Aviation Meteo

Weather is complex and at times difficult to understand. Our restless atmosphere is almost constantly in motion as it strives to reach equilibrium. These never-ending air movements set up chain reactions, which culminate in a continuing variety of weather. The climate of any particular region is largely determined by the amount of energy received from the sun, but the local geography of the area also influences the climate. We are prepared to face "problems" in areas where winter is unavoidable but there can be a hidden danger at regions where winter weather aspects are not so obvious. The main point is to be aware of how, where and why ice, in its different forms (and relating forms of frost and snow), can build up.

Water can have many forms; vapour, liquid, snow or ice. Water can be visible (fog, mist, drizzle, rain etc.) or invisible but evident (high humidity). Excluding the obvious ice and snow, water can form into ice with the appropriate temperature and surface settings. Traditionally, two common temperature references are the melting point of pure ice (±0 ºC) and the boiling point of pure water (+100 ºC) at sea level. However, ice can form when the difference between the air temperature and dew point is small (indicating a high humidity) and when surface temperature (e.g. wing) is close to ±0 ºC even if the outside air temperature is well above freezing. This phenomenon can happen whenever the wing tank contains cold fuel and conditions are right. Icing is perhaps more of a problem for the flight crew in flight but whenever the right conditions exist on ground each trained and qualified de-icing ground crew should be aware of the event.

Training Recommendations and Background Information for De-Icing / Anti-Icing of Aircraft on the Ground. 2008