Inclusion of mountain-wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

摘要

An important source of polar stratospheric clouds (PSCs), which play acrucial role in controlling polar stratospheric ozone depletion, is from thetemperature fluctuations induced by mountain waves. However, this formationmechanism is usually missing in chemistry–climate models because thesetemperature fluctuations are neither resolved nor parameterised. Here, weinvestigate the representation of stratospheric mountain-wave-inducedtemperature fluctuations by the UK Met Office Unified Model (UM) at climatescale and mesoscale against Atmospheric Infrared Sounder satelliteobservations for three case studies over the Antarctic Peninsula. At a highhorizontal resolution (4 km) the regional mesoscale configuration of the UMcorrectly simulates the magnitude, timing, and location of the measuredtemperature fluctuations. By comparison, at a low horizontal resolution(2.5° × 3.75°) the global climateconfiguration fails to resolve such disturbances. However, it isdemonstrated that the temperature fluctuations computed by a mountain waveparameterisation scheme inserted into the climate configuration (whichcomputes the temperature fluctuations due to unresolved mountain waves) arein relatively good agreement with the mesoscale configuration responses fortwo of the three case studies. The parameterisation was used to include thesimulation of mountain-wave-induced PSCs in the global chemistry–climateconfiguration of the UM. A subsequent sensitivity study demonstrated thatregional PSCs increased by up to 50% during July over the AntarcticPeninsula following the inclusion of the local mountain-wave-induced coolingphase.