Correlation between equatorial Kelvin waves and the occurrence of extremely thin ice clouds at the tropical tropopause

F. Immler (1) , K. Krüger (2) , M. Fujiwara (3) , G. Verver (4) , M. Rex (5) , O. Schrems (5)

1 MOL-RAO - Lindenberg Meteorological Observatory - Richard Assmann Observatory
2 IFM-GEOMAR - Leibniz-Institut für Meereswissenschaften
3 Hokkaido University [Sapporo, Japan]
4 KNMI - Royal Netherlands Meteorological Institute
5 Department of Bentho-pelagic processes

A number of field-campaigns in the tropics have been conducted in the recent years with two different LIDAR systems at Paramaribo in Suriname (5.8° N, 55.2° W). The lidars detect particles in the atmosphere with high vertical and temporal resolution and are capable of detecting extremely thin cloud layers which frequently occur in the tropical tropopause layer (TTL). Radiosonde as well as operational ECMWF analysis show that temperature anomalies caused by equatorial Kelvin waves propagate downward, well below the cold point tropopause (CPT). We find a clear correlation between the temperature anomalies introduced by these waves and the occurrence of thin cirrus in the TTL. In particular we found that extremely thin ice clouds form regularly where cold anomalies shift the tropopause to high altitudes. This finding suggests an influence of Kelvin wave activity on the dehydration in the TTL and thus on the global stratospheric water vapour concentration.

Domaines: Océan, Atmosphère

F. Immler, K. Krüger, M. Fujiwara, G. Verver, M. Rex, et al.. Correlation between equatorial Kelvin waves and the occurrence of extremely thin ice clouds at the tropical tropopause. Atmospheric Chemistry and Physics Discussions, 2008, 8 (1), pp.2849-2862. ⟨hal-00303970⟩