小型与E-601型蒸发皿蒸发量对比分析及其折算系数——以江苏省为例

本文基于江苏省16个台站小型和E-601型蒸发皿同步对比观测资料,以南京站为例,采用比值法和多元线性回归法对长时间序列小型蒸发皿蒸发量进行估算及效果检验,结果表明:通过比值法计算得到的月折算系数介于0.490～0.609之间,年折算系数介于0.476～0.621之间,二者平均折算系数相同,均为0.537,两种蒸发皿月蒸发量相关系数高达0.952 4,年蒸发量相关系数仅0.496 2,表明在利用比值法进行计算时,月折算系数较为合理,具有较好适用性;基于各气象因子和E-601型蒸发量建立的各月小型蒸发皿蒸发量多元线性回归方程,决定系数介于0.809～0.940,效果较理想;比值法和多元线性回归法模拟检验中,比值法年平均误差为7.9%,多元线性回归法年平均误差仅2.5%,比值法预测结果决定系数为0.861 9,回归模型决定系数高达0.953 4,可见回归模型效果更为理想。总结研究结果后,本文详细给出江苏省各台站小型及E-601型蒸发皿折算系数,为有效完整利用江苏省各台站长时间序列小型蒸发皿资料提供合理依据。     

利用区域气候模式RIEMS产品分析日蒸散量及其影响

利用区域气候模式RIEMS输出的各种气象参数,采用了BEF等4种不同方法计算了沂沭河上游流域的潜在蒸散量,并与该流域6个气象站实测蒸发数据计算的陆面潜在蒸散量进行了比较。结果表明,根据平均偏差、平均绝对偏差、均方根差和相关系数指标的综合判断,该4种方法的估测精度从高到低依次为双线性曲面回归经验函数法(BEF)、Hargreaves-Samani(Harg)法、Pristley-Tayler(P-T)法和Penman-Monteith(P-M)法。在时间序列上,4种方法计算的逐日蒸散量与观测值呈相同的变化趋势,但计算值在蒸散发最强、最弱和降水最多、气温最高的7-9月有较大差异。BEF法估测的精度最高,与观测值最接近,Harg法、P-M法和P-T法都有明显的偏高现象。BEF法只需要较少的参数就能得到较高的估测精度,因此可作为利用区域气候模式RIEMS产品计算沂沭河流域蒸散量的首选方法,进而为RIEMS模式中耦合的陆面水文过程模型TOPX提供满足精度要求的日蒸散量驱动参数。     

Estimating daily pan evaporation using artificial neural network in a semi-arid environment

The objective of this study was to test an artificial neural network (ANN) for estimating the evaporation from pan (E _Pan) as a function of air temperature data in the Safiabad Agricultural Research Center (SARC) located in Khuzestan plain in the southwest of Iran. The ANNs (multilayer perceptron type) were trained to estimate E _Pan as a function of the maximum and minimum air temperature and extraterrestrial radiation. The data used in the network training were obtained from a historical series (1996–2001) of daily climatic data collected in weather station of SARC. The empirical Hargreaves equation (HG) is also considered for the comparison. The HG equation calibrated for converting grass evapotranspiration to open water evaporation by applying the same data used for neural network training. Two historical series (2002–2003) were utilized to test the network and for comparison between the ANN and calibrated Hargreaves method. The results show that both empirical and neural network methods provided closer agreement with the measured values (R ²?>?0.88 and RMSE?<?1.2 mm day^?1), but the ANN method gave better estimates than the calibrated Hargreaves method.     

空气动力学阻抗的测量研究

利用涡旋相关方法和蒸发皿方法分别测量了裸地和玉米田的空气动力学阻抗, 分析了空气动力学阻抗的日变化特征, 同时对两种测量方法进行了比较。结果表明:实测空气动力学阻抗的日变化比较明显, 但变化幅度不大 (0~200 s/m)。两种方法得到的空气动力学阻抗具有可比性, 但蒸发皿方法测量的空气动力学阻抗普遍小于涡旋相关方法的测量值。     

Pan coefficient (K p) estimation under uncertainty on fetch

The FAO Penman–Monteith (F-PM) method is a frequently applied approach for calculating the daily reference evapotranspiration (ET₀). This method requires long records of meteorological data, which makes it quite hard to employ in locations with no or limited available data. Evaporation pans are widely used to estimate the reference ET₀, but this method requires reliable estimates of the pan coefficient (K _p). The objectives of this study were to determine the proper values of monthly and annual K _p, as well as the best method among those available for the estimation of K _p values in the study area. Measured weather data from 1992 to 2006 were obtained from 18 stations in the North and Northwest of Iran. Daily ET₀ calculated using methods by Bernardo et al. and Pereira et al. were compared with those calculated by the F-PM method. The employed methods at all stations, except those located in the north of the study area with high relative humidity, overestimated the ET₀ compared to the F-PM method. The constant parameters of these methods were optimized by a trial and error scheme to minimize the root mean square error. The results indicated that modified K _p coefficients from Bernardo et al.’s method ranged between 0.41 and 0.87 and the optimal coefficient of Pereira et al.’s method ranged between 0.49 and 0.95. Modified monthly K _p from Bernardo et al.’s method ranged between 0.3 and 1.07 and those from Pereira et al.’s method ranged between 0.4 and 1.18. Modified K _p of the methods by Bernardo et al. and Pereira et al. showed the higher estimation accuracy of daily ET₀ values. In general, the performance of the modified K _p of Bernardo et al.’s method was higher than Pereira et al.’s method for all stations. Thus, in the study region and under the same climatic conditions [in areas with only pan evaporation (E _p) records], the use of climatic monthly modified K _p to calculate ET₀ based on class A E _p is recommended.     

Estimating daily pan evaporation using adaptive neural-based fuzzy inference system

Estimation of evaporation is important for water planning, management, and hydrological practices. There are many available methods to estimate evaporation from a water surface, comprising both direct and indirect methods. All the evaporation models are based on crisp conceptions with no uncertainty element coupled into the model structure although in daily evaporation variations there are uncontrollable effects to a certain extent. The probabilistic, statistical, and stochastic approaches require large amounts of data for the modeling purposes and therefore are not practical in local evaporation studies. It is therefore necessary to adopt a better approach for evaporation modeling, which is the fuzzy sets and adaptive neural-based fuzzy inference system (ANFIS) as used in this paper. ANFIS and fuzzy sets have been evaluated for its applicability to estimate evaporation from meteorological data which is including air and water temperatures, solar radiation, and air pressure obtained from Automated GroWheather meteorological station located near Lake E?irdir and daily pan evaporation values measured by XVIII. District Directorate of State Hydraulic Works. Results of ANFIS and fuzzy logic approaches were analyzed and compared with measured daily pan evaporation values. ANFIS approach could be employed more successfully in modeling the evaporation process than fuzzy sets.     

湘江流域蒸发皿蒸发量的变化趋势及原因分析

利用1960-2006年湘江流域内44个气象观测站蒸发皿观测资料,采用气候倾向率、相关系数分析法,以及反距离权重插值来分析湘江流域蒸发皿蒸发量的时空变化特征及其影响因子。结果表明：湘江流域年蒸发皿蒸发量在47年间以21.29 mm/10a速率显著减少,通过了90%信度检验;且有75%的站点蒸发皿蒸发量下降趋势显著。从季节变化来看,蒸发皿蒸发量的下降趋势主要在夏季,以15.58 mm /10a的速率显著下降,并通过了99%信度检验。从空间分布来看,湘江流域蒸发皿蒸发量自西南向东北逐渐减少,且下游地区减少趋势最显著。流域饱和差的减小及风速的显著下降导致大部分站点蒸发皿蒸发量呈下降趋势。     

Single and dual crop coefficients and crop evapotranspiration for wheat and maize in a semi-arid region

In this study, weighing lysimeters were used to investigate the daily crop coefficient and evapotranspiration of wheat and maize in the Fars province, Iran. The locally calibrated Food and Agriculture Organization (FAO) Penman–Monteith equation was used to calculate the reference crop evapotranspiration (ET_o). Micro-lysimetry was used to measure soil evaporation (E). Transpiration (T) was estimated by the difference between crop evapotranspiration (ET_c) and E. The single crop coefficient (K _c) was calculated by the ratio of ET_c to ET_o. Furthermore, the dual crop coefficient is composed of the soil evaporation coefficient (K _e) and the basal crop coefficients (K _cb) calculated from the ratio of E and T to ET_o, respectively. The maximum measured evapotranspiration rate for wheat was 9.9 mm?day^?1 and for maize was 10 mm?day^?1. The total evaporation from the soil surface was about 30 % of the total wheat ET_c and 29.8 % of total maize ET_c. The single crop coefficient (K _c) values for the initial, mid-, and end-season growth stages of maize were 0.48, 1.40, and 0.31 and those of wheat were 0.77, 1.35, and 0.26, respectively. The measured K _c values for the initial and mid-season stages were different from the FAO recommended values. Therefore, the FAO standard equation for K _c-_mid was calibrated locally for wheat and maize. The K _cb values for the initial, mid-, and end-season growth stages were 0.23, 1.14, and 0.13 for wheat and 0.10, 1.07, and 0.06 for maize, respectively. Furthermore, the FAO procedure for single crop coefficient showed better predictions on a daily basis, although the dual crop coefficient method was more accurate on seasonal scale.     

近50年来(1960—2007年)长江流域20 cm口径蒸发皿蒸发量与太阳辐射变化的对比

利用长江流域147个气象站点1960—2007年的地面观测数据,通过计算,对比分析了长江流域20 cm口径蒸发皿蒸发量与太阳辐射的变化关系.结果表明:长江流域近50年来蒸发皿蒸发量变化和太阳辐射变化呈显著正相关关系,二者均呈现显著下降趋势,蒸发皿蒸发量随太阳辐射的变化产生相应波动变化,而且中下游地区蒸发皿蒸发量变化受太阳辐射变化的影响程度更为明显;就季节变化而言,春夏秋冬4个季节长江流域蒸发皿蒸发量变化和太阳辐射变化同样呈现明显下降趋势,春、夏、秋3个季节二者变化关系高度相关,这三季对于流域全年蒸发皿蒸发量减少的贡献也最大;长江流域太阳辐射的显著下降是导致20 cm口径蒸发皿蒸发量持续降低的主要原因之一.     

Estimation of daytime downward longwave radiation under clear and cloudy skies conditions over a sub-humid region

Downward longwave radiation (LW _↓ ) is a relevant variable for meteorological and climatic studies. Good estimates of this term are vitally important in correct determining of the net radiation, which, in turn, modulates the magnitude of the terms in the surface energy budget (e.g., evaporation). In remote sensing applications, the determination of daytime LW_↓ is required for estimation of the net radiation using satellite data. LW_↓ is not directly measured in weather stations and then is estimated using models with surface air temperature and humidity as input. In this paper, we identify the best models to estimate daytime downward longwave radiation from meteorological data in the sub-humid Pampean region. Several well-known models to estimate LW_↓ under clear and cloudy skies were tested. We use downward radiation components and meteorological data registered at Tandil (Argentina) from 2006 to 2010 (840 days). In addition, we propose two multiple linear regression models (MLRM-1 and MLRM-2) to estimate LW_↓ at the surface for all sky conditions. The new equations show better performance than the others models tested with root mean square errors between 12 and 16 W m^?2, bias close to zero and best agreements with measured data (r ²?≥?0.85).     

Important factors governing the incompatible trends of annual pan evaporation: evidence from a small scale region

Many studies reported the coexisting trends of decreasing and increasing pan evaporation in some large scale regions. This study proved that the coexisting trends also occurred in small scale region as well as in large scale region. To discover the important factors governing the incompatible trends of annual pan evaporation, annual climatic data of ten meteorological stations at the Liaohe Delta over recent 45 years were analyzed by the partial correlation analysis, and the results showed the strongest statistically correlation between annual relative humidity and annual pan evaporation. Researches on two extreme cases suggested there was obvious contrary trend between annual relative humidity and annual pan evaporation for one case, in despite of slight contrary trend for another case. Generally, annual relative humidity most likely was an important factor relating to the trend of annual pan evaporation. At the same time, an expanded urbanization and irrigation were seen around these meteorological stations. Urbanization and irrigation exerted opposite effects on pan evaporation, they therefore were speculated to be the ultimately inducements causing unbalanced relative humidity, and led to incompatible pan evaporation.     

珠江流域实际蒸散发与潜在蒸散发的关系研究

采用水量平衡模型和Penman公式分别计算了珠江流域七个子流域1961—2000年实际蒸散发(I_(ETa))和潜在蒸散发(I_(ETp)),并对供水条件变化下I_(ETa)与I_(ETp)的关系进行了定量化分析,对各子流域I_(ETa)和I_(ETp)关系的理论从属性进行判定,主要结论如下:1)珠江流域年实际蒸散发量远低于潜在蒸散发量,多数子流域I_(ETa)值不到I_(ETp)值的1/2。7个流域面积加权平均I_(ETa)为681.4 mm/a,I_(ETp)为1 560.8 mm/a。从蒸散发的变异性来看,则实际蒸散发I_(ETa)的变异性明显要高于潜在蒸散发I_(ETp)。2)东江、西江、北江、柳江和盘江等5个流域实际蒸散发I_(ETa)都与降水量呈现正相关关系,韩江、郁江两个流域I_(ETa)随降水变化的变化趋势不明显。各子流域的潜在蒸散发I_(ETp)与降水量呈现显著负相关关系。7个子流域平均情况下,随着降水量的增加,I_(ETa)呈现明显的增加趋势,而I_(ETp)呈现明显的下降趋势。3)通过对降水量P与实际蒸散发I_(ETa)及潜在蒸散发I_(ETp)的联合回归方程P-IET回归系数的T检验,判定韩江、柳江和盘江等三个子流域以及七流域面积加权平均I_(ETa)与P和I_(ETp)与P的关系满足理论意义上的严格互补相关;东江、西江、北江等三个流域I_(ETa)与P和I_(ETp)与P的关系满足"非对称"互补相关。4)基于极端干旱和极端湿润的边界条件,推导出非对称条件下的实际蒸散发互补相关理论模型。     

Application of the Priestley-Taylor evaporation model to assess the influence of soil moisture on the evaporation from a large weighing lysimeter and class a pan

The influence of soil moisture on evaporation from a 6-m grass-covered lysimeter and from Class A pans was assessed for one summer using the -parameter of the Priestley-Taylor evaporation model appropriate for the individual surfaces computed on a daily basis. Net radiation over the pan was estimated from above-grass measurements using a correlation established between the two, using measurements made in the previous two summers. Changes in heat storage of the water were considered in the derivation of for the pan. A unique relationship for the particular conditions of the site was determined between the for the lysimeter and soil moisture, approaching 1.29 at soil moisture near field capacity, but decreasing to as low as 0.5 for dry soil. The corresponding relationship for the pan showed more scatter, but this was improved by using 5-day running means of evaporation and stratifying the data in terms of wind speed to yield a family of curves. Values for at wet soil conditions varied from 1.07 for 100 km day^–1 wind run to 1.17 for 250 km day^–1 wind run. For each curve, values of increased by about 20%; as the soil dried. The relationships may be used to reduce observed Class A pan evaporation to equivalent values for wet-soil conditions and to estimate near-surface soil moisture and actual evapotranspiration for this particular site. Extension of the technique to other areas requires derivation of similar relationships appropriate for those other locations     

Seasonal reversal at Miryang Eoreumgol (Ice Valley), Korea: observation and monitoring

Climate change information required for impact studies is of a much finer scale than that provided by Global circulation models (GCMs). This paper presents an application of partial least squares (PLS) regression for downscaling GCMs output. Statistical downscaling models were developed using PLS regression for simultaneous downscaling of mean monthly maximum and minimum temperatures (T _max and T _min) as well as pan evaporation to lake-basin scale in an arid region in India. The data used for evaluation were extracted from the NCEP/NCAR reanalysis dataset for the period 1948?C2000 and the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1, and COMMIT for the period 2001?C2100. A simple multiplicative shift was used for correcting predictand values. The results demonstrated that the downscaling method was able to capture the relationship between the premises and the response. The analysis of downscaling models reveals that (1) the correlation coefficient for downscaled versus observed mean maximum temperature, mean minimum temperature, and pan evaporation was 0.94, 0.96, and 0.89, respectively; (2) an increasing trend is observed for T _max and T _min for A1B, A2, and B1 scenarios, whereas no trend is discerned with the COMMIT scenario; and (3) there was no trend observed in pan evaporation. In COMMIT scenario, atmospheric CO₂ concentrations are held at year 2000 levels. Furthermore, a comparison with neural network technique shows the efficiency of PLS regression method.     

1971-2010年黑龙江省蒸发量气候变化特征

利用1971-2010年黑龙江省63个气象站地面气象观测数据,应用气候趋势系数、气候倾向率等方法分析黑龙江省蒸发皿蒸发量和实际蒸发量的时空演变特征。结果表明：近40 a来,黑龙江省蒸发皿蒸发量总体呈下降趋势,气候倾向率达-62.7 mm/10 a,春季和夏季下降显著。从空间分布看,全省蒸发皿蒸发量呈下降趋势,但局部地区与气候变化趋势并不完全同步。在影响蒸发皿蒸发量的气象因子中,风速和气温日较差是影响其下降的关键因素。黑龙江省大部分地区年实际蒸发量占蒸发皿蒸发量的30 %,实际蒸发量呈微弱上升趋势,但不显著。实际蒸发量与降水、日照时数和气温日较差显著相关,日较差是影响其变化的首要原因。     

1960—2009年北京地区城市化背景下蒸发皿蒸发量的时空变化

利用1960—2009年北京地区20个气象台站的观测资料,分析了北京城区和郊区蒸发皿蒸发量的季节和年际变化趋势和特点,并探讨了城市化对北京地区局地气候的影响。结果表明:近50 a北京地区蒸发量有明显减小趋势,城区和郊区变化趋势分别为-88.1 mm/10a和-76.0 mm/10a。受城市化影响,北京城区蒸发量的变化主要与降水、日照时数、最低气温、气温日较差和平均风速的变化有关;郊区蒸发量的变化主要受相对湿度、日照时数、平均风速和空气饱和差的变化影响。总体而言,相对湿度、日照时数、最低气温、气温日较差和平均风速的变化对北京地区蒸发量的变化有显著影响。     

Evaporation from coastal and open waters of the central zone of the red sea

Abstract

Monthly evaporation was estimated from the coastal and open waters in the central region of the Red Sea between latitudes 21 and 22°N. A recent equation based on the bulk aerodynamic method was used to calculate the evaporation using two sets of observations collected over the coastal and open waters. The annual evaporation from coastal water was 194 cm with a maximum in May and a minimum in October; from open water, it was 144 cm with a maximum and a minimum in November and September, respectively. The application of Sverdrup's (1937) equation was attempted, first when the roughness parameter z₀ in his equation was set equal to 0.6 cm as he proposed, and when z₀ was set equal to the most acceptable value of 0.01 cm. Our study shows that the evaporation values obtained in the first case are closer to those obtained either from the recent equation or from direct measurements than those obtained in the second case.     

泾河流域温度与器皿蒸发量时空特征及变化趋势

利用泾河流域周边14个气象站点1957～2002年逐日温度、器皿蒸发数据,分析了近45 a来气温、器皿蒸发量的时空变化特征。Mann-Kendall统计检验结果表明：泾河流域气温变化趋势与同期我国气温变化趋势基本一致,年均温存在显著变暖的总趋势,增温率为0.29℃/10 a。流域北部气候变暖趋势高于流域南部,变暖的季节主要是秋冬季节。年器皿蒸发量呈逐渐减少的趋势,倾向率为-39.3 mm/10 a,在空间上变率表现为流域南部、北部减少趋势明显,中部变化趋势不明显。     

烟台市蒸发量变化趋势及影响因子

利用烟台市1971—2010年蒸发量、气温、日照、降水和总云量资料,采用线性回归、相关分析、小波分析、逐步回归方法,对蒸发量变化趋势及其影响因子进行分析。结果表明,烟台年蒸发量存在2～3年的主周期和4～8、8～12年的次周期变化,春季、夏季、秋季和冬季蒸发量分别存在3～5、5～7、7～11和2～4年的周期变化。平均相对湿度的增加和日照时数的减少是蒸发量减少的主要原因,而影响各季节蒸发量变化的气象因子各有不同。日照时数和总云量是影响夏秋季节蒸发量变化的最主要因子,秋冬季节的蒸发量主要受平均相对湿度、日照时数和总云量的共同影响。     

Potential evaporation in the peace river region of British Columbia

Abstract

Micrometeorological data collected over pasture in the Peace River area of British Columbia during the wet summer of 1977 were used to test the Priestley and Taylor (1972) model for potential evaporation. The model performed very well. RMSE was less than 10% of the mean evaporation rate on a daytime basis using an alpha value of 1.26. Since the model is mainly dependent on net radiation, which is rarely measured in such remote areas, this quantity was also estimated from more readily available meteorological data and used to calculate evaporation. Results were encouraging; calculated values were generally within 20 and 10% of energy balance estimates on daily and 5‐day mean bases.