1Lecture Ch. 8a• Review of Ch.7 Concepts– Homework Ch. 7, Prob. 3• Cloud Classification• Precipitation ProcessesCurry and Webster, Ch. 8Please complete online evaluations!2Lifting Condensation Level• Liftingcondensation levelvaries with initialrelative humidityand is a weakfunction of initialtemperature10.1Seinfeld and Pandis, Fig. 15.11Cloud ClassificationCumulus CloudsSwelling CumulusActive heaped-up cloudwith flat bottom andgrowing cauliflower top.[http://www.fox8wghp.com/spacious.htm]10.2Cumulonimbus CloudsCumulonimbusMassive cloud systemproducing heavy showers,sometimes with hail. Mostactive clouds may havelightning and thunder. Afew spawn tornadoes.[http://www.fox8wghp.com/spacious.htm]10.2Stratus CloudsStratusLow lying layer of cloud(called fog if on theground) with no structure.[http://www.fox8wghp.com/spacious.htm]10.23Cirrus CloudsCirrus An ice crystal cloud, wispyin appearance. Mayproduce ice crystal snow inwinter or in mountains.[http://www.fox8wghp.com/spacious.htm]Altostratus CloudsAltostratusThickly layered waterdroplet cloud. Sun seen asthrough ground glass.[http://www.fox8wghp.com/spacious.htm]Nimbostratus CloudsNimbostratusThick layered cloud -usually dark gray.Produces continuous rainor snow over large area.[http://www.fox8wghp.com/spacious.htm]Stratus CloudsStratusLow lying layer of cloud(called fog if on theground) with no structure.[http://www.fox8wghp.com/spacious.htm]10.2Ship Tracks• What are they?• aerosol “signatures” from ships• Ship tracks form in non polluted areas– Last 1-2 days• Counter global warmingWhy?10.2What are the characteristics of“ship tracks”?Ship Track Observations Remote/Optical In situ/AerosolConover 1966⇑ albedo = 20%Coakley, Bernstein, Durkee 1987⇑ R(3.7µm) = 3.9%⇑ R(0.63µm) = 1.6%R(11µm) = 0.0%Radke, Coakley, King 1989⇑R(0.63µm) = 13.6%⇑τ =260%⇓re = 21%King, Radke, Hobbs 1993⇑I(τ,-1)(0.74µm) = 220%⇓I(τ,-1)(2.20µm) = 87%⇑Ndrop = 220%⇑CN = 250%⇑LWC = 250%10.24Ship Track in Clean Air10.2Shiptrack in“clean”air12410241000.0012 40.012 40.12 41Diameter (µm)12410241000.0012 40.012 40.12 41Diameter (µm)371 cm-3In track82 cm-3BackgroundNOAA11, 3.7µm dndlogDp10.2Ship Track in Polluted Air10.2Ship trackin“polluted”airNOAA11, 3.7µm 10241002410000.0012 40.012 40.12 41Diameter (µm)10241002410000.0012 40.012 40.12 41Diameter (µm)1050 cm-3In track396 cm-3BackgrounddndlogDp10.2Processes Governing Ship TracksHypothesisRadke, Coakley, King 1989ship stacks ⇒ ⇑CCNAlbrecht 1989⇓Nprecip ⇒ ⇑LWC Hudson 1991⇓CCN ⇒ ⇑NprecipAckerman, Toon, Hobbs 1994⇓CCN ⇒ ⇓h, ⇓τ10.2What are the mechanisms forCCN growth in ship tracks?Growth MechanismCN ⇒ CCN (cm-3 hr-1)Conditions H2SO4(g) condensation 10OH ~ 106 molec cm-3, SO2(g) ~ 3.5 ppb(daytime only)Interparticle coagulation < 1CN ~ 104 cm-3(high CN concentration only) Supersaturation inhomogeneities 3Sc ~ 0.3% ± 0.1, SO2(g) ~ 3.5 ppb(Kaufman and Tanré, 1994)• In-situ observations suggest particle growth intrack10.25FogGlobal Cloud Distribution• Zonallyaveragedclimatologyof cloud typeCloud Types and Drop Sizes• Frequencydistributions of themean cloud dropletsize for variouscloud typesPrecipitation Processes• Warm clouds (liquid water droplets only)• Cold clouds (ice
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