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Title: Observations and modelling of tropical marine boundary layer clouds
Author: Barber, Claire
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2012
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Marine boundary layer (MBL) cloud and fog are ubiquitous over the global oceans, overlying more than 30% of the ocean surface. Due primarily to their large spatial extent, relat ively speaking minor changes in cloud radiative properties have the potential to sub-stantially affect the global radiation budget, and so future climate. Changes to a particular cloud property are often a small residual effect due to many competing processes. Therefore, modelled cloud changes can be associated with large uncertainties, and :MEL clouds were identified in the most recent IPCC report as the largest contributor to the spread in modelled cloud feedbacks . This thesis exploits the existence of long-term (30yr+ ), consistent, global satellite records of cloud extent and properties to evaluate the representation of MBL clouds in the recent Hadley Centre HadGEM-2A global climate model. In general, the position and fraction of MBL clouds is much improved over previous versions of the model. The representation of cloud liquid water path (L\VP), however, still requires improvement, with the model consistently underestimating LWP by as much as 50% relative to microwave-derived observations. Large differences between the retrieval of L\VP from different satellite platforms may contribute to the poorly constrained model representation of L\VP. The final part of this thesis constructs a well-constrained observational climatology of LWP, using microwave and visible-spectrwn derived satellite retrievals, for the West African Stratocwnulus region. For overcast, single layer cloud, latent heat flux (LHF) is found to be the best indicator of observed cloud L\VP compared to other surface and atmospheric measurements of heat and moisture. The advantages of well characterised and accurate measurements from multiple observational platforms for the purposes of model evaluation are emphasised throughout this thesis. ii
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available