Weather or Climate?

Weather is the state of the atmosphere at any point in time.
The elements of weather are:
1. Wind: speed and direction
  1. Precipitation: moisture through the atmosphere
    1. Sun: intensity of sun and duration
      1. Temperature: how hot or cold
        Visibility: Mist or fog
        Air Pressure: High pressure brings stable weather. Low pressure brings changeable weather.
        Cloud cover: amount or type of cloud
        Water vapour is formed by the sun warming the ocean, which causes water to evaporate to give a gas (water vapour).
        Once the water vapour has mixed with the air, the air rises and cools, which causes the water vapour to condense again into small clouds of small water droplets.
        Rain is formed after these two steps.
        If temperatures are below freezing or cold, it can be seen as sleet or snow. It can also condense as fog.
        You can prove water vapour exists by feeling some water vapour mixed through air and wind. This way you can know that water vapour's telling you you are miles from water.
        Water vapour
    2. RAIN, HAIL, SLEET, SNOW
Climate is the average weather expected in a place based on 30 years of data.
Weather can be dangerous: heavy winds can cause hurricanes, droughts, etc.
1. The troposphere reaches up to 10km.
  1. In the stratosphere, there is no rain because the amount of water in the stratosphere is lower than in the atmosphere, which means the condensation of the water vapour that creates rain doesn't occur in that kind of atmosphere.
What causes the weather?
1. The sun heats the Earth but not evenly, because the Earth is round so the top and bottom don't warm up much. Therefore during December, the southern hemisphere is tilted towards the sun. When tilted towards the sun, the hemisphere tilted towards the sun receives a larger amount of the sun's incoming rays. So when tilted away, a smaller part of the rays reflects upon the Earth, leaving it with less thermal energy.
  1. Places get warm because of the sun. It heats the earth, and the earth in turn warms the air. The sun also causes wind. Thats because the warm air raises, so chilly air rushes in from somewhere else to take its place. Rushing air is called wind. During winter, there is not much sun, so the weather can be chilly.
    1. Water vapour is the second main cause of the weather. It is the water that has been evaporated after the sun warms the oceans.
There are 3 main ways in which air is forced to rise / rain occurs.
1. Relief rainfall:
  1. Wind is moving air. When the wind meets the line of high hills or mountains, there is only one way to go (windward, up). The air rises and cools and we get rain. The prevailing wind is from the south west, so a lot of relief rainfall on the high land along the west coast is where our relief rainfall is from.
2. Convectional rainfall:
  1. The air rises because the ground heats it. It rises as currents of warm air. We call these convection currents, so we call the rain convenctional rainfall. In the UK we get convectional rainfall inland in the summer, where the ground gets hottest, away from the cooling effect of the sea.
3. Frontal rainfall:
  1. When a warm air mass meets a cold one, the warm air is forced to rise. The rising air cools, the vapour condenses. So we get rain = frontal rainfall. It can fall anywhere, since air masses can travel anywhere.
Clouds
1. Clouds are condensed water droplets. They come in various shapes, sizes and help inform us of what the weather is likely to do.
  1. Fluffy clouds = cumulolus
    1. Wispy clouds = cirrolus
      1. Layered clouds = stratolus
        High clouds = alto
        Dark clouds = nimbolus
Air Pressure
1. Air pressure is a measure of how heavy the air is. Low pressure means that air is rising and it cools and condenses to give rain and changeable conditions. High pressure means that the air is sinking, it is heavy and the result is weather that changes little from day to day.
  1. Low pressure is a sign of unsettled weather, the lower the pressure the stormier it will be. High pressure brings clear skies, which means very hot weather in the summer and very cold weather in winter.
Air Masses
1. Polar Maritime = cold, wet
  1. Arctic = cold, wet
    1. Polar contintental = cold, dry
      1. Tropical Maritime = hot, wet
        tropical continental = hot, dry
        If one of these sits over us, then we have an anticyclone. High pressure area in winter is a polar continental, in summer it is the tropical continental.
        But in reality our weather comes from the west and the polar maritime and tropical maritime air masses fight to pass over the UK.

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	Created by mrutta almost 10 years ago