High static stability in the mixing layer above the extratropical tropopause

Kunz, A.; Konopka, P.; Pan, L.L.; Rohrer, F.; Schiller, C.; Müller, R.

doi:10.1029/2009JD011840

Journal Article

High static stability in the mixing layer above the extratropical tropopause

Kunz, A.FZJ* ; Konopka, P.FZJ* ; Müller, R.FZJ* ; Pan, L. L. ; Schiller, C.FZJ* ; Rohrer, F.FZJ*

2009
Union Washington, DC

Journal of Geophysical Research 114, D16305 (2009) [10.1029/2009JD011840]

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Please use a persistent id in citations: http://hdl.handle.net/2128/20446 doi:10.1029/2009JD011840

Abstract: The relationship between the static stability N-2 and the mixing in the tropopause inversion layer (TIL) is investigated using in situ aircraft observations during SPURT (trace gas transport in the tropopause region). With a new simple measure of mixing degree based on O-3-CO tracer correlations, high N-2 related to an enhanced mixing in the extratropical mixing layer is found. This relation becomes even more pronounced if fresh mixing events are excluded, indicating that mixing within the TIL occurs on a larger than synoptic timescale. A temporal variance analysis of N-2 suggests that processes responsible for the composition of the TIL take place on seasonal timescales. Using radiative transfer calculations, we simulate the influence of a change in O-3 and H2O vertical gradients on the temperature gradient and thus on the static stability above the tropopause, which are contrasted in an idealized nonmixed atmosphere and in a reference mixed atmosphere. The results show that N-2 increases with enhanced mixing degree near the tropopause. At the same time, the temperature above the tropopause decreases together with the development of an inversion and the TIL. In the idealized case of nonmixed profiles the TIL vanishes. Furthermore, the results suggest that H2O plays a major role in maintaining the temperature inversion and the TIL structure compared to O-3. The results substantiate the link between the extratropical mixing layer and the TIL.

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Meteorology & Atmospheric Sciences

Note: This work is supported by the HGF programme EOS (Earth Observing System). We thank P. Hoor and H. Fischer for providing the SPURT CO data, P. M. Forster for support and permission to use his radiation scheme, and T. Birner for review and useful discussions on the paper. Furthermore, the reviews and comments of two anonymous referees were very helpful.

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