Estimation and Comparison of Zones with Permanent Snow in Glacial and Interglacial Periods Case Study: Haraz Catchment Area

Alternation of cold and warm climatic periods is of distinguished features of quaternary in Iran. The present rough and uneven areas of Iran indicate the erosion processes in warm and cold conditions. Alborz mountain chain has numerous evidences which indicate the involvement of glacial and interglacial processes. These evidences are visible as deep and large holes also naked and destroyed rocky valleys. Review of zones with permanent snow in quaternary era can be the determinant of involvement limit of glacial and interglacial processes in Iran. This research has been performed to estimate the line changes of permanent snow of Haraz catchment area in central Alborz Mountains. To estimate the zones with permanent snow in the latest cold period, climatic heritages and morphological evidences have been identified by satellite photos and field observations. Then height of permanent snow has been determined by the use of Wright method. Day-degree method has been used for achieving temperature threshold of snow fallings and regression analysis has been used for estimating temperature differences of permanent snow limit in cold and warm periods. Through implementing NDSI index in MODIS sensing photos, the snow zones in March 2005-2008 years were recognized to be compared with temperature threshold of snow falling. The findings of the studies showed that in the last cold period, the zone of permanent snows has lowered up to height 1800m in this catchment area, and now this zone is about 3200m which indicates that more than 80% of the zones with cold periods were under the domination of glacial erosion. Also field visits confirms it. The average difference of air temperature in glacial periods was 6 Celsius degrees lower than the interglacial periods. In fact, the air temperature difference indicates the presence of two different forming systems in Haraz catchment area.