Vivek Sant Group Meeting

ECHAM activities – Ulrike Lohmann’s group

1February 1, 2011

• Sylvaine Ferrachat: Maintainance of ECHAM6-HAM and previously developed aspects (entrainment, PBL clouds, shallow convection)

• Philipp Reutter/Betty Croft: aerosol processing and scavenging of aerosols

• Ana Sesartic: bioaersols and their possible importance as ice nuclei (IN)

• Vivek Sant: drizzle and giant CCN• Miriam Kübbeler: heterogeneous vs. homogeneous

freezing in cirrus clouds• Sebastian Bretl: possible influence of aerosols on

tropical cyclones

Reference scavenging ratios changed following a study in the Arctic study by Bourgeious and Bey (2011).

Impact of wet scavenging on global aerosol and cloudproperties in ECHAM5 (Philipp Reutter)

Less cloud droplet number burden and less soluble nucleation and Aitken mode particles when scavenging ratios are reduced

Mechanism: Initially more aerosol particles. Nucleation of new particles impeded, more condensation of SO4

and organics on pre-existing particles. Coagulation and less new particle formation lead to a reduction

of the number mixing ratio of smallest modes.

Impact on clouds & radiation • small global impact

• regional impact suspected

Possible future research• models with dynamic

vegetation• regional modelling

• observations & lab studies

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Bacteria and fungal spores in ECHAM (Ana Sesartic)

Vivek Sant Group Meeting

Introducing a drizzle class in ECHAM5 (Vivek Sant)

5

today

future

Courtesy of R. Posselt

February 1, 2011

Bretherton et al., 2001

Impact of aerosols on cirrus clouds (Miriam Kübbeler)

Kärcher et al., JGR, 2006

Impact of aerosols on cirrus clouds (Miriam Kübbeler)

Influence of aerosols on hurricanes? (Sebastian Bretl)