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Properties and Distribution of Clouds ENVI3410 : Lecture 7 Ken Carslaw Lecture 1 of a series of 5 on clouds and climate Properties and distribution of.

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Presentation on theme: "Properties and Distribution of Clouds ENVI3410 : Lecture 7 Ken Carslaw Lecture 1 of a series of 5 on clouds and climate Properties and distribution of."— Presentation transcript:

1 Properties and Distribution of Clouds ENVI3410 : Lecture 7 Ken Carslaw Lecture 1 of a series of 5 on clouds and climate Properties and distribution of clouds Cloud microphysics and precipitation Clouds and radiation Clouds and climate: forced changes to clouds Clouds and climate: cloud response to climate change

2 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Content of Lecture 7 Cloud types, classification and distribution Importance in the climate system Basic physical properties

3 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Recommended Reading for This Lecture Hamblyn, R (2001) The Invention of Clouds. New York: Farrar, Straus and Giroux Houze’s Cloud Atlas –http://www.atmos.washington.edu/gcg/Atlashttp://www.atmos.washington.edu/gcg/Atlas WMO International Cloud Atlas –Stack Geography D-0 WOR Stack Geography D-0 WOR

4 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 What is a Cloud? World Meteorological Organisation definition: “An aggregate of minute, suspended particles of water or ice, or both, that are in sufficient concentrations to be visible.” Now also includes clouds that are nearly invisible to the eye, but visible from satellite: sub-visible clouds

5 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Development of Cloud Classification Luke Howard in 1803 (English Chemist) and Jean Baptiste Lamarck in 1802 (French naturalist) Howard’s Latin-based nomenclature adopted (Published in Tilloch’s Philosophical Magazine) Three basic cloud types: –Cirrus (Latin: hair) - fibrous and wispy –Stratus (Latin: flat) – sheet-like laminar clouds –Cumulus (Latin: heaped up) - strong vertical architecture

6 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Development of Cloud Classification 1880s: Observations suggested that clouds occupy 3 distinct levels –High clouds (cloud base >7 km above ground level) –Middle-level clouds (cloud base between 2 and 7 km) –Low clouds (cloud base <2 km) Further refinements in 1891 and 1926 Publication of International Cloud Atlas in 1932 and by WMO in 1956. Pictorially updated 1989. World Meteorological Organisation (1987) International Cloud Atlas, vol II. Geneva: WMO

7 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 The Ten Cloud Types, Species and Varieties GeneraSpeciesVarieties Cirrus (Ci) uncinus, fibratus, spissatus, castellanus intortus, radiatus, vertebratus Cirrostratus (Cs)nebulosus, fibratus Cirrocumulus (Cc)castellanus, floccus, lenticularisundulatus Altocumulus (Ac)castellanus, floccus, lenticularis translucidus, opacus, undulatus, perlucidus Altostratus (As)nonetranslucidus, opacus Nimbostratus (Ns)none Stratocumulus (Sc)castellanus, lenticularis perlucidus, translucidus, opacus Stratus (St)fractus, nebulosus Cumulonimbus (Cb)calvus, capillatus Cumulus (Cu) fractus, humulis, mediocris, congestus

8 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Low Stratiform Clouds usually liquid deep (up to cirrus levels) Drops, snowflakes, ice Stratus Stratocumulus NimbostratusFog Fog/Stratus <2 km Humid air passing over a cold surface. Can drizzle. Nimbostratus form in warm fronts. Steady precipitation Diagrams redrawn from Houze’s Cloud Atlas

9 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Stratus/Stratocumulus

10 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Global Distribution of Stratus Clouds

11 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Stratiform Clouds and Climate Net cooling effect on the climate Largest areal coverage of any cloud type Coverage greatest over the dark oceans Susceptible to changes in reflectivity (albedo) due to changes in aerosol The only cloud type in climate models that responds to changes in aerosol

12 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Cumuliform Clouds strong winds ice liquid -40 o C liquid and ice liquid Updraughts of air (1 ms -1 to >30 ms -1 ), unstable atmosphere, warm surface Cumulus congestus Cumulonimbus ice, hail, snow

13 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Cumuli

14 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Global Distribution of Deep Cumulonimbus Clouds

15 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Cumuli Clouds and Climate Cb account for substantial vertical transport of latent heat Cb account for much of world’s hazardous/damaging weather and flooding Response to changing aerosol is being investigated –Possible changes in precip intensity, cloud depth, latent heat release

16 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Alto Clouds liquid and ice AltostratusAltocumulus 2-7 km Large-scale uplift of air (e.g., in a front) at rate of a few cm s -1

17 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Global Distribution of Altocumulus Clouds

18 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Cirrus Clouds CirrostratusCirrocumulus >7 km 22 o halo ice Ice blown off top of cumulonimbus, large scale uplift

19 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Global Distribution of Cirrus Clouds

20 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Cloud Systems A group of convective storms covering several hundred km. Severe rainfall, damaging winds, flooding Mesoscale Convective SystemMid-latitude frontal cyclone Form in westerly wind belts of mid-latitudes. Contain fronts and most of the cloud types of previous slides.

21 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Occurrence of Clouds (Oceanic areas) TypeFrequency of occurrence (%) Areal coverage over oceans (%) Stratus and Stratocumulus4534 Cumulus3312 Cumulonimbus106 Nimbostratus66 Altostratus and altocumulus4622 Cirrus3713 Global average over oceans64.8

22 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Occurrence of Clouds (Land areas) TypeFrequency of occurrence (%) Areal coverage over oceans (%) Stratus and Stratocumulus27 (45)18 (34) Cumulus14 (33)5 (12) Cumulonimbus7 (10)4 (6) Nimbostratus6 (6)5 (6) Altostratus and altocumulus35 (46)21 (22) Cirrus47 (37)23 (13) Global average over oceans52.4 Ocean area values are given in parentheses

23 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Surface Observations

24 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1

25 1 Surface Observations http://www.atmos.washington.edu/~ignatius/Clou dMap/index.html

26 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 International Satellite Cloud Climatology Project http://isccp.giss.nasa.gov/products/browsed2.html A huge range of satellite-derived cloud products available for download

27 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1

28 1 Physical Characteristics of Stratus Clouds LocationSc cloud base (km) St cloud base (km) St Thickness (km) Moscow (USSR) 1.070.470.38 Hamburg (DE)0.980.850.46 Cologne (DE)1.360.870.36 Mildenhall (UK)1.220.960.74 Susterberg (UK)0.90.70.5 Why are Sc cloud bases higher than St?

29 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Microphysics of Stratus Clouds Droplet concentration (cm -3 ) Liquid water content (g m -3 ) Mean droplet diameter (volume weighted) (  m) Location <5000.09-0.63<19Arctic stratus 312-- Washington State 350 (Marine) 500 (Continental) <0.37-11 Off California coast 100-2500.1-0.912-22Over UK From Aerosol-Cloud-Climate Interactions, Ed P. V. Hobbs, Academic Press

30 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Liquid Water Content of St and Sc Clouds liquid water content (g m -3 ) % frequency of occurrence 0.1 g m -3 is equivalent to 0.1 ml per m -3 of air

31 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Microphysics of Altostratus Clouds Droplet concentration (cm -3 ) Liquid water content (g m -3 ) Mean droplet diameter (volume weighted) (  m) Location 3000.03-0.099-11Alaska 100<0.007<9Central USA 35-75<0.214-19USA 100-5000.1-1.07-22STRATUS From Aerosol-Cloud-Climate Interactions, Ed P. V. Hobbs, Academic Press

32 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Liquid Water Content of As and Ac Clouds liquid water content (g m -3 ) % frequency of occurrence 0.1 g m -3 is equivalent to 0.1 ml per m -3 of air

33 ENVI3410 : Coupled Ocean & Atmosphere Climate Dynamics1 Microphysics of Cirrus Clouds 10 -4 10 -3 10 -2 10 -1 10 0 -80 -70 -60 -50 -40 -30 -20 Ice water content (g m -3 ) Temperature ( o C) Tropical cirrus Continental cirrus Typical crystal concentration in continental cirrus is 0.01-1 cm -3 Particle size varies with IWC and T mm-size at –40 o C 10-100  m at – 60 o C

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