Weather
Meaning of Weather
Weather is a day to day condition of the atmosphere recorded within a short period of time, usually hours or days. The atmosphere may be cloudy, sunny, rainy or windy.
Atmosphere is the air that is surrounding us.
Conditions or elements of the atmosphere are called elements of weather. The elements of weather are rainfall, temperature, wind, sunshine, cloud cover, humidity and pressure.
Elements of weather
1. Temperature
Temperature is the degree of hotness or coldness of a body or place.
Temperature can be high or low.
Temperature is measured by an instrument called thermometer. Amount of temperature is recorded in degree Celsius (0C ). These are the measures through which we can tell the amount of temperature of a given body or place.
2. Wind
Wind is moving air or air in motion. Wind moves at different rates, speed and in different directions.
(a) Wind direction
Direction of wind is measured by an instrument called wind vane. It may also be determined using a wind sock.
When wind blows, it causes the arrow of a wind vane to rotate. It also makes a sock to turn towards the wind direction. Winds are named according to the direction they come from.
For example, winds from East are called Easterly winds.
(b) Wind speed
Wind speed is measured by an instrument called anemometer. When wind blows, the cups of the anemometer rotate. If the speed of the wind is low, the cups will rotate slowly. Wind speed is measured in kilometres per hour (km/h)
Importance of winds
(i) Used in winnowing.
(ii) Used to sail boats.
(iii) Source of energy.
(iv) Refreshes the body.
(v) Distributes heat.
(vi) Transports clouds and rainfall.
3. Rainfall
Rainfall is the water droplets from the sky as a result of cloud cover in the sky. When it rains, the weather is said to be rainy.
Rainfall amount is measured by an instrument called a rain gauge.
Rainfall is measured in millimetres (mm).
Signs of rainfall
(i) Thunder and lightning.
(ii) Dark cloud cover on the sky.
(iii) Wind starts blowing strongly.
(iv) Rainfall falling in the distance.
(v) Heavy rainfall starts.
Ways of protecting yourself against rainfall
(i) Staying inside a house.
(ii) Do not shelter yourself under a tree because trees can easily be hit by lightning.
(iii) Put on gumboots and rain jackets if walking in the rain.
(iv) Wear heavy clothes because rainfall causes coldness.
(v) Do not stand near electric poles.
Importance of rainfall
(i) Lowers the temperature.
(ii) Source of water.
(iii)Important for organisms living in water and land.
(iv) Source of water for rivers and lakes.
(v) Source of water in the soil.
(vi) Makes plants grow.
4. Humidity
Humidity is the amount of water vapour in the atmosphere.
Humidity is measured by an instrument called hygrometer. A hygrometer measures percentage of moisture in the air.
5. Sunshine
Sunshine is the heat and light that comes from the sun. The heat and the light reaches the earth's surface through sunrays.
The instrument used to measure sunshine is called sunshine recorder.
Importance of sunshine includes:
(i) Drying crops.
(ii) Warming the atmosphere.
(iii) Drying clothes.
(iv) Enabling us to see.
(v) Causes water to evaporate, which form clouds then rainfall.
6. Air pressure
Air pressure is the weight of air pressing down on the earth.
Air pressure is also known as atmospheric pressure.
Air pressure is measured by using an instrument called barometer. A barometer has a sealed tube and a container of mercury. The standard units for air pressure is millibars (mb).
7. Cloud cover
Cloud cover means part of the sky is covered by clouds. Cloud covers is measured by estimating how much the fraction of the sky covered by clouds. Cloud cover is measured in units called oktas. If the sky is completely covered by clouds, it is 8 oktas. It is 4 oktas if only half of the sky has cloud cover.
Seasons of the year
There are our main seasons of the year.
(i) Hot and dry season.
(ii) Dry and cold season.
(iii) Long rainy season.
(iv) Short rainy season.
(i) Hot and dry season
This is between January and March. During this period, there is no rain. It is sunny.
(ii) Long rainy season
This is between March and May. During this time, heavy rains are experienced in some areas.
(iii) Dry and cold season
This is between June and September. No rains are experienced. The period is very cold and dry.
(iv) Short rainy seasons
This is between September and December. Little rains are experienced during this period.