عنوان مقاله [English]
There are a lot of methods in order to estimate the height of permanent snow lines. The first group is mentioned as the half of the height, which is the mediocre of current permanent snow line (kerovosky according to Homelom, 1998). The second group of glaciology experts has proposed a height for quaternary snow line, which seems to be suited with the incipient signs of watchable glacial trends in large scale not permanent snow line. But they might have perused the signs of glacial trends in those heights. The third group was those who have paid attention to valleys, glaciers or the moraines in different scales.
It is proposed two theories about the Determination of permanent snow lines or glacial region. Some researchers such as Lewis and Schweitzer declare that the snow line is in the beneath boundary of glacial class. However some like Homelom believes that the lowest boundary of glacial climate is the glacial equilibrium line. While King and Ritter & et al. believed that the snow line was completely different from the equilibrium glacial line and it cannot be considered equivalent, because each one of them is at a different heights.
It is tried to announce a relation with the use of effective variables on the height of the permanent snow line such as latitude, temperature, amount and direction of land surface slope in the radiation gauge stations, to evaluate the height of permanent snow line. As a matter of fact the amount of solar energy doesn't have many changes in flat areas. So it is used 16 stations in whole of Iran. Because of the Importance of direction and slope as the most important effective parameters & its changes in the solar elevation angle and the energy of the sun, it is tried to use relations which we can evaluate the temperature change due to solar elevation angle and its tilt in different directions. Consequently, it can have a relationship between different directions & resultant temperatures with the use of temperature situation & solar elevation angle in stations & changes of solar elevation angle in steep surfaces, what are more these relations can be used to estimate permanent snow line or ice and the water equilibrium line.
It was resulted that each boost or decrease in slope situation, boosts or decreases the height of snow line of about 23 meters in leeward & also each percentage increase or decrease in address, increases or decreases 16.75 meters of the height of snow line. Consequently there is an A-south west land surface with a slope of 13Â° or 23.3%, which could have more temperature of 5 to 6 degrees in contrast with an A-northeast land surface in equal height, & as a conclusion it could be, effective in water evaporation, snow melting and soil moisture loss. This factor leads to an increase in plant height and temperature belts. And also the processes of cold areas extend to higher elevations in southwest in contrast with the A-northeast land surface.
There is a bit difference between the figures estimated in this paper with some previous studies, which is due to several factors including:
1-The estimation of height of snow line in Wright's method is involved a loads of paying attention in the time of circus floor in topographic maps. What is more, a few handling marks on topographic maps, causes a large change in elevation determined.
2-This study has been done nationally. The average slope is (23.3%) and the decrease of mean temperature of Quaternary is (8/8 Â° C) which considered generally, & could have a great various in the environment and cause to reduce the temperature of the article & as a result its decrease is more than what assumed in most cases.