Joos, Hanna, Dr.

CHN  M 18 

Universitätstrasse 16

8092 Zürich


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Additional information

Additional information


Peer-reviewed articles

  • Catto, J.L., E. Madonna, H. Joos, I. Rudeva, and I. Simmonds, 2015. Global relationship between fronts and warm conveyor belts and the impact on extreme precipitation, J. Clim, published online,
  • Martinez-Alvarado, O., E. Madonna, S. L. Gray, and H. Joos, 2015. A route to systematic error in forecasts of Rossby waves, Quart. J. Roy. Meteorol. Soc., published online, doi:10.1002/qj.2645.
  • Miltenberger, A.K., A. Seifert, H. Joos, and H. Wernli, 2015. Scaling relation for warm-phase orographic precipitation - A Lagrangian analysis for 2D mountains, Quart. J. Roy. Meteorol. Soc., 141, 2185-2198.
  • Madonna, E., M. Boettcher, C. Grams, H. Joos, O. Martius and H. Wernli, 2015. Verification of North Atlantic warm conveyor belt outflows in ECMWF forecasts, Quart. J. Roy. Meteorol. Soc., 141,1333-1344.
  • Madonna, E., S. Limbach, C. Aebi, H. Joos, H. Wernli, and O. Martius, 2014. On the co-occurence of warm conveyor belt outflows and PV streamers. J. Atmos. Sci., 71, 3668-3673.
  • Joos, H., P. Spichtinger, P. Reutter and F. Fusina, 2014. Influence of heterogeneous freezing on the microphysical and radiative properties of orographic cirrus clouds. Atmos. Chem. Phys., 14, 6835-6852, doi:10.5194/acp-14-6835-2014, PDF
  • Martinez-Alvarado, O., H. Joos, J. Chagnon, M. Boettcher, S.L. Gray, R.S. Plant, J. Methven and H. Wernli, 2014. The dichotomous structure of the warm conveyor belt. Quart. J. Roy. Meteorol. Soc., 140, 1809-1824, DOI:10.1002/qj.2276
  • Pfahl, S., E. Madonna, M. Boettcher, H. Joos, H. Wernli, 2014. Warm Conveyor Belts in the ERA-Interim Dataset (1979–2010). Part II: Moisture Origin and Relevance for Precipitation. J. Clim., 27, 27-40, DOI: 10.1175/JCLI-D-13-00223.1
  • Madonna, E., H. Wernli, H. Joos, and O. Martius, 2014. Warm conveyor belts in the ERA-Interim dataset (1979-2010). Part I: Climatology and potential vorticity evolution. J. Clim., 27, 3-26, DOI: 10.1175/JCLI-D-12-00720.1
  • Martius, O., H. Sodemann, H. Joos, S. Pfahl, A. Winschall, M. Croci-Maspoli, M. Graf, E. Madonna, B. Mueller, S. Schemm, J. Sedlacek, M. Sprenger, and H. Wernli, 2013. The role of upper-level dynamics and surface processes for the Pakistan flood in July 2010. Quart. J. Roy. Meteorol. Soc., 139, 1780-1797
  • Bornmann, L., H. Herich, H. Joos, and H.-D. Daniel, 2012. In public peer review of submitted manuscripts, how do reviewer comments differ from comments written by interested members of the scientific community? A content analysis of comments written for Atmospheric Chemistry and Physics. Scientometrics, 93, 915-929,doi:10.1007/s11192-012-0731-8, PDF
  • Joos, H., and H. Wernli, 2012. Influence of microphysical processes on the potential vorticity development in a warm conveyor belt: a case study with the limited area model COSMO. Quart. J. Roy. Meteorol. Soc., 138, 407-418, PDF
  • Joos, H., P. Spichtinger, and U. Lohmann, 2010. Influence of a future climate on the microphysical and optical properties of orographic cirrus clouds in ECHAM5. J. Geophys. Res., 115, D19129, doi:10.1029/2010JD013824, PDF
  • Quaas, O. Boucher, A. Jones, G.P. Weedon, J. Kieser, H. Joos, 2009. Exploiting the weekly cycle as observed over Europe to analyse aerosol indirect effects in two climate models. Atmos. Chem. Phys., 9, 8493-8501., PDF
  • Joos, H., P. Spichtinger, and U. Lohmann, 2009. Orographic cirrus in a future climate. Atmos. Chem. Phys., 9, 7825-7845, PDF
  • Joos, H., P. Spichtinger, U. Lohmann, J.-F. Gayet, and A. Minikin, 2008. Orographic cirrus in the global climate model ECHAM5. J. Geophys. Res., 113, D18205, doi:10.1029/2007JD009605, PDF

Submitted and under review


  • Modeling of orographic cirrus clouds, H. Joos, Diss. ETH No. 18492, 2009
  • Analyse von Aerosoleffekten: Simulation eines Wochenzyklus im globalen Klima-Aerosol-Modell ECHAM5-HAM, H. Joos, Diplomarbeit, Max-Planck-Institut für Meteorologie, Hamburg, 2006

Research Interests

My main research interest is on the diabatic modification of the atmospheric flow with a special focus on warm conveyor belts.

Warm conveyor belts (WCBs) are strongly ascending airstreams within extratropical cyclones. They originate in the warm sector of the cyclone and ascend until the upper troposphere. During the ascent, clouds are forming. Thus, WCBs can be seen on satellite pictures as an elongated cloud band ahead of the cold front (see figure 1). During the cloud formation many microphysical processes like condensation, freezing or depositional growth (direct transfer from gas to solid) occur. These processes lead to the release of latent heat which further enhances the WCB ascent.

The latent heat release in the ascending airstream can modify the potential vorticity (PV). In a first order, PV is produced below the maximum heating and destroyed above. Thus, a WCB produces a positive PV anomaly in the mid-troposphere and a negative anomaly in the upper troposphere. These PV anomalies which are produced or enhanced by microphysical processes have the potential to modify the large-, as well as the meso-scale flow and might also be important for the evolution of the cyclone.

In figure 2, trajectories representing a WCB in January 2009 (same WCB as on satellite picture) are shown.

Figure 1 - Meteosat SEVIRI Infrared Satellite Image valid for 06 UTC 30 January 2009 (Taken from
Figure 1 - Meteosat SEVIRI Infrared Satellite Image valid for 06 UTC 30 January 2009 (Taken from

Figure 2 - Trajectories representing the WCB
Figure 2 - Trajectories representing the WCB. Colours denote the pressure and black lines the sea level pressure.

In figure 3, a vertical cross section through the WCB at 38°N is shown. The results are obtained with the NWP-model COSMO. The colors denote the latent heat release that occurs in a WCB due to the different microphysical processes. It can be seen that the main processes contributing to the latent heating are the condensation of cloud water and the depositional growth of snow. Further interesting features are the cooling regions below the cloud. The cooling regions form when the sedimenting hydrometeors, rain or snow, start to sublimate/evaporate below cloud base in sub-saturated air. Thus, the WCB does not only produce areas with strong latent heat release but also areas where a strong cooling occurs.

Figure 3 - Vertical Cross Section at 38° North through the WCB - The colours denote the latent heat release, grey lines the isentropes, green lines 99% relative humidity with respect to water (solid) and with respect to ice (dotted), and the black line the 0° C isotherm
Figure 3 - Vertical Cross Section at 38° North through the WCB - The colours denote the latent heat release, grey lines the isentropes, green lines 99% relative humidity with respect to water (solid) and with respect to ice (dotted), and the black line the 0° C isotherm.

Another research interest is on cirrus clouds. These are clouds that consist purely of ice crystals and have the potential to strongly modify the Earth radiative budget. Depending on their microphysical properties like the ice water content or the ice crystal number concentration, they can lead to a cooling or warming. The microphysical properties are in turn determined by the dynamical forcing and the thermodynamical environment. The vertical velocity under which the cloud forms, strongly determines the ice crystal number concentration. The relative humidity with respect to ice has also an influence on the ice crystal number concentration but also on the ice water content of the cloud. This complicated interaction of dynamical and thermodynamical processes on different scales is not fully understood. Therefore it is important to investigate the formation mechanisms of cirrus clouds as well as their representation in climate models.

Course Catalogue

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