A weather map is a map of the world or part of it showing, at a stated time, the weather conditions like temperature, pressure, direction and velocity of the wind, humidity, clouds, visibility, nature and amount of precipitation with the help of symbols. It reveals the prevailing weather condition.
1. Weather Elements and Their Instruments
Weather varies with the changes in weather elements such as temperature, pressure, wind, humidity, cloudiness, precipitation, sunshine and visibility. The weather is measured with particular instruments and recorded in weather stations.
| Element | Instruments and What They Do |
|---|---|
| Temperature | Thermometers (Centigrade, Fahrenheit, Wet Bulb, Dry Bulb, Tele); Tele thermometer – records temperature continuously within and outside the building; Thermograph – continuous trace of changing temperature |
| Pressure | Barometer and Aneroid Barometer – pressure above and below sea level; Altimeter – air pressure at a height above sea level; Barograph – continuous record of air pressure |
| Wind | Wind vane – direction (points out from which direction it blows); Cup Anemometer – wind velocity (in knots); Wind Sock – origin of wind direction and speed |
| Humidity | Hygrometer – relative humidity; Hygrograph – automatic, shows change in relative humidity; Hygrothermograph – both humidity and temperature |
| Cloudiness | Ceilometer – uses a laser to find the height of the cloud base; Ceiling projectors – height of the cloud base above the ground; Cloud mirror – percentage of cloud cover |
| Precipitation | Rain gauge (conventional); Automated Weather Station (AWS) – records rainfall with sensors |
| Sunshine | Sunshine recorder – duration of sunshine in hours per day |