1) Explain the ways in which the circulation cells in the atmosphere help to redistribute energy 4 marks

Answer

Solar energy at the equator heats the air immediately above it and consequently the air expands, becoming less dense allowing it to rise to higher altitudes whilst creating a zone of low pressure. Since the temperature is cooler at high altitudes, the air cools and becomes more dense and falls back down. The cooler, more dense air falls as an area of high pressure. Trade winds move the air back to be reheated at the equator and the cycle continues. This is known as the Hadley cells which appear at both 23.5 N and 23.5 S.

There are also cells at the poles called Polar cells and these poles are here due to the very cold air in these areas becoming very dense and falling to create more zones of high pressure. Due to earth rotation, some of the air from the high pressure zone at the poles falls to lower latitudes. In these lower latitudes the air is heated and rises back towards the poles where it is cooled again, creating a zone of low pressure. The ferrel cell arises from the differences in temperature between the polar cell and the hadley cell. The Hadley and Polar cells both power this middle cell. Warm air from the hadley cell at the tropics feeds into higher altitudes whilst cooler air from the polar cell feeds into lower latitudes.

2)Describe the origin, nature and weather characteristics of the Tropical Maritime and Tropical Continental air masses 4 marks

Answer

The tropical continental air mass(cT) originates over the Sahara Desert in Northern Africa and moves South-West over Africa. The air forming over the Sahara Dessert has particular name - the Harmattan. It has a very hot,dry and stable nature. This air mass brings hot and dry weather to other areas of Africa throughout the year.

The tropical maritime(mT) originates over the warm water in tropical regions of the Atlantic Ocean and moves North-East over Africa. This gives it a warm, moist and unstable nature. This brings brings warm but wet weather to different parts of Africa throughout the year.

3) Describe the latitudinal variation of the Eath's energy balance. 2 marks

Answer

The Earth recieves more insolation at the tropics than at the poles because the rays from the sun are more perpendicular so the energy is more intense. The energy at the equator is also spread over a smaller area than the same amount at a higher latitude, therefore the equator receives more heat energy. Also, at the equator the rays must pass through less of the atmosphere before they reach the Earth, so less energy is lost through atmospheric absorption and radiation. The amount of energy received is also affected by the albedo effect as the dark forest surfaces near the equator absorb more energy than the ice at the poles which reflects the sun's rays. The way the Earth revolves around the Sun and spins on its axis which is at an angle, means that while the equator receives solar energy all year round, the Poles are in darkness for 6 months of the year, so at these times they receive no insolation.

4)Explain the physical and human factors that might have led to the changes in global temperatures since 1980

5) Explain the variations in the earths energy balance 8 marks