In everyday language, weather means such qualities as wet or fine, warm or cold. For most people, such descriptive terms are adequate. However, many industries today require more quantitative assessments of the weather, with the use of standardised terms measured by suitably designed instruments. The science of the study of weather is called meteorology. The meteorologist measures temperature, rainfall, pressure, humidity, sunshine and cloudiness, and makes predictions and forecasts about what the weather will do in the future.
Meteorologists still use simple ground-based instruments to measure the various elements of the weather, including thermometers, rain gauges and barometers. However, to make really accurate weather forecasts it is useful to know what the current weather is like over a large geographical area. Weather radar and satellite photography can offer the meteorologist a snapshot of the weather in a single image across an entire continent. Radar uses microwaves to scan for raindrops. Wherever it is raining the raindrops bounce the signal and by listening to the returning pulse, the radar can compute the location and intensity of the rain. Satellites allow meteorologists to track the path and development of weather systems. Satellites don't just "look" in the visible part of the spectrum. They can also measure the temperature of the ground and the clouds by "seeing" in infrared. Some satellites even measure the amount of water vapour in the atmosphere.