Learn social studies with Ndeapo Alma Nambahu

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A typical weather station  A weather station is a meteorological service. Weather station works by measuring atmospheric conditions and transmitting them to a network, forecaster or display. Figure 1.1 shows a typical weather station  How the elements of weather influence human activities in their local environment  •Raising animals and growing plants depend on the type of weather. •Houses are built differently according to the weather. •There are seasonal diseases that come with each type of weather. •The clothes we choose to wear are also based on the weather. •Some people do certain sporting activities depending on the weather.

  A Stevenson screen or instrument shelter is a shelter or an enclosure used to protect meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them. Figure 1.1 shows a Stevenson screen  Characteristics of the Stevenson screen: •It has a double roof to help keep out the direct rays of the sun. The roof is also slightly sloped to allow the rainwater to run off. •The screen is made of wood and painted white to reflect the direct rays of the sun. •It is placed away from buildings and trees so that it is not standing in the shade. •The sides are slatted or louvered to allow a gentle flow of air , so that the temperature of moving air can be measured. •The door must face south so that the direct rays of the sun do not fall on the instruments if the door is open. •It is raised about 1.2 m off the ground and planted in grass to ensure accurate air temperatures are measured. Grass radiates les...

 Wind direction and speed How to calculate wind direction and speed  Wind is moving air and it is described by the compass direction from where it is blowing, for example north, south-east etc. Figure 1.1 A wind vane Figure 1.2 Windsock A wind vane (see Figure 1.1) can be used to determine the wind direction. At airports or on runways a windsock is used (see Figure 1.2). You can also determine wind direction by looking at flags or at smoke coming from a fire. The wind vane is normally made of metal and you will find it on a high building or on top of a long pole. The wind vane must be in an area where there is free flow of wind. Wind will push against the largest surface of the arrow (the tail) until the arrow swings around to be parallel with the windand offers no resistance any more. The arrow head will therefore always point in the direction from where the wind is coming. As well as wind direction,  it is also important to measure wind speed. This is measured with an a...

 Humidity  How to measure Humidity  Humidity is the amount of water vapour in the air and is expressed as a percentage (%). The instrument that we use to measure humidity is called a wet and dry bulb thermometer, also known as a hygrometer. Figure 1.1 A wet and dry bulb thermometer  The wet and dry bulb thermometer consists of two normal thermometers that are exactly the same. These thermometers are mounted parallel to each other. Underneath one of the thermometers is a small bottle filled with distilled water. The bulb of this thermometer is covered with a small wick or cloth. The end of the wick hangs in the bottle with distilled water. ( see Figure 1.1). As the water rises up the wick, it evaporates causing the wet bulb thermometer to cool down, and to measure a lower temperature. The dry bulb thermometer will indicate the real air temperature. Watch video on how to measure humidity  Sunshine How to measure sunshine Sunshine is measured with a Sunshine record...

Air pressure  How to measure air pressure  Air pressure is the force with which the atmosphere (air) is pressing down on us. It is measured in units called millibars (mb) or hectopascals (hPa) by means of a barometer or a barograph. Figure 1.1 Aneroid Barometer The aneriod barometer in Figure 1.1 I a commonly used barometer. On the faceplate of the instrument the units are calibrated (indicated) in millibars. Words like 'RAIN' (low pressure side of scale), 'CHANGE' and 'FAIR' (high pressure side of scale) appear on the faceplate. Inside the instrument you will find a metal container from which the air has been removed (forming a vacuum) and a set of levers. These levers are connected to a pointer on the faceplate. When air pressure rises, the container contracts and the levers force the pointer to move towards the 'FAIR' side. If the pressure becomes lower the container expands and the pointer moves towards the 'RAIN' side. The arrow indicates ai...