جستجوی مقالات مرتبط با کلیدواژه "wg" در نشریات گروه "فیزیک"

It is expected that projected changes in the frequency and severity of extreme climate events, such as increased frequency of heat stress, droughts and flooding will have significant consequences on water resources. Increasing pressure on water resources due to climatic and anthropogenic changes as well as increasing competition among users is recognized challenges worldwide. Global scale studies identified the Mediterranean region as one of the most vulnerable regions to climatic and anthropogenic changes and thus as one of the world’s water crisis hot-spots. So investigation about this phenomenon in these areas will be very crucial. Yazd is located in arid regions and due to increasing population and industrial growth, has been highly regarded by planners and authorities. Water shortages in the past decades, lead to the water transfer of from Isfahan. But recently, due to increasing in rising water demand, the inadequacy of this project clearly felt. In the other hand, ground water resources of Yazd province are recharged from Shirkouh region. So due to this issue, to determine water stress risks in study area, considering climate change projections in shirkouh and Yazd as water supply and water consumption area is necessary.
Research In the present study, to assess future climate changes in the study area, historical data from the Yazd and Dehbala stations -as water recharge and water depletion areas of Yazd-Ardakan aquifer-were analyzed by Lars software.
To do this, daily values of minimum and maximum temperature, precipitation, and sunshine were used. GCM model in this research is HadCM3. These data are derived from two scenarios, A2, A1B and B1 for 2010-2030 periods.
Validation of the predicted values was conducted using the statistical parameters, including bias, P Value of t Student statistics. To better analyze the results using Excel software, the moving average of predicted parameters for every month of the year was calculated for the 2010 to 2030 period and the corresponding graphs were drawn.
Discussions and Results of two climate scenarios were evaluated and summarized below. The results of statistical validation of the predicted values, showed no significant differences between historical and predicted values of precipitation, maximum temperature, minimum temperature and sunshine. Therefore, suitability of Lars model to simulate climatic data of the study area is confirmed. Investigation of the precipitation in the Dehbala station showed that in autumn season will be declining and in spring will be increasing. In other words, the distribution of precipitation in the future will have significant changes and as winter precipitation decreases the spring precipitation will have increasing trend. On the other hand, due to the significant decline in January precipitation it is expected that the proportion of precipitation falling as snow vs. rain decrease. Such a change would affect the hydrological response of the basins and increasing flooding in this season. Similar process will happen in plain area.
Based on the results, it can be said that in future, mountain stations has more variations in precipitation parameter than plain stations. These differences may be related to the amount of rainfall, in other words, in areas with higher precipitation, more variations in rainfall and rainfall distribution will be happen.
Results showed that in studying stations, monthly minimum and maximum temperature increasing in almost all months.
According to this study, recharge area of Yazd-Ardakan aquifer will experience climate change and changes in the type of precipitation. As a result, by increasing in rainfall to snow coefficient, there would be more flood and less aquifer recharge. In the other hand by increasing in maximum temperature in water consumption (plain) area in future, water needs will grow significantly. Therefore planners and authorities should consider this fact in future water resources allocation.

Global warming caused by human activity and climate change is one of the issues attracted that has attention of many climate scientists. The relationship between climate parameters should be used in climate change studies to understand the complex nature of the environment and predict changes in the future. The reliable tool to investigate climate change effects on different systems is using the climate simulations by coupled general circulation of atmosphere and ocean. These models are capable to model the oceanic and atmospheric parameters for a long time period using IPCC scenarios. Due to the low spatial resolution of down scaled phenomena, in general circulation climate models, these models cannot provide accurately approximation of climate conditions of study areas. Therefore, outputs of these models should be down scale to weather station. The use of statistical methods especially when lower cost and faster assessment of climatic factors is required, have more advantages and capabilities. These models downscale the large scale circulation data by using outputs of GSM models and applying specific scenarios that produce climate data. In this study a type of GCM model as HADCM3 for the period 2046-2065 was used. To simulate climatic parameters in Tamar Basin, the HADCM3 data downscaled using LARS-WG mode under A2 and A1B scenarios. Tamar river basin is located in Golestan Province north-east of Iran that have 1525.3 km2 area. There are a few climatology and rain gauges in Tamar river basin. Most of these gauges except Tamar station that have more than 40 years precipitation and temperature data have short inventory period data (15 years rainfall data and 8 temperature data). According to the International organization WMO standards which at least thirty years considered as reference period, therefore, in this study the Tamar climatology data that were recorded for 30 years were used. For this purpose the temperature and rainfall data of Tamar station In a 30-year period (1981-2011) Was extracted. Due to the lack of sunshine data in stations, the Maravehtappe synoptic data, located at 30 km from the centre of the basin, was used. According to the Tamar basin area and variation in hypsometry of basin and also Tamar station located at outlet of basin, the rainfall and temperature data collected in this station cannot present the whole of basin changes. To solve the mentioned problem the temperature data was generalized for the whole of basin using a gradient equation with the differences between altitude of the station and the average altitude of the basin. The rainfall data also after the hydrologic processing, was transfered to the average altitude of basin using gradient equation. So the 30 day data in the month was randomly selected and the minimum and the maximum temperature data based on Tamar, Rebat-e-Ghrabil and Cheshmekhan station that located at the outside of the basin was extracted. Also the rainfall data of Tamar station with Tangrah, Rebat-e-Gharabil and cheshmekhan that are located at the outside of the basin were used. Then according to the obtained data, the gradient related to 30 days for each year was plotted, and a relationship was obtained. Totally, 2700 gradient relationship for 30 year also for maximum and minimum temperature and rainfall data were generated. Then, 30 gradient relationships for the maximum temperature and the minimum temperature and the rainfall data were selected with the gradient relationship of each year with higher correlation coefficient. Then the gradient relationship for each year and according to the highest percentage of watershed area that was located in the same altitude of centroid of the basin was acquired. Maximum and minimum temperature data for each year were moved to the center of the basin and data corresponding to the height of centroid the basin for log to climate models were obtained. In this study, in order to down scale of the atmospheric general circulation model data HADCM3, the LARS-WG model which is one of the weather generator models was used. To run this model in this research, calibration period was selected between 1981-2011, years then the model was run after preprocessing the input data.In the next step the model was assessed with NSE and RMSE and MAE indices. Results show that the simulation data for this period are in good agreement with observation data. To evaluate climate fluctuations in the Tamar basin, general circulation model data were down scaled using LARS-WG model according to both A1B and A2 scenarios and thus the daily values of the parameters were generated. The results showed that the average temperature will increase under A2 scenario about 2.48 ° C and under A1B scenario about 2.43 ° C. Meanwhile the maximum temperature change will be higher than the minimum temperature change. From this subject we can conclude that the changes (increases) in the average air temperature in the future will be most affected by the minimum temperature. The results show that 16% increase in precipitation under A2 scenario and 2% rainfall under A1B scenario during 2046-2065 periods. Also, sunshine hours in the study period will be reduced under both scenarios. The results indicate that for the A2 scenario has the highest emissions of carbon dioxide, methane and nitrous oxide, higher temperatures and more rain are expected.