Long-term lidar observations of polar stratospheric clouds at Esrange in northern Sweden

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Blum, U. ; Fricke, K. H. ; Müller, K. P. ; Siebert, J. ; Baumgarten, G. (2011)

Polar stratospheric clouds (PSCs) play a key role in the depletion of polar ozone. The type of cloud and the length of time for which it exists are crucial for the amount of chlorine activation during the polar night. The Bonn University backscatter lidar at Esrange in northern Sweden (68°N, 21°E) is well equipped for long-term observation and classification of these clouds. Nearly continuous measurements through several winters are rare, in particular in wave-active regions like Esrange. Lidar measurements have been performed each winter since 1997—a total of more than 2000 h of observation time has been accumulated, including more than 300 h with PSCs. Analysis of this unique data set leads to a classification scheme with four different scattering characteristics which can be associated with four different cloud types: (1) supercooled ternary solution (STS), (2) nitric acid trihydrate (NAT), (3) ice and (4) mixtures of solid and liquid particles. The analysis of observations over seven winters gives an overview of the frequency of appearance of the individual PSC types. Most of the clouds contain layers of different PSC types. The analysis of these layers shows STS and mixed clouds to occur most frequently, with more than 39% and 37% of all PSC observations, respectively, whereas NAT (15%) and ice clouds (9%) are seen only rarely. The lidar is located close to the Scandinavian mountain ridge, which is a major source of orographically induced gravity waves that can rapidly cool the atmosphere below cloud formation temperatures. Comparing the individual existence temperature of the observed cloud type with the synoptic-scale temperature provided by the European Centre for Medium-range Weather Forecasts (ECMWF) gives information on the frequency of synoptically and wave-induced PSCs. Further, the analysis of ECMWF temperature and wind data gives an estimate of the transparency of the atmosphere to stationary gravity waves. During more than 80% of all PSC observations in synoptic-scale temperatures which were too warm the atmosphere was transparent for stationary gravity waves. Our measurements show that dynamically induced cooling is crucial for the existence of PSCs above Esrange. In particular ice PSCs are observed only in situations where there are gravity waves.DOI: 10.1111/j.1600-0889.2005.00161.x
  • References (49)
    49 references, page 1 of 5

    Biele, J., Beyerle, G. and Baumgarten, G. 2000. Polarization lidar: corrections of instrumental effects. Opt. Express 7, 427-435.

    Biele, J., Tsias, A., Luo, B. P., Carslaw, K. S., Neuber, R. and co-authors 2001. Nonequilibrium coexistence of solid and liquid particles in Arctic stratospheric clouds. J. Geophys. Res. 106, 22 991-23 007.

    Blum, U. 2003. Lidarbeobachtungen der Polaren Atmospha¨re: Wolken und Wellen-Pha¨nomene und Mechanismen. PhD Thesis BONN-IR2003-11. Universita¨t Bonn, Bonn.

    Blum, U. and Fricke, K. H. 2005. The Bonn University Lidar at the Esrange: technical description and capabilities for atmospheric research. Ann. Geophys. 23, 1645-1658.

    Blum, U., Fricke, K. H., Baumgarten, G. and Scho¨ch, A. 2004. Simultaneous lidar observations of temperatures and waves in the polar middle atmosphere on the east and west side of the Scandinavian mountains: a case study on 19/20 January 2003. Atmos. Chem. Phys. 4, 809-816.

    Browell, E. V., Butler, C. F., Ismail, S., Robinette, P. A., Carter, A. F. and co-authors 1990. Airborne lidar observations in the wintertime Arctic stratosphere: polar stratospheric clouds. Geophys. Res. Lett. 17, 385-388.

    Carslaw, K. S., Kettleborough, J. A., Northway, M. J., Davies, S., Gao, R.-S. and co-authors 2002. A vortex-scale simulation of the growth and sedimentation of large nitric acid hydrate particles. J. Geophys. Res. 107, doi:10.1029/2001JD000467.

    Carslaw, K. S., Wirth, M., Tsias, A., Luo, B. P., Do¨rnbrack, A. and co-authors 1998a. Particle microphysics and chemistry in remotely observed mountain polar stratospheric clouds. J. Geophys. Res. 103, 5785-5796.

    Carslaw, K. S., Wirth, M., Tsias, A., Luo, B. P., Do¨rnbrack, A. and co-authors 1998b. Increased stratospheric ozone depletion due to mountain-induced atmospheric waves. Nature 391, 675-678.

    Crutzen, P. and Arnold, F. 1986. Nitric acid cloud formation in the cold Antarctic stratosphere: a major cause for springtime 'ozone hole'. Nature 324, 651-655.

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