Evaluation of thermal stress on military activity in Khorasan Razavi province based on Suzbad index.

Climate has a major impact on all human activities, including military operations, and should be carefully considered in any military activity. This means using the principles and concepts of climate in a practical context. Many of the common effects of atmospheric elements can be due to the conditions of operation and any military operation without coordination with the climatic conditions of the place is doomed to failure. Geographical criteria, especially climate and geomorphology, have a great impact on natural hazards. Due to this importance, military climatology is one of the important topics in military geography. This field discusses the climate of operational areas. The experiences of the imposed war and other world wars have shown that the element of temperature, which is one of the elements of climate, can be effective along with humidity and wind speed in the fate of a great power involved in war. Military climate is one of the branches of military geography that studies the effects of climate on military affairs at different levels of operation. For example, Operation Typhoon 1341, which was carried out in the Soviet Union, and the German army was confident of victory over the Stalinist regime and victory in Moscow, but the weather conditions and the scorching cold of Russia caused the defeat of Germany. According to the public opinion, cold, along with biting winds, and heat, along with high humidity, are the worst combination of climates. Dry temperatures below zero degrees weaken frostbite among people with poor clothing and poor training. In the winter of 1942-1941, one hundred thousand German armed forces were injured in Russia for this reason, of which 15 thousand were forced to amputate. Wet cold in some cases, even more severe, causes weakness and exhaustion of forces. Disability due to prolonged exposure of the feet to trench water, at temperatures slightly above zero degrees, is an old case of injury. During World War II, the disease became a rampant among American infantry in the operational arenas of Europe, because in the last days, they had to jump into the water instead of walking on dry land and pass through icy mud and into trenches. They lived full of water and did not have access to shelter or dry shoes and socks. In the dampening heat, the armed forces face another set of problems. To prevent the body from losing weight, water consumption increases.

area of study Khorasan Razavi province is located in northeastern Iran and is the fourth largest province in the country. This province covers an area of 127,700 square kilometers, 7.7% of the area of Iran and is located between 34 to 38 degrees' north latitude and 57 to 61 degrees' east longitude of the Greenwich meridian. Khorasan Razavi province shares 531.6 km border with Turkmenistan and 302 km with Afghanistan and is limited to South Khorasan from the south, North Khorasan from the northwest and Semnan and Yazd provinces from the west.

In this study, in order to evaluate the role of climatic elements on the activity of military forces in Khorasan Razavi province, among the synoptic stations in the region, 9 stations that had data and a suitable statistical period (20 years) were selected. Then, data related to climatic parameters including dry air temperature and relative humidity in the monthly period during the statistical period (1999-2019) were received from the Meteorological Organization.One of the most important indicators to identify climatic conditions, in line with the activities of military forces, the Wind chill index was used. Burn index can be a good indicator of cold sensitivity and is very useful in deciding on the type of clothing or planning for outdoor activities. Low levels of burnout are associated with risks, one of which is a sudden drop in body temperature or hypothermia. Under these conditions, the body temperature drops to such an extent that the muscles and the brain are damaged. In some countries, the Wind chill index is used to issue forecasts and warnings. When this indicator reaches the point where frost and frost occur, it is predicted and issued a warning in case of dangerous conditions. Another factor of human comfort is the wind speed index or in fact the cooling effect of wind. This index represents the energy dissipation in terms of kilograms per hour from the surface of one square meter of the body and in normal conditions, in inactivity and normal skin temperature, ie about 33 degrees Celsius.

Shows the day and night comfort coefficient based on Wind chill index in the stations of the province. Accordingly, the months of January, February and December show cool conditions in all stations except Sarakhs and Kashmar stations, and very cool physiological conditions in all other stations. In March, Sabzevar, Sarakhs, Kashmar and Gonabad stations show cool conditions and the rest of the stations show very cool conditions. Cool weather prevails in all stations in April and November. During May and October, favorable conditions for military activity in Sabzevar, Sarakhs (May and October) and Gonabad (May) prevail, and in other stations, cold conditions prevail. In June and September, Torbat Heydariyeh and Mashhad stations (June and September), Kashmar (June), Gonabad (September) have comfortable conditions, and other stations have cold to warm conditions. During July, comfort conditions are limited to only 3 stations of Golmkan, Quchan and Neishabour and the rest of the stations are in hot condition. Finally, in September in all stations except Sabzevar, Sarakhs and Kashmar (warm) and Golmkan (cool) There is desirable. The results of day-to-day dispersal maps of Wind chill index show that Wind chill climate index is favorable for the development of the province's military activity in the center, south and southeast of the province and the appropriate period in these parts is longer than other parts of the province.Key words: Military Climate, Thermal Stress, Wind chill index, Khorasan Razavi Province