| Land surface process is an important factor of affecting the atmospheric circulation and climate change. Soil moisture, as a basic physical factors that characterize the water status of land surface, have a significant impact on climate change clearly. At present, most research on soil moisture are around two aspects which are the statistical analysis of observational data and numerical simulations, and both of then are difficult to get specific characteristics of soil moisture anomalies feedback on climate change. As such, after selecting soil moisture anormalies of east Asia as a key factor presenting the land surface impacts on climate, generalized equilibrium feedback assessment method (referred to GEFA) developed in recent years is applied to study the feedback of summer soil moisture anomalies on summer climate in China and its statistical evaluation in this paper. Based on the observations of China 753 stations and monthly soil moisture data of ERA-interim during the period 1979-2012 summer, response of summer temperature and precipitation in China to soil moisture anomalies in east Asia is calculated by using GEFA. And then combined with synthesis of difference methods, this study discuss the possible physical process of that how soil moisture anomalies affecting climate change, according to the feedback of summer soil moisture anomalies in East Asia to atmospheric circulation by using GEFA. The main conclusions are summarized as follows:(1) The connections of China summer temperature and soil moisture anormalies in East Asia are very close in both early summer and summer. Further analysis shows that the response of summer temperature in China to the first EOF mode of soil moisture anomalies is the most significant:when soil moisture in mid-latitude of east Asia and eastern China is abnormally dry, China summer temperature is consistently warming. The second mode of temperature response evidently to the second mode of soil moisture (the soil moisture is wetter in the north of Yangtze river and drier in the South China Sea coast) and warming appears from the western China to the Yangtze region and cooling appears in the Northeast China. Response of the third mode of soil moisture to the second mode of temperature is also notably and the cooling over the southwest to the southeast China is especially significant.(2) The response of the overall summer precipitation in the eastern china to the first and third EOF mode of soil moisture anomalies is significant. It shows that the summer precipitation in the northeast reduced significantly, has a less quantity in central china and southwest and increases in parts or southern Inner Mongolia. The response of summer precipitation anomaly sequence in different parts of eastern is very different. It is the most significant for the response of northeast China summer precipitation anomaly in to the first EOF mode of soil moisture, and the else is relatively weaker.(3) The feedback of soil moisture to the air temperature is via the change of atmospheric circulation. Take the feedback of first EOF mode of soil moisture as example, which has the most significant impact on temperature, the possible process is simply discussed as follows. When the soil is dry at the south of Baikal lake and eastern China, the abnormal heating on land surface is likely to cause significant positive anomalies in upper-level atmosphere and anticyclonic circulation anomalies in low-level atmosphere in northern China. Combine all this with the relationship of anomalous temperature (precipitation) and the upper-level circulation on northern China, at this condition, anomalies in upper-level atmosphere and anticyclonic circulation anomalies in low-level atmosphere in northern China may lead to a higher temperature and may against the occurrence of precipitation in this area at the meantime, and soil moisture will be lower. The positive feedback mechanism mentioned above may be a possible way linking between soil moisture and the atmosphere in this region. |
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