Cirrus clouds in the extratropical tropopause and lowermost stratosphere region

• Applicant: Reinhold Spang, Ph.D.
• Subject Area: Atmospheric Science
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 316588738

Large uncertainties in climate prediction caused by processes involving cirrus clouds highlight the importance of more quantitative information on cirrus clouds by observations. Especially around the tropopause, where cirrus may have a large warming effect in comparison to lower and thicker cirrus only very little information is available. Ground based lidar observations and satellite based IR limb sounding are suggesting a new class of cirrus clouds, the presence of cirrus in the lowermost stratosphere (LMS), which are so far not well characterised by measurements and not considered in global models studies at all.The proposed study CiTroS will investigate Cirrus clouds in extratropical Tropopause and lowermost Stratosphere region based on measurements during the proposed HALO mission WISE in Sep/Oct 2017. Special emphasis will be taken on the analysis of measurements of cloud structures with the novel Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) instrument. With its ability to image tomographically volumes of air in the IR wavelength region 780 to 1400 cm-1, it may provide a three-dimensional reconstruction of the observed cloud structures. IR limb sounders are extremely sensitive to measure optically thin cirrus clouds due to the long limb path integration along the line of sight. In combination with the HALO-based lidar instrument WALES the payload will present the most sensitive remote sensing measurements for the characterisation of micro- and macrophysical parameter of cirrus clouds around the tropopause. Together with the in situ measurement for water vapour and ice water content the HALO mission WISE represents a high-capacity payload for cloud studies around the tropopause and enables the proof of existence for clouds in the LMS. One major part of study will be the development of new retrieval techniques for the exploration of optically thin cirrus clouds around the tropopause with the IR imager GLORIA. The analysis of the tomographic cloud measurements will make it possible to retrieve much better constrained microphysical properties like ice water content or particle radius information.Model studies and forecasts form the Chemical Lagrangian Model for the Stratosphere (CLaMS) and CLaMS will be available after the campaign for detailed studies. Research questions regarding the impact of meteorological conditions on the formation of ice particles in the extratropical tropopause und LMS region, or the relevance of mixing processes at the subtropical jet in conjunction with Rossby wave breaking events and the link to cirrus clouds in the LMS at mid and high latitudes, will be investigated. Together with the new CLaMS-Ice module, which simulates formation and evolution of cirrus clouds along trajectories with a detailed double-moment bulk microphysical scheme, it is possible to investigate in case studies very detailed the key formation processes of cirrus in the LMS and tropopause region.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1294: Atmospheric and Earth System Research with the "High Altitude and Long Range Research Aircraft" (HALO)
• Co-Investigator: Dr. Martina Krämer