Showing 3 results for Modelling
Mr Mohammad Safaei, Dr Hani Rezayan, Dr Parviz Zeaiean Firouzabadi, Dr Ali Asghar Torahi,
Volume 22, Issue 65 (6-2022)
Abstract
Examining the effects of climate change on the oak spatial distribution, as the main species of Zagros forests and its ecological and economic values is of significant importance. Here, we used species distribution models for simulating current climatic suitability of oak and its potential changes in 2050 and 2070. For this purpose, five regression-based and machine learning approaches, four climatic variables related to temperature and precipitation and two optimistic (RCP 2.6) and pessimistic (RCP 8.5) greenhouse-gas scenarios were used. The results of measuring the accuracy of models by AUC indicated the good performance of all algorithms and Random Forest achieved the highest accuracy (AUC = 0.95) among other methods. The results showed that in both time periods and under both scenarios, changes will occur in oak spatial distribution and the most severe one would be a 42.9 percent loss in the oak climatic suitability in 2070 under pessimistic scenario (RCP 8.5).
Mr Omid Mahpeykar, Dr Mohammadreza Khalilabadi,
Volume 23, Issue 68 (3-2023)
Abstract
General circulation of Persian Gulf has a cyclonic pattern that affected by tide, wind stress and thermohaline force. Although tidal force is very effective in values of current speed, but thermohaline force is dominant in long time because tidal forcing has a short period and returning nature. Tide and density parameters are important in navigating and shipping, especially when ships approaching the shore and shallow water to determine the drainage of them. In this study using the Mike model based on the three-dimensional solution of the Navier Stokes equations, assumption of incompressibility, Boussinesq aproximation, and hydrostatic pressure, Persian Gulf circulation modelled. After model stability, the effects of tidal force on horizontal and vertical distribution of density were investigated. Results show that forcing of tide caused current direction be regular and without tidal force, wind stress dominates on isopycnal and turbulent pattern forms in sea surface layer especially in cool season. Also, with the elimination of the tide effect, the velocity of current is reduced to 75% and the water density is increased to 1-2 kg/m3. Density profile show that the Persian Gulf is a baroclinic environment and it is stronger in cool season relative to warm season. The impact of forces is not the same in different regions of the Persian Gulf, so that the effects on the change in density in the Strait of Hormuz are more perceptible and moving inward to the Gulf, the intensity of its effect is reduced.
Fariba Esfandiary Darabad, Morteza Gharachorlu,
Volume 23, Issue 69 (6-2023)
Abstract
This study was aimed at identification and determination the spatial variations of sediment yield in Qarasu watershed located in Ardebil province, NW Iran, considering the negative consequences of erosion and sediment yield. In this regard, the monthly time scale, as the basis of work, was used to prepare the sediment rating curves. Preparation of monthly sediment rating curves based on sample flow and corresponding sediment discharge data in 19 hydrometry stations at the watershed during 14 years (2002-2015). All of statistical analyses were done by SPSS statistical software. Also, presentation of spatial variations in sediment yield over the watershed were made possible through the capability of GIS. The results of regression relations between flow and sediment discharge showed a close and significant relationship on a monthly time scale. The regional generalization of these relations for the whole basin showed that the seasonal difference was evident and the highest and lowest coefficient of determination was allocated to May (R2 = 0.74) and August (R2 = 0.55), respectively. Also, the highest and lowest sediment transport was observed in spring and summer, respectively, indicating the type of rainfall-runoff regime dominated on Qarasu watershed. In terms of the annual sediment yield, Yamchi station with 3970 tons per year and Nanakaran station with 66 tons per year, have the highest and lowest sediment yield among 19 stations of Qarasu watershed, respectively. According to the high levels of sediment yield in the Balikhly and Khyav sub-watersheds, it was recommended that more attention be paid to protecting and strengthening the water and soil elements and reducing the driven forces of erosion and sediment production in these sub-watersheds.
