Weather and Climate

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					Weather and Climate
You will find the following topics in this
• The difference between weather and climate.

•Microclimates (including the role of aspect, shelter, buildings,
surface and natural features)

• The global water cycle (including interception, surface run-off
and infiltration)

• Types of Rainfall (Relief, Convectional, Frontal)

• Temperature and rainfall variations in the British Isles (and what
causes them).
               Weather is the condition of the atmosphere in a place at one
                  moment. It can change from one second to the next.

Weather includes rainfall, temperature, visibility, wind speed, wind direction and cloud cover.

          Climate is the average weather in a place measured over 30 years. It is
                                what we expect in a place.

       Climates include Mediterranean, Polar, Temperate, Hot Desert and Equatorial.
     A microclimate is a small area where the
   climate is different to the surrounding area.
                They can be affected by:

 ASPECT                                    SHELTER


BUILDINGS                                    SURFACE
            This is the direction a place faces. Places that face the sun are
            warmer than those that face away from the sun. In the UK
 ASPECT     (where Common Entrance is written) places with a south-
            facing aspect get more sun and higher temperatures.

               These can change wind speed and direction, creating
BUILDINGS      either calm or very windy areas. On warm, sunny days,
               buildings absorb heat and give it out at night. This means
               that cities can have night-time temperatures 2-3⁰C
               warmer than areas outside the city.

    SHELTER                       Walls, buildings, cars, hedges and trees provide
                                  shelter from wind. Sheltered places often feel
       &                          warmer and also get less rain. Lakes and their
                                  shores are often more windy than surrounding
NATURAL FEATURES                  areas.

SURFACE         Dark, artificial surfaces like tarmac warm up faster and
                give off more heat than light, natural surfaces like grass.
     The Global Water Cycle


               Groundwater flow
               or Through flow.
                      Water Cycle definitions
Evaporation is the process of water turning into water vapour due to warming.

Transpiration is evaporation from tree leaves or plants.

Precipitation is rain, drizzle, snow, sleet or hail.

Condensation is where water vapour cools and turns back into water. In this case it happens
high up and forms clouds.

Interception is where precipitation lands on tree leaves etc. and so does not reach the

Infiltration is where the water sinks into the ground prior to experiencing Groundwater flow.

Groundwater flow or Through flow is where water flows downhill under the surface.

Surface run-off (or overland flow) is where water flows downhill overland, mainly in rivers.
   Types of Rainfall

     There are 3 types of rainfall:

   1. Relief Rainfall

2. Convectional Rainfall

  3. Frontal Rainfall
             1. Relief Rainfall

               4. Condensation occurs and
               clouds are formed.

                                          5. Precipitation.

                   3. Air cools as it rises.

           2. Air is forced up by
           high land.

1. Warm, moist air
blows in from the sea.
2. Convectional Rainfall
                          4. Condensation
                          forms clouds

                 5. Precipitation

  1. Sun’s
  energy heats
  up the earth      3. Warm, moist air
                    cools as it rises

                    2. Evaporation and
           3. Frontal Rainfall

                                           4. Condensation
                                           forms clouds

                                        5. Precipitation
                   3. Warm, moist air
                   cools as it rises

  2. Warm air rises over the
  cold air as it is less dense

1. Warm air and cold
air meet at a front
            Temperature and Rainfall in the
                    British Isles
                                                 Facts about the
             Wet                                 British Isles climate:
             Mild Winters
             Mild Summers
                                                1. The west is wetter than the east
Summer prevailing wind         Dry              all year round.
                               Cold Winters
                               Mild Summers
                                                2. In winter, the west is mild and
                                                the east is cold.
                Wet            Cold Winters 3. In summer, the north is mild and
                Mild Winters   Warm Summers the south is warm.
                Warm Summers

Winter prevailing wind
      What causes these variations?
  1. The west is wetter than the east all year round.
     This is because the prevailing wind is always from the South-West or the West.
     This brings moisture off the Atlantic Ocean and the mountains down the west
     coast force this upwards to form relief rainfall in the west. The east is in a rain
     shadow and so gets less rain.

 2. In winter, the west is mild and the east is cold.
      Again, this is caused by the prevailing wind, which is from the South-West in
      winter. This causes the South and West of the British Isles to be slightly
      warmer as the wind has travelled across the warm Atlantic Ocean to get to

3. In summer, the north is mild and the south is warm.
      This is due to the distance from the equator. The north is further away and hence
      cooler. Also, the prevailing wind comes in from the west and so does not have a
      cooling effect on the south coast. The north can also be vulnerable to Arctic winds
      at times, reducing the temperature there.

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