According to geometry dimensions and installation characteristic of the 20 cm pan, the evaporation model of 20 cm pan was built by modifying the radiation and thermal storage items in Penman formula. Following, the model was calibrated by the continuous 14-day hourly measurements which were from Gulang Heterogeneous Underlying Surface Layer Experiment (GHUSLE). The analysis results showed that the model could simulate the diurnal variation of pan evaporation. In addition, the results indicated that day performance of the model was good with a root-mean-square error of 0.72 mm·d-1 and a mean relative error ratio of 6.7%. The simulation analysis showed that the contributions of radiative and aerodynamic components in the 20 cm pan evaporation process accounts for about 1/3 and 2/3 of the total pan evaporation, respectively. Sensitivity tests of four kinds of convention meteorological factors on pan evaporation showed that the pan evaporation were most sensitive to the wind speed, followed by air relative humidity, solar radiation and air temperature, and the corresponding rates of changes were 0.602, -0.590, 0.528 and 0.370, respectively.
[1]Stanhill G. Is the Class A evaporation pan still the most practical and accurate meteorological method for determining irrigation water requirements?[J] Agricultural and Forest Meteorology, 2002, 112 (34): 233-236.
[2]IPCC. Climate Change 2007: The Physical Science Basis[R]//Solomon S D, Qin M M, Chen Z, et al, eds. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, New York: United Kingdom and New York, 2007: 241-254.
[3]Peterson T C, Golubev V S, Groisman P Y. Evaporation losing its strength[J]. Nature, 1995, 377: 687-688.
[4]Brutsaert W, Parlange M B. Hydrological cycle explain the evaporation paradox[J]. Nature, 1998, 396: 30-31.
[5]Brutsaert W. Indications of increasing land surface evaporation during the second half of the 20\+th century[J]. Geophys Res Lett, 2006, 33, L20403, doi:10.1029/2006GL027532.
[6]Roderick M L, Farquar G D. The cause of decreased pan evaporation over the past 50 years[J]. Science, 2002, 298: 1410-1411.
[7]Rayner D P. Wind run changes: The dominant factor affecting pan evaporation trends in Australia[J]. J Climate, 2007, 20: 3379-3394.
[8]Zuo Hongchao, Li Dongliang, Hu Yinqiao, et al. Characteristics of climatic trends and correlation between pan-evaporation and environmental factors in the last 40 years over China[J]. Chinese Sci Bull, 2005, 50(12): 1235-1241.
[9]左洪超,鲍艳,张存杰,等. 蒸发皿蒸发量的物理意义、近40年变化趋势的分析和数值实验研究[J]. 地球物理学报,2006,49(3): 680-688.
[10]刘波, 肖子牛, 马柱国. 中国不同干湿区蒸发皿蒸发和实际蒸发之间关系的研究[J]. 高原气象, 2010, 29(3): 629- 636.
[11]Penman H L. Natural evaporation from open water, bare soiland grass[J]. Royal Society of London Proceedings(Series A), 1948, 193: 120-146.
[12]Monteith J L. Evaporation and the environment[J]. Symposium of the Society of Experimental Biology, 1965, 19: 245-269.
[13]Thom A S, Thony J L, Vauclin M. On the proper employment of evaporation pans and atmometers in estimating potential transpiration[J]. Quart J Roy Meteor Soc, 1981, 107: 711-736.
[14]Pereira A R, Villa Nova N A, Pereira A S, et al. A model for the class A pan coefficient[J]. Agriculture and Forest Meteorology, 1995, 76: 75-82.
[15]Chu Chiaren, Li Minghsu, Chen Yiying, et al. A wind tunnel experiment on the evaporation rate of Class A evaporation pan[J]. J Hydrol, 2010, 381: 221-224.
[16]Rotstayn L D, Roderick M L, Farquhar G D. A simple pan-evaporation model for analysis of climatesimulations: Evaluation over Australia[J]. Geophys Res Lett, 2006, 33, L17715, doi:10.1029/2006GL027114.
[17]Roderick M L, Rotstayn L D, Farquhar G D, et al. On the attribution of changing pan evaporation[J]. Geophys Res Lett, 2007, 34, L17403, doi:10.1029/2007GL031166.
[18]Rong Yanshu, Wang Wen, Jiang Haiyan. Changes of pan evaporation in the upper reach of the Yangtze river[J]. Journal of Hydrodynamics, 2011, 23(4): 503-509.
[19]马耀明, 王介民. 非均匀陆面上区域蒸发(散)研究概况[J]. 高原气象, 1997, 16(4): 446-452.
[20]刘波, 马柱国, 丁裕国. 中国北方近45年蒸发变化的特征及与环境的关系[J]. 高原气象, 2006, 25(5): 840-848.
[21]Yang Hanbo, Yang Dawen. Climatic factors influencing changing pan evaporation across China from 1961 to 2001[J]. J Hydrol, 2012, 414-415: 184-193.
[22]Ji Yuhe, Zhou Guangsheng. Important factors governing the imcompatible trends of annual pan evaporation:evidence from a small scale region[J]. Climatic Change, 2011, 106: 303-314.
[23]顾欣, 康为民, 龙先菊, 等. 黔东南气温变化对蒸发皿蒸发量的影响分析[J]. 高原气象,2012, 31(6): 1761-1766.
[24]陈伯龙, 左洪超, 高晓清, 等. 20 cm蒸发皿蒸发量的数学物理模型研究[J]. 地球物理学报, 2013, 56(2): 422-430.
[25]王丽娟, 左洪超, 陈继伟, 等. 遥感估算绿洲-沙漠下垫面地表温度及感热通量[J]. 高原气象, 2012, 31(3): 646-656.
[26]Linacre E T. Estimating U.S. Class A pan evaporation from few climate data[J]. Water International, 1994, 19(1): 5-14.
[27]Liu Qiang, Xia Xinghua. Contribution of meteorological variables to changes in potential evaporation in Haihe River Basin, China[J]. Procedia Environmental Sciences, 2012, 13: 1836-1845.
[28]Xu Chongyu, Gong Lebing, Jiang Tong, et al. Analysis of spatial distribution and temporal trend of reference evapotranspiration and pan evaporation in Chang jiang (Yangtze River) catchment[J]. J Hydrol, 2006, 327(1-2): 81-93.