importance of clouds - eth zmotivationcloud types extra importance of clouds electricity aqueous...

Motivation Cloud types Extra

Importance of clouds

electricityaqueous

chemistry

clouds & precip

+ aerosols

hydrological

cycle

life ocean

latent heat

+ loadingdynamics

radiation

climate

Ulrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 1 / 39


Global mean energy budget [W m−2]Incoming solar

340Thermal outgoing

239

Thermal outgoing199

Solar absorbed

79

Solar downsurface

185

Up surface398

Down surface342

Absorbed solar161

Latentheat84

Sensibleheat20

Solar re�ected by clouds, aerosol and gases

76 Atmospheric window

40

Solar re�ected100 TOA

Earth`s surface

Greenhousegases

Atm

osph

ere

Imbalance1

Imbalance1

24

Fig. 11.1 (Lohmann et al., 2016)



Cloud radiative effect (CRE) & precipitation

IPCC, AR5, Fig. 7.7: Annual mean CRE (2001-2011) from CERES satellite data and precipitation (1981-2000) from GPCP

(Boucher et al., 2013)



Robust cloud responses to greenhouse warming

Equator 30º Pole60º

Broadening of the Hadley Cell

Rising of the Melting Level

More Polar Clouds

Poleward Shift of Storms

Less Low Clouds

Narrowing of Tropical Ocean Rainfall Zones

Rising High Clouds

Rising High Clouds

IPCC, AR5, Fig. 7.11 (Boucher et al., 2013)



Summary of different cloud types

Fig. 1.3 (Lohmann et al., 2016)



Cloud types

I Cumulus (Cu): vertical development

I Stratus (St): layered cloud

I Cirrus (Ci): ice clouds

I Low base with vertical extent: Cu, Cb, Ns

I Low base and layered (0-2 km1): St, Sc

I Mid level clouds (2-7 km): As, Ac

I High altitude ice clouds (5-13 km): Ci, Cs, Cc

1heights refer to mid latitudesUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 8 / 39


Cloud type exercise

Take 10 minutes to discuss with your neighbor:

I What cloud type is that?

I Which synoptic situation could have caused its formation?

I Is it composed of cloud droplets or ice crystals?

I Will it form precipitation?

I Does it predominantly cool or warm the Earth surface?

Sources:

I Karlsruher Wolkenatlas: http://www.wolkenatlas.de

I Mainzer Wolkenbildergalerie:

http://www.cloudgallery.mpich.de/index_1.htm

I Houze’s cloud atlas: http://www.atmos.washington.edu/Atlas/


http://www.wolkenatlas.de

http://www.cloudgallery.mpich.de/index_1.htm

http://www.atmos.washington.edu/Atlas/


Altocumulus (Ac): gray or white broken sheets, elements, bands, rounded masses



Stratus (St): very low, gray, uniform layer (sun outline very distinct when visible)



Cumulus (Cu): white, detached, dense elements with shape outlines and vertical

growth



Cumulus (Cu): white, detached, dense elements with shape outlines and vertical

growthUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 12 / 39


Cirrocumulus (Cc): thin, white sheet or patch without shading composed of very

small ripples, grains



Cirrocumulus (Cc): thin, white sheet or patch without shading composed of very

small ripples, grainsUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 13 / 39


Nimbostratus (Ns): gray, dark, diffuse, uniform cloud with steady precipitation



Cirrostratus (Cs) with 22◦ halo: thin, white, translucent veil either fibrous or

smooth in appearance (halo)



Cumulonimbus (Cb): very deep, dense and precipitating with flattened top



Stratocumulus (Sc): low, gray-white, patch or layer with elements, rolls or

rounded masses



Cirrus (Ci): detached, white, filaments or patches with fibrous appearance or

silky sheen



Altostratus (As): uniform or striated gray/blue sheet (no halo but sun behind

grounded glass)



Banner cloud: A cloud plume often observed to extend downwind from isolated,

sharp, often pyramid-shaped mountain peaks, even on otherwise cloud-free days



Banner cloud: A cloud plume often observed to extend downwind from isolated,

sharp, often pyramid-shaped mountain peaks, even on otherwise cloud-free daysUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 20 / 39


Fog: Water droplets suspended in the atmosphere in the vicinity the earth’s

surface that affect visibility



Contrail: A cloud like streamer frequently observed to form behind aircraft flying

in clear, cold, humid air



Cb penetrates cirrus: Wind shear above the anvil cause the upper part of the

anvil to be transported to the left



Cb penetrates cirrus: Wind shear above the anvil cause the upper part of the

anvil to be transported to the leftUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 23 / 39


Chaotic sky



Mother-of-pearl cloud or polar stratospheric cloud: Thin cloud between 20-30 km

altitude



Mother-of-pearl cloud or polar stratospheric cloud: Thin cloud between 20-30 km

altitudeUlrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 25 / 39


Kelvin-Helmholtz wave cloud: Kelvin-Helmholtz instability can occur when

velocity shear is present within a continuous fluid or, when there is sufficient

velocity difference across the interface between two fluids. It’s manifested in form

of waves.



Roll cloud: relatively rare type of arcus cloud.

Arcus cloud: low, horizontal cloud formation associated with the leading edge of

thunderstorm outflow, or occasionally with a cold front even in the absence of

thunderstorms.



Roll cloud: relatively rare type of arcus cloud.

Arcus cloud: low, horizontal cloud formation associated with the leading edge of

thunderstorm outflow, or occasionally with a cold front even in the absence of

thunderstorms.Ulrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 27 / 39


Asperatus cloud: rare, newly recognized cloud formation. Asperatus (roughened

or agitated waves) are related to undulatus (wavy bases) clouds. They appear

dark and storm-like, but tend to dissipate. Particularly common in the US Plains

during morning or midday after thunderstorms.



Asperatus cloud: rare, newly recognized cloud formation. Asperatus (roughened

or agitated waves) are related to undulatus (wavy bases) clouds. They appear

dark and storm-like, but tend to dissipate. Particularly common in the US Plains

during morning or midday after thunderstorms.Ulrike Lohmann (IACETH) Physics and Dynamics of Clouds and Precipitation Sept 19, 2017 28 / 39


Noctilucent cloud: can be found around 75-85 km (just below the mesopause)

over the summer pole between 50-70◦ N/S. They can only be observed when the

Sun is below the horizon.

Picture courtesy Blaz Gasparini



Schematic of layer clouds

Houze’s cloud atlas: www.atmos.washington.edu/Atlas/


www.atmos.washington.edu/Atlas/


Stratus cloud cover

Figure: Stratus cloud cover averaged over 1983-1990 from the International

Satellite Cloud Climatology Project (ISCCP)



Importance of microphysics for stratus



Importance of microphysics for stratus

Durkee et al., J. Atmos. Sci., 2000



Importance of dynamics for stratus

Klein and Hartmann, J. Atmos. Sci., 1993



Schematic of cumulus clouds

Houze’s cloud atlas



Schematic of mid-level clouds




Schematic of cirrus clouds




Importance of dynamics for cirrus (Fig. 5.29 Houze, 1993)



Importance of microphysics for cirrus


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