Leipzig Graduate School for Clouds, Aerosol & Radiation:

Mineral Dust

A. Macke, IfT Leipzigpresented by H. Herrmann, IfT Leipzig

Berlin, 23.09.2011

Leipzig Graduate School

● A Leibniz Graduate School on Atmospheric Research● Integrating expertise in atmospheric research in Leipzig at the

University and the IfT together with University expertise from physics and chemistry

● University partners: Leipzig Meteorology (LIM) Profs. Haase and Grundmann (Physics Faculty) Prof. Abel (Physical Chemistry, Chemistry Faculty)

● Leibniz Partner: IfT Leipzig with all its three departments

● Combining structured and cross-compartimental Ph.D. education with research at a frontline atmospheric sciences topic – mineral dust

The research: Why care about mineral dust ?

● Atmosphere radiation water cycle chemistry

● Health air quality, bacteria

● Economy transportation solar energy

● Climate desertification

● Fertilization ocean & land

The Leipzig Graduate School

Global Modelling(Quaas)

Clouds & Radiation

(Wendisch)

Microwave Remote Sensing

(Pospichal)

Physical Chemistry

(Abel)

Solid State Physics (Haase,

Grundmann)

Leipzig University Research Groups

Non-spherical Dust

Absorbing Dust

Cloud and Dust Particle Interaction

Dust Surface

Chemistry

Dust and Ice

Formation

Projects

Topic

Clouds & Radiation(Macke)

Regional Modelling

(Tegen)

Vis & IR Remote Sensing

(Ansmann,Deneke)

Cloud Laboratory(Stratmann)

Multiphase Chemistry

(Herrmann)

IfT Research Groups

Polarization in radiative transfer in modeling and observations

● Non-spherical (mineral dust, vulcanic ash, ice crystals, ...) particles polarize light in a characteristic manner

● Active/passive polarized remote sensing offers new and largely unexplored detection possibilities

● Objectives Heterogeneous ice formation (mandatory condition for precipitation

in mid latitudes) determine volcanic ash concentration determine the effect of Saharan mineral dust on cloud formation and

microphysics over the Atlantic Ocean distinguish mineral dust from biomass burning and other aerosols

Polarization Lidar

4 Feb 2008, SAMUM 2, Cape Verde

Time (UTC = Local Time)

depolarization ratio: liquid water0.0

ice0.4-0.6

mineral dust 0.3 biomass burning

aerosol 0.02

marine particles 0.01

● Absorbing aerosol (soot, mineral dust) affects climate by heating the atmosphere, changing cloudiness and circulation

● Net effect strongly depends on vertical placement of aerosol layers; it is expected to be warming but offsetting effects exist

● Objectives Quantification of aerosol absorption (including mineral dust as natural

background) in climate models Characterization of altitude and placement of aerosol layers with

respect to clouds Assessment of climate effects by aerosol-climate modeling

Absorbing Aerosols: Effect on atmospheric dynamics and cloud properties

Satellite data analysis (A-Train): Anthropogenic absorbing aerosol forcing

Albedo enhancement

Albedo reduction

Seasonal mean TOA absorption effect

[Wm-2]

Peters, Quaas, Bellouin, ACP 2011

Brightness effected by absorbing aerosols regional to global distribution

Indirect aerosol effect: diagnostics from combination of ground and satellite data

● Amount in type of aerosol particles effect size and concentration of cloud droplets and thus cloud brightness (first indirect aerosol effect, Twomey effect)

● Passive satellite measurements of cloud particles and cloud brightness very indirect and uncertain

● Increasing load of mineral particles from various sources ● Objectives

Combine active and passive ground and satellite based observations to more accurately determine the indirect aerosol effect

Identify and analyze situations with mineral dust advection over measurement site Leipzig

Cloud radiative effects

illustrativeexample: ship tracks

Heterogeneous chemistry at (modified) mineral dust surfaces

● Mineral Dust is an active player in atmospheric composition change● Trace gases can be taken up at the surface and undergo chemical change● Key components of mineral dust are suspected to be photocatalysts:

surface-bound OH available (!)

● Objectives Investigate uptake of key atmospheric tracegases (NOx, SO2,

Organics) und realistic conditions (T, RH) Study chemical processing directly Deliver key process parameters (Reaction rates, uptake and mass

accommodation coefficients)

Knudsen Cell – IfT Chemistry

Pressure: 10-5 bis 10-3 mbar = mean free pathlength of molecules is bigger than the cell dimension = there are mainly gas-surface collisions rather than gas-gas collisions

Determination of (reactive) uptake-coefficients γRate constants Detection limit: 1010 molec cm-3

T Range: -140 bis 425 °C

Movable stamp Gas inlet

To analytics

Sample holder

Equip with illumination of target to study heterogeneous photochemical reactions

13/30

Physical Chemistry – Abel: Detection and chemical investigation of tropospheric particles and of reactions near their interfaces

• AFM on mineral particles, together with local Raman spektroscopy (TERS). With this method, chemical conversions on nano-particles (and on nano-particles coated with ice) can be investigated

• Röntgen microscopy at BESSY

• Photoelectron spektroscopy (ESCA) to follow reactions in a time-resoved manner on wet mineral nanoparticles embedded into a micro water jet (for the study of reactions near the water-interface) or on solid interfaces and surfaces.

• Measuring the kinetics of chemical reactions with/without the presence of mineralic nanoparticles by time-resolved spectrocopic method in a Laval nozzle experiment (alternatively by dispersion by ultrasound)

Mass Spectrometry Imaging (MSI) und chemische Analyse von Nanoteilchen

Heterogeneous ice nucleation and solid state physics

● Heterogeneous ice nucleation at mineral dust particles is one of the most important ice formation processes in the atmosphere

● Heterogeneous ice formation not well understood because of the insufficiency of existing techniques concerning the in-situ

observation of ice nucleation processes the distinction between ice and water on micrometer scales, as well as

mass, and mass growth measurements are not possible● Objectives

Adapt a temporally high resolution Streak camera to directly infer ice formation and growth for individual drops and defined ice nuclei (dust particles)

Establish the nuclear magnetic resonance technique to determine ice mass

Leipzig Aerosol Cloud Interaction Simulator (LACIS)

NMR spectra forwater and ice

StreakCamera

Leipzig Graduate School cross cutting / connectivity

Work Packages

Non-spherical Dust

Absorbing Dust

Cloud and Dust Particle Interaction

Dust Surface Chemistry

Dust and Ice Formation

Non-spherical Dust

vertical structure, model eval.

cloud particle modification

non-sphericity & surface chemistry

ice formation & atm. condition

Absorbing Dust

correlate absorption & polarization

dust entraine-ment & ice formation

identify dust contact with cloud drops

semidirect vs indirect aerosol effect

Cloud and Dust Particle Interaction

cloud bottom & top properties

top-of-cloud dust from obs, cloud props

macroscopic cloud props & chemistry

cloud life cycle & ice formation

Dust Surface Chemistry

polarization by surface films

change in absorption by surface mod.

ice formation, activation of advected dust

chemistry at ice surfaces

Dust and Ice Formation

ice formation in the polari-zation signal

ice formation after dust entrainement

ice formation in dust plumes

surface modi-fication and ice formation

Leipzig Graduate School Structure

● Accompanying lectures from Master modules in Meteorology, Chemistry, Solid State Physics

● Ring-lecture of supervisors on recent research results● Supervisor team for each PhD student● Active participation in relevant international conferences and summer schools● Workshops jointly with supervisor teams● PhD-only workshop, Supervisor-only workshop● Participation in IfT/LIM PhD seminar● 3 month visit at specified guest institutes● Participation in “Research Academy Leipzig”● Family- and dual-career friendly work conditions

Leipzig long term perspectives

● Establish the “Leipzig Center for Clouds, Aerosols and Radiation”● Open paths for joint University-Leibniz Research & Teaching

Share laboratories Combine knowledge create Leibniz/university supervisor teams

● Follow-Up Graduate School on “Clouds, Aerosols and Radiation” with new focus

● Basis for a Leibniz-Campus jointly with Leipzig University