Weatherwatch: what is the dew point?

The dew point is the temperature at which air must be cooled to become saturated with water vapour and for dew to formThe dew point is the temperature at which a certain area of air must be cooled to for dew to form. It is also commonly interpreted as a measure of the air's moisture content. As air cools, the amount of the gaseous form of water it is capable of holding decreases, and as such, cooling will eventually result in it reaching saturation point, beyond which condensation into liquid water droplets occurs. This is the main process behind cloud formation in the atmosphere.Of course, dew can also form on surfaces on earth. When the surface (for example grass or cars) cools below the dew point temperature of the air adjacent, condensation droplets from the air deposit onto that surface. If surface temperatures fall below 0C and below the dew point temperature, instead of water vapour gas condensing to water droplets, it transitions directly to crystals of ice, in the form of frost. Continue reading...