Improved MIPAS Classification of Polar Stratospheric Cloud Types: Methodology, Validation, and Applications
Spang, Reinhold1; Griessbach, Sabine2; Grooß, Jens-Uwe1; Hoffmann, Lars1; Müller, Rolf1; Höpfner, Michael3; Fromm, Mike4; Pitts, Mike5; Poole, Lamont5
1Forschungszentrum Jülich, GERMANY; 2Forschungszentrum Jülich, Jülich Supercomputing Centre, GERMANY; 3Karlsruher Institut für Technologie, IMK, GERMANY; 4Naval Research Laboratory, UNITED STATES; 5NASA Langley Research Center, UNITED STATES
The MIPAS instrument onboard the ESA Envisat satellite operated from July 2002 to April 2012. The infra-red limb emission measurements compile a unique dataset of day and night measurements of polar stratospheric clouds (PSC) up to the poles. Cloud detection sensitivity is similar to space borne lidars, and it is possible to classify different cloud types (NAT, STS, and ice) from the spectral measurements.
In this paper we present improvements of the well established PSC classification scheme based on two color ratios which was originally developed by Spang and Remedios (2003), improved by Hopfner et al. (2006), and of more recent methods developed during the ESA funded MIPclouds study (Spang et al., 2012). The original method allows discriminating clouds dominated by small NAT particles or ice clouds with high volume density from STS and mixed type clouds. Here we will describe limitations and refinements of the old scheme as well as a more sophisticated classification by a multi brightness temperature difference (BTD) approach based on 2D probability density functions in conjunction with radiative transfer model calculations of realistic PSC particle size distributions.
Results for various northern and southern hemisphere winters will be presented. The temporal evolution of the PSC types with respect to the temporal development of the meteorological conditions of the polar vortex is investigated with special emphasis on the NH winter 2009/10, when the RECONCILE campaign took place. Comparison with the CALIPSO lidar, coincident airborne in situ and remote sensing measurements, and the modeled PSC distribution of Chemical Lagrangian Model of the Stratosphere (CLaMS) are planned. The processing and analysis of the complete and unique MIPAS data set of almost 10 years of PSC observations are work in progress.
Hopfner, M., et al., Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds, Atmos. Chem. Phys., 6, 1201-1219, doi:10.5194/acp-6-1201-2006, 2006.
Spang R. and Remedios, J., Observations of a distinctive infrared spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument, Geophys. Res. Lett., 30, 1875, doi:10.1029/2003GL017231, 2003.
Spang, R., Arndt, K., Dudhia, A., Hopfner, M., Hoffmann, L., Hurley, J., Grainger, R. G., Griessbach, S., Poulsen, C., Remedios, J. J., Riese, M., Sembhi, H., Siddans, R., Waterfall, A., and Zehner, C.: Fast cloud parameter retrievals of MIPAS/Envisat, Atmos. Chem. Phys., 12, 7135-7164, doi:10.5194/acp-12-7135-2012, 2012.