نگرشي بر تفاوت نرخ افزايش دماي حداقل و حداكثر و كاهش دامنه شبانه روزي دما در كشور

A Look at the Difference between Increase Rates of Minimum and Maximum Temperature and the Decrease Rates of Diurnal Temperature Range (DTR) in Iran.

Temperature is one of the important thermodynamic meteorological elements the change of which can cause many physical, chemical and environmental variations. The history of measuring temperature is relatively long compared to that of other elements in meteorology. In spite of some evidence and expertsʹ belief about the global warming in the years 1947 and 1948, the idea of stationary climatic condition persisted till 1970s. Many research done at national, regional, and global levels indicate an increase in temperature in many parts of the world. In other words they prove an increase in the mean global temperature. Although there is a marked increase in maximum temperature luany parts of the world owing to its lower increase rate, compared to that of minimum temperature, DTR has decreased. The results obtained for maximum, minimum, and mean temperatures are quite different from one another. Positive trend for minimum temperature in majority of Iranian synoptic stations especially in those located in cities with high urban growth rate, are remarkable. For instance, it is strong in Esfahan. Moreover, we found a jump in annual temperature series in the 1970s that is consistent with the jump in many places in the world. DTR in large cities like Esfahan, Shiraz, and Tehran has decreased significantly. In this regard, a 4 °C decrease in Esfahan can be noticed. In addition to some exceptions, quality and quantity of trends are also discussed.