3.4. Temperature Ranges

Temperature of a place varies within a day and also differs in different seasons. Range of temperature is the difference between maximum and minimum temperatures. There are two terms which are used to consider temperature ranges.

1. Diurnal range of temperature: the daily pattern of temperature change that we normally experience illustrates energy changes on a small time scale. On a calm day with little cloud, air temperatures usually reach their minimum just before sunrise, because the ground has

been giving off long-wave radiation all through the night, gradually becoming colder and cooling the air above by conduction. With sunrise, temperature of the ground begins to rise. Maximum insolation receives at midday. But the peak of air temperature is usually about 2:00 PM. After sun-set, the air initially remains fairly warm as it is still being heated by long-wave radiation from the ground, but this gradually expires. Desert areas typically have the greatest diurnal temperature variations while Low lying, humid areas typically have the least range.

2. Annual average range of temperature: it is the monthly range of temperature or the difference between the average temperature of hottest month and average temperature of the coldest month of the year. The annual range is lower in low latitudes and higher in high latitudes. In the same latitudes, it is higher over the continents and lower over the oceans and coastal regions. The highest annual range of temperature is more than 60° C over the north-eastern part of Eurasian continent. This is due to continentality. The least range of temperature, 3°C, is found between 20° S and 15° N.