Whats the difference between a ground frost and an air frost?
A. In day-to-day meteorology, the temperature of the lowest layer of the atmosphere is measured at a height of 1.25 m (about 4 feet) above local ground level. Usually, though not always, this is achieved by placing thermometers in a double-louvered screen with the bulbs of the thermometers, or the sensor heads (for distant reading thermometers), placed so that they cluster around the 1.25 m standard. The temperature so read is usually called ‘the air temperature’ and it is these values that appear, for example, in the World Cities reports in newspapers/teletext, or plotted on standard synoptic charts, and also it is at this level that the forecast temperatures seen on tv weather maps are based. When the temperature as measured in this way falls below 0.0 deg C, then an AIR FROST is recorded. For other purposes though, e.g. horticulture, road gritting operations etc., we need to know what the temperature is at the surface of the ground, and most weather stations set at least two thermom
