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PARAMETERIZATION OF THE INFLUENCE OF NITRIC ACID
ON AEROSOL ACTIVATION Sami Romakkaniemi, Harri
Kokkola, Ari Laaksonen Department of Applied
Physics University of Kuopio, Finland
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Introduction
HNO3 increases cloud droplet number
concentration Smaller mean cloud droplet
size Longer cloud lifetime and higher albedo
Overall cooling effect
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Introduction

• Number of cloud droplets depends on updraft
  velocity, environmental variables, condensing
  gases, and properties of CCN.
• Number of cloud droplets can be calculated with
  an adiabatic air parcel model.
• Calculation time
• CCN activation is parameterized to form that can
  be used in GCMs
• Effect of condensing volatile gases must be also
  parameterized

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Parameterizations for cloud droplet formation
1) Based on measurements
Nd -595298log(Na)
(Gultepe and Isaac, Journal of Climate, 12,
1268-1279,1998)
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Parameterizations for cloud droplet formation
(Boucher and Lochmann, Tellus B, 47, 1995)
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Parameterizations for cloud droplet formation
2) Based on analytical calculations modeling
Critical saturation as a function of dry diameter
Equilibrium (Köhler) curves
Scrit(D0)
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Parameterizations for cloud droplet formation
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Parameterizations for cloud droplet formation

• Number of cloud droplets can be estimated if Smax
  can be solved.
• Smax can be solved from differential equations
  descriping the water condensation on droplets
• Parameterization for cloud droplet formation

Activated
Nonactivated
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Parameterizations for cloud droplet formation
Nenes and Seinfeld, JGR, 108, 2003
Abdul-Razzak et al., JGR, 103, 1998
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Nitric acid increases the amount of hygroscopic
material in droplets Scrit changes Parameterizat
ions made for pure water condensation can not be
used (or are at least difficult to use)
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What must be taken into account in the new
parameterization
Amount of nitric acid

• Aerosol population
• Number of particles
• mean diameter
• deviation, shape
• composition

Temperature
Total pressure
Updraft velocity
(Activated fraction without nitric acid)
Total number of variables is more than 6
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x HNO3 concentration (ppb) F0 activated
fraction without HNO3
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rgS geometric mean surface radius Xm
hygroscopic massfraction CHNO3 HNO3
concentration T temperature V updraft
velocity Nparticle concentration F0 activated
fraction without HNO3 sigmastandard
deviation PTOT total pressure
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N1 200cm-3 , V 0.1m/s N2 2 cm-3 rg1
15nm HNO3 0.1ppb
N1 1000cm-3 , V 0.1m/s N2 10 cm-3 rg1
15nm HNO3 0.5ppb
N1 1000cm-3 , V 0.1m/s N2 10 cm-3 rg1
15nm HNO3 0.5ppb
N1 1000cm-3 , V 0.5m/s N2 100 cm-3 rg1
15nm HNO3 0.5ppb
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N1 200cm-3 , V 0.1m/s rg1 15nm rg2 250
nm HNO3 0.1ppb
N1 1000cm-3 , V 0.1m/s rg1 15nm rg2 30nm
HNO3 0.3ppb
N1 1000cm-3 , V 1.0m/s rg1 15nm rg2 30nm
HNO3 0.3ppb
N1 1000cm-3 , V 0.1m/s rg1 15nm rg2
30nm HNO3 0.1ppb
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• Coming up...
• Chemical composition, HCl
• Testing the parameterization in ECHAM?
• Parameterization of the effect of ammonia on
  cloud droplet formation