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Island convection and its interaction with larger scales
Islands can be used as a natural laboratory for the study of both shallow and deep convection for decades. Islands serve as real-world examples of surface inhomogeneities that may trigger convection through different driving mechanisms. Most commonly, the diurnal cycle of heating over islands forces sea breeze circulations that trigger and organise afternoon convection over larger islands, and downwind of smaller islands when sufficient synoptic-scale wind is present. Further, relatively flat islands can help isolate the role of thermal forcing from the mechanical influence of topography. Insights from island convection may be particularly pertinent for new convection parameterization developments designed for model resolutions at which convection is partially resolved. In many numerical weather prediction systems, islands are poorly resolved (if at all). Therefore, the forcing related to cloud trail formation is not well resolved and the resulting atmospheric perturbations are missing.
The project focuses particularly on the island of Bermuda and research questions include: What are the typical spatio-temporal distributions and characteristics of island convection at Bermuda? How does island convection behave in and alter different large-scale environments? How can convection parameterization schemes be augmented to improve the representation of island convection at coarser resolutions?
Some links for this work:
Publications:
1. Simulations of idealized cloud trails.2. PhD thesis by Michael Johnston.
3. A climatology of cloud trails downstream of Bermuda.
4. A discussion of heavy rainfall events on Bermuda.
Talks:
1. A talk on the effects of sensible heat fluxes on cloud trails (presented by Chris Holloway), at a workshop on Cloud Organisation and Precipitation Extremes.2. A talk (with recording) on the effects of wind speed on cloud trails (presented by Michael Johnston), at an AMS conference on hurricanes and tropical meteorology.
3. A talk on the simulation of cloud trails (presented by Michael Johnston), at the CPCC convection parameterization conference in Exeter.
Posters:
1. A poster on large-eddy simulations of cloud trails, (presented by Michael Johnston), at the 2019 EGU conference.2. A poster on observations of cloud trails off Bermuda, (presented by Michael Johnston), at the Future of Cumulus Parameterization conference in Delft.