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GLOBAL SULFUR BUDGET [Chin et al., 1996] (flux terms in Tg S yr -1 ) Phytoplankton (CH 3 ) 2 S SO 2 ...
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Transcript of GLOBAL SULFUR BUDGET [Chin et al., 1996] (flux terms in Tg S yr -1 ) Phytoplankton (CH 3 ) 2 S SO 2 ...
GLOBAL SULFUR BUDGET [Chin et al., 1996](flux terms in Tg S yr-1)
Phytoplankton
(CH3)2S
SO2
1.3d
DMS1.0d
OHNO3
Volcanoes CombustionSmelters
SO42-
3.9d
22
10 64
OH
cloud42
8184
dep27 dry20 wet
dep6 dry44 wet
H2SO4(g)
GLOBAL SULFUR EMISSION TO THE ATMOSPHERE
[Chin et al. 2000]
2001 estimates (Tg S yr-1): Industrial 57 Volcanoes 5 Ocean 15 Biomass burning 1
FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS
2
2
2
22 4 4
3 4
3 3
3 3 4 3
( ) 2
( )
( )
( ) ( ) ( )
H O
H O
H O
H SO g SO H
NH g NH OH
HNO g NO H
NH g HNO g NH NO aerosol
Sulfate always forms an aqueous aerosol
Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first
Nitrate is taken up by aerosol if (and only if)excess NH3 is available after sulfate titration
HNO3 and excess NH3 can also form a solid aerosol if RH is low
Thermodynamic rules:
Highest concentrations in industrial Midwest(coal-fired power plants)
Observed aerosolacidity in US
GLOBAL EMISSIONS OF AMMONIA
GLOBAL UNITED STATES
Ammonia,Tg N yr-1
55 2.8
[Bouwman et al., 1997]
SULFATE-NITRATE-AMMONIUM AEROSOLS IN U.S. (2001)
Highest concentrations in industrial Midwest(coal-fired power plants)
Sulfate Nitrate
Ammonium
STRATOSPHERIC AEROSOL
TROPOPAUSE
Transport of long-lived S
gases (eg. COS)
Injection of volcanic ash
(SiO2, Al2O3, Fe2O3) as well as gases (H2S, SO2, HCl)
Aerosols in the stratosphere are long-lived due to absence of precipitation and “layered” transport (due to stability)
PSCs (nitric acid / water vapor)
PSCs (nitric acid / water vapor)
HOW COMPOSITION AND SIZE FIT TOGETHER…
Image from: C. Leck
SURFACE AEROSOL NUMBER CONCENTRATION
Dec July
Continental: > 250 cm-3
Urban/polluted: > 2000 cm-3
Marine BL: ~ 200 cm-3
[Spracklen et al., 2006]
GLOMAP: 2 moment sectional model simulating sulfuric acid / sea salt
RAOULT’S LAW
water saturation vapor pressureover pure liquid water surface
water saturation vapor pressureover aqueous solution of watermixing ratio xH2O
2 ,oH O SATP 2 , 2 2 ,
oH O SAT H O H O SATP x P
An atmosphere of relative humidity RH can contain at equilibrium aqueous solution particles of water mixing ratio 2 ,
22 , 100
H O SATH O o
H O SAT
P RHx
P
HOWEVER, AEROSOL PARTICLES MUST ALSO SATISFY SOLUBILITY EQUILIBRIA
Consider an aqueous sea salt (NaCl) particle: it must satisfy
2
(solubility equilibrium)
(electroneutrality)
1 (closure)
Na Cl s
Na Cl
Na Cl H O
x x K
x x
x x x
This requires:1
2100(1 2 ) "deliquescence RH"sRH K
At lower RH, the particle is solid at equilibrium, though it can also remain in metastable aqueous state
UPTAKE OF WATER BY AEROSOLS
RELATIVE HUMIDITIES FOR DELIQUESCENCE/CRYSTALLIZATION OF AEROSOLS
IN CONTRAST TO OZONE, HEMISPHERIC AEROSOL BACKGROUND IS NOT AN AIR QUALITY ISSUE (wrt NAAQS)
TRACE-P aircraft observations over NW Pacific (Mar-Apr 2001) and GEOS-Chem model simulations
…because of efficient precipitation scavenging in continental outflow
P3B DATA over NW Pacific (30 – 45oN, 120 – 140oE)
[Park et al. 2005]
HOWEVER, DESERT DUST CAN BE TRANSPORTED ON INTERCONTINENTAL SCALES
GlenCanyon, Arizona
clear day April 16, 2001: Asian dust!
Annual mean PM2.5 dust (g m-3), 2001
Asia
Sahara
Most fine dust in the U.S. (except in southwest) is of intercontinental origin
LONG RANGE TRANSPORT OF DUST FROM AFRICA TO THE AMAZON (2008)
[Prenni et al., 2009]
Timeseries of dust @ field site N of Manaus
Model simulation of the African dust plume
[IPCC 2007]
AEROSOL CLIMATE FORCING
SCATTERING OF RADIATION BY AEROSOLS:“DIRECT EFFECT”
By scattering solar radiation, aerosols increase the Earth’s albedo
Scattering efficiency is maximum when particle diameter = particles in 0.1-1 msize range are efficient scatterers of solar radiation
Mt. Pinatubo eruption
1991 1992 1993 1994
-0.6
-0
.4
-0.
2
0
+0
.2Te
mp
era
ture
C
ha
nge
(oC
)
Observations
NASA/GISS general
circulation model
Temperature decrease following large volcanic eruptions
EVIDENCE OF AEROSOL EFFECTS ON CLIMATE:
SCATTERING vs. ABSORBING AEROSOLS
Scattering sulfate and organic aerosolover Massachusetts
Partly absorbing dust aerosoldownwind of Sahara
Absorbing aerosols (black carbon, dust) warm the climate by absorbing solarradiation
AEROSOL “INDIRECT EFFECT” FROM CLOUD CHANGES
Clouds form by condensation on pre-existing aerosol particles (“cloud condensation nuclei”) when RH>100%
clean cloud (few particles):large cloud droplets• low albedo• efficient precipitation
polluted cloud (many particles):small cloud droplets• high albedo (1st indirect)• suppressed precipitation (2nd indirect)
Particles emitted by ships increase concentration of cloud condensation nuclei (CCN) Increased CCN increase concentration of cloud droplets and reduce their avg. size Increased concentration and smaller particles reduce production of drizzle Liquid water content increases because loss of drizzle particles is suppressed Clouds are optically thicker and brighter along ship track
N ~ 100 cm-3
W ~ 0.75 g m-3
re ~ 10.5 µm
N ~ 40 cm-3
W ~ 0.30 g m-3
re ~ 11.2 µm
from D. Rosenfeld
EVIDENCE OF INDIRECT EFFECT: SHIP TRACKS
AVHRR, 27. Sept. 1987, 22:45 GMTUS-west coast
NASA, 2003Atlantic, France, Spain
SATELLITE IMAGES OF SHIP TRACKS
Aircraft condensation trails (contrails) over France, photographed from the Space Shuttle (©NASA).
OTHER EVIDENCE OF CLOUD FORCING:CONTRAILS AND “AIRCRAFT CIRRUS”