Thomas Pleavin

Postgraduate Student

Telephone number: +44(0) 113 34 34931
Email address: lec5tdp@leeds.ac.uk
Room: 11.121

Biography

Qualifications: B.Sc. Environmental Science, University of Leeds

Project Details

Project Title: Modelling Summertime Arctic Stratus Clouds

Supervisors: Dr Ian Brooks (ICAS, Leeds), Dr Steven Dobbie (ICAS, Leeds), and Dr Adrian Lock (Met Office)

Start Date: 1st October 2008

Project Description:

The Arctic is a region of exceptional sensitivity to climate change: the observed rate of temperature increase is twice that of the rest of the world, and there is strong evidence for thinning and retreat of Arctic ice pack ice, which reached a record minimum during 2007. Although models agree that the Arctic will continue to have a strong response to increasing greenhouse gas concentrations, they also show much greater variability between models here than elsewhere, and fail even to reproduce current conditions adequately. The response of the Arctic to continued climate change is thus extremely uncertain. Model performance in the Arctic is poor in large part because the parametrizations used are derived from observations in mid-latitudes or the tropics; there are very few measurements within the Arctic, with the result that our understanding of the processes controlling local conditions: cloud dynamics and microphysics, radiative forcing, surface exchange, etc, is poor.

This PhD project will study the dynamical and microphysical processes in summertime Arctic stratus clouds using the Met Office Large Eddy Model and a single column version of the Unified Model. The aims are to understand the interactions between the cloud dynamics and microphysics, radiative forcing, and surface coupling, with the ultimate objective of improving the representation of Arctic boundary layer clouds in climate models. The project will assess 1) how the dynamics of Arctic stratus differ from typical marine stratocumulus, 2) what the role of entrainment is in maintaining the cloud in the unique humidity structure of the Arctic lower atmosphere, 3) how the cloud responds to different sources of aerosol: from the surface or entrained from above, since it is currently unknown where the CCN required to maintain Arctic stratus derive from. Such studies are of paramount importance since Arctic stratus is the dominant controlling factor for the surface energy budget, and differ substantially from their mid-latitude counterparts; failure to adequately represent these clouds in climate models makes it impossible to properly simulate Arctic climate.