Morphology of the tropopause layer and lower stratosphere above a tropical cyclone: a case study on cyclone Davina (1999)
1Istituto di Scienze dell'Atmosfera e del Clima, CNR, Roma, Italy
2Environmental Science Department, Lancaster University, Lancaster, UK
3Institute for Stratospheric Research, Forschungszentrum Jülich GmbH, Jülich, Germany
4Institute for Atmosphere and Environment, J. W. Goethe University, Frankfurt, Germany
5Observatoire Cantonal Neuchatel, Neuchatel, Switzerland
6Ente per le Nuove Tecnologie, l'Energia e l'Ambiente, Frascati, Rome, Italy
7Central Aerological Observatory, Dolgoprudny, Russia
8Istituto Nazionale di Geofisica e Vulcanologia, Boulogne, Italy
9Airborne Platform for earth Observation, Comitato di Gestione, Florence, Italy
*now at: United Kingdom Meteorological Office, Exeter, UK
**now at: Istituto di Fisica dello Spazio Interplanetario, INAF, Rome, Italy
***now at: Geophysica Gruppo Europeo di Interesse Economico, Florence, Italy
Abstract. During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame.
Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400–430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics.
Citation: Cairo, F., Buontempo, C., MacKenzie, A. R., Schiller, C., Volk, C. M., Adriani, A., Mitev, V., Matthey, R., Di Donfrancesco, G., Oulanovsky, A., Ravegnani, F., Yushkov, V., Snels, M., Cagnazzo, C., and Stefanutti, L.: Morphology of the tropopause layer and lower stratosphere above a tropical cyclone: a case study on cyclone Davina (1999), Atmos. Chem. Phys., 8, 3411-3426, doi:10.5194/acp-8-3411-2008, 2008.