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What creates the weather



When considering the atmosphere as a whole, it can largely be considered as a fluid. It may not look like a fluid, but it behaves in very much the same way that a fluid would. The impacts of a number of natural phenomena has an effect on this fluid atmosphere in the following ways.

  • Rotation which is in part responsible for creating air exchange between the equator and the mid latitudes, and the mid latitudes and the polar regions
  • The sun, which has a stronger heating effect at the equator, than it does at higher latitudes
  • Reflectivity which is responsible for reflecting back light and heat from the sun - stronger at higher latitudes than the equator
  • Angle of the sun to the earth, which differs at higher latitudes to lower latitudes and therefore receives less heating at higher latitudes.

The Seasons

In addition to this the Earth has a wobble which creates the seasons. In summer the Southern Hemisphere is more exposed to the sun, and therefore recieves more heating than it would do in Winter. The impact on the weather is not as noticeable in the tropics, where the difference between seasons is less pronounced (eg they tend to just have a "rainy season") as it is in mid to higher latitudes, where ther is a definite sense of Spring, Summer, Autumn and Winter

Localised effects

More localised effects can occur. For example the sun heating a large body of water such as the Pacific Ocean, has a different effect than it does heating large areas of land such as Europe. In the Nothern Hemisphere, New Zealands latitude is similar to that of Spains, which typically has warmer weather due to the warm ocean currents. But it's latitude neighbour of northern Italy often experiences snow during winter due to the fact that the land surrounding that area is cooler because it is not heated by the sun as much during winter and the land tends to hold its heat (or cold) more readily than the sea.

Sea Temperature and currents

Sea temperature and currents (again a fluid in the system, but just a thicker or more dense fluid) also plays a major part.
For example sea currents generated by many of the same processes outlined above that drive the atmospheric weather, bring warmer water from the Atlantic to the UK, which means that the climate in the UK is warmer than it would be at that latitude normally. The warmer sea currents around New Zealand lead to a more mild winter than we would normally experience if the country was surrounded by land.

At a more local level the Southern Alps of New Zealand have a significant impact on the amount of rain that falls on the Canterbury plains vs on the West Coast

The 3 Dimensional Atmosphere

Finally the atmosphere varies with height. The atmosphere can be considered as the meat in the sandwich between two heat sources, one being the earth from below, and the other the sun from above. So for example atmospheric temperature cools to a point as you go up the further it gets from the earths heat source, and then increases in temperature once through a boundary layer where the predominant heating force is the sun. Density or thickness of the air (fluid) also changes as height increases, which also has an impact.
comparison us standard atmosphere 1962

The study of meteorology is essentially the study of these natural variables and the many ways they interact to form the weather that we experience.
TC Lucas

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