جستجوی مقالات مرتبط با کلیدواژه "ساعات آفتابی" در نشریات گروه "آب و خاک"

One of the climate variables with relatively large gaps in observation and significant importance in estimation of evapotranspiration is sunshine hours. In the present study, in order to reconstruction the sunshine hour data of several selected stations in Tabriz province, Iran namely,Tabriz, Sarab, Sahand and Maragheh during the period of 1990 to 2019, skill of intelligent approaches of SVR, ANN and RF was compared with statistical methods of normal ratio, geographical coordinates and weight correlation coefficient. Statistical indices of R, RMSE, MAD and Taylor diagrams were used for evaluation of comparisons. The obtained results showed that ANN and geographical coordinate methods have the highest accuracy in reconstruction sunshine hours among the selected intelligent and statistical methods, respectively. In Tabriz and Sahand stations, the geographical coordinate method with RMSE of 1.04 and 1.13 hours, respectively, in the Sarab station SVR with RMSE of 1.58 hours and in Maragheh station the normal ratio method with RMSE of 1.45 hours showed the highest accuracy in generating sunshine hours. Besides, RF method had the lowest accuracy in reconstruction of sunshine hours data. It can be concluded that in Tabriz, Sarab and Sahand stations, both types of intelligent and statistical methods have almost same accuracy, but in Maragheh station, statistical methods provided slightly better estimations.

Solar radiation is one of the most important climate parameters that has direct relationship with many hydrological and meteorological processes. Due to the lack of real time records of this parameter in meteorological stations, solar radiation estimation models based on meteorological parameters are usually applied in practical issues. The Angstrom-Prescott equation that works on the basis of the sunshine hours has been widely applied for calculating solar radiation values due to its simplicity and acceptability. So far, many studies have been conducted about calibrating coefficients of this equation based on the meteorological parameters. The purpose of this study was to evaluate the atmospheric air polutions effects on received solar radiation using the Angstrom-Prescott model. Calibration of the Angstrom-Prescott equation coefficients was performed using daily radiation data of Urmia and Tabriz stations during 3 years period (2014-2017) with taking into account the Air Pollution Index (API). Also,in order to compare the results of modified models with general equation of Angstrom-Prescott,different linear,exponential and logarithmic models were developed. In order to evaluate the models precision, RMSE, MABE, NSE and R2 indices were employed. The results of statistical analysis of the models indicated that the calibrated models of Urmia and Tabriz stations on the basis of the API and the logarithmic structure had the best perfermace to general equation of Angstrom-Prescott. The average values of the RMSE of the modified logarithmic model for Urmia and Tabriz were obtained 0.1263 and 0.1050 jcm-2day-1, respectively.

Food security depends on production of basic agricultural crops such as wheat. In rain-fed wheat cultivation, climatic parameters such as temperature and rainfall have much effect on the wheat production. In this research, multi-year meteorological parameters and rain-fed wheat production data of Dezful, Shooshtar, Andimeshk and Masjed-Soleiman counties were used to determine the climatic model production at north of Khouzestan province. To estimate the amount of the effect of different meteorological factors on wheat yield, the linear regression methods at the local and regional scales were used. The findings showed that for estimation of wheat yield, local models need less data model than the regional ones. However, in comparison the local models had more accuracy than the regional model. Also, sensitivity analysis showed that, the mean of maximum temperature and that of precipitation of winter months were most sensitive parameters on wheat yield. In addition, wheat yield increases by the increase in the rain fall. But, rainwater productivity has had wide fluctuation between 0.07 to 0.39 kg/m3 in various years in the region. This shows that more attention should be paid to other factors such as farming factors for increasing rainwater productivity.

Solar radiation is an essential factor in irrigation scheduling, hydrological cycle, crop growth simulation models and estimation of reference evapotranspiration. The aim of the present research was to investigate the accuracy of solar radiation estimation models and their effects on reference evapotranspiration. For this purpose, the meteorological data of 4 synoptic stations including Urmia, Takab, Salmas and Mahabad in West of Urmia lake catchment in daily scale were used. Solar radiation was estimated using seven models including, Hargreaves-Samani, Allen, Self-Calibrating, Samani, Annandale, Bristow-Campbell and Angstrom–Prescott. Then, the obtained values were used in FAO- Penman-Monteith equation to estimate the reference evapotranspiration. In order to evaluate the model's accuracy, the statistical indicators including root mean square error, mean bias error and determination coefficient were used. The evaluation results of the models showed that the Angstrom – Prescott model had the best performance, and the Samani method was the weakest method in the studied stations. The average values of the root mean square error for the Angstrom–Prescott and Samani methods in the studied region were obtained 0.48 and 1.43 mm/day, respectively.

Solar radiation on the earth surface has a wide range of applications in hydrology, agriculture and meteorology. Solar radiation is an important parameter of estimated models of reference crop potential evapotranspiration such as the Penman–Monteith equation. Also, total sunshine hours are one of the most important factors affecting climate and environment, and its long-term variation is of much concern in climate studies. Reference crop potential evapotranspiration is one of the most important parts of water cycle in the nature but, direct measurement of this crop parameter is so difficult and not practical. Therefore, equations that can estimate the value of evapotranspiration only by using meteorological data are necessary. As mentioned before, the Penman–Monteith equation can be used for estimating reference crop potential evapotranspiration, however this equation needs solar radiation data, and the measurement of solar radiation is done in a limited numbers of weather stations in Iran, and also in Fars province, south of Iran. Since, the measurement of solar radiation is expensive, therefore many models have been derived for its estimation in different climates of the world., Many investigators also have been tried to estimate solar radiation for different locations of the world based on more simple measured weather data such as air temperature (minimum, maximum or mean) and sunshine hours. Hence, the derived equations for estimating solar radiation based on other weather data can be used for estimating reference crop potential evapotranspiration with the Penman–Monteith equation.
In this study, solar radiation was estimated in Shiraz, central part of the Fars province in south of Iran. For this purpose, the daily measured of solar radiation data in Shiraz synoptic station were used. Also, other needed weather data were used. All available data was for the years 2006 to 2010. Measured data of years 2006 to 2008 were used for calibrating fourteen estimated models of solar radiation in seasonally and annual time steps and the measured data of years 2009 and 2010 were used for evaluating the obtained results. The equations were used in this study divided into three groups contains: 1) The equations based on only sunshine hours. 2) The equations based on only air temperature. 3) The equations based on sunshine hours and air temperature together. On the other hand, statistical comparison must be done to select the best equation for estimating solar radiation in seasonally and annual time steps. For this purpose, in validation stage the combination of statistical equations and linear correlation was used, and then the value of mean square deviation (MSD) was calculated to evaluate the different models for estimating solar radiation in mentioned time steps.
The mean values of mean square deviation (MSD) of fourteen models for estimating solar radiation were equal to 24.16, 20.42, 4.08 and 16.19 for spring to winter respectively, and 15.40 in annual time step. Therefore, the results showed that using the equations for autumn enjoyed high accuracy, however for other seasons had low accuracy. So, using the equations for annual time step were appropriate more than the equations for seasonally time steps. Also, the mean values of mean square deviation (MSD) of the equations based on only sunshine hours, the equations based on only air temperature, and the equations based on the combination of sunshine hours and air temperature for estimating solar radiation were equal to 14.82, 17.40 and 14.88, respectively. Therefore, the results indicated that the models based on only air temperature were the worst conditions for estimating solar radiation in Shiraz region, and therefore, using the sunshine hours for estimating solar radiation is necessary.
In this study for estimating solar radiation in seasonally and annual time steps in Shiraz region, three groups of equations were used (1: based on only sunshine hours. 2: based on only air temperature, and 3: based on sunshine hours and air temperature). Final results of this study for estimating solar radiation in Shiraz region were: 1) For autumn season the best equation was based on the extraterrestrial radiation, the ratio of daily actual sunshine hours to daily maximum sunshine hours, and minimum and maximum air temperatures. 2) For annual time step the best equation was based on the extraterrestrial radiation and the ratio of daily actual sunshine hours to daily maximum sunshine hours.

Drought prediction for in many regions of the world has critical importance for strategic planning agriculture and water management. The occurrence of droughts cannot be predicted with certainty and thus must be treated as random variables. It is the main purpose of this paper to develop a new concept of drought features assessments based on triple drought related hydro meteorological and meteorological variables¡ namely¡ rainfall¡ solar irradiation and sunshine duration. At first scatter diagram of rainfall¡ solar irradiation and sunshine duration are drawn as named Dual Graphic Method (DGM) and observed monthly drought condition are change compare SMP values table. Equal standard rainfall lines are drawn as a map with two reference variables as solar irradiation and sunshine duration. These are referred to as the triple graphical method (TGM) approach. It furnishes rich features of drought behavior variation based on the rainfall¡ solar irradiation and sunshine duration. This analysis and the solar irradiation estimation method are applied to Kermanshah stations in the Republic of Iran for the monthly data period 1970–2010. The linear relations between drought and the variables of the Angstrom equation are found 0.61. TGM graphs help to identify not only precipitation surplus (wet spells) or deficits (dry spells droughts) but also their variations with two more meteorological variables as solar irradiation and sunshine duration.

Correct estimation of reference evapotranspiration (ETo) needs to estimate accurate solar radiation values. There are many models to estimate solar radiation so that one of these relationships is Angstrom-Prescott (A-P) equation. The accuracy of Angstrom-Prescott equation in estimating solar radiation value depends on the estimation accuracy of a and b coefficients of the mentioned equation. The purpose of the present research was to investigate the accuracy of models for estimating coefficients in A-P equation and their effects in the solar radiation and reference evapotranspiration values. To do this purpose, the meteorological data of four synoptic stations including Urmia, Takab, Mahabad and Salmas in the Urmia lake watershed in the daily scale from 1998 to 2008 were used. The models which used for the determination of Angstrom-Prescott equation coefficients were included models based on the annual average of relative sunshine hours , elevation and , elevation and latitude and , elevation and latitude, annual average of air temperature, elevation. The obtained coefficients were used to compute the solar radiation values in Angstrom-Prescott equation and then reference evapotranspiration was calculated by FAO-Penman-Monteith equation. To evaluate the models accuracy, statistical indices including RMSE, MBE, MPE and R2 were used. The evaluation results of the models showed that the model based on annual average of relative sunshine hours (Rietveld model) had the best performance in determining the coefficients of AngstromPrescott equation. The average values of RMSE, MBE, MPE and R2 indices for actual reference evapotranspiration and reference evapotranspiration obtained from coefficients of mentioned model were found 0.33 and 0.25 mm/day, 6.27% and 0.9977, respectively. For AngstromPrescott equation coefficients from selected model, a=0.26 and b=0.43 were suggested in the studied stations in the Urmia lake watershed.

Desalination by solar radiation is one of the efficient ways to filter sea water and regarding the renewable solar radiation energy application as a way to provide sweet water is regarded in line with sustainable development and adaptable to environment. Condensation irrigation system is a developed modern idea which takes into consideration environmental issues together with application of sea water. This system is being used for providing drinking water and plantation. The major part of this system that is responsible for providing sweet water is solar still. Solar stills utilize solar radiation for sea water desalination. In the present research, the effect of atmospheric factors and solar still base surface parameter on the evaporation potentiality in solar stills has been investigated in a one-year statistic period that purpose of this study, is trying to determine and recommend using stills with high evaporation potential. Results of this study indicate high dependency degree of stills evaporation potential to atmospheric factors that the intensity dependency of this parameter is including: positive relationship of ambient air temperature (R=0.95), the positive relationship of the number of sunshine hours per day (R=0.73) and negatively relationship relative humidity (R=-0.72). These observations also showed that by reducing the solar stills surface, evaporation potentiality in solar stills will increase and Investigate the effect of solar still base surface by ANOVA results indicated significant differences at the one percent level between evaporation from Solar Stills.

Assessment of effective climate parameters and planning for their managing and or arranging agronomic activity with those trend changes, that result to improving production baseline and prediction for future. In order to determination of climate-yield production functions, analyzed eight crop seasons data (1998-2006) of 25 climate parameters and rainfed barley grain yields of four cold and semi-cold regions of Lorestan province.These regions were including Kohdasht and PoleDokhtar regions. By path analysis method, correlationcoefficient separated to direct and indirect effects. Results showed that in local and common models ofproduction functions, the role of crop season vapor pressure deficit is very important. The local models necessary small input data but common model need more input data (Tmin, RHmean, n, PWinter, PStart, Pend, Tmin-abs, PAzar, PDay, PFar., POrd., Tmax-azar). Rain water productivity of all regions determined for eight crop seasons, and amounts of maximum, minimum and average of rain water productivity were 0.422, 0.137 and 0.304 kg per cubic precipitation, which its average was 27.2 percent more than national average (0.239 kg.m-3). The sunshine,minimum temperature, average relative humidity, start rain and winter precipitation parameters, were the most sensitive parameters on barley grain yield prediction. We conducted the climate-yield models are useful tools to predict rainfed barley yield and so to assist managers and farmers for making decisions in rainfed agronomic activity under climate parameters changes.

Solar radiation, nowadays has a lot of application in different fields of agriculture, irrigation, and hydrology engineering and due to these various applications, different models has been proposed for it’s estimation. Angstrom-Prescott equation is one of the most important well known models for solar radiation estimation. This equation has empirically coefficient that various for each location. In this paper, the data gathered in Mashhad Synoptic station during 1378 and 1380, Angstrom-Prescott coefficient has been identified according to the ratio of actual sunshine hours (n) to the maximum sunshine hours (N). Also a Regression local equation has been proposed considering several meteorology parameters including daily gathered data of saturation vapor pressure deficit, precipitation, air temperature mean, relative humidity percentage and n/N. Finally the proposed model has been evaluated according to the independent measured data during 1381 to 1382. The statistical analysis of the results not show a significant difference between multi coefficients-local equation with Angstrom-Prescott equation, and therefore without more accuracy and more additional meteorology data and only with the data including sunshine hours and calculating extraterrestrial solar radiation, global solar radiation can be used with a high precision. For instance our model for Mashhad can be used with a=0.23 and b=0.44 which are the coefficient of the Angstrom-Prescott equation. This coefficient should be calibrated and validated for each zone individually.