Ventilation of the atmospheric boundary layer

The atmospheric boundary layer usually has an inversion at its top, which separates it from the troposphere above. Turbulence within the boundary layer mixes temperature, moisture and pollutants within the boundary layer. But the presence of the inversion inhibits mixing to greater heights. So how is air ventilated out of the boundary layer into the free troposphere above? This question has important implications for the total concentration of pollutants that accumulate in the boundary layer, and for the transport of moisture, which is evaporated from the surface, through the climate system. In this talk we present a range of processes that facilitate ventilation of the atmospheric boundary layer, including (i) convection in clouds, (ii) advection by the warm conveyor belt in mid-latitude weather systems, (iii) uplift as air travels over hills and mountains, and (iv) outflow at coastal regions. Idealised models are used to illustrate and quantify the different processes, and re-analysis products are used to give a global perspective on the most important processes for boundary layer ventilation.