Weather and climate: scales and conversions
Describing weather and climate quantitatively relies on agreed scales for temperature, wind and other atmospheric quantities. Temperature is the most familiar. Three scales are in common use: Celsius, on which water freezes at 0 and boils at 100 degrees under standard pressure; Fahrenheit, still widely used in the United States, on which the same points fall at 32 and 212 degrees; and Kelvin, the SI scale, which starts at absolute zero and shares the same step size as Celsius. Simple formulas convert among them, and reference tables list equivalent readings side by side.
Wind is described both by speed and by its effects. The Beaufort scale, devised in the early nineteenth century, rates wind force from 0 (calm) to 12 (hurricane force) using observable signs on land and sea, such as smoke drift, moving branches or the state of the waves. Each Beaufort number corresponds to a range of wind speeds, so the scale links plain observation to measured values. Conversion factors translate wind speed between metres per second, kilometres per hour, miles per hour and knots.
Other indices combine several measurements to express how conditions feel or behave. Wind chill estimates the cooling effect of moving air on exposed skin, giving an apparent temperature lower than the air temperature when wind is strong. Related tables cover humidity, pressure in different units, and the conversions needed to compare data from different instruments and countries. Such constants, scales and conversion factors form the practical backbone of meteorology, letting forecasts and climate records be expressed consistently and compared over time.
Frequently asked questions
- How are Celsius and Fahrenheit related?
- To convert Celsius to Fahrenheit, multiply by nine-fifths and add 32; to go the other way, subtract 32 and multiply by five-ninths. The scales meet at minus 40 degrees.
- What does the Beaufort scale measure?
- It rates wind force from 0 to 12 based on observable effects on land and sea, with each step corresponding to a range of wind speeds.
- What is wind chill?
- Wind chill is an estimate of how cold the air feels on exposed skin when wind increases the rate of heat loss, expressed as an apparent temperature.
