Geib, Anika (2010) Transportprozesse in der Tropischen Tropopausenschicht im Nordhemisphärischen Winter mit ERA-Interim Assimilationsdaten. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 45 pp.

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Abstract

The aim of this diploma thesis is to analyse transport processes in the tropical tropopause layer (TTL) in northern hemisphere winter. The data sets ERA-Interim and ERA-40 are compared in the band of the TTL during boreal winter regarding temperature, verticla velocity and all sky heating rates. In a second part, the impact of different forcing types on calculating trajectories is investigated in reference to trajectory temperatures and residence times between different levels of potential temperature. In the tropopause, ERA-Interim temperatures are lower than those from ERA-40. Heating rates and vertical velocities are of much smaller values, too. Additionally, the vertical profile of ERA-Interim vertical velocities is more realistic. Clear sky heating rates result in the coldest trajectories in this thesis, around the maritime continent are minimum temperatures below 183K. These heating rates are yet inapplicable to calculate trajectories below the potential temperature of 465K. All sky heating rates and total heating rates provide similar trajectories, regarding temperature (<184K near the maritime continent) as well as residence time (about one day difference between 360K and 400K). Vertical-wind-forced trajectories are still warmer. Furthermore, in comparison between the types of forcing, by far the fewest trajectories calculated using vertical wind speed actually passed the TTL. Generally, trajectories driven by vertical winds are ill-suited for a realistic modelling. Clear sky heating rates give good results above 370K. In lower layers, the analysis of all-sky- or total heating rates is required.

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