Aerosol-fog interactions

The goal of this project is to improve the forecasts of radiation fog; i.e. fog that forms on a cold, humid, calm night. Fog is one of the highest impact weather events in the UK. The Met Office is the CASE partner. A poor forecast of fog -- e.g predicting that fog will occur over Heathrow and no fog forms -- could result in losses of millions of pounds. Equally, thick fog that was not forecast properly can cause severe traffic accidents resulting in loss of life. Major health problems can also occur due to air-pollution events that are caused by the same meteorological conditions, which can cause enhancements in fog intensity (e.g. the Beijing smog). The formation of radiation fog can occur when there are calm or light winds, high relative humidity and rapid cooling. However, whether fog does or does not form depends on the balance between radiative cooling, turbulent mixing, the growth of aerosol particles by the uptake of water vapour, the activation of fog droplets on the aerosol particles and cold-air advection. The development of the fog upwards depends on condensation on aerosols above the fog and continued cooling.