The Big Chill - Observing and modelling cold air outbreaks

In this project you will investigate cold-air outbreaks using a number of case studies gathered from aircraft-based field campaigns. You will run the Met Office's Unified Model (the MetUM) at high resolution to simulate these cases and make use of the detailed in-situ observations to challenge the model forecasts. You will test various new model parameterizations, for example, testing the 'blended' 3D/1D turbulence scheme; testing new developments in cloud microphysics parameterization; and simulating cloud streets (Liu et al. Geophysical Res. Lett. 2004). The MetUM is a state-of-the art numerical weather and climate prediction model, which is used for operational weather forecasting, seasonal forecasting and climate modelling on all scales. Consequently your research with the MetUM is expected to lead to direct improvements in these applications. You may also make use of a 'Single Column Model' version of the MetUM, which is simpler to run and allows controlled single point experiments.

The observational data includes one cold-air outbreak case from GFDex (the Greenland Flow Distortion Experiment; Renfrew et al., Bull. Amer. Meteorol. Soc., 2008) in which the aircraft followed a Lagrangian 'air parcel', thus allowing sources and sinks of heat and moisture to be accurately observed. It also includes several cold-air outbreak flights from the ACCACIA project (flying over sea ice around Svalbard in the Arctic during March 2013), and from the PIKNMIX project (flying over the sea between Iceland and the UK). Several case studies will be chosen for closer examination and simulation. You will also have the opportunity to take part in a major international field campaign focused on the Iceland and Greenland Seas in March 2018, when new aircraft-based and ship-based boundary-layer observations of cold-air outbreaks will be made. The Iceland Sea is relatively little-studied, but this is now changing, as we are discovering it plays a critical role in creating and transporting dense water from the subpolar seas into the North Atlantic and this role is now being affected by Arctic sea-ice retreat (Moore et al., Nat. Clim. Change, 2015; and see https://theconversation.com/declining-winter-sea-ice-near-greenland-spells-cooler-climate-for-europe-42976). This field campaign will enable a considerable step forward in our understanding of these processes, and your contribution will contribute to furthering our understanding of the role that cold-air outbreaks play in this critical region.