Weather and Climate

 Introduction

~ Hello again learners, welcome back to our ßlog, I'm Mrs Makuyana and today we are going to learn about Weather and Climate.

- Various processes on Earth depend on weather and climate. When people greet each other they often refer to how hot or cold the weather is. They also talk about the rain or dryness being experienced. If there are strong winds and clouds they will mention that as well. The weather is always there and it affects human and physical processes.

- Our main aim this month is looking at the difference between weather and climate, the elements of weather & their instruments, weather forecasting, calculations, interpretation of weather symbols, formation & types of clouds and the water cycle. 

• Weather is the daily condition of the atmosphere at a given place and time.

• The weather is not static but changes within a short period of time such as hours or days.

• A given place can be cold in the morning but hot later in the afternoon, It can be raining in the morning but turn out to be dry in the afternoon.

• Climate is the average conditions of the atmosphere for a particular place observed and recorded over a long period of time such as 10-40 years.

• In simpler terms we refer it to the average weather conditions experienced in a particular place over a long period of time.

• It can also be defined as the weather in a place averaged over a long period of time.

- Weather is different from climate in that weather shows an area's conditions for a short period of time. Weather can be for an hour, days or week while climate gives average weather conditions observed over a long time.

- Climate enables us to know the different seasons experienced by an area and to expect certain conditions during certain seasons.

- In Zimbabwe we expect rains in summer that is between November and March. From May to August it will be cold and dry. 

- These conditions were mastered through observing weather conditions over long periods of time. We will cover this under weather forecasting.

• Weather elements are those components that we observe or feel, which determine the condition of the atmosphere.

• The weather elements include :

A. Temperature

• lt is the degree of hotness or coldness of the air. This element is measured using the thermometer.

• Examples of thermometers you might know : - maximum & minimum thermometers

- six's Thermometer

- infrared thermometers

• Temperature is measured in degrees Celsius(°C), Fahrenheit (°F) and Kelvin(K). Its SI unit is the Kelvin (K).

• When we cannot go outdoors to play because it is too hot or when we put on our jerseys because it is too cold, that's temperature.

B. Humidity

• It is the amount of water vapour in the air. The blowing air may be dry but, in some cases, it carries moisture such as when it is raining. 

• Humidity is measured using an instrument called a hygrometer (wet and dry bulb thermometer) and is given as a percentage (%)

C. Rainfall

• This is moisture falling from the atmosphere to the ground. It is a form of precipitation. The rain falls from the atmosphere in various forms.

• It is measured using a rain gauge in millimeters (mm).

D. Wind direction

• Wind is air in motion. The direction from which the wind is blowing is also an important weather element. Human activities depend on this direction of the wind. 

• Wind direction is shown using cardinal points. Cardinal points are the principal directions on a compass. These are north, south, east and west. The cardinal points are further branched to give ordinal points which give the exact directions such as north-east, south-west, north-west, and south west.

E. Wind speed

• Wind speed shows how strong the wind is. It shows the rate at which the wind is blowing. 

• It is measured using an instrument called a cup anemometer in km/hr or knots.

F. Atmosphere Pressure

• It is the force exerted by the air at a given time and place. 

• It is measured using a mercury or aneroid barometer and recorded in millibars.

G. Cloud cover

• This refers to the proportion of the sky covered by clouds. Sometimes we cannot see the blue sky, sometimes the sky is completely blue without any patches of white and in some cases, it is covered with clouds. 

• Cloud cover is measured in oktas and we estimate cloud cover using eyesight. When we look into the sky we should be able to tell the proportion of the sky covered by clouds. This proportion is given as a fraction out of 8(oktas)

H. Sunshine

• Sunshine is the heat energy received from the sun. The rays of the sun come in form of radiation and this radiation is called incoming solar radiation. 

• Sunshine is measured using a sunshine recorder and recorded in hours and minutes.