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| DOI：10.13522/j.cnki.ggps.2019224 |
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| The “Evaporation paradox” in Wudaogou Area and Its Underlying Mechanisms |
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WANG Yining, YANG Miao, WANG Bing, LU Lu, MEI Haipeng, WANG Zhenlong
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1.Nanjing Hydraulic Research Institute, Nanjing 210029, China; 2.Hohai University, Nanjing 210098, China; 3.Water Resources Research Institute of Anhui Province, Bengbu 233000, China; 4.Hebei University of Engineering, Handan 056021, China
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| Abstract: |
| 【Objective】“Evaporation paradox” is the contradiction between the predicted increase in evaporation due to climate change and the real evaporation measured in most parts in the norther hemisphere. This paper analyzed its existence and the underlying mechanisms in Wudaogou area.【Method】The study was based on the metrological data measured from 1970 to 2017 from a weather station in the Wudaogou Experimental Station. We analyzed the variation of annual evaporation and its determinants including wind speed, temperature, sunshine hours, water vapor pressure difference, rainfall and relative humidity, using trend-line analysis and entropy methods.【Result】①The annual evaporation had been in decline from 1970 to 2017 at average rate of 8.7 mm/a. The GM(1,1) model coupled with the Verhulst model in the gray system can describe the inter-annual evaporation. ②The evaporation was positively correlated with wind speed, sunshine hours and evaporation, and negatively correlated with temperature, relative humidity and rainfall. The temperature had risen from 1970 to 2017 at rate of 0.25 ℃ per decade, while the evaporation decreased at rate of 86.9 mm per decade, typical "evaporation paradox". ③The linear trend method and the entropy method gave consistent results that the factors that impacted on the evaporation more significantly were in the order of wind speed > temperature > relative humidity > sunshine hours > rainfall > water vapor pressure difference, indicating that the reduction in wind speed and sunshine hours, along with the increase in relative humidity, combined to yield the “evaporation paradox” in the studied area. ④The decrease in sunshine hours was likely to be caused by the increase in aerosol content, while the slowing wind speed induced by urbanization could have made the aerosol increase. The increased relative humidity gave rise to more foggy weather thereby reducing sunshine hours.【Conclusion】There was an “evaporation paradox” in the Wudaogou area which was likely to be caused by the increased aerosol content which in turn reduced solar radiation and evaporation. |
| Key words: pan evaporation; trend variation; meteorological factors; Wudaogou area |
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