Rainy Weather. Image by Sodahead.
ZIMSEC O Level Geography Notes: Introduction to Weather and Climate
Weather-the state of the atmosphere at a particular place and time as regards heat, cloudiness, dryness, sunshine, wind, rain, etc. The weather is all around us, all the time. It is an important part of our lives and one that we cannot control.
Climate- meanwhile is defined as the weather conditions prevailing in an area in general or over a long period. It is the long term weather pattern of a given area. It is especially important in activities such as agriculture. It is measured by assessing the patterns of variation in temperature, humidity, atmospheric pressure, wind, precipitation, atmospheric particle count and other meteorological variables in a given region over long periods of time.
Differences between weather and climate
| Climate | Weather |
|---|---|
| Describes the average conditions expected at a specific place at a given time. | Describes the atmospheric conditions at a specific place at a specific point in time. Weather generally refers to day-to-day temperature and precipitation activity (e.g rain or snow) |
| Measured over a long period typically 30 years. | Measured for short term e.g on a day to day basis |
| The study of the climate is called climatology. | The study of weather is called meteorology. |
Elements of weather and their instruments and units of measurement
Zimbabweans typically use the metric system of measurement for example meters for distance and kilograms for weight. Weather is made up of several elements such as temperature which are measured using various specilized instruments and expressed in their units. While the metric units is common in most areas of our lives, weather elements are sometimes measured in imperial units for example wind speed is measured in knots. In other instances different countries use different units. For example the United States uses Degrees Fahrenheit to measure temperature. In the real world you should study the unit used to express weather carefully before making comparisons for example a temperature of 45 °F (around 7 °C )could be described as cool which is not what you would think if you just thought of it as 45 °C “hot” which is a temperature associated with hot deserts.
The following elements are some of the most commonly used to express weather.
- Temperature- Six’s thermometer otherwise known as the maximum and minimum thermometer. It is expressed in Degrees Celsius.
- Humidity-Hydrometer/psychrometer/satellites-Humidity is measured as a percentage. See Humidity for more details.
- Pressure-is measured using a Barometer and expressed in millibars.
- Wind direction-Wind Vane- it is expressed using the cardinal points of a campus e.g SE.
- Wind speed-Cup anemometer and expressed in knots.
- Sunshine-sunshine recorder and it is express in hours and minutes.
- Cloud cover-observed using the eyes and is measured in Oktas.
Weather report
- a systematic statement of the existing and usually the predicted meteorological conditions over a particular area.
- The information is obtained from a weather station e.g Kutsaga.
Weather forecast
- Is a prediction of weather phenomena, trend and events.
- Weather forecasts are made by collecting as much data as possible about the current state of the atmosphere (particularly the temperature, humidity and wind) and using understanding of atmospheric processes (through meteorology) to determine how the atmosphere evolves in the future.
- the chaotic nature of the atmosphere and incomplete understanding of the processes mean that forecasts become less accurate as the range of the forecast increases.
- Information gained from the observations is used in conjunction with complicated models and computer simulations are used to predict future weather.
Importance of weather to people
- People can be made aware of looming weather hazards such as thunderstorms and cyclones and take precautionary measures such as evacuating the areas that will be affected.
- So that people can know which type of clothes to wear for example whether to carry a rain coat or umbrella or not.
- Farmers can make more informed planning decisions e.g. when to spray, plant or harvest.
- Pilots know which routes to take when flying and how to land and take off.
- When making sporting calenders for example games like cricket are hugely affected by weather so we can choose to play indoor sports instead.
