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1.
Application of linear stochastic models for drought forecasting in the Büyük Menderes river basin, western Turkey 总被引：6，自引：3，他引：3
Ömer Faruk Durdu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(8):1145-1162
In the present study, a seasonal and non-seasonal prediction of the Standardized Precipitation Index (SPI) time series is
addressed by means of linear stochastic models. The methodology presented here is to develop adequate linear stochastic models
known as autoregressive integrated moving average (ARIMA) and multiplicative seasonal autoregressive integrated moving average
(SARIMA) to predict drought in the Büyük Menderes river basin using SPI as drought index. Temporal characteristics of droughts
based on SPI as an indicator of drought severity indicate that the basin is affected by severe and more or less prolonged
periods of drought from 1975 to 2006. Therefore, drought prediction plays an important role for water resources management.
ARIMA modeling approach involves the following three steps: model identification, parameter estimation, diagnostic checking.
In model identification step, considering the autocorrelation function (ACF) and partial autocorrelation function (PACF) results
of the SPI series, different ARIMA models are identified. The model gives the minimum Akaike Information Criterion (AIC) and
Schwarz Bayesian Criterion (SBC) is selected as the best fit model. Parameter estimation step indicates that the estimated
model parameters are significantly different from zero. Diagnostic check step is applied to the residuals of the selected
ARIMA models and the results indicated that the residuals are independent, normally distributed and homoscedastic. For the
model validation purposes, the predicted results using the best ARIMA models are compared to the observed data. The predicted
data show reasonably good agreement with the actual data. The ARIMA models developed to predict drought found to give acceptable
results up to 2 months ahead. The stochastic models developed for the Büyük Menderes river basin can be employed to predict
droughts up to 2 months of lead time with reasonably accuracy. 相似文献
2.
Declining trends in pan and lake evaporation have been reported. It is important to study this trend in every region to evaluate the validity of the trend and water management implications. Data from nine pan evaporation sites in South Florida were evaluated to see if there is a trend and if the quality of the data is sufficient for such analysis. The conclusion is that pan evaporation measurements are prone to too many sources of errors to be used for trend analysis. This condition is demonstrated in South Florida and in other regions by differences in magnitude and direction between spatially related pan stations and unexplainable observations. Also, potential evapotranspiration (ETp) was estimated with the Simple (Abtew equation) and the Penman–Monteith method. Both cases indicated no decline in evapotranspiration for the period of analysis. Based on the decline in humidity and the increasing trend in vapor pressure deficit for the short period of analysis, 1992–2009, it appears that South Florida is experiencing increase in evaporation and evapotranspiration at this time assuming no systematic error in the weather stations' observations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
4.
利用长江上游最近30年(66个测站)蒸发皿蒸发量和最近50年(90个测站)的7种气象要素,分析了蒸发皿蒸发量的区域变化趋势和影响蒸发皿蒸发量变化的因素;针对7个水文站的年径流量变化,探讨了蒸发皿蒸发量变化后对水分循环的影响.结果表明,长江上游蒸发皿蒸发量的变化可以划分为三个分区,研究区域东西两侧(青藏高原和大巴山一带)为显著减少区,分别命名为RⅠ和RⅡ,中间(云贵高原北部到黄土高原南缘以及由二者包围的四川盆地一带)为显著增大区,命名为RⅢ区.影响区域蒸发皿蒸发量变化的原因各有不同,青藏高原一带(RⅠ区)蒸发皿蒸发量减少的原因可归结于太阳辐射强度和风动力扰动减弱所致.大巴山一带(RⅡ区)减少原因是太阳辐射强度、风动力扰动强度、湿度条件都在显著下降所引起的.云贵高原到四川盆地一带(RⅢ区)蒸发皿蒸发量增加是环境气温强烈升高,导致其上空大气水汽含量显著减少,大气很干燥,引发蒸发过程加强所致.蒸发皿蒸发量发生变化的直接后果就是导致水分循环强弱发生变化,对于RⅠ区,尽管蒸发皿蒸发量减少,由于降水量和径流量增加的作用,这一区域的水分循环有所加强.在RⅡ区,降水量、径流量和蒸发量都在减少,因此RⅡ区水分循环显著减弱.在RⅢ区,降水量和径流量同时减少,而蒸发量增大,水量消耗增大,因此RⅢ区水分循环有减弱趋势. 相似文献
5.
Abstract Evaporation is an important reference for managers of water resources. This study proposes a hybrid model (BD) that combines back-propagation neural networks (BPNN) and dynamic factor analysis (DFA) to simultaneously precisely estimate pan evaporation at multiple meteorological stations in northern Taiwan through incorporating a large number of meteorological data sets into the estimation process. The DFA is first used to extract key meteorological factors that are highly related to pan evaporation and to establish the common trend of pan evaporation among meteorological stations. The BPNN is then trained to estimate pan evaporation with the inputs of the key meteorological factors and evaporation estimates given by the DFA. The BD model successfully inherits the advantages from the DFA and BPNN, and effectively enhances its generalization ability and estimation accuracy. The results demonstrate that the proposed BD model has good reliability and applicability in simultaneously estimating pan evaporation for multiple meteorological stations. Citation Chang, F.J., Sun, W., and Chung, C.H., 2013. Dynamic factor analysis and artificial neural network for estimating pan evaporation at multiple stations in northern Taiwan. Hydrological Sciences Journal, 58 (4), 813–825. 相似文献
6.
Development of pan coefficients for estimating evapotranspiration from riparian woody vegetation 
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下载免费PDF全文 Tanya M. Doody Richard G. Benyon S. Theiveyanathan Vijay Koul Leroy Stewart 《水文研究》2014,28(4):2129-2149
The long‐term ‘Millennium Drought’ has put significant pressure on water resources across Australia. In southeastern Australia and in particular the Murray‐Darling Basin, removal of exotic, high‐water‐use Salix trees may provide a means to return water to the environment. This paper describes a simple model to estimate evapotranspiration of two introduced Salix species under non‐water‐limited conditions across seven biogeoclimatic zones in Australia. In this study, Salix evapotranspiration was calculated using the Penman–Monteith model. Field measurements of leaf area index and stomatal conductance for Salix babylonica and Salix fragilis were used to parameterize the models. Each model was validated using extensive field estimates of evapotranspiration from a semi‐arid (S. babylonica, r2 = 0.88) and cool temperate (S. fragilis, r2 = 0.99) region. Modelled mean annual evapotranspiration showed strong agreement with field measurements, being within 32 and 2 mm year?1 for S. babylonica and S. fragilis, respectively. Monthly pan coefficients (the ratio of mean evapotranspiration to mean pan evaporation) were developed from 30 years of meteorological data, for 30 key reference sites across Australia for both species using the validated Penman–Monteith models. Open‐water evaporation was estimated from field measurements and was used to develop a simple linear regression model for open‐water evaporation across the 30 reference sites. Differences between modelled evapotranspiration and open‐water evaporation at each site provide an indication of the amount of water that might be returned to the environment from removal of in‐stream Salix species. The monthly pan coefficient method reported has application across riparian environments worldwide where measured evapotranspiration is available for model validation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Guangyong You Yiping Zhang Yuhong Liu Qinghai Song Zhiyun Lu Zhenghong Tan Chuansheng Wu Youneng Xie 《水文研究》2013,27(18):2676-2682
Negative trends of measured pan evaporation are widely reported. Studies of the factors that underlie this reduction in pan evaporation have not reached a consensus about the controlling factors. Most studies employ statistical analysis (correlation analysis or stepwise regression) to identify the controlling climatic variables; in contrast, few studies have employed physical‐based theories. In addition, observations of pan evaporation and related climatic variables are reported to be influenced by anthropogenic activities. Consequently, the observed trends of climatic variables in a nature reserve would be useful for understanding regional climate change. The present study site is located in Ailaoshan National Nature Reserve, SW China, which is free of anthropogenic activity. In this study, we firstly applied the adjusted PenPan model to estimate the pan evaporation. Then, using this physical‐based model, we identified a positive trend in pan evaporation, with a much larger increase in the dry season than in the wet season. The model results indicate that the change in the aerodynamic component is larger than that in the radiative component. In contrast to the reduction in wind speed and sunshine hours that has been reported in previous studies at various sites, we found that wind speed and sunshine hours have increased in recent decades, thereby explaining the increase of the pan evaporation rate. Wind speed made the greatest contribution to the change in pan evaporation, followed by sunshine duration. This study indicates that the potential evaporation has increased at this site despite the widely reported reduction in measured pan evaporation. During the dry season, the availability of water for agriculture and agroforestry could be threatened. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
We applied the maximum likelihood method produced by Kijko and Sellevoll (Bull Seismol Soc Am 79:645–654, 1989; Bull Seismol Soc Am 82:120–134, 1992) to study the spatial distributions of seismicity and earthquake hazard parameters for the different regions in western Anatolia (WA). Since the historical earthquake data are very important for examining regional earthquake hazard parameters, a procedure that allows the use of either historical or instrumental data, or even a combination of the two has been applied in this study. By using this method, we estimated the earthquake hazard parameters, which include the maximum regional magnitude $ \hat{M}_{\max } , $ the activity rate of seismic events and the well-known $ \hat{b} $ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. The whole examined area is divided into 15 different seismic regions based on their tectonic and seismotectonic regimes. The probabilities, return periods of earthquakes with a magnitude M?≥?m and the relative earthquake hazard level (defined as the index K) are also evaluated for each seismic region. Each of the computed earthquake hazard parameters is mapped on the different seismic regions to represent regional variation of these parameters. Furthermore, the investigated regions are classified into different seismic hazard level groups considering the K index. According to these maps and the classification of seismic hazard, the most seismically active regions in WA are 1, 8, 10 and 12 related to the Alia?a Fault and the Büyük Menderes Graben, Aegean Arc and Aegean Islands. 相似文献
9.
The extremely high rate of evaporation from water surfaces in arid and semi-arid areas greatly reduces optimal utilization of water reservoirs. In Algeria, which is at 80% an arid country, water resources are scarce and renewable due to low annual precipitation. Considering the importance of optimal utilization of renewable water resources, about 70 dams with capacity of 7.4 billion m3 were constructed. One of the biggest problems of water in dams in Algeria is the huge amount of water loss through evaporation due to high evaporation rate. Therefore, applying techniques to reduce evaporation are greatly needed. One of the most recommended techniques for reducing evaporation is the application of a thin chemical film on the surface of the water. The present study aims to investigate the effect of this technique under arid conditions. Experiment was conducted for 20 weeks in Touggourt with three Colorado-type evaporation pans. Fatty alcohol with various doses were used in different pans. First pan was filled with water without adding fatty alcohol while in second pan, fatty alcohols was added with recommended concentration (0.3 kg/104 m2/day) and similarly in third pan fatty alcohol was added with concentration (0.5 kg/104 m2/day). The preliminary results of the study indicated that evaporation rate from surface water was reduced overall up to 16 and 22% in the second pan and the third one, respectively as compared to the non covered pan. 相似文献
10.
Evaporation modelling by heuristic regression approaches using only temperature data 总被引：1，自引：1，他引：0
Accurate estimation of pan evaporation (Epan) is very important in water resources management, irrigation scheduling and water budget of lakes. This study investigates the accuracy of two heuristic regression approaches, multivariate adaptive regression splines (MARS) and M5 model tree (M5Tree) in estimating pan evaporation using only temperature data as input. Monthly minimum temperature, maximum temperature and Epan data from three Turkish stations were used, with month number (periodicity information) added as input to see its effect on estimation accuracy. The models were compared with the calibrated Hargreaves-Samani (CHS), Stephens-Stewart (SS) and multiple linear regression methods. Three different train-test splitting strategies (50%–50%, 60%–40% and 75%–25%) were employed for better evaluation of the applied methods. The results show that the MARS method generally estimated monthly Epan with higher accuracy compared to the M5Tree, CHS and SS methods. When extraterrestrial radiation, calculated from Julian date and latitude information, was used as input to the SS instead of solar radiation, satisfactory estimates were obtained. A positive effect on model accuracy was observed when involving periodicity information in inputs and increasing training data length. 相似文献
11.
Lisa Shevenell 《水文研究》1999,13(4):577-596
Values of evapotranspiration are required for a variety of water planning activities in arid and semi‐arid climates, yet data requirements are often large, and it is costly to obtain this information. This work presents a method where a few, readily available data (temperature, elevation) are required to estimate potential evapotranspiration (PET). A method using measured temperature and the calculated ratio of total to vertical radiation (after the work of Behnke and Maxey, 1969) to estimate monthly PET was applied for the months of April–October and compared with pan evaporation measurements. The test area used in this work was in Nevada, which has 124 weather stations that record sufficient amounts of temperature data. The calculated PET values were found to be well correlated (R2=0·940–0·983, slopes near 1·0) with mean monthly pan evaporation measurements at eight weather stations.In order to extrapolate these calculated PET values to areas without temperature measurements and to sites at differing elevations, the state was divided into five regions based on latitude, and linear regressions of PET versus elevation were calculated for each of these regions. These extrapolated PET values generally compare well with the pan evaporation measurements (R2=0·926–0·988, slopes near 1·0). The estimated values are generally somewhat lower than the pan measurements, in part because the effects of wind are not explicitly considered in the calculations, and near‐freezing temperatures result in a calculated PET of zero at higher elevations in the spring months. The calculated PET values for April–October are 84–100% of the measured pan evaporation values. Using digital elevation models in a geographical information system, calculated values were adjusted for slope and aspect, and the data were used to construct a series of maps of monthly PET. The resultant maps show a realistic distribution of regional variations in PET throughout Nevada which inversely mimics topography. The general methods described here could be used to estimate regional PET in other arid western states (e.g. New Mexico, Arizona, Utah) and arid regions world‐wide (e.g. parts of Africa). Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
12.
Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises. 相似文献
13.
On the basis of the mean air temperature, precipitation, sunshine duration and pan evaporation at 23 meteorological stations in the headwater catchment of the Yellow River basin from 1960 to 2001, the long‐term monotonic trend and abrupt changes for major climate variables have been investigated. The plausible monotonic trend of annual climatic time series are detected using a non‐parametric method. The abrupt changes have been investigated in terms of a 5 year moving averaged annual series, using the moving t‐test (MTT) method, Yamamoto method and Mann–Kendall method. The results showed that the annual air temperature has increased by 0·80 °C in the headwater catchment of the Yellow River basin during the past 42 years. One obvious cold period and one warm period were detected. The warmest centre was located in the northern part of the basin. The long‐term trend for annual precipitation was not significant during the same period, but a dry tendency was detected. According to the Kendall slope values, the declining centre for annual precipitation was located in the eastern part and the centre of the study area. The long‐term monotonic trend for annual sunshine duration and pan evaporation were negative. The average Kendall slopes are ? 29·96 h/10 yr and ? 39·63 mm/10 yr, respectively. The tests for abrupt changes using MTT and Yamamoto methods show similar results. Abrupt changes occurred in the mid 1980s for temperature, in the late 1980s for precipitation and in the early 1980s for sunshine duration and pan evaporation. It can be seen that the abrupt changes really happened in the 1980s for the climate variables. Different results are shown using the Mann–Kendall method. Both the abrupt changes of temperature and precipitation took place in the early 1990s, and that of pan evaporation occurred in the 1960s. The only abrupt change in sunshine duration happened during the similar period (in the 1980s) with the results detected by the MTT and Yamamoto methods. The abrupt changes which occurred in the 1990s and 1960s are not detectable using the MTT and Yamamoto methods because of the data limitation. However, the results tested by the MTT and Yamamoto methods exhibited great consistency. Some of the reasons may be due to the similar principles for these two methods. Different methods testing the abrupt climatic changes have their own merits and limitations and should be compared based on their own assumption and applicable conditions when they are used. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
14.
It is of importance to comprehensively investigate the spatial–temporal changes in potential evaporation patterns, which helps guide the long-term water resource allocation and irrigation managements. In this study, the Cloud model was adopted to quantify the average, uniformity, and stability of the annual potential evaporation in the Wei River Basin (WRB), a typical arid and semi-arid region in China, with the purpose of objectively and comprehensively characterizing its changing patterns. The cross wavelet analysis was then applied to explore the correlations between annual potential evaporation and Arctic Oscillation (AO)/El Niño Southern Oscillation (ENSO) with an aim to determine the possible causes of annual potential evaporation variations. Results indicated that: (1) the average of annual potential evaporation in the WRB first declined and then increased, and its stability also showed the same change characteristics, whilst its dispersion degree exhibited a decreasing trend, implying that potential evaporation has a smaller inter-annual variation; (2) the average of annual potential evaporation in the western basin was obviously smaller than that in the other areas, while its uniformity and stability in the Guanzhong plain and the Loess Plateau areas are larger than those in other areas, especially in the western basin where the uniformity and stability are the smallest; (3) both AO and ENSO exhibited strong correlations with annual potential evaporation variations, indicating that both AO and ENSO have played an important role in the annual potential evaporation variations in the WRB. 相似文献
15.
Two analyses, one based on multiple regression and the other using the Holt–Winters algorithm, for investigating non‐stationarity in environmental time series are presented. They are applied to monthly rainfall and average maximum temperature time series of lengths between 38 and 108 years, from six stations in the Murray Darling Basin and four cities in eastern Australia. The first analysis focuses on the residuals after fitting regression models which allow for seasonal variation, the Pacific Decadal Oscillation (PDO) and the Southern Oscillation Index (SOI). The models provided evidence that rainfall is reduced during periods of negative SOI, and that the interaction between PDO and SOI pronounces this effect during periods of negative PDO. Following this, there was no evidence of any trend in either the PDO or SOI time series. The residuals from this regression were analysed with a cumulative sum (CUSUM) technique, and the statistical significance was assessed using a Monte Carlo method. The residuals were also analysed for volatility, autocorrelation, long‐range dependence and spatial correlation. For all ten rainfall and temperature time series, CUSUM plots of the residuals provided evidence of non‐stationarity for both temperature and rainfall, after removing seasonal effects and the effects of PDO and SOI. Rainfall was generally lower in the first half of the twentieth century and higher during the second half. However, it decreased again over the last 10 years. This pattern was highlighted with 5‐year moving average plots. The residuals for temperature showed a complementary pattern with increases in temperature corresponding to decreased rainfall. The second analysis decomposed the rainfall and temperature time series into random variation about an underlying level, trend and additive seasonal effects and changes in the level; trend and seasonal effects were tracked using a Holt–Winters algorithm. The results of this analysis were qualitatively similar to those of the regression analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
Junfeng Chen Xue Xie Xiuqing Zheng Jing Xue Chunyan Miao Qi Du Yongxin Xu 《水文研究》2020,34(13):2830-2842
Control of evaporation from seasonally frozen soil is an important method for alleviating water shortages in arid and semi-arid areas. To investigate the inhibition of soil evaporation by sand and the major factors that influence soil evaporation, a series of field experiments with five sand-mulch thicknesses (0 cm, bare soil [BS], 1 cm [T1], 2 cm [T2], 3 cm [T3] and 4 cm [T4], with an average diameter of 1 mm) were conducted during the freeze–thaw period in Northern China. Soil evaporation characteristics in the three freeze–thaw stages were revealed and the major factors influencing soil evaporation were analysed using grey correlation analysis. The results showed that the cumulative soil evaporation decreased with increasing sand-mulch thickness during the freeze–thaw period, and only small differences in soil evaporation were observed between the T3 and T4 treatments. The reduction in soil evaporation under different sand-mulch thicknesses was 19.2–62.6% in the unstable freezing stage (P1), 2.0–28.3% in the stable freezing stage (P2) and 4.8–20.4% in the thawing stage (P3). In P1, solar radiation was a major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the sand-mulch treatments, and the influence of relative humidity on soil evaporation decreased in the T4 treatment. During the coldest P2, solar radiation was lowest so that relative humidity and wind speed became the more dominant influence factors on soil evaporation in all treatments, and surface soil water content was a major factor in the sand-mulch treatments. In P3, average air temperature and solar radiation were major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the BS and T1 treatments, whereas water surface evaporation was the major factor in the T2, T3 and T4 treatments. The results suggest that the addition of sand mulch in agricultural fields may be a beneficial practice to reduce water stress in arid and semi-arid areas. 相似文献
17.
Evapotranspiration (ET) is one of the major water exchange processes between the earth's surface and the atmosphere. ET is a combined process of evaporation from open water bodies, bare soil and plant surfaces, and transpiration from vegetation. Remote sensing-based ET models have been developed to estimate spatially distributed ET over large regions, however, many of them reportedly underestimate ET over semi-arid regions (Jamshidi et al., Journal of Hydrometeorology, 2019, 20, 947–964). In this work, we show that underestimation of ET can occur due to the open water evaporation from flooded rice paddies ignored in the existing ET models. To address the gap in ET estimation, we have developed a novel approach that accounts for the missing ET component over flooded rice paddies. Our method improved ET estimates by a modified Penman-Monteith algorithm that considered the fraction of open water evaporation from flooded rice paddies. Daily ET was calculated using ground based meteorological data and the MODIS satellite data over the Krishna River Basin. Seasonal and annual ET values over the Krishna Basin were compared with two different ET algorithms. ET estimates from these two models were also compared for different crop combinations. Results were validated with flux tower-based measurements from other studies. We have identified a 17 mm/year difference in average annual ET over the Krishna River Basin with this new ET algorithm. This is very critical in basin scale water balance analysis and water productivity studies. 相似文献
18.
贵州蒸发皿蒸发量变化趋势及影响因素分析 总被引：4，自引：0，他引：4
以贵州境内18个气象站1961-2001年逐日气象观测数据为基础,采用Mann-Kendal非参数检验方法、相关分析和主成分分析方法对贵州近41年来蒸发皿蒸发量及其主要影响因子(太阳净辐射、气温、相对湿度和风速等)进行了相关性及趋势性分析.结果表明:近41年来,贵州年平均蒸发皿蒸发量呈显著下降趋势,通过99%的置信度检验,蒸发量的下降主要表现在冬、春、夏三季.从区域分布来看,蒸发皿蒸发量整体上东部及西北部分地区显著减少,其他地区趋势变化不明显.蒸发皿蒸发量下降的主要原因是太阳净辐射的显著下降. 相似文献
19.
Linlin Ye Guofeng Zhu Longhu Chen Dongdong Qiu Yinying Jiao Rui Li Siyu Lu Jiangwei Yang 《水文研究》2024,38(1):e15064
The study of below-cloud evaporation effects under clouds in the Yellow River source region is of great significance for regional water resource generation as well as for water resource security in the arid and semi-arid regions of northern China. In this study, we quantitatively assessed the evapotranspiration effect in the Yellow River source region from March to November based on the improved Stewart model. The study concluded that: (1) below-cloud evaporation was slightly higher in summer than in other seasons (residual fractions of raindrop evaporation were 80.57% in summer, 81.12% in spring, and 84.2% in autumn, respectively); and (2) sub-cloud evaporation diminishes with increasing altitude (residual fractions of raindrop evaporation were 83.09% in the western part of the area, 81.82% in the central part of the area, and 81.36% in the eastern part of the area, respectively). (3) The total linear index between study areas f and ∆d is 2.24, where f > 95%, it is 1.19; that is, the evaporation of raindrops increases by 1% and the reduction in the excess of mercury by about 2‰. (4) Local meteorological factors (temperature, precipitation, and relative humidity) and raindrop diameter have a cross-influence on below-cloud evaporation, with relative humidity having the most significant effect, with the highest correlation coefficient of 3.03 when relative humidity is less than 70%. The results of the study can provide a parameter basis for hydrological and climatic models in the Yellow River Basin. 相似文献
20.
RICHARD N. WEISMAN 《水文科学杂志》2013,58(3):371-377
Abstract The effect that evapotranspiration has on recession curves during low flow periods is explored. Recession constants are obtained from flow data and plotted against the average daily pan evaporation occurring during the recession. The results for the three study basins are similar, showing a decrease in recession constant with an increase in average daily pan evaporation. For low values of average daily pan evaporation, the recession constant approaches a constant value. 相似文献