Climate

• Climate


  A description of the average weather conditions that occur in a place, measured over a long period of time- usually thirty years
• Weather


  Relatively temporary states of the atmosphere, including elements such as temperature, humidity, rainfall, snowfall, frost, drought, sunshine, wind speed and hurricanes
• The atmosphere is an envelope of gases that surrounds the Earth
• We all have some interest in the state of the atmosphere because it includes the air that we breathe
• When we say that it is raining, or the sun is shining, we are describing the weather
• Elements of weather


  • Temperature
  • Humidity
  • Rainfall
  • Snowfall
  • Frost
  • Drought
  • Sunshine
  • Wind speed
  • Hurricanes
• Weather station


  Instruments that measure the elements of weather and collect information about it
• Meteorologists


  Scientists who use weather station information to forecast the weather for 24 hours or for several days
• The weather forecast is of importance to fishermen, farmers, air and sea travellers and outdoor recreational enthusiasts
• Instruments usually included in a weather station

  • Thermometer
  • Barometer
  • Dry and wet bulb thermometer or hygrometer
  • Rain gauge
  • Wind vane
  • Anemometer
  • Campbell Stokes recorder
• Thermometer


  Measures temperatures in °C or °F
• Maximum and minimum thermometer

  Records the highest and lowest temperatures over a 24-hour period
• Barometer


  Measures atmospheric pressure in millibars (mb)
• Dry and wet bulb thermometer or hygrometer

  Measures relative humidity or wetness of the atmosphere on a scale of 0 to 100%
• Rain gauge


  Measures rainfall in mm
• Wind vane


  Indicates wind direction
• Anemometer


  Measures wind speed in km/h
• Campbell Stokes recorder


  Measures the amount of sunshine in a daily period
• Some satellites also provide data about the weather. They are fitted with cameras and are in fixed locations, called geostationary orbits, about 35 000 km above the equator. They transmit photographs of the clouds. These can help meteorologists to predict the weather quite accurately.
• Barometer


  An instrument that records the pressure exerted by the atmosphere on the Earth. If the pressure drops, then the weather may be rainy. If it rises, the weather may be fine.
• The Earth receives energy from the Sun in the form of short-wave radiation (light, infra-red and ultra-violet rays). This is called insolation. It does little to heat the atmosphere. The radiation is absorbed by the Earth and is transmitted to the atmosphere as terrestrial energy in the form of heat. The higher a point is above the Earth's surface, the less heat it receives. The temperature of the atmosphere decreases by 0.6 of a Celsius degree for every 100 m above the Earth's surface.
• The surface of the land heats up much faster than the sea does. A body of water requires much more heat to raise its temperature than land with the same surface area does. Water also cools down more slowly than land does.
• Places that are near to the sea have fewer variations in temperature than inland places, because the sea cools the coast in summer and warms it in early winter.
• Away from the coast, in the Interior of continents, the sea has little influence. Temperatures are more extreme - summers are hot and winters are cold.
• Land and sea breezes

  1. Air blows from sea to land during the day and from land to sea during the night

  2. In hot and calm weather in the tropics, during the day the sea is cooler than the land

  3. The pressure over the land is low and over the sea it is high

  4. The winds blow from the sea to the land as a cool sea breeze, but only for a short distance

  5. The cool air is heated and rises, then flows back towards the sea
• Temperature generally decreases as you move from the equator to the poles.
• At the Equator, and within the tropics, the Sun is almost directly overhead. In this region, the Sun's rays travel the shortest distances through the atmosphere to reach Earth and hit the Earth almost at right angles, so that there is more energy per unit area.
• Temperature decreases towards the poles because, in the latitudes nearer the poles, the Sun's rays travel further through the atmosphere to reach the Earth, so more of their energy is lost, and hit the Earth at angles that are less than 90°, so the energy is spread over relatively larger areas.
• The temperature of the atmosphere decreases by 0.6 of a Celsius degree for every 100 m above the Earth's surface.
• The upper levels of high mountains are snow-covered, although they are nearer to the Sun than the lowland areas are.
• latitude is how far north or south a place is on earth's surface
• altitude is how high above sea level an area is