Weather Variations | Seasons | Climate Change

The current condition and the state of the atmosphere at given time is called Weather. The axes of the earth are imaginary lines on which the earth rotates. It links up the two poles, South & North Pole. Both the axes and the two poles are tilted at the degree of 23.5⁰ during a revolution. The tilting of the axes result in direct sun light falling on different places during different seasons. This causes variations in the durations of days, nights and seasons.

Relationship between the location of the overhead sun and the seasons: similarly the revolution of the earth and the titling of the axes result in different angle of the sun during different periods. When the sun is directly overhead we call this overhead Sun. At this time the earth’s surface and midday sun forms a 90⁰angel. Different locations of the overhead sun results in variations in the amount of solar radiation received in different areas under different periods.

Spring Equinox – 21 or 22 March:

            The overhead sun is over the equator, the equator receives the largest amount of solar radiation. At this time the northern hemisphere in is Spring Equinox, whereas the southern hemisphere is in the autumn equinox. The angle of the sun decreases towards the poles. On this day the two hemispheres receive a similar amount of solar radiation, and the length of the day and the night is the same at all places on the earth. After this it is spring in the northern hemisphere where the day is longer than the night. In the southern hemisphere it becomes autumn when the day is shorter than the night.

Summer Solstice – 21 or 22 June:

            The overhead sun is over the Tropic of Cancer, it receives the largest amount of solar radiation. At this time the northern hemisphere is in the summer solstice, whereas the southern hemisphere is in the winter solstice. Then the angle of the sun decrease towards the poles. On this day the length of the day time on the northern hemisphere is the longest in the year, whereas in the southern hemisphere it is the shortest of the year. Besides, there are 24 hour of daylight on the Arctic Circle and 24 hours of darkness/night on the Antarctic Circle.

Autumn Equinox – 22 or 23 September:

            Again the overhead sun is over the equator, the equator receives the largest amount of solar radiation.  On this day the northern hemisphere is in autumn equinox, whereas the southern hemisphere is in spring equinox. The angle of the sun decreases towards the poles. On this day the two hemispheres receive a similar amount of solar radiation, and the length of the day and the night is the same at all places on the earth. After this it is autumn in the northern hemisphere where the day is shorter than the night. In the southern hemisphere it becomes spring when the day is longer than the night.      

Winter Solstice – 21 or 22 December:

            The overhead sun is over the Tropic of Capricorn, it receives the largest amount of solar radiation. On this time the northern hemisphere is in the winter solstice, whereas the southern hemisphere is in the summer solstice. Then the angle of the sun decrease towards the poles. On this day the length of the day time on the northern hemisphere is the shortest in the year, whereas in the southern hemisphere it is the longest of the year. Besides, there are 24 hour of daylight on the Antarctic Circle and 24 hours of darkness/night on the Arctic Circle.