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Trends of Lower- to Mid- Stratospheric Water Vapor Simulated in Chemistry-Climate Models |
HU Ding-Zhu1, HAN Yuan-Yuan1, SANG Wen-Jun1,XIE Fei2 |
1College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
2College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China |
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Abstract Using the outputs from 16 chemistry-climate models (CCMs), the trends of lower- to mid- stratospheric water vapor (WV) during the period 1980–2005 were studied. Comparisons were made between the CCM results and European Centre for Medium-Range Weather Forecasts (ECWMF) Interim Reanalysis (ERA-Interim). The results of most of the CCMs, and those based on ERA-Interim, showed the trends of lower- to mid- stratospheric WV during the period 1980–2005 to be positive, with the extent of the trend increasing with altitude. The trend of lower- to mid- stratospheric WV in the ensemble mean of the CCMs was 0.03 ppmv per decade, which was about twice as large as that based on ERA-Interim. The authors also used a state-of-the-art general circulation model to evaluate the impacts of greenhouse gas (GHG) concentration increases and ozone depletion on stratospheric WV. The simulation results showed that the increases of lower- to mid- stratospheric WV affected by the combined effect of GHG and ozone changes happened mainly via warming of the tropopause and enhancement of the Brewer-Dobson circulation (BDC), with the former being the greater contributor. GHG increase led to a higher and warmer tropopause with stronger BDC, which in turn led to more WV entering the stratosphere; while ozone depletion led to a higher and cooler tropopause, which caused the decreases of lower- to mid- stratospheric WV, despite also causing stronger BDC.
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Received: 14 November 2014
Revised: 08 December 2014
Accepted: 09 December 2014
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Corresponding Author:
1College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
2College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
E-mail: xiefei@lasg.iap.ac.cn
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