Contribution to Book
Encyclopedia of World Climatology
Season is term for a period of time during the calendar year characterized by or associated with a set of coherent climatic activities or weather phenomena. Traditionally, there are four seasons of three months each winter, spring, summer, and autumn (fall), which are reversed in each hemisphere. The seasons are terrestrial responses to solar heating inequities that are governed by the dynamic relationship that exists between the Earth and the sun at various times during the year. The single most important heat source on the surface of the Earth is the sun. Endogenic heat flow from the earth’s interior is three orders of magnitude less than solar energy. The amount of solar heat intercepted by the Earth can be expressed as a fixed value referred to as the solar constant, which is approximately 1.95 cal/ cm2/min. Seasonality is a response to the different attitudes in the reception of the solar constant at locations on the Earth’s spherical surface. Variations in the reception of the solar constant lead to terrestrial heating imbalances that are largely a latitudinal phenomenon. The amount of terrestrial heating accomplished by the sun depends on (1) the intensity of the sun’s rays; and (2) the duration of time to which the land is exposed to the sun’s rays. These two variables are regulated partly by the fact that the Earth is a sphere but mainly by the fact that the Earth is in orbit around the sun. Of greatest import are the orbital characteristics of the Earth, i.e., revolution, inclination, and parallelism.
Alsop, Ted J., "Seasons" (2005). Environment and Society Faculty Publications. Paper 997.