Particles and Cirrus Clouds (PAZI-2)


PAZI-2 is a national project funded by DLR (German Aerospace Center) and supported by the Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF). It is a vital part of the Institute of Atmospheric Physics' (IPA) contribution to DLRs aviation and space program.

The main goal of PAZI-2 is to better understand the formation of the ice phase in cirrus clouds from natural and anthropogenic aerosols and to improve microphysical and optical parameterizations of cirrus clouds in global models. This will allow us to determine the impact of aviation soot-induced cirrus and contrail cirrus relative to cirrus formed on particles from other anthropogenic and natural sources and to (i) compare the climate impact from aviation with the climate impact caused by other atmospheric changes and (ii) develop means to reduce the aviation impact through changes in engine technology or air traffic management.

To understand the possible aviation impact on clouds, it is important to distinguish two effects.

Direct effect (contrail-cirrus). Linear and spreading contrails, initially formed from exhaust water vapor and particles, constitute and additional cloud type and enhance cirrus cloud coverage. Initial contrail occurrence relies on well understood thermodynamic principles, initial contrail properties depend on soot and sulfur emissions and near-field exhaust (jet/vortex) dynamics. The spreading process of persistent contrails is controlled by wind shear and relative humidity. Contrail-cirrus are advected with the wind field over large distances, even into regions without significant air traffic. The direct effect is largest in regions without background cirrus.

Indirect effect (soot-induced cirrus). Soot particles associated with aqueous coatings of sulfur and organics are emitted together with gaseous sulfur oxides and may perturb cirrus formation processes and cirrus coverage on regional scales. The perturbation depends on the ice-forming ability of coated soot particles that interact with ambient air, on the ability of other atmospheric particles to form ice, and on dynamic processes that set the stage for the generation of cirrus clouds in supersaturated regions. Coagulation of soot and sulfur particles in diluting aircraft wakes changes the size distribution and the chemical composition of aerosol particles available for freezing. The indirect effect is less important in regions where cloud forms on more efficient ice nuclei than aircraft soot.
It is important to recognize that contrail-cirrus also imply an indirect effect on cirrus. If cirrus clouds form in the presence of aged contrail-cirrus, the cirrus may have different properties because its crystals nucleate in regions with preexisting ice. When embedded in background cirrus, contrail-cirrus may compete with background cirrus for the available water vapor, altering its microphysical and optical properties.
The following workflow diagram summarizes the project structure designed to achieve the project goal.

A comprehensive aerosol-cloud module is set up in the climate model ECHAM to predict global aerosol distributions and their impact on clouds, and two airborne field campaigns are carried out (CirrusCloudExperiment CIRCLE-1/-2) in 2005 and 2006 to study aerosol-cirrus interaction and radiative properties in more detail. The PAZI-2 team also participates in the TROCCINOX project and the LAUNCH campaign organized by the German Weather Service (DWD) in Lindenberg near Berlin. The measurements are complemented by process-oriented modeling. Global modeling is supported by efforts to provide parameterization schemes of subgrid-scale processes controlling cirrus formation and coverage as well as radiative impact. Basic soot formation and oxidation properties are studied with the help of laminar flame burners and kinetic soot models. Aircraft-type soot particles are experimentally characterized in a high pressure combustion chamber test facility, and a module predicting soot particle properties in jet engines is developed. Further activities include the construction of a new global 4D aircraft soot inventory, a new European high cloud climatology, and freezing experiments using insoluble aerosol particles (soot, dust) in the Karlsruhe aerosol-cloud chamber AIDA with close-to-atmospheric conditions.

General Information

Research in this project is performed within DLR (Institut für Physik der Atmosphäre, IPA Oberpfaffenhofen, Institut für Verbrennungstechnik, Stuttgart, and Institut für Antriebstechnik, Köln) and with associated partners from Forschungszentrum Karlsruhe (FZK, IMK-AAF), Forschungszentrum Jülich (FZJ, ICG-1), and the Alfred-Wegener-Institut Bremerhaven (AWI). Further partners actively joining the project include the University of Mainz, Max-Planck-Institut für Chemie, Max-Planck-Institut für Meteorologie, Max-Planck-Institut für Kernphysik, Stockholm University, ETH Zürich, KNMI DeBilt, ECMWF Reading, IPSL/CNRS, and LaMP/CNRS.

Some externally-funded projects are partly co-funded by PAZI-2, such as the EU-projects PARTS (ending 2004), SCOUT-O3 (started May 2004), and QUANTIFY (started March 2005). PAZI-2 is recognized as a German contribution to the CORSAIRE cluster (Coordination of Research for the Study of Aircraft Impact on the Environment). The CORSAIRE activity is coordinated by the European Ozone Research Coordinating Unit, Cambridge, UK. PAZI-2 contributes to the COSMOS (Community Earth System Models) initiative within its aerosol working group; COSMOS is devoted to the development of an Earth System Model framework under the lead of MPI Hamburg. 

The CIRCLE-2 campaign addresses optical properties of aerosols and cirrus clouds and will be carried out in concert with our French colleagues, establishing a potentially fruitful DLR/CNES (Centre National d'Etudes Spatiales) collaboration on this issue. The French partners (J.-F. Gayet, J. Pelon et al.) have set up a CNES research project concerning the validation of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) products. The CALIPSO mission is led and managed by NASAs Langley Research Center for the NASA Earth System Science Pathfinder (ESSP) program and collaborates closely with CNES, Ball Aerospace and Technology Corporation, Hampton University, VA, and the Institut Pierre Simon Laplace (IPSL) in France. Coordinated CIRCLE-2 and CALIPSO flights will address the validation of level 2 products in fall 2006, the exact mission time depends on the actual launch date.  During the LAUNCH campaign, the goal is to carry out airborne measurements of the spreading of persistent contrails along with the microphysical and optical characteristics of developing contrail-cirrus. This will support cloud- and mesocale simulations of contrail-cirrus within PAZI-2. More detailed information on all atmospheric measurements of the PAZI-2 project are offered at the PAZI-FALCON webpage.

PAZI-2 started January 2004 and will end December 2007. It is a follow-on project that continues the work from the PAZI-project which was funded over a three-years period from July 2000 until June 2003 (see PAZI project plan and final report, both in German). The final report includes a list of publications 2000-2003. A concise summary of PAZI results is available from:

B. Kärcher et al., Particles and cirrus clouds (PAZI) - Overview of results 2000-2003. In: Proceed. European Workshop Aviation, Aerosols and Climate, R. Sausen and G.T. Amanatidis (Eds.), Air Pollution Research Report No. 83, Commission of the European Communities, 197-206, 2004.

The PAZI-2 project structure contains, besides a management workpackage, three main workpackages (HAP) and a number of workpackage activities (AP). Each AP is led by one Principal Investigator, as inidcated below. Overall coordinator is Prof Bernd Kärcher (contact). 

       HAP 1        Soot emissions                                                          PI
                            AP 1.1        Measurement and modeling                P. Gerlinger                   
                            AP 1.2        Global aircraft soot inventory               M. Plohr
       HAP 2        Aerosols and cirrus clouds
                            AP 2.1        In situ measurements                            A. Minikin
                            AP 2.2        Aerosol precursor gases                      H. Schlager
                            AP 2.3        Remote sensing with satellites             H. Mannstein
                            AP 2.4        Freezing experiments                           O. Möhler
       HAP 3        Climate
                            AP 3.1        Cirrus formation processes                  B. Kärcher
                            AP 3.2        Radiative processes                              B. Mayer
                            AP 3.3        Contrail-cirrus                                         K. Gierens
                            AP 3.4        Global modeling                                    J. Hendricks

The PAZI-2 project plan, including milestones and detailed workpackage descriptions, is available here (in German). The overall budget of PAZI-2 amounts to ~9.5 Mio. € (DLR contribution only).

Project reports

Minutes of the 1st Annual Meeting, Oberpfaffenhofen, 5./6. April 2004

Minutes of the 2nd Annual Meeting, Oberpfaffenhofen, 17./18. January 2005

Minutes of the 3rd Annual  (Mid-Term) Meeting, Oberpfaffenhofen, 27. January 2006

Flyer Midterm Results Summary

Minutes of the 4th Annual  Meeting, Oberpfaffenhofen, 30. January 2007

Final colloquium, Oberpfaffenhofen, 14 February 2008

Final report including list of publications (2004-2007)

DLR-Mitteilung 2008-01