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Correlation of Surface Air Temperature and Precipitation in the Qingjiang River basin and Its Connection with the East Asian Summer Monsoon

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    The Precipitation-surface air Temperature Relationship (PTR) constitutes an important indicator of the ecological environment and is closely related to the occurrence of extreme drought/heat wave (or flood/coldness) events. Research has been taking place in several caves of the Qingjiang River basin of the Three Gorges Area. The cave sediments are characterized by long carbon and oxygen isotope sequences which may lead to the construction of a long sequence PTR. Based on modern meteorological observation and reanalysis data, the evolution characteristics and forming reason of the PTR in the Qingjiang River basin can be analyzed, which can provide some physical basis for understanding the relationship between the carbon–oxygen coupling coefficient of the stalagmites and PTR. Based on daily surface air temperature and precipitation observations from six stations, namely Badong (31°2'N, 110°22'E), Jianshi (31°36'N, 109°43'E), Lichuan (30°17'N, 108°56'E), Enshi (30°17'N, 109°28'E), Wufeng (30°12'N, 110°40'E), and Yichang (30°42'N, 111°18'E), and three sets of reanalyses, namely the NCEP Climate Forecast System Reanalysis (CFSR), Japan Meteorological Agency 55-year reanalysis (JRA55), and European Centre for Medium-range Weather Forecasts Interim Reanalysis (ERA-interim), this study investigated the seasonal, interannual, and decadal variability of the PTR and its connection with the East Asian summer monsoon. The following results were obtained: 1) PTR exhibits an obvious seasonality while a significant negative correlation is observed only in summer. 2) Summer PTR exhibits a decadal variability with a periodicity of 20–25 years, close to IPO/PDO. Significant shifts occurred in 1974, 1986, and 1992, with PTR altering from “insignificant” to “significant” and back to “insignificant” again. Specifically, PTR between 1977 and 1992 was significantly negative. 3) There is an overall correspondence between the decadal variability of summer PTR and the strength of the East Asian Summer Monsoon (EASM). When PTR was significantly negative (1977–1992), EASM was weak. However, when PTR was insignificant (1965–1976 and 1993–2011), EASM was strong. 4) Physically, when the summer monsoon weakens, the north and south air flow converges to the south. When the water vapor and ascending motion increases in Qingjiang River basin, it causes an increase in the cloud coverage and precipitation but it reduces the surface heat flux and decreases the surface temperature, leading subsequently to a negative PTR. When the summer monsoon strengthens, the north and south air flow converges to the north, which is not beneficial for the increase of water vapor. On the contrary, it is beneficial for the descending motion. In addition, cloud coverage reduces and temperature increases, resulting in the increase of the adiabatic rate and the positive contribution of precipitation efficiency to precipitation. It is important that, on one hand, the increase of temperature can increase precipitation, and on the other hand, the impact of cloud coverage/precipitation on the temperature weakens but does not disappear. Both conditions make PTR insignificant. 5) The decadal variability of PTR may be linked to the IPO/PDO.

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何源,李双林,胡超涌.2020.清江流域水热关系与东亚夏季风的联系[J].气候与环境研究,25(6):677-694. HE Yuan, LI Shuanglin, HU Chaoyong.2020. Correlation of Surface Air Temperature and Precipitation in the Qingjiang River basin and Its Connection with the East Asian Summer Monsoon[J]. Climatic and Environmental Research (in Chinese],25(6):677-694.

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  • Received:March 28,2020
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  • Online: December 02,2020
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