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Trends in Annual and Seasonal pan evaporation in the Lower Yellow River Basin from 1961 to 2010

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Advances in Climate Change Research 2012年第4期3卷 195-204页

作者： JI Xing-Jie WANG Ji-Jun GU Wan-Long ZHU Ye-Yu LI Feng-Xiu Henan Climate Center Henan Meteorological Bureau

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.

关键词： lower Yellow River Basin pan evaporation trend meteorological factors

Comparison of pan evaporation and actual evaporation estimated by land surface model in Xinjiang from 1960 to 2005

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Journal of Geographical Sciences 2009年第4期19卷 502-512页

作者：刘波马柱国徐晶晶肖子牛 Chinese Academy of Sciences Key Laboratory of Regional Climate-Environment Research for Temperate East Asia START TEA for East AsiaInstitute of Atmospheric PhysicsCAS Laboratory for Climate Studies National Climate CenterChina Meteorological Administration

pan evaporation,an indictor of potential evaporation,has decreased during the last several decades in many parts of the world;the trend is contrary to the expectation that the increase of actual evaporation will accompany global warming,known as the pan evaporation *** is the essential relationship between pan evaporation and actual evaporation? This is still an uncertain *** this paper,the trends of pan evaporation and actual evaporation are investigated using observational data and observation-constrained simulation results using NCAR Community Land Model(CLM) in Xinjiang from 1960 to *** analysis suggests that the decreasing trend of annual pan evaporation accompanies the increasing trend of annual actual evaporation,the tendencies of them both have statistical significance(at 99% level and at 95% level,respectively).We also find that there is the same turning point in precipitation,pan evaporation and actual evaporation of 1986,and either before the point or after,pan evaporation has inverse trend comparing with actual evaporation and *** above analysis indicates that pan evaporation and actual evaporation have complementary *** results support the issue of evaporation paradox described by Brutsaert and Parlange(1998) and suggest that decrease of pan evaporation indicates an increase of actual evaporation in Xinjiang in the past half *** correlation analysis shows that diurnal temperature range(DTR),wind speed,low cloud cover and precipitation are the most likely driving forces for the reduced pan evaporation and the ascending actual evaporation.

关键词： Xinjiang pan evaporation actual evaporation numeral simulation

Trend in pan evaporation and its attribution over the past 50 years in China

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Journal of Geographical Sciences 2010年第4期20卷 557-568页

作者： LIU Min SHEN Yanjun ZENG Yan LIU Changming Center for Agricultural Resources Research Institute of Genetics and Developmental Biology CAS Shijiazhuang 050021 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Jiangsu Institute of＇Meteorological Sciences Nanjing 210008 China Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China

Trends in pan evaporation are widely relevant to the hydrological community as indicators of hydrological and climate change. pan evaporation has been decreasing in the past few decades over many large areas with differing climates globally. This study analyzes pan evaporation data from 671 stations in China over the past 50 years in order to reveal the trends of it and the corresponding trend attribution. Mann-Kendall test shows a significant declining trend in pan evaporation for most stations, with an average decrease of 17.2 mm/10a in China as a whole, the rate of decline was the steepest in the humid region （29.7 mm/10a）, and was 17.6 mm/10a and 5.5 mm/10a in the semi-humid/semi-arid region and arid region, respectively. Complete correlation coefficients of pan evaporation with 7 climate factors were computed, and decreases in diurnal temperature range （DTR）, SD （sunshine duration） and wind speed were found to be the main attributing factors in the pan evaporation declines. Decrease in DTR and SD may relate to the increase of clouds and aerosol as well as the other pollutants, and decrease in wind speed to weakening of the Asian winter and summer monsoons under global climate warming.

关键词： pan evaporation Mann-Kendall test diurnal temperature range wind speed compete correlation China

Comparison of Different Ann Approaches in Daily pan evaporation Prediction

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Journal of Water Resource and Protection 2014年第4期6卷 319-326页

作者： Yildirim Dalkilic Umut Okkan Nesrin Baykan Department of CE Faculty of EngneeringErzincan UniversityErzincanTurkey Department of CE Faculty of EngneeringBalikesir UniversityBalikesirTurkey Department of CE Faculty of EngneeringPamukkale UniversityDenizliTurkey

Nowadays, one of the most important effects on water resources under climate change is increasing of free water surface evaporation which depends on the increasing of temperature. In basins, where there are no observed data, free water surface evaporation is taken into account depending on historical temperature and similar data and their long-term statistics. Predicting of real value of evaporation contains some uncertainties. The modeling of evaporation with a small number of predictors has crucial importance on the regions and basins where measurements are not sufficient and/or not exist. In this presented study, daily evaporation prediction models were prepared by using empirical Penman equation, Levenberg-Marquardt algorithm based on 'Feed Forward Back Propagation Artificial Neural Networks (LMANN)', radial basis neural networks (RBNN), generalized regression neural networks (GRNN). When the models were compared, it was noticed that the results of neural network models are statistically more meaningful than the Penman equation.

关键词： Daily evaporation pan evaporation evaporation Prediction Penman LMANN RBNN GRNN

Stilling and its Aerodynamic Effects on pan evaporation

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Hydro Science & Marine Engineering 2020年第2期2卷 12-19页

作者： Qiang Liu Sirui Yan Liqiao Liang Liya Su Key Laboratory for Water and Sediment Sciences Ministry of EducationSchool of EnvironmentBeijing Normal UniversityBeijing 100875China State Key Laboratory of Water Environment Simulation School of EnvironmentBeijing Normal UniversityBeijing100875China Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China

Declines in wind speed(u)(termed as“stilling”)has been reported in many regions of the *** explore the temporal trends of u and its aerodynamic effects is vital to understand the changes in water *** study analyzed the changes of temporal trends for u and its aerodynamic effects using the data during 1959-2000 at 266 stations across *** improved Penpan model was used to estimate pan evaporation(Epan)and quantify the contribution of radiative and aerodynamic components(aerodynamic component separated into wind speed u,vapour pressure deficit D,and air temperature Ta).Climate factors include Epan measured with the standard Chinese 20 cm diameter pan,u,Ta,relative humidity(rh)and sunshine hours(sh).The results showed:stilling occurred in most of stations(206 among 266)and 105 stations presented significant decreasing trends at 99%confidence level;stilling was the main cause for controlling the trends in Epan in most part of China,especially in the west and north of *** results indicated that decreasing trends in Epan due to stilling would inevitably alter water resources,and should be put further investigation incorporation other factors.

关键词： Wind speed pan evaporation Stilling Penpan model Aerodynamic effect

Evapotranspiration of an oasis-desert transition zone in the middle stream of Heihe River, Northwest China

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Journal of Arid Land 2014年第5期6卷 529-539页

作者： LiWen ZHAO WenZhi ZHAO Linze Inland River Basin Research Station Chinese Ecosystem Network Research Key Laboratory of Ecohydrology of Inland River Basin Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences

As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been conducted for a long time, studies concentrated on oasis-desert transition zone are very limited. On the basis of the meteorological data and other parameters（e.g. leaf area index（LAI）） of an oasis-desert transition zone in the middle stream of Heihe River from 2005 to 2011, this paper calculated both reference（ET0） and actual evapotranspiration（ETc） using FAO56 Penman-Monteith and Penman-Monteith models, respectively. In combination with pan evaporation（Ep） measured by E601 pan evaporator, four aspects were analyzed：（1） ET0 was firstly verified by Ep;（2） Characteristics of ET0 and ETc were compared, while the influencing factors were also analyzed;（3） Since meteorological data are often unavailable for estimating ET0 through FAO56 Penman-Monteith model in this region, pan evaporation coefficient（Kp） is very important when using observed Ep to predict ET0. Under this circumstance, an empirical formula of Kp was put forward for this region;（4） Crop coefficient（Kc）, an important index to reflect evapotranspiration, was also analyzed. Results show that mean annual values of ET0 and ETc were 840 and 221 mm, respectively. On the daily bases, ET0 and ETc were 2.3 and 0.6 mm/d, respectively. The annual tendency of ET0 and ETc was very similar, but their amplitude was obviously different. The differences among ET0 and ETc were mainly attributed to the different meteorological variables and leaf area index. The calculated Kc was about 0.25 and showed little variation during the growing season, indicating that available water（e.g. precipitation and irrigation） of about 221 mm/a was required to keep the water balance in this region. The results provide an comprehensive analysis of evapotranspiration for an oasis-desert transition zone in the middle stream of Heihe

关键词： evapotranspiration pan evaporation water requirement arid region oasis-desert transition zone

Comparison of Ten Potential Evapotranspiration Models and Their Attribution Analyses for Ten Chinese Drainage Basins

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Advances in Atmospheric Sciences 2020年第9期37卷 959-974页

作者： Ruiheng XIE Aihui WANG School of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610225China Nansen-Zhu International Research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

Potential evapotranspiration(EPET)is usually calculated by empirical methods from surface meteorological variables,such as temperature,radiation and wind *** in-situ measured pan evaporation(ETpan)can also be used as a proxy for *** this study,EPET values computed from ten models are compared with observed ETpan data in ten Chinese river basins for the period 1961−*** daily observed meteorological variables at 2267 stations are used as the input to those models,and a ranking scheme is applied to rank the statistical quantities(ratio of standard deviations,correlation coefficient,and ratio of trends)between ETpan and modeled EPET in different river *** are large deviations between the modeled EPET and the ETpan in both the magnitude and the annual trend at most *** eight of the basins(except for Southeast and Southwest China),ETpan shows decreasing trends with magnitudes ranging between−0.01 mm d−1 yr−1 and−0.03 mm d−1 yr−1,while the decreasing trends in modeled EPET are less than−0.01 mm d−1 yr−*** comparisons among different models in different river basins suggest that PETHam1 is the best model in the Pearl River basin,PETHam2 outperforms other models in the Huaihe River,Yangtze River and Yellow River basins,and PETFAO is the best model for the remaining *** analyses reveal that wind speed and sunshine duration are two important factors for decreasing EPET in most basins except in Southeast and Southwest *** increasing EPET trend in Southeast China is mainly attributed to the reduced relative humidity.

关键词： potential evapotranspiration model pan evaporation model comparison sensitivity analysis China

Tomato and cowpea crop evapotranspiration in an unheated greenhouse

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Water Science and Engineering 2008年第2期1卷 112-120页

作者： Xu Junzeng Peng Shizhang Luo Yufeng Jiao Xiyun State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering College of Water Resources and Environment Hohai University Nanjing 210098 P. R. China Institute of Water-Saving Irrigation Hohai University Nanjing 210098 P. R. China

With the development of protected cultivation of vegetables in China, it is necessary to study the water requirements of crops in greenhouses. Lysimeter experiments were carried out to investigate tomato （2001） and cowpea （2004） crop evapotranspiration （ETc） in an unheated greenhouse in Eastern China. Results showed remarkably reduced crop evapotranspiration inside the greenhouse as compared with that outside. ETc increased with the growth of the crops, and varied in accordance with the temperature inside the greenhouse and 20-cm pan evaporation outside, reaching its maximum value at the stage when plants’ growth was most active. Differences between the variation of crop evapotranspiration and pan evaporation inside the greenhouse were caused by shading of the pan in the later period when the crops were taller than the location where the pan was installed, 70 cm above ground. The ratio of crop evapotranspiration to pan evaporation was not constant as reported in previous studies, and the variation of the inside ratio αin lagged behind that of the outside ratio αout. Simulation of crop evapotranspiration based on 20-cm pan evaporation inside the greenhouse is more reasonable than that based on 20-cm pan evaporation outside, although pan evaporation outside is more consistent with ETc than that inside. The value of αin, calculated based on air temperature, relative humidity, and ground temperature inside, plays a dominant role in the calculation of ETc. As the crop height increases, altering the location of the inside pan and placing it above the canopy, out of the shade, would help to achieve more reasonable values of crop evapotranspiration.

关键词： crop evapotranspiration pan evaporation unheated greenhouse tomato cowpea