Interactions of aerosols and gases with clouds and precipitation
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Interactions of aerosols and gases with clouds and precipitation in the online-coupled regional chemistry transport model COSMO-ART . Christoph Knote, Dominik Brunner Empa, Materials Science and Technology, Dübendorf, Switzerland CMAS annual conference, Chapel Hill (NC), 2011. meteorology.

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Interactions of aerosols and gases with clouds and precipitation in the online-coupled regional chemistry transport model COSMO-ART

  • Christoph Knote, Dominik Brunner

  • Empa, Materials Science and Technology, Dübendorf, Switzerland

  • CMAS annual conference, Chapel Hill (NC), 2011


meteorology precipitation

preprocessor

inorganics

SOA

gas-phase

natural emissions

photolysis

MADEsoot extended

12 modes

explicit soot aging

PAPA

online calculation of photolysis rates

INT2COSMO-ART

IC/BC, emissions

ISORROPIA II

SORGAM / VBS

COSMO

non-hydrostatic NWP

BVOCs

RADMK

extended RADM2

+ add. isoprene reactions

+ updated rate constants

+ hetero. N2O5 hydrolysis

Seasalt

aerosols

Dust

Pollen

COSMO-ART (Vogel et al., ACP, 2009)

  • regional chemistry transport model based on COSMO

  • online-coupled gas-phase chemistry and aerosol processes

  • studies of aerosol direct and indirect effects


Evaluation results emep

Henne et al., ACP, precipitation 10, 2010

Evaluation results (EMEP)

summer

winter

spring

fall

O3

NO2

overestimation of SO2 concentrations

SO2

Knote et al., Geosci. Model Dev. Disc., 4, 1809-1874, 2011

meas.

model

model

meas.


Evaluation results eucaari ams
Evaluation results (EUCAARI AMS) precipitation

too low sulfate

too high nitrate

Knote et al., Geosci. Model Dev. Disc., 4, 1809-1874, 2011


Coupling to messy scav
Coupling to MESSy SCAV precipitation

Tost et al., ACP, 2006

Scavenging (cloud droplets & rain drops)

  • gases: explicit description of transfer process kinetics (option for Henry‘s law equilibrium)

  • aerosols: Brownian motion + interception + impaction, parameterized nucleation

    Aqueous-phase chemistry

  • MECCA (Sander et al., 2005) + additions from CAPRAM (Ervens et al., 2003)

    • reduced version with sulfur-oxidation-focused mechanism

    • 45 transfer + chemical reactions, 35 species

    • ODE system solved via KPP


Cloud processing of aerosols

droplet precipitation

evaporates

net mass transfer from smaller to larger (Acc. mode) aerosols

Cloud processing of aerosols

HNO3

SO2

aqueous

chemistry

H2O2

O3

NH3

dN/dlogDp

diameter

MADEsoot modes:

2 nucleation, 2 accumulation, 1 fresh soot


Adaptations to regional scale

t = t precipitation 0

t = t0 + dt

gas/aq. transfer

washout

condensation

aq. chemistry

evaporation

Adaptations to regional scale

Original SCAV

formulation:

  • OK for GCMs with dt = O(1 h)NOT OK for COSMO-ART with dt = O(1 min)

  • liquid-phase species are now transported,partial evap./cond. of cloud possible(consistent with COSMO microphysics)


Adaptation activation scheme

time-step dependent! precipitation

apply only to fraction of aerosols:

fraction of freshly

condensed cloud water

(from COSMO microphysics)

Adaptation: activation scheme

empirical. derived from meas. of Svenningsson (1997) and Martinsson (1999)

Stier et al. 2005

nucleation and growth

brownian motion

Tost et al., ACP 6, 565-574, 2006


2d flow over hill study
2D flow-over-hill study precipitation

  • initial values / boundary profile:from 3D COSMO-ART simulation, 12 UTC summer in Payerne (CH)

  • 100 x 40 grid cells, 0.0045° (~500m)

  • Runge-Kutta time integration, dt = 15s

  • T/qv profile: Weisman Klemp, MWR, 1982u = 20 m/s

Liquid precipitation content („rainfall“)

Liquid water content (LWC)


2d study results

△SO2 (gas-phase) precipitation

2D study results

△SO42- (aerosol)

S wet deposition


2d study results1

△SO2 (gas-phase) precipitation

2D study results

SO2 scavenged

△SO42- (aerosol)

SO42- produced

S wet deposition

mass deposited


2d study results2

△SO2 (gas-phase) precipitation

2D study results

SO2 scavenged

SO42- Aitken mode

△SO42- (aerosol)

SO42- produced

SO42- accumulation mode

S wet deposition

mass deposited


2d study results3

△SO2 (gas-phase) precipitation

2D study results

SO2 scavenged

SO42- Aitken mode

△SO42- (aerosol)

SO42- produced

SO42- accumulation mode

S wet deposition

mass deposited

cloud processing active


2d study results4
2D study results precipitation

Chemistry boundary profile:

Swiss midlands, 12 UTC, summer.

measured pH: 5.9

(NABEL station Dübendorf,

Swiss midlands, summer 2008 mean)

simulated pH: 5.6 - 6

cloud droplet acidity

Conclusions

  • scavenging working for gases and aerosols

  • oxidation of sulfur visible

  • cloud processing active

let‘s go 3D!


Realistic simulation

Sulfate aerosols (level slice at 1 km) precipitation

Realistic simulation

COSMO-ART-SCAV

October 2008

17 km horiz. resolution

40 vertical levels

full gas-phase chemistry

and aerosols

efficient sulfate aerosol production on cloud evaporation

Cloud pH

large variability in cloud pH


Realistic study results
Realistic study results precipitation

ref.

EMEP station data

SCAV

meas.

SO2

ref.

ref.

meas.

SCAV

SCAV

meas.

EUCAARI AMS


Conclusions
Conclusions precipitation

  • Successfulcouplingof COSMO-ART with SCAV

  • Detaileddescriptionofscavengingandaqueous-phase chemistry

  • Strong reductions in SO2concentrations

  • Improvedchemicalcompositionof PM1,nonref, but reduced total mass

  • Assumptionsmade in aq.-phase schemesmight not workfor online-coupledmodels


Coupling overview

prognostic precipitation

prognostic

prognostic

prognostic

Coupling overview

gases

kinetic transfer (ODE system)

kinetic transfer

evaporation

evaporation

rain droplets

aqueous

chemistry

production

aqueous

chemistry

cloud droplets

wet deposition

Brownian motion / nucleation

Brownian motion / interception / impaction

evaporation

evaporation

particles


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