Weather and Climate
1. Weather is the condition of the lower atmosphere at one time and in one place.
- Weather conditions include air temperature, air pressure, precipitation, wind speed, wind direction, cloud and sun.
2. Climate is the average or expected pattern of weather for a place, based on weather records over a long time.
- A climate graph shows average monthly temperatures and rainfalls for a particular place.
- The data is collected over many years.
World Climate Zones
1. The world is divided into major climatic zones. These are based on variations in precipitation and temperature between places.
- The angle of the sun and rotation of the earth affect the temperature and climate of different parts of the world.
- The sun's rays hit the earth overhead near the equator all year round, making these places hot.
- The sun's rays hit the poles at an oblique angle all year round, making these places cold.
- Whichever part of the earth is tilted towards the sun is going through summer, while the part tilted away from the sun is going through winter.
- The sea heats up more slowly and cools down more slowly than land.
- Places closer to the sea therefore have a smaller temperature range than those inland.
Weather and people
1. A hurricane is a low pressure system, or depression. It is sometimes called a tropical storm or a tropical cyclone.
- Hurricanes develop in the tropics above a warm sea(over 27⁰C) and move away from the equator westwards.
2. Hurricanes happen when the weather is hottest. This is between May and November in the Northern hemisphere and November and April in the Southern hemisphere.
3. Areas vulnerable to hurricanes include: the Indian subcontinent, South East Asia, Central America and the Caribbean.
4. A hurricane can stretch up to 800km in diameter and be up to 20km in height.
- The eye of the storm is made up of very low pressure encourages air to rise and cool, clouds to form and rain to fall. The lower the pressure, the faster the winds, often over 300km/h.
- Hurricanes weaken and blow themselves out when they meet land, as they are cut off from the warm sea that is their main source of energy.
5. The effect on humans can be devastating.
- Winds destroy buildings, crops, trees and power lines.
- Heavy rainfall causes river flooding and landslides.
- Low pressure temperarily raises the water level, creating storm surges that flood costal areas.