جستجوی مقالات مرتبط با کلیدواژه "potential evapotranspiration" در نشریات گروه "علوم انسانی"

Considering the phenomenon of climate change and subsequent changes in plant water requirements, it is crucial to recognize and estimate climate change in the coming decades with the aim of proper environmental planning to adapt to future climate conditions and reduce its effects. The main factor in the consumption of water resources in arid and semi-arid areas is agriculture and, accordingly, evaporation-transpiration, therefore, awareness of the process of changes and its prediction plays an effective role in planning, development, and water resources management. Since evaporation-transpiration accounts for an important part of the water balance of arid and semi-arid regions, its correct estimation is very important in the optimal preservation of water resources. On the other hand, knowledge of evaporation-transpiration process is necessary to estimate plant water consumption and design irrigation systems. According to the conducted research, estimation of evapotranspiration in the present and future periods is one of the basic needs of development managers, therefore, this research aims to evaluate the evapotranspiration potential in the base period (1991-2005), and predict temperature changes, using 3 scenarios (RCP2.6, RCP4.5, and RCP8.5) and evapotranspiration based on CMIP5 models (1.1 BCC-CSM and CCSM4) in the 75 year period (2025-2100) was carried out in Tabriz city.

For this purpose, the Penman-Monteith method was used as a standard algorithm to estimate potential evaporation and transpiration in the basic period (1991-2005). Then, potential evaporation and transpiration in the period of 2025 to 2100 were estimated using 2.6 RCP, 4.5 RCP, and 8.5 RCP scenarios and the LARS-WG6 model. Finally, the predicted values of evaporation and transpiration in future periods were predicted using the statistical indicators and the calculated evaporation and transpiration values for the base period (1991-2005). The ROC skill score curve also was used in order to general assessment of the quality of the estimations.

The results showed an increase in the predicted potential evaporation and transpiration under the RCP scenarios. In all three scenarios, the highest amount of evaporation-transpiration was obtained in July and the lowest amount was obtained in December. Moreover, an increase in the predicted transpiration evaporation was observed in July, August, January and February, compared to the base period. In addition, a decrease in the predicted transpiration evaporation was obtained in November and December, compared to the base period. In the RCP 8.5 scenario, the difference was much higher than in the base period. The evaluation of the model performance showed that for the hot months of the year, the model had a better ability to estimate the amount of potential evaporation-transpiration compared to the cold months, and the lowest RMSE error was in the hot months, so that in January with a value of 0.15 mm, the lowest value Dara showed the error. A comparison between the months indicated the two months of February and August as the best estimation for the estimation of annual evapotranspiration values. Likewise, the results showed that in all future periods and under all scenarios, the average reference evaporation and transpiration in annual scales will increase significantly at the level of 0.01 compared to the base period. The verification results also showed an acceptable ability for the predictions of the potential transpiration evaporation model.

This research amed at investigation of the amount of reference evapotranspiration changes based on RCP radiative forcing scenarios and climate models from 2025 to 2100 in Tabriz. The obtained results indicate the increase of reference evapotranspiration in all RCP scenarios for each of the future periods. In addition, the highest percentage of the reference evapotranspiration changes in the 8.5 RCP scenario is more than other scenarios because this scenario predicts the worst climate conditions and obvious changes in evapotranspiration will occur. The results of this research can be beneficial to solve the challenges of managers and relevant officials in the future periods. Considering this, the water, environment and health sector planners should adopt the necessary solutions for adaptation and reducing the consequences. Reasonable use of water resources is inevitable under the conditions of warming weather in Tabriz. Increasing evaporation and creating important changes in the quality and quantity of water resources, consequently changes in the quantity and quality of agricultural products. This situation determines the necessity of planning changes in the exploitation of water resources and agriculture. The future plans should be such that the upcoming changes have less harmful effects on the water and agriculture sector in this region. It is necessary to consider measures to improve the irrigation system, reduce evaporation, reuse wastewater and improve the cultivation pattern.

evapotranspiration is one of the most important components in water balance and management. In this research, to evaluate the effects of climate change on the amount of potential evapotranspiration in the southern part of the Aras River Basin using the downscaled data of the GFDL-ESM2M model in the CORDEX dynamic downscale under the RCP8.5 scenario during the period of 2021-2050 and its comparison. It is treated with the values ​​of the base period (1985-2005). Data with a horizontal resolution of 22 x 22 km from the GFDL-ESM2M model were used in this research. The findings of the research showed that the minimum and maximum temperature and, accordingly, the ETp of the future period will increase compared to the base period in all six studied stations of Aras Basin (Ardebil, Ahar, Jolfa, Khoi, Mako and Pars-Abad). The value of this minimum temperature increase is estimated between 1.4 and 3.8 ºC and for the maximum temperature between 1.7 and 2.2ºC. The range of annual ETp increase varies from 133 mm to 189 mm. In the monthly ETp scale of all stations from January to July with an increase between 3.9 and 1.64 mm and from August to December with a decrease of 0.7 to 38.2 mm. Estimating the increase of ETp in the future period in the basin, especially in the months of spring, which is very important in terms of water demand, requires special attention to the possibility of this estimated increase in the planning of the water and energy sector.

Determining reference evapotranspiration is considered as a key factor for estimating crop water requirement and managing irrigation plans. Different methods have been presented to estimate this parameter. The accuracy of those methods varies based on meteorological data and climate conditions. So, it is necessary to evaluate different methods and determine appropriate method for estimating reference evapotranspiration in each region. In this study, reference evapotranspiration values were measured using lysimeter data collected from Ismail Abad research station located in Qazvin province, Iran, during a 4-years period. In order to compare different methods, lysimeter values was considered as reference method. So as to find the best evaporation method, Hargreaves-Samani, Blany-Criddle, Turc, FAO-Penman-Monteith, Makkink, Priestly- Taylor, FAO-Penman and Evaporation Pan were used. Evaporation Pan was the most appropriate method to estimate reference evapotranspiration based on the highest correlation coefficient (0.973) and the lowest standard error (3.81). In addition, Priestly- Taylor had the lowest accuracy based on with the lowest correlation coefficient (0.896) and the highest standard error (23.16). FAO-Penman-Monteith and Hargreaves-Samani ranked 2nd and 3rd among other methods because of high correlation coefficients and low standard error.

Reference evapotranspiration (ETo) is one of the main parameters in water resource planning and water management. Pan coefficient Class A (Kp) is an important factor for calculation of reference evapotranspiration (ETo). There are several ways to estimate Kp using different parameters such as wind speed, relative humidity and vegetation. In this study, using daily meteorological data for 4 years period from Shahrekord Meteorological Station using different equations such as Cuenca, Allen Pruitt, Snyder, Orang and Pereira, pan coefficient was estimated. Then, those values were estimated FAO-Penman-Monteith, Penman-24, Turk, Blaney-Cridle and Hargreaves-Samani equations. Results were comprised to lysimeter data collected from this region. Also for choosing the best model, between three parameters, Root mean square error, Mean absolute error and Standard Estimation Error rank test was performed. Results showed that pan evaporation methods had better accuracy compared to empirical methods. In addition, Turk equation ranked as the best and most accurate method and Penman-24 was the worst one.

In irrigation science, accurate estimation of the water requirement of crops and horticultural products is one of the most basic pillars of design and engineering calculus (Islami and Qahreman, 2013).Observations on evaporation through the pans have not always been accompanied by precision. Also, the dense network of evapometry stations is not available and, on the other hand, the use of direct methods involves a lot of time and cost. Therefore, developing an alternative approach for estimating evaporation rates based on meteorological variables with the ability to measure and estimate more easily is necessary. In order to estimate reference evapotranspiration, using mathematical models with measurements of meteorological parameters as independent variables will be inevitable (Islami and Qahreman, 2013).Mohammad-Reza-Pour et al. (2015) presented modeling of monthly potential evapotranspiration using genetic programming in Sistan and Baluchestan Province. For this purpose, the reference evapotranspiration on a monthly scale using the Penman-Monteith method and based on meteorological data such as mean temperature, relative humidity, sunshine hours, wind speed and precipitation amount over a 40-year period at Zabol, Iranshahr, Chabahar and Zahedan stations was calculated and arranged in 16 separate time delay patterns. Then, modeling of monthly evapotranspiration values based on genetic programming using the GeneXproTools software was used to develop and implement genetic programming based models. The purpose of this study was to provide a simple, yet practical and accurate model for calculating potential evapotranspiration in order to calculate the evaporation rate from the surface using effective climatic elements in evaporation.

Kermanshah Province accounts for 1.5% of the total area of the country. This province is limited from north to Kurdistan Province, south to Ilam and Lorestan Provinces and east to Hamedan Province. In this study, due to the importance of growing season and water requirement for the growth and development of crops and pasture products, in order to estimate potential evapotranspiration at selected stations in the region, the sum of months of the year during the statistical period of 1995-2012 was considered. In this study, the GEP model was used to determine drought and evapotranspiration indices. The stations in the region were statistically surveyed and 5 stations in Kermanshah Province were selected. Then quantitative and qualitative data were analyzed by the run test in both Excel and SPSS. Then, the GEP model and software were used to determine the dry and semi-arid seasons and the seasons that were suitable for growing and cultivating. The accuracy of the estimated data was evaluated and finally, the zoning map of potential evapotranspiration of the province was prepared.

Important factors affecting the saturation deficit are temperature, wind, and relative humidity. Increasing the temperature and wind speed give rise to increasing the amount of the saturation deficit, thereby increasing the evaporation, and increasing the relative humidity, in contrast, decreases the saturation deficit, thereby decreasing the evaporation. Therefore, in this study, four factors of temperature, wind speed, relative humidity and saturation deficit as independent variables and the input of the model were used to estimate potential evaporation using the GEP model, and evaporation from the pan was also considered as a dependent variable in order to fit and evaluate the performance of the model. In examining the calculated values, it was observed that evaporation values estimated by the GEP model were close to the evaporation values measured through the evaporation pan and showed a very high correlation (r=0.98), which indicates the great efficiency of the GEP model to estimate the potential evapotranspiration in Kermanshah Province. In the present study, the IWD method was used for geostatistical interpolation, so that after calculating the potential evapotranspiration rate using the GEP model and generalizing the obtained values to the surface using the ArcGis software, the zoning map of evapotranspiration of Kermanshah Province based on the estimated and observed values was drawn. The survey of the zoning maps showed that there was very little difference between the results of the GEP model and the recorded rate of the evaporation pan and in the both cases, the highest evaporation was related to the western and southwest counties to near the center, and the least was related to the east and northeastern counties of the province.

In this study, the GEP model based on genetic algorithm was used to estimate the potential evapotranspiration. The results showed that there was a high correlation between the data obtained from the model and the evaporation pan. An absence of sufficient facilities such as the pan to record the potential evaporation rate and the incompleteness of existing statistics in most parts of the country reveal the importance of various methods and models in estimating the potential evapotranspiration based on the factors affecting it with a high coefficient of certainty. In this study, it was shown that the GEP model is an efficient model for estimating potential evapotranspiration in Kermanshah Province, and it can be used with high confidence to rebuild incomplete statistics and modify outlier data in the province. The analysis of the zoning maps of the potential evapotranspiration rate based on the measure of the evaporation pan and the GEP model showed that by moving from east to west and north to south, the evaporation rate was increased. The very important result obtained from the comparison of the annual rainfall of the province with evaporation was that from the beginning to the middle of the growing season, the plants of the eastern counties had a monthly precipitation more than evaporation, and this amount is reduced to the west, so that a little after the central areas (Islamabad), the amount of precipitation and evaporation is equal and then it decreases, and as we approach the end of the growing season, the situation is generalized to the whole of the province, that is more evaporation than rainfall, which indicates water scarcity and high water requirement of the plant, especially in the west to the provincial capital at the end of the growing season.

Drought is a climatic phenomenon that begins slowly and has a hidden nature. The duration of its occurrence and the resulting damage occur gradually in different sectors. Therefore, assessment and investigation of drought is very important in planning and implementation of actions to cope with drought. Droughts are divided into different types. One of the common methods of drought assessment is the use of drought indices which everyone can describes a type of droughts. In recent years, the use of Composite Drought Index (CDI) have attracted the attention of researchers. In this study, a new Composite Drought Index was developed that combined the three components, including the Groundwater Resource Drought Index (GRI), the Modified Standardized Precipitation Index (SPImod) and the potential evapotranspiration (ETP). In the next stage, the drought condition of Shahrekord plain located in Chaharmahal and Bakhtiari province was assessed in a 31-year period (1985-2015) using the Composite Drought Index (CDI). The results showed that the Shahrekord Plain was frequently experienced some wet conditions during the years 1985 to 2000, but it has suffered from consecutive severe droughts from 2008. In general it can be said that the developed CDI index is well able to describe the composite behavior of meteorological and groundwater droughts in the study area and is recommended as a new index for monitoring and assessing regional drought.

One of the atmospheric cycle properties is climatic changes which can cause the fluctuations in meteorological parameters. These fluctuations in many world regions are considerable and water and soil resources are affected by them. To prepare against undesirable effect of climate change and adopt suitable development programs and water resources management، it is necessary to investigate the meteorological variable changes. The objective of this research was to investigate the climate change in Urmia region. In this research، the changes trend of temperature، precipitation، relative humidity، sunshine and potential evapotranspiration were studied. To achieve this goal، Urmia synoptic station daily data with 40 years period (1971-2010) were used. The Mann-kendall statistical test at confidence level of 95% was used to investigate the significance of trend in the mentioned parameters. The results showed that the trend slope of maximum، minimum and average of temperature was positive and this trend in 95% confidence level was significant. Urmia precipitation was decreased with slope of -2. 26 so that this decrease was significant. The sunshine had positive slope and significant trend، but the negative trend of relative humidity and the positive trend of potential evapotranspiration (0. 0068) were not significant. The monthly investigations showed that the average temperature in all months had positive slope، but this slope was not significant in all months. The other parameters in some months had positive or negative slopes.

The accurate estimation of potential evapotranspiration is very important in water source management، agriculture، forestry and pasture sciences. Recently using of Geographical Information Systems (GIS) for accurate estimation has been developed and has showed good results. In this paper we estimate potential evapotranspiration in eastern Azerbaijan by Estefnz method. For calculation of coming net radiation (Rs) we used DEMSRTM images and solar analyst in ArcGIS software for 31 May، 10-11 am. After calculation of slope and aspects through digital elevation model، net radiation was estimated. The average temperature calibrates for elevation was imported in equation. Final maps show that the amount of potential evapotranspiration is between 0~15 mm/hour. Northern aspect and areas with high temperature have the higher potential evapotranspiration. Elevation and aspects are important factors than other factors in potential evapotranspiration control in the study area. The amount of evapotranspirtaion is higher than precipitation and therefore it is better that agricultural activities move to higher areas

Greenhouse gases cause damage on the equilibrium of the climatic system which makes a very necessary investigation on climate change impact on the hydrological parameters such as evapotranspiration; on the other hand، in the future decade climatic forecast would play a major role to make a planning. LARS-WG is one of the most famous stochastic weather generators، and the generated data is simulated by the collection of the atmospheric data which can be used for the investigation of weather parameters. At this research، the observed data including precipitation، maximum and minimum temperatures، sunshine duration at the base time and by using climatic fluctuations caused by the general circulation model، HadCM3، under emission scenarios A1B، A2 and B1 are used for the evaluation of potential evapotranspiration in the West Azerbaijan province. The results from LARS-WG model indicated that at this region according to (2046 - 2065) toward to the time frame (2011 - 2030) statistics generated for the variables mean annual temperature and mean annual potential evapotranspiration، total annual rainfall، respectively are by A1B scenario، 50. 40 mm، 2. 13 °C would increase، and 113. 89 mm per year will be reduced، and by the scenario A2، 30. 82 mm and 1. 57 °C increase، and 4. 81 mm per year will be reduced. The statistics generated by the scenario B1 are 32. 49 mm، 1. 25 °C and 33. 07 mm per year will increase. According to the results، under the A2 and A1B scenarios for (2011 - 2030) and (2046 - 2065) are the most critical forecasting for the future status respectively.

Drought is a random characteristic of natural phenomena, brought about by the irregulardeficit or shortage of available water, affects injuriously the plant growth and reduces their yield. Drought does not begin when rain ceases but rather only when plant roots can no longer obtain soil moisture in needed amounts. To estimate the intensity and the frequency of droughts will help to reduce the injurious effect of drought. In this Study we used the water-budget methods and Thornthwaite's aridity index and its standard deviation for Shiraz during 88<8-9228to show the frequency and the intensity of drought effects in this place. During this period this station is faced :<times different type of droughts on that five time severe and from the years of 9222its severity and intensity is increased. We also find out that every ten year this station will affect :times severe type of drought. The most severe drought was the years 9228,and it was repeated lower intensity in the year of 9221.