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AEROSOL SIZE DISTRIBUTIONS, PROPERTIES AND VERTICAL PROFILES OVER THE PACIFIC: TOWARDS AN AEROSOL CLIMATOLOGY. A.D. Clarke, V.N. Kapustin School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, USA. REGIONAL AEROSOL AND LONG RANGE TRANSPORT OVER THE PACIFIC. - PowerPoint PPT Presentation
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A.D. Clarke, V.N. Kapustin
School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, USA
AEROSOL SIZE DISTRIBUTIONS, PROPERTIES AND VERTICAL PROFILES OVER THE PACIFIC: TOWARDS AN AEROSOL CLIMATOLOGY
A.D. Clarke, K.G.Moore, V.N. Kapustin
School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, USA
REGIONAL AEROSOL AND LONG RANGE TRANSPORT OVER THE PACIFIC
FOCUS
Contribute to the understanding of the climatology and variability of aerosol over the remote oceans (Pacific) and the processes that establish its characteristics (size, concentration, chemistry, optical properties)
STUDY REGIONS
Various research programs have explored the aerosol fields in the Central Pacific remote marine boundary layer (MBL) and free troposphere (FT) - PEM-Tropics A&B, ACE-1, GLOBE 1&2, CPACE, SAGA 1, 2&3, RITS 88, 93&94 ...
AC E 1 G LO B E 1 & 2
WE HAVE OBSERVED
In regions free of continental influence the marine boundary layer (MBL) aerosol mass and optical properties are dominated by sea-salt (e.g. ACE-1 Tasmania ) with some natural sulfate.
Continental aerosol can influence or dominate (MBL) aerosol and optical properties over extensive regions until depleted by removal processes in MBL.
Lofting of continental aerosol above 2km often creates structured rivers of aerosol (dust, pollution) that is advected over global scales before re-entrainment into the surface boundary layer.
(CONT.)
Deep convection and precipitation removes MBL aerosol mass and number and vents cleaned surface air aloft. Can provide favorable region for natural nucleation with enhanced “new” aerosol number but with little mass.
Cloud venting aloft and larger scale subsidence and entrainment will couple free troposphere (FT) aerosol and MBL aerosol cycles including their evolution and properties.
Column aerosol properties (satellite) will reflect the above processes and a mix of natural and anthropogenically influenced aerosol. In general – surface based in-situ measurements will provide uncertain assessments of column aerosol properties.
Aerosol Size Distributions - Basics and Interpretation
0
1000
2000
3000
4000
Background Marine DOY323.4-323.6
Background Marine DOY327.0-327.2Continental DOY331.7-331.9
dN/d
logD
p (
cm -3
)
0.01 0.1 1 100.1
1
10
100
1000
Dp (m)
dN/d
logD
p (
cm -
3 )
Ultrafine Aitken Accumulation Coarse
0 40 80 120 1600
1
NUCLEATION:HIGH SULF.ACIDHIGH HUMIDITYLOW TEMPERATURELOW SURF.AREA
COAGULATION &CONDENSATION
ULTRAFINE MODE
AITKEN MODEdN/d
logD
Diam, nm
0 40 80 120 160
0.0
0.1
0.2 AITKEN MODE
CCN - CLOUDS - ACCUM. MODE
dN/d
logD
0 40 80 120 1600
1
300C
CLEAN
SOOT "OLD"
SOOT "NEW"
POLLUTION
dN/d
logD
Diam, nm
0 40 80 120 160
0.0
0.1
0.2
0.3
0.4
0.5
MBL AEROSOL
POLLUTION
dN/d
logD
Modal structure of an MBL aerosolMBL processes
FT processes
MBL - polluted and clean case
Volatility and size distributions
0.01 0.1 1 100
10
20
30
40
50
DMAOPC
NOTE: Scale
dA/dlogDp
0.01 0.1 1 100
500
1000
1500
2000
OPCDMA
dN/dlogDp
0.01 0.1 1 100
1
2
3
4
5
DMAOPC
NOTE: Scale
dV/dlogDp
0.01 0.1 1 100
10
20
30
40
50
NOTE: Scale
0.01 0.1 1 100
500
1000
1500
2000
0.01 0.1 1 100
1
2
3
4
5
NOTE: Scale
0.01 0.1 1 100
50
100
150
200
250polluted MBL
clean MBL
clean FT
Dp (m)0.01 0.1 1 10
0
500
1000
1500
2000
DMA 40 DMA 150 DMA 300 OPC 40 OPC 150 OPC 300
Dp (m)0.01 0.1 1 10
0
5
10
15
Dp (m)
0.01 0.1 1 100
500
1000
1500
2000
0.01 0.1 1 100
5
10
15
polluted FT
0.01 0.1 1 100
50
100
150
200
250
Size Distributions and Volatility as a Tool to Study Particles Composition
= 550 nm
sp=2.6x10-7 (1/m)tot. A =2.71 (m2/cm3)(ref. V)/(unht V) =0.01 sub-m
=(sp+ ap)/sp=0.999
=0.98sp=1.2x10-5 (1/m)tot A =46.2 (m2/cm3)(ref. V)/(unht V) =0.06 sub-m
=0.94 sp=9.51x10-5 (1/m)tot A =123.1 (m2/cm3)(ref. V)/(unht V) =0.12 sub-m
=0.80 sp=2.94x10-5 (1/m)tot A =65.1 (m2/cm3)(ref. V)/(unht V) =0.23 sub-m
PageSize Distributions and Volatility...
• Some selected examples of size distributions (number, surface, volume) for various cases (clean/polluted free troposphere - FT, clean/polluted marine boundary layer -MBL).• Some related properties (single scattering albedo - ω, scattering coefficient, surface area and refractory volume fraction) indicated in panels on the left.
PageRCN Ratio - an Indicator ..
• A lidar image from the NASA DC8 at 8-10km from Darwin to Tokyo.• Variable low level clouds are evident alone with a dramatic Asian dust plume reaching 7km over Japan. • Regions of no backscatter are very clean regions where elevated new particle concentrations can be see over the ITCZ and where refractory surface derived CNs (@300C) are at minimum.
Comments
Zonal Aerosol Features in the Pacific Free Troposphere (FT)
-60 -40 -20 0 20 40 60 800
2
4
6
8
10
NASA GLOBE2 Expt. (1990) Alt. > 3 km only
UFCN
(>3n
m) t
o CN
(>12
nm) R
atio
-60 -40 -20 0 20 40 60 800.0
0.5
1.0
NS
HotC
N(30
0C) t
o Co
ldCN
(40C
) Rat
io
Latitude
0
2
4
6
RefrCN CN (Dp>15nm)
CN(#
/cm
3)*1
000
@ST
P
0
30
60
Altitude ~ 10kmDARWIN TOKYO
UCN (Dp>3nm)
UCN(
#/cm
3)*1
000
@ST
P
0.00
0.05
0.10
0.15
Tota
lVol
(um
3/cm
3)
TotVol@40C RefrVol
-10 0 10 20 300.0
0.5
1.0
Latitude
RefrCN(@300C)/TotCN(@40C))
RefR
atio
0
25
50
75
UCN
/CN
Ratio UCN(>3nm)/CN(>15nm)
• A flight from Darwin to Tokyo revealed zonal variations in aerosol properties. Enhanced nucleation in clean air near the equator changed to continental air aloft above Tokyo with high mass loading and large surface derived refractory aerosol fraction.
• The ratio of total (UCN) to larger CN and ratio of refractory CN (soot, dust, sea salt) to total CN show zonal regions aloft where clean or polluted air is most prevalent.
INDOEX99 - Aerosol Plumes from India.
0.01 0.1 10
500
1000
1500
2000
0.01 0.1 10
500
1000
1500
2000
1750 -- 2000 1500 -- 1750 1250 -- 1500 1000 -- 1250 750.0 -- 1000 500.0 -- 750.0 250.0 -- 500.0 0 -- 250.0
Inversion
"mix" layer
MBL plume
biomass plume
"clean" layer
0
2
4
6
8
10
{
10.0
OPCDMA
Isopleths of dN/dlogDp
0.01 0.10
Dp (m)
Altit
ude
(km
)
40 deg C 300 deg C
dN/d
logD
p
Dp (m)
40 deg C 300 deg C
dN/d
logD
p
Dp (m)
-90 -80 -70 -60 -50 -20
-10
0
800
600
400
200
Pres
sure
(mb)
Latitude (deg)
Longitude (deg)
Structure of Aerosol Plumes over Pacific South America Pollution (PEMT-A)
Regional haze(biomass)
Clean marine air
NASA PEMT-AE. Browell
-40
-30
-20
-100
800
600
400
200
Longitude (deg)-90-1351801359045
Pres
sure
(mb)
Latitude (deg)
Structure of Aerosol Plumes over PacificAfrican Biomass Burning (PEMT-A)
Structure of Aerosol Plumes over Pacific African Biomass Burning (cont.)
0
2
4
6
8
10
0 500 1000 1500 20000
2
4
6
8
10
20 40 60 80 100
CN conc.
CN concentration (#/cm3)
Palt
(km
)
0.0 0.2 0.4 0.6 0.8 1.0RCN ratio
RCNratio
0.0 5.0x10 -6 1.0x10 -5 1.5x10 -5
sp (1/m)
sp @ 550 nm
O3
O3 concentration (ppbv)
40 60 80 100
CO concentration (ppbv)
CO
0.01 0.1 1 100
200
400
600
800
1000
Inversion
875.0 -- 1000 750.0 - - 875.0 625.0 - - 750.0 500.0 - - 625.0 375.0 - - 500.0 250.0 - - 375.0 125.0 - - 250.0 0 - - 125.0
0
2
4
6
8
10
Elevated sp region
Biomass plume (Africa?)
Nucleation region
High altitude plume
Tahitian Plume-No OPC data
10.00.100.01
OPCDMA
Dp (m)
Altit
ude
(km
)
Isopleths of dN/dlogDp
DMA 40 deg OPC 40 deg
dN/d
logD
p
Dp (m)
0.01
0.1Hawaii
ITCZ
Diverg.Easterlies
SPCZTahiti
PEM Tropics, Flt10
1000
600
• A PEMT flight over the ITCZ and the SPCZ separated by a zone of subsidence. • Marked changes in aerosol size reveal regions of nucleation aloft above the ITCZ and SPCZ, with larger aerosol at intermediate altitudes. • Size distributions in the MBL are even larger and show a cloud processed mode with intermodal minimum near 0.09 um.
Variability of Aerosol Size Distributions
A 3D latitude-longitude distributions of small differential condensation nuclei - DCN (3nm<Dp<12nm) are highest aloft (above 3km) near ITCZ and SPCZ and almost no DCN particles are present in the MBL (observations from all PEM Tropics flights).
20 10 0 -10 -20 -30-160
-150
-140
-130-120-110
0
500
1000
1500
2000
2500
SPCZITCZ
Above 3 km
Lon
gitu
de
DCN
(3nm
<Dp<
12nm
), cm
-3
Latitude20 10 0 -10 -20 -30
-160
-150
-140
-130-120-110
0
500
1000
1500
2000
2500
Below 3 km
Lon
gitu
de
DCN
(3nm
<Dp<
12nm
), cm
-3
Latitude
Number Concentration is Enhanced in FT as the Result of New Particles Production.
The modulations in MBL aerosol number distributions in passing through the key Pacific meteorological zones.
Covert et al.
The data suggest some predictable features of the size distributions associated with key meteorological zones in the Pacific. Each zone has characteristic aerosol sources (natural and anthropogenic) and mean processes associated with FT/MBL exchange, removal mechanisms, wind and cloud fields.
Zonal Structure of MBL Aerosol Size Distributions
Cloud processed bimodal structure is the most obvious signature of the MBL aerosol in equatorial regions. Exchange with FT also plays a major role in shaping size distribution (note the same size of the particles below and just
above inversion).
An example of a sharp transition to aged MBL equatorial region aerosol upon passing through SPCZ region with strong convection.
-12
-9
-6
-3
0.550.1350.030.005
800 -- 1000 400 -- 800 200 -- 400 100 -- 200 0 -- 100
A
Transition
Dp, Diam,
dN/dlogDp, cm-1
Divergent Easterlies
SPCZLatit
ude
0.01 0.10
200
400
600
800 C
SPCZ
ITCZ
SPCZ and ITCZ
dN/d
logD
p, c
m
-3
0.01 0.10
200
400
600
800 B
dN/d
logD
p, c
m -3
Divergent Easterlies
Inversion
MBL
FTInversion
MBL
Vert.Profile
ITCZ
800.0 -- 1000 600.0 -- 800.0 400.0 -- 600.0 200.0 -- 400.0 0 -- 200.0
dN/dLogDp, cm-3
1205010
Dp, nm
3
6
9
12
Lat
itude
42
Altitude, km
FT / MBL exchange and size distributionsin the equatorial Pacific
FT/MBL exchange affects shape the size distributions: UFCN (Dp<20nm) appeared in the MBL after the frontal passage (a) and as the result of cumulus clouds mixing( b). No UFCN (<20nm) during the stratus clouds period (c).
A vertical profile near the ITCZ shows recent nucleation near 4 km with monomodal aerosol size increasing as particles subside toward the inversion near 1km. Below the inversion the particles entrained into MBL become bimodal as a result of MBL cloud processing.
FT / MBL exchange and size distributionsin the equatorial Pacific (cont.)
40 8010
MBL
Dp, nm
1600 -- 2400 800.0 -- 1600 400.0 -- 800.0 400.0 -- 400.0 0 -- 400.0 0 -- 0
0
2
4
6
-10 0 10 20
Alti
tude
, km
T, deg
AmbTemp
0 30 60 90 RH, %
RH
b.346
344
Day
of Y
ear
Aerosol size distribution,dN/dlogD
10 24 50 108 261
c.
Dp, nm
325
323
a.333
332
Some Aerosol Optical and Microphysical Properties of Aerosol Plumes over South
Pacific
0 1 2 3 4 50.0
1.0x10-5
2.0x10-5
3.0x10-5
4.0x10-5
y-int.=-5.67x10-7 (1/m)slope=7.51x106 (1/m)R2=0.998
F18 F17 F12
sub-m
sp
(1/m
)
sub-m unheated V (m3/cm3)0.0 1.0x10-5 2.0x10-5 3.0x10-5 4.0x10-5 5.0x10-5
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
=sp/(sp+ap)=1/(1+slope) =0.81
F18 F17 F12
ap (
1/m
)
sp (1/m)
0 1 2 3 4 50.0
0.5
1.0
1.5
NOTE: sp =550 nm & ap =565 nm
y-int.=-0.03 (m3/cm3)slope=0.26R2=0.980
y-int.=-3.54x10-7 (1/m)slope=0.242R2=0.890
F18 F17 F12
sub-m
ref.
V (
m3 /c
m3 )
sub-m unheated V (m3/cm3)
0.0 0.5 1.0 1.50.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
y-int.=-3.34x10-7 (1/m)slope=7.33x106 (1/m)R2=0.910
F18 F17 F12
ap (
1/m
)
sub-m ref. V (m3/cm3)
Scattering vs. absorption coefficients suggest a typical single scattering albedo of 0.81
Submicrometer total and refractory (soot) volume are related for these plumes indicating similar refractory fraction in aerosol
Submicrometer scattering and volume are strongly linear indicating a similar particle size independent of concentrationLight absorption and refractory volume are related with values indicative of a soot carbon core
CONCLUSIONS
The relative simplicity of an unperturbed marine aerosol system makes it possible to identify links of FT and MBL size distributions to regional meteorological regimes and processes
The evaporating regions of ITCZ cloud outflow layers [4 to >12km] are sources of new particles (nucleation) that could populate extensive regions of the tropical free troposphere.
Nucleation is linked to elevated sulfuric acid derived from oceanic DMS for these near-cloud environments and appeared consistent with classical binary nucleation theory.
CONCLUSIONS (cont.)
Exchange (entrainment/subsidence) with the free troposphere (FT) plays a major role in shaping the particle size distribution in the remote MBL.
Cloud processing of the aerosols have an important effect on aerosol size distributions in the MBL and the bimodal structure is the most obvious signature of the MBL aerosol in equatorial regions.
The relative simplicity of an unperturbed marine aerosol system makes it possible to identify links of FT and MBL size distributions to regional meteorological regimes and processes