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Title: The impact of deep convection on the structure of, and transport through, the tropical tropopause layer
Author: Hosking, J. S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2010
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The UK Met Office’s Unified Model is used at a high global resolution to assess the impact of deep tropical convection on the tropical tropopause layer (TTL) and the transport of short-lived species. The modelled horizontal and vertical structure of organised convection, as well as the distribution of tropical tropopause temperatures and humidity, is shown to match closely with satellite data. Furthermore, the structure of the TTL is found to be similar for both weather and climate setups. In weather mode, monthly integrations are performed with idealised tracers of varying lifetimes. Novel diagnostics complement classic diagnostics to reveal how efficient rapid vertical transport can be in the model. These diagnostics, so-called ‘surface-to-TTL matrices’, utilise idealised tracers that are released regionally at the surface and are monitored at given regions and heights in the TTL. Deep convection is more frequent over the tropical warm pool compared to other tropical regions for all periods analysed. Convective ‘elevators’ rapidly lift air from 4-5km up to 12-14km. Nonetheless, the influx of tropospheric air entering the TTL (11-12km) is similar for all tropical regions with most convection stopping below ~14km. Above this height, regional tracer signatures associated with deep convection become clearer. The deepest convective elevators are seen to directly inject between 10-20% of surface tracer concentrations up to 15km. However, convection almost never reaches higher than this. The tropopause is coldest and driest between November and February, coinciding with the greatest upwelling over the tropical warm pool. From here, modelled tracers are lifted from the surface up to 15-17km where they are advected eastwards before descending over the East Pacific in accordance with the Walker circulation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available