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Cloud microphysicsClaudia Emde
Meteorological Institute, LMU, Munich, Germany
WS 2011/2012
Introduction Contents References Atmospheric thermodynamics
Cloud formation and cloud dynamics
Cloud movies by B. Mayer
Cloud microphysics October 20, 2011 2 / 16
Introduction Contents References Atmospheric thermodynamics
Cloud types
http://www.wolkenatlas.de/
Cloud microphysics October 20, 2011 3 / 16
Introduction Contents References Atmospheric thermodynamics
Rain drops
Villermaux et al. Nature Physics, 2009Cloud microphysics October 20, 2011 4 / 16
Introduction Contents References Atmospheric thermodynamics
Ice crystals
In situ measurements ofice crystals in a tropicalcirrus cloud
Heymsfield et al., Journal ofAtmospheric Sciences, 2002
Cloud microphysics October 20, 2011 5 / 16
Introduction Contents References Atmospheric thermodynamics
Snow flakes
www.snowflakes.com by K.G. Libbrecht
Cloud microphysics October 20, 2011 6 / 16
Introduction Contents References Atmospheric thermodynamics
Energy balance of the Earth
IPCC report, 2007
Cloud microphysics October 20, 2011 7 / 16
Introduction Contents References Atmospheric thermodynamics
Impact of clouds on climate change
IPCC report 2007Cloud microphysics October 20, 2011 8 / 16
Introduction Contents References Atmospheric thermodynamics
IPCC Bericht 2007
Ringer et al., GRL 2006
“Cloud feedbacks (particularlyfrom low clouds) remain thelargest source of uncertainty.”IPCC Report 2007, Technical Summary
Cloud microphysics October 20, 2011 9 / 16
Introduction Contents References Atmospheric thermodynamics
Overview of cloud physics
Atmospheric thermodynamicsMicrophysics of warm clouds
Nucleation of water vapor by condensationGrowth of cloud droplets in warm clouds (condensation, fall speedof droplets, collection, coalescence)formation of rain
Microphysics of cold cloudshomogeneous nucleationheterogeneous nucleationcontact nucleationcrystal growth (from water phase, riming, aggregation)formation of precipitation
Observation of cloud microphysical propertiesParameterization of clouds in climate and NWP models
Cloud microphysics October 20, 2011 10 / 16
Introduction Contents References Atmospheric thermodynamics
Literature
John M. Wallace and Peter V. Hobbs. Atmospheric Science, Anintroductory survey. Elsevier, 2006.
R. R. Rogers. A short course in cloud physics. Pergamon Press,1976.
Hans R. Pruppacher and James D. Klett. Microphysics of clouds andprecipitation. Springer, 1996.
IPCC. Climate change 2007. Technical report, IntergovernmentalPanel of Global Climate Change, 2007.
Additional publications and slides on website:www.meteo.physik.uni-muenchen.de/~emde/doku.php?id=
teaching:cloud_microphysics:cloud_microphysics
Cloud microphysics October 20, 2011 11 / 16
Introduction Contents References Atmospheric thermodynamics
Exam
Written exam in last week of semester: 9th February 2012, 14-16 h
Please let me know if date is inconvenient!
Cloud microphysics October 20, 2011 12 / 16
Introduction Contents References Atmospheric thermodynamics
Gas laws and the ideal gas equation
Sir Robort Boyle (1627–1691) Jacques Charles (1746–1823)
pV = mRT pα = RT pV = nR∗T p = n0kT
John Dalton(1766–1844)
Amedeo Avogadro(1776–1856)
Ludwig Boltzmann(1844–1906)Images from Wikipedia
Cloud microphysics October 20, 2011 13 / 16
Introduction Contents References Atmospheric thermodynamics
The hydrostatic equation
Figure from Wallace and Hobbs
∂ p∂ z
= −gρ gdz = −αdp
Sir Issac Newton (1642–1727)Image from Wikipedia
Cloud microphysics October 20, 2011 14 / 16
Introduction Contents References Atmospheric thermodynamics
First law of thermodynamics
Figure from Wallace and Hobbs
energy conservation
dq = du + dwdq = du + pdαdq = cpdT − αdp· · ·
Cloud microphysics October 20, 2011 15 / 16
Introduction Contents References Atmospheric thermodynamics
Adiabatic processes
adiabatic = change in physical state without heat exchange⇒ dq = 0
Figure from Wallace and Hobbs
dq = du + pdα
T rises in adiabaticcompressionT=const. in isothermalprocess
TC > TB ⇒ pC > pB
Cloud microphysics October 20, 2011 16 / 16