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Title: Modelling ice supersaturation in the upper atmosphere and predicting persistent contrail coverage
Author: Dickson, N.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2011
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Contrail formation and the occurrence of ice supersaturation in the atmosphere (which is needed for contrails to persist) is the focus of the thesis. The global observation and prediction in numerical models of ice supersaturation are crucial if the climate impact of contrails is to be fully understood. In this thesis the research presented uses observations and models to further understand the occurrence frequency and spatial extents of ISS regions. In chapter 2, in-situ observations of RHi made using radiosondes and commercial aircraft were used to investigate, respectively, the vertical and horizontal spatial extents of ISS regions. This showed that up to ~71-90% (vertical) and ~52% (horizontal) of ISS regions will be sub grid scale compared to the coarse resolutions of modelled and observed datasets. Chapter 3 shows the use of high-resolution radiosonde datasets to provide evidence of an s-shaped relationship between average RHi and the occurrence of ice supersaturation in thick (50 and 100hPa) vertical pressure layers. Chapter 4 shows the use of Lagrangian trajectory model coupled to a cirrus cloud parameterisation (Lagrangian-cirrus model) to represent ISS regions. Results showed up to a ~62-68% improvement in the prediction of RHi compared to ECMWF analyses. In chapter 5, the Lagrangian-cirrus model was coupled to the Aero2k emissions inventory to calculate contrail coverage (of 0.05-1.65%) over the North Atlantic Flight Corridor (NAFC). These results were used with the Edwards-Slingo Radiative Forcing (RF) model to calculate an RF impact due to contrail coverage of up to a net 400mWm-2. Overall, the studies presented in this thesis remove some of the uncertainties in persistent contrail coverage calculations and RF estimates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available