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Tuesday 20 Oct 20201st year PhD student presentations 2

Brett McKim and Ross Castle - University of Exeter

Zoom 13:30-14:30

On the logarithmic scaling of Earth’s outgoing longwave radiation - Brett McKim

Earth’s tropics exhibit relatively uniform surface temperatures but dry regions act like radiator fins and emit substantially more radiation to space than moist regions. ‘Radiator fins’ are important for stabilizing Earth’s tropics, but it is unclear how strong their radiative effect should be. Our results show that when conditioned upon surface temperature, Earth’s outgoing radiation depends logarithmically on the vertically averaged relative humidity. Using pencil-and-paper theory and a line-by-line radiation model, we show a direct connection between the logarithmic dependence and water vapor’s absorbance spectrum.

What is necessary to capture a “well resolved” stratosphere for the purpose of climate change prediction? - Ross Castle

Stratospheric dynamics have a direct influence on the tropospheric circulation, but are not always well resolved in climate models. This is due to computational expense and the difficulty to define the what is required for a stratosphere to be well resolved. Using an idealised GCM it is possible to quantify the influence of a well resolved stratosphere on the model base state climatology and in response to a climate change perturbation. Similar studies and preliminary results show that this influence is significant, and has the potential to impact regional and global climate predictions. It is therefore important to ascertain what is necessary to capture a well resolved stratosphere in a GCM.

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