The seasonal climate is the climate of those climatic zones in which warm and cold seasons differ significantly from one another over the course of the year . The fluctuations in mean monthly temperatures within a year are higher than the fluctuation between the daily high and the night low of a day. The seasons are mainly caused by the different lengths of day , but also by the fact that the angle of the sun's rays varies over the course of the year (see Seasons ).
The climate zones, which are characterized by Jahreszeitenklimata ( polar regions , temperate climate , subtropics ) are collectively known as Except tropics or Ektropen designated. The opposite is the case in the tropics and is known as the time of day climate .
Creation of the seasonal climate
The seasonal temperature changes can be traced back to the constant inclination angle of the earth's axis during one orbit of the earth around the sun. A tilt angle of the earth's axis of 0 ° would not cause any seasons . However, the greater the inclination, the greater the impact on the distribution of the radiation energy hitting the northern and southern hemisphere .
The angle of inclination of the earth's axis of rotation is 23.5 °. The effect of this is that in higher latitudes the days in summer are considerably longer than the nights and therefore the earth's surface absorbs a greater number of hours of radiant energy and heat per day than it gives off at night. Conversely, longer nights and shorter days release longer and thus more heat into the atmosphere than is absorbed during the day (see day lengths ).
The fact that the annual mean temperatures in the high latitudes are significantly lower than in the tropics and subtropics is due to the fact that a packet of rays hits the polar latitudes at a different angle than the tropical ones: Due to the low angle of incidence, it covers a relatively large area. In addition, more energy is absorbed by the atmosphere on its oblique and therefore relatively long path through the earth's atmosphere. For both reasons, less energy reaches the earth's surface here. In the time of the year in which a hemisphere faces the sun due to the inclination of the earth's axis, the area to be supplied by a packet of rays is reduced and the path of the sun's rays through the atmosphere is shortened, so that the ground can be warmed up.
Comparable to a heating system that supplies a small room with thermal energy, the same amount of radiation serves a relatively small surface in one hemisphere in summer, while it is winter in the other hemisphere and a larger room has to be "irradiated" - with correspondingly lower energy input per area , while also the bright days on the winter side of the earth are shorter than the nights and therefore the duration of irradiation is significantly shorter.
- The effect of the earth's axis inclination is particularly strong in the polar zone. At the poles, the differences in day lengths are so extreme that the sun does not set for half a year in summer ( polar day ) and does not rise for half a year in winter ( polar night ).
- In the subpolar latitudes, the year is divided into a short, relatively low-precipitation summer and a long, dry winter .
- With increasing approach to the equator, milder transitional areas in the temperate latitudes - spring and autumn - subdivide the year: Here the equinox marks the date of the equinox in spring and autumn.
- In the subtropics there are rainy seasons and dry seasons : These create a "tightening" of the seasonal climatic conditions: There are seasons with extremely low to no precipitation as well as more precipitation.
- In the tropics , the intra- tropical convergence zone (ITC) forms as a decisive factor with a considerable influence on the climate zoning and the global or geozonal characteristics of the seasonal climate . For the reasons mentioned, there are no seasons at the equator : the angle of inclination has the least effect here. Day and night are always either exactly or almost the same length and the angle of incidence is steep, so that the sun sets very quickly all year round and rises again very quickly after the night is over (very short twilight ). Only the times of the day have an effect on the development of temperatures and humidity: the daytime temperature amplitude remains the same all year round ( daytime climate ). In addition, a secondary ITC usually forms , so that no or only very short drying times occur ( always humid tropics ).