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weather - Coggle Diagram
weather
weather instruments
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stevenson screen
The instruments used to measure temperature, atmospheric pressure and humidity are placed in a Stevenson screen.
This is a box that is painted white to reflect the heat of the sun. It has slatted sides to allow air to pass through the screen. This ensures accurate readings as the instruments are not in direct sunlight.
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A dry bulb thermometer which measures the temperature of the air and;
A wet bulb which is covered by a muslin sleeve dipped in water, which keeps it moist. If the air is not saturated, evaporation will take place. This cools the bulb and the temperature will drop.
Humidity is the amount of water vapour or moisture in the air. Warm air is able to hold more moisture than cold air.
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Sunshine is measured using a Campbell-Stokes sunshine recorder. A glass sphere focuses the sun’s rays onto a spot on a sensitive strip of paper slotted into the semi-circular frame surrounding the ball. The sun’s rays burn a mark on the paper. As the sun moves across the sky during the day, the burn marks move along the paper. At the end of the day, the paper can be examined to see how much the sun shone during the day.
Sunshine is measured in hours per day.
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Precipitation is any form of liquid or solid water particles that fall from the atmosphere and reach the surface of the Earth. It includes rain, snow, sleet, hail and drizzle.
A rain gauge is used to measure the amount of rainfall. A measuring cylinder with a funnel on top is placed in an open area, not sheltered by buildings and trees, in order to ensure an accurate reading. The rain falls through a funnel into the cylinder, which is marked in millimetres. When the cylinder is removed, the amount of rain that has fallen can be recorded
he unit of measurement of rainfall is millimetres (mm).
The lines on a weather map showing areas of equal rainfall are called isohyets.