Temperature: hot zones, cold zones

The minimum temperature of the Earth’s surface is registered at dawn, the maximum temperature between 3.00 p.m. and 4.00 p.m. The mathematical average of the two figures gives the average daily temperature. From the average of the daily temperatures in one month, the monthly average is obtained and from the average of these monthly averages, the average annual temperature is calculated. The annual average temperature of the Earth’s surface is about 15°C, but local variations are considerable, with a wide range of daily and seasonal temperatures and significant differences from one point of the Earth to another. The lowest temperatures ever registered were taken at the Antarctic station of Vostok (- 91.5°C), while the highest were taken in Death Valley in California (+ 55.6°C).
The temperature of the atmosphere varies vertically too, decreasing from 15°C on the Earth’s surface to -57 °C in the highest part of the tropopause.
Atmospheric temperature depends firstly on the latitude, as a result of the different inclination with which the Sun’s rays reach the ground. For this reason different thermal zones can be identified: the torrid zone, between the Tropics of Cancer and Capricorn, two temperate zones in the two hemispheres situated between the tropics and the polar circles, and two polar zones, found at latitudes beyond the Arctic and Antarctic Polar Circles.

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