Climate and Seasons

Seasons
Seasons are caused because of the 23.5-degree tilt of the earth. The spherical shape of the earth means that the same amount of solar radiation hits constantly, if the earth had no tilt the seasons would not change. The tilt of the earth means that both north and south poles will face towards and away from the sun at specific points during its orbit.

When the North Pole is inclined towards the sun the Northern Hemisphere experiences summer, this is the time where areas in the north are facing towards the sun and so receive more direct light for longer periods of time. During this time the sun rises high in the sky providing a more direct force of energy for up to 15 hours. The more direct energy has fewer atmospheres to travel through so less energy is absorbed before it reaches the surface.

The energy provided to the Northern Hemisphere during the summer months causes changes to occur on the surface and in the atmosphere, energy absorbed by the sun is often emitted from sources as heat, the raised temperature drives the process of evaporation as well as most weather patterns. The Northern Hemisphere summers are times of reduced precipitation and dryer airs as well as increased temperatures.

When the Northern Hemisphere is in summer the Southern is in its period of winter because at is facing away from the sun. As the earth orbits the solar energy is reduced in both intensity and length, as the tilt of the north turns further away from the sun the seasons change through to autumn and then winter.

Winter is the time when the pole receives the least amount of the energy emitted from the sun. In the Northern Hemisphere during winter the sun is most direct over the tropic of Capricorn giving more energy to the south. The north is farther away from the sun directional radiation and so the sun is low in the sky with its energies spread thinner on the surface and having to go through a larger density of atmosphere before it reaches the surface, meaning more radiation could be absorbed by particles in the atmosphere and clouds.

The cooler temperatures means that the air gets more saturated with moisture during winter allowing for more movement of moisture. The cold temperatures mean heavier cold air forces underneath the warmer air creating high pressures and plenty of “mixing”, resulting in more cloud and precipitation.

During this time the Southern Hemisphere is experiencing its summer.

The climate of different areas is dependant on the variations of sunlight it receives during the earths orbit. Areas closest to the equator receive more constant levels of radiation and so their seasons are not divided into spring, summer, autumn, winter as they are in temperate zones but are classified as wet and dry seasons as the temperature is pretty much consistent throughout the year. Theses seasons are more influenced by the direction of moisture, extreme heat leads to rapid evaporation, which is deposited either north or south at different times of the year.


Climate Influence by Oceans
Oceans account for 75% of the earth’s surface, and has had a direct influence on climate throughout history. Long-term continental changes have helped to direct ocean movement, resulting in the ocean currents that we now experience.

Temperature changes during different seasons are experienced faster over land than oceans this is because water stores heat for longer periods of time. It means that the ocean will take longer to heat and to cool than the land. Land and water in close vicinity experience the same variations in energy as the earth tilts towards and away from the sun but have different rates of temperature increase and decrease.

The suns energy is absorbed by the ocean and as a result the temperature rises, it takes a long time for the massive body of water to heat up after the cold winter, which is why the hottest temperatures are not recorded until the late summer months when land temperature is actually reducing.

The heated water is moved over great distances through water currents and circulation caused by wind, rotation of the earth and the presence of continents. The currents and streams carry warm water to cooler areas. The change in air temperature causes evaporation of water molecules with their retained heat energy; the warmed air is transported overland warming the temperature. After the summer season has gone, the land is cool, but warm air is still carried in from the warm ocean until late in the winter.

The ocean also carries cooler temperatures inland through wind; this is after the winter has passed and the land is getting warmer. The land is heating rapidly with increased sun energy, but the ocean is taking much longer to heat, so cool breezes keep the temperature low until the water heats up.

The slow change of temperature in water is the reason why in Britain summers are not as hot as they could be and winters are milder than expected.
The effects of warming or cooling by oceans are experienced most in areas close to or surrounded by the water, further inland the air that has heated/cooled over the sea has already mixed with the air over the land and so temperature changes by oceans are not such an influence.




Reference:
www,niwascience.co.nz
www.gdre.org/oceans/fsheet-01.html
www.astronomy.org/programs/seasons/index.html
www.earthguide.ucsd.edu
www.wikipedia.com