Anthropogenic snowfall events in the UK: examples of urban weather modification?

摘要

Snowfall is not confined to frontal or con-vective weather systems. This was evident from a striking weather image in the August 2008 issue of Weather, which showed a satellite picture of scattered snow patches over the Low Countries immediately following a period of foggy anticyclonic weather (van den Berg, 2008). The snowfall illustrated was typically downstream of urban and industrial areas, raising the possibility that the events were anthropogenic snowfall events (ASEs), associated with fog andartificially injected particles. Studying such snowfall from fog is important because of the associated local changes and the potential hazard it produces. Since the snow might not have been forecast, a hazard might arise from inadequate gritting of roads; but - perhaps more worryingly - as snowfall is such an obvious event, it provides an objective basis on which the forecast may be widely perceived to have been 'wrong'. Even a light covering of snow alters the local surface albedo.