series of statistical diagnosis analysis and numerical simulations,this paper studies the relationship between the soil moisture over Qinghai Tibet Plateau in spring and summer precipitation in eastern China. Firstly, the quality of GLDAS soil moisture data in the Qinghai Tibet Plateau is tested. On this basis, the relationship between soil moisture anomalies over Qinghai Tibet Plateau and the summer precipitation in eastern China was analyzed using SVD method. And Mont-Carlo significance test was carried out. Secondly, using the synthetic analysis method, the variation characteristics of atmospheric circulation in eastern China during anomaly of soil moisture over Qinghai-Tibet Plateau in spring were analyzed,and the significance test was carried out by t test. Finally, using the numerical model CESM1.2.0, two sets of sensitivity tests are designed to verify the above statistical relationship. The main conclusions are as follows:(1) The change of soil moisture over Qinghai Tibet Plateau has a significant effect on the summer precipitation in eastern China. The correlation between soil moisture in different regions and different depths over Qinghai Tibet Plateau and summer precipitation in eastern China is different. But the correlation between 10-40 cm,40-100 cm, 100-200 cm deep layer of soil moisture over Qinghai Tibet Plateau and summer precipitation in eastern China are consistent.(2) The surface soil moisture in the northeast and northwest over Qinghai Tibet Plateau is positively related to the summer precipitation in North China and NortheastChina, while it is negatively related to the Southern China area. There is a strong negative correlation between the surface soil moisture in the central and southern part of the Qinghai Tibet Plateau and the summer precipitation in North China. The deep soil moisture in the northern over Qinghai Tibet Plateau is positively correlated with the summer precipitation in North China and central China region, while the southeast coastal area is negatively correlated with the soil moisture; The deep soil moisture in the eastern and central regions of the Qinghai Tibet Plateau has a negative correlation with the summer precipitation in most parts of Southern China.(3) Synthetic analysis of the results showed that when the spring soil moisture over Tibetan Plateau is relatively small, much of eastern China summer precipitation is significantly reduced, only coastal region of southern China a small part of the summer precipitation increases slightly. When most of the Qinghai Tibet Plateau spring soil moisture value increases, much of eastern China summer precipitation increased significantly, only coastal region of southern China of the summer precipitation decrease slightly.(4) Numerical simulation results show that when the spring soil moisture increase in the northeast and northwest over Qinghai Tibet Plateau, reduce the summer precipitation in the southeast coastal area of China, instead in the northeast and North China summer rainfall anomalies increase; when the abnormal increase in the eastern and central regions of the Qinghai Tibet Plateau of soil moisture in spring, the summer precipitation in the most areas of middle and lower reaches of the Yangtze River and central China increased significantly. This confirmed the statistical results.(5) The spring soil moisture over the Tibetan Plateau anomaly and the South Asia High, Western Pacific Subtropical High, summer monsoon system has significant correlation, and has a close relationship with the summer precipitation in eastern China. When the spring soil moisture in the Qinghai Tibet Plateau increases, surface non adiabatic heating is decreased, the South Asia High is in the western part of the process, and the intensity of the South Asia High is relatively weak and the center position is relative to the west. At the same time the Western Pacific Subtropical High is relatively weak and the center position is relative to the east. Besides, China Southern 850 hPa wind field intensity is relatively strong, and relative humidity and specific humidity is larger, South Asian summer monsoon and East Asian summer monsoon system strength relatively strong. And then lead to most parts of eastern China summer precipitation is relatively more, only in the southeast coastal areas inthe Western Pacific Subtropical High system control area precipitation is usually less.