|Seasons are division of the year into time periods, marked by changes in weather, ecology, and hours of daylight. |
Seasons can be:
Each of these occurs during a defined period of the year and has typical characteristics which do not or seldom occur in other seasons.
You can see the different seasons by looking a the temperature distribution on the world temperature maps.
|Seasons are caused by the changes in the inclination of the earth towards the sun during one year. In the example image, the earth has reached the northern solstice on 21 June, when the Northern Hemisphere is most inclined to the sun, and receives most of the sunlight. This causes "summer" in the Northern Hemisphere, and "winter " (or cool season) in the Southern Hemisphere. |
Six months later, on 21 December, the earth reaches the Southern solstice, when the Southern Hemisphere is most inclined towards the sun, and receives most of the sunlight. This causes "summer" in the Southern Hemisphere, and "winter" in the Northern Hemisphere.
The 4 meteograms show different seasons in Campinas (São Paulo, Brazil).
Campinas lies in the semi-humid (wet-dry) Subtropics on 22.9° southern latitude. There are 2 pronounced seasons: Summer (with rain) and winter (dry season). Between both, there are short transition seasons, in which the temperatures rises (spring) and drop (autumn), and during which the characteristics can alternate between summer and winter at short notice.
Due to the proximity to the Tropical zone, the temperature differences are only small between winters and summers.
The large meteogram to the right shows the current weather forecast for Campinas, São Paulo, Brazil. Which season do we have now?
Pay attention to the date in the summer and winter meteograms (you find it on the top left of the meteogram). What differences do you notice, if you compare the date and weather parameters with the same season meteograms in the temperate zone ? Do not forget during this consideration, where both places lie.
The seasons on the temperate zone are shown by the example of Basel (Switzerland). To the right, the current weather forecast for Basel is displayed.
Hint: Do you remember the position of the sun? Compare the daylight hours of the winter meteograms with those of the summer meteograms.
In the following we present the seasons in Kiruna. Kiruna lies in the north of Sweden on 67.8°N, in the cold climate zone.
To the right you see the current weather forecast for Kiruna, and below samples of the seasons.
The day length changes more in the cold zone than in the other climate zones. In the summer, the sun in Kiruna shines 24 hours a day. In the winter, it does not rise at all. In the meteogram for the spring (May) one can recognize, how the days become longer: the temperatures rise. Starting from the beginning of June, the sun shines continuously: for nearly 2 months, polar day prevails, so that despite the weaker solar radiation sunlight, a short summer occurs with temperatures up to 30°C - and an invasion of flies which is nearly intolerable for foreigners.
Then, the days become shorter again. in September, the solar radiation is no longer sufficient to warm the temperatures significantly during the day. The autumn begins. At the beginning of of December, the sun disappears under the horizon for the entire day: the onset od polar night . Without sunlight, temperatures fall far under the freezing point, and the harsh polar winter prevails for months, with icy temperatures and darkness.