Analysis of variation in pan evaporation and its influencing factors in Haihe River Basin

Based on meteorological data of 17 meteorological stations from 1960 to 2012 in Haihe River Basin, the panel data model was used to analyze the variatio n trend and regressio nrelationship between panev aporation and other climate variables such as relative humidity, wind speed, sunshine hours, average temperature and diurnal temperature range. This paper was focused on analyzing the influencing factors of the " evapor ation parado x" in the Haihe River Basin, and exploring the feasibility of the panel data model for the study of w ater and heat balance and climate chang e. The r esults showed t hat during the period from 1960 to 2012, pan ev apo ratio n show ed a significant decrease at t he rate o f 221 89 mm/ ( 10a) and aver age t em perat ur e in2 cr eased at a rate o f 01 27 e / ( 10a) , r espectiv ely. There w as a phenomeno n o f evapor ation paradox exist in t he basin. Based on the Unit Root test, H ausman test and F2test, the results showed that t he variable coefficient of the fix ed effect mo del was mor e suitable fo r mo deling and analy sis o f pan evapor ation and o ther meteoro lo gical fact ors in the Haihe River Basin. From the per2 spect ive of sing le facto r reg ressio n, the co ntribut ion of sunshine hours to the pan ev apo ration w as the larg est, fo llow ed by rela2 tive humidit y, diur nal temper ature rang e, w ind speed and av erag e temper ature. The full factor reg ression analysis show ed t hat the pan evapor ation w as negatively co rr elated w ith relativ e humidity, and was po sitiv ely co rrelated w ith sunshine hours, av erag e temper atur e, diurnal temperatur e range and w ind speed. In t erms of fit ting effects of the averag e temper atur e and diur na l tem2 peratur e r ang e respect ively, the av erag e t emperat ur e was mor e suit able for the model fit ting. Comparing the reg ression r esults of aver age temperature and sunshine hours, the g lo bal dimming contributed mor e to the change in pan ev apo ration than global warming.

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