Middle and Upper Atmosphere

Group Leader: Hauke Schmidt

 

Our aim is to better understand how dynamical, physical and chemical processes operate and interact within the stratosphere, mesosphere and lower thermosphere, and how they couple to surface climate. Of particular interest for us is the susceptibility of the middle atmosphere to external factors as for instance greenhouse gases, solar activity, and stratospheric aerosols. We compare these influences to natural variability, and study to what extent they provide a contribution to climate predictability. The interest in volcanic aerosols and their effects has prompted our studies in the field of climate engineering.

 

For many decades it was assumed that vertical coupling in the atmosphere is efficient only in the upward direction. Today also downward coupling processes are discussed that imply a middle atmosphere influence on tropospheric climate. With respect to this topic we strongly benefit from the close collaboration with the Minerva group of Elisa Manzini on “Stratosphere and Climate” (STC).

 

In our studies, different numerical models based on the ECHAM atmospheric general circulation model are used. Depending on the question these are either the standard version of ECHAM6 reaching up to the mesosphere, eventually integrated in the MPI-Earth System Model MPI-ESM, ECHAM-HAMMOZ (i.e. ECHAM coupled to the Aerosol module HAM and/or the MOZART chemistry module), or the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). The latter is an upward extension of ECHAM into the thermosphere.

 

 

 

Selected recent publications:

 

Bunzel, F., and H. Schmidt, 2013: The Brewer-Dobson Circulation in a changing climate: Impact of the model configuration, J. Atmos. Sci., 70, 1437-1455, 2013.

Miller, A., Schmidt, H., & Bunzel, F., Vertical coupling of the middle atmosphere during stratospheric warming events. J. Atmos. Solar-Terr. Phys., 97, 11-21, 2013.

Misios, S. and H. Schmidt: The role of the oceans in shaping the tropospheric response to the 11-year solar cycle, Geophys. Res. Lett, 40, 6373-6377, 2013.

Niemeier, U., H. Schmidt, K. Alterskjær and J. E. Kristjánsson:  Solar irradiance reduction via climate engineering: Impact of different techniques on the energy balance and the hydrological cycle, J. Geophys. Res., 118, 12195–12206, 2013.

Schmidt, H., K. Alterskjær, D. Bou Karam, O. Boucher, A. Jones, J. E. Kristjansson, U. Niemeier, … and C. Timmreck: Solar irradiance reduction to counteract radiative forcing from a quadrupling of CO2: climate responses simulated by four earth system models, Earth Syst. Dynam., 3, 63-78, 2012.

Schmidt, H., Rast, S., Bunzel, F., Esch, M., Giorgetta, M. A., Kinne, S., Krismer, T., Stenchikov, G., Timmreck, C., Tomassini, L., & Walz, M.: The response of the middle atmosphere to anthropogenic and natural forcing in the CMIP5 simulations with the MPI-ESM. Journal of Advances in Modeling Earth Systems, 5, 98-116, 2013.

Timmreck, C.: Modeling the climatic effects of volcanic eruptions, Wiley Interdisciplinary Reviews: Climate Change, 3, 545-564, 2012.

Timmreck, C., Graf, H.-F., Zanchettin, D., Hagemann, S., Kleinen, T., & Krüger, K.: Climate response to the Toba super-eruption: regional changes. Quaternary International, 258, 30-44, 2012.