بررسي تغييرات زماني و مكاني تبخير بر اساس مهمترين عوامل هواشناختي مؤثر بر آن در ايران مركزي

Investigating the Spatial and Temporal Variations of Evaporation Using the Climatic Parameters in Central Iran

Evaporation is one the most important climatic parameters in water resources management. This parameter depends on many other climatic factors and plays an important role in arid and semiarid regions. In this study, 14 weather stations were selected in arid areas in central and southern parts of Iran. The climatic historical data including cloudiness, maximum and minimum temperatures, the differences between maximum and minimum temperatures, mean relative humidity, wind speed, and some other factors were provided. An Attempt was made to determine the most important factors affecting evaporation by using Factor Analysis (FA). Then, by conducting Cluster Analysis (CA) through Minitab software, homogeneous regions were separated. Taking advantages of multiple regressions in each region, the relationship between climatic factors and evaporation on the basis of monthly routine was maintained. The verification and evaluation of derived regression equations was calculated using MAE or RMSE statistics. At the end, through applying the geo-statistic technique (Kriging) on calculated evaporation data of investigating stations, the monthly co-evaporation map for each homogeneous region was drawn and the resultant histograms were analyzed. The results show factor analysis is an appropriate method for determining the relative importance of climatic parameters affecting evaporation. Also, division of a vast region to small subdivisions using cluster analysis increases the precision of derived evaporation equations. Results showed that the multiple regressions may be used in calculation of evaporation and consequently potential evaporation with great confidence. Utilization of geo-statistic technique is a proper approach for estimating potential evaporation in low or no data areas.