Trends in Annual and Seasonal Pan Evaporation in the Lower Yellow River Basin from 1961 to 2010

The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1....

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Bibliographic Details
Published in:Advances in climate change research 2012-12, Vol.3 (4), p.195-204
Main Author: JI Xing-Jie WANG Ji-Jun GU Wan-Long ZHU Ye-Yu LI Feng-Xiu
Format: Article
Language:English
Subjects:
lower Yellow River Basin
meteorological factors
pan evaporation
trend
下游流域
地表气温
季节变化
平均增长率
年际
日照时数
蒸发皿蒸发量
黄河流域
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Summary:The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1.15~C increasing in annual mean surface air temperature over the past 50 years （0.23°C per decade）, the annual pan evaporation has steadily declined by an average rate of-7.65 mm per year. By comparison, this change is greater than those previously reported in China. Significant decreasing trends in annual pan evaporation have been observed at almost all stations. As a whole, seasonal pan evaporation decreased significantly, especially in summer, whereas seasonal temperature increased significantly, except in summer. Thus, the pan evaporation paradox exists in the lower Yellow River Basin. The trend analysis of other meteorological factors indicates significant decrease in sunshine duration and wind speed, but no significant variations in precipitation and relative humidity at annual and seasonal time scales. By examining the relationship between precipitation and pan evaporation, it did not show a concurrent decrease in pan evaporation and increase in precipitation. The partial correlation analysis discovered that the primary cause of decrease in annual and seasonal pan evaporation is the decrease in wind speed. A further examination using a stepwise regression shows that decrease in wind speed and sunshine duration, and increase in mean temperature axe likely to be the main meteorological factors affecting the annual and seasonal pan evaporation in the lower Yellow River Basin over the past 50 years.
ISSN:1674-9278
1674-9278
DOI:10.3724/SP.J.1248.2012.00195