Transcript Document 7573965

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
A.D. Clarke, K.G.Moore, V.N. Kapustin
School of Ocean and Earth Science and Technology, University of Hawaii,
Honolulu, USA
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 ...
ACE1
GLOBE 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
)
Modal structure of an MBL aerosol
dN/dlogD
Continental DOY331.7-331.9
4000
CCN - CLOUDS - ACCUM. MODE
0.1
MBL processes
0.0
0
Background Marine DOY323.4-323.6
40
80
120
160
1
ULTRAFINE MODE
2000
COAGULATION
&
CONDENSATION
dN/dlogD
dN/dlogDp ( cm
-3
Background Marine DOY327.0-327.2
3000
AITKEN MODE
0.2
1000
NUCLEATION:
HIGH SULF.ACID
HIGH HUMIDITY
LOW TEMPERATURE
LOW SURF.AREA
FT processes
AITKEN MODE
0
0
0
40
80
120
160
Diam, nm
0.5
1000
0.4
100
MBL - polluted
and clean case
MBL AEROSOL
0.2
0.1
10
0.0
0
40
80
120
160
1
1
300C
Ultrafine Aitken
Accumulation
Coarse
0.1
0.01
0.1
Dp (m)
1
10
dN/dlogD
dN/dlogDp ( cm
-3
dN/dlogD
)
POLLUTION
0.3
Volatility and
size distributions
SOOT "NEW"
SOOT "OLD"
POLLUTION
CLEAN
0
0
40
80
Diam, nm
120
160
Size Distributions and Volatility as a Tool to Study
Particles Composition
dN/dlogDp
DMA
 =( sp+  ap)/ sp=0.999
-7
 sp=2.6x10
40
OPC
1500
 = 550 nm
dA/dlogDp
50
2000
2
DMA
30
500
0
0.01
2000
1
10
0
0.01
50
(1/m)
2
3
500
0
0.01
0.1
1
10
2000
NOTE: Scale
3
0.1
clean FT
1
10
0.1
1
10
clean MBL
0.1
1
10
polluted MBL
0.1
1
Dp ( m)
10
NOTE: Scale
20
2
10
1
0
0.01
250
0.1
1
10
0
0.01
15
10
100
5
500
0
2000
50
0.01
0.1
1
10
0
0.01
250
0.1
1
10
10
150
(1/m)
3
tot A =65.1 (  m /cm )
(ref. V)/(unht V) =0.23 sub-  m
0
0.01
15
200
1500
 =0.80
2
0.01
5
1000
2
-5
0
3
150
(1/m)
tot A =123.1 (  m /cm )
(ref. V)/(unht V) =0.12 sub-  m
 sp=2.94x10
10
200
1500
 =0.94
-5
1
1000
tot A =46.2 (  m /cm )
(ref. V)/(unht V) =0.06 sub-  m
 sp=9.51x10
0.1
4
30
-5
 sp=1.2x10
NOTE: Scale
1
40
1500
 =0.98
OPC
2
10
0.1
DMA 40
DMA 150
DMA 300
OPC 40
OPC 150
OPC 300
DMA
3
NOTE: Scale
20
3
tot. A =2.71 (  m /cm )
(ref. V)/(unht V) =0.01 sub-  m
4
OPC
1000
(1/m)
dV/dlogDp
5
1000
100
5
500
0
50
0
0.01
0.1
1
Dp ( m)
10
0.01
0.1
1
Dp ( m)
10
0
0.01
polluted FT
Comments
Page
Size 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.
Page
RCN 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.
Zonal Aerosol Features in the Pacific Free Troposphere (FT)
TOKYO
0.15
0.10
30
0.05
0
0.00
6
RefrCN
CN (Dp>15nm)
4
NASA GLOBE2 Expt. (1990)
Alt. > 3 km only
10
8
6
4
2
0
-60
-40
-20
0
-40
-20
0
20
40
60
20
40
60
80
1.0
75
1.0
UCN(>3nm)/CN(>15nm)
50
0.5
25
0
0.0
-10
0
10
Latitude
20
30
UCN/CN Ratio
RefrCN(@300C)/TotCN(@40C))
HotCN(300C) to ColdCN(40C) Ratio
2
0
RefRatio
• 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.
UFCN(>3nm) to CN(>12nm) Ratio
60
Altitude ~ 10km
UCN (Dp>3nm)
TotVol@40C
RefrVol
TotalVol(um3/cm3)
DARWIN
CN(#/cm3)*1000 @STP
UCN(#/cm3)*1000 @STP
• 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.
0.5
0.0
-60
S
Latitude
80
N
INDOEX99 - Aerosol Plumes from India.
Structure of Aerosol Plumes over Pacific
South America Pollution (PEMT-A)
200
400
600
0
800
-10
-90
-80
-70
-60
eg)
e (d
itud
Lat
Pressure (mb)
Regional
haze(biomass)
-50 -20
Longitude (deg)
Isopleths of dN/dlogDp
10
DMA
1750 -- 2000
1500 -- 1750
1250 -- 1500
1000 -- 1250
750. 0 -- 1000
500.0 -- 750.0
250.0 -- 500.0
0 -- 250.0
OPC
8
6
dN/dlogDp
2000
biomass plume
4
2
"mix" layer
1000
500
0.01
0. 1
1
Dp ( m)
{
2000
"clean" layer
Inversion
MBL plume
0
0.10
Dp (m)
10.0
40 deg C
300 deg C
1500
1000
500
0
0.01
40 deg C
300 deg C
1500
0
dN/dlogDp
Altitude (km)
Clean marine air
0.01
0. 1
Dp ( m)
1
Structure of Aerosol Plumes over Pacific
African Biomass Burning (PEMT-A)
NASA
PEMT-A
E. Browell
200
Pressure (mb)
400
600
0
-20
eg)
e (d
itud
Lat
-10
800
-30
-40
45
90
135
180
Longitude (deg)
-135
-90
Structure of Aerosol Plumes over Pacific
African Biomass Burning (cont.)
sp (1/m)
0.0
5.0x10
-6
1.0x10
-5
1.5x10
-5
CO concent ration (ppbv)
RCN ratio
0.0
0.2
0.4
0.6
0.8
1.0
10
40
60
80
100
Isopleths of dN/dlogDp
10
10
OPC
DMA
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
CN conc.
O3
RCNratio
8
s p @ 550 nm
CO
8
8
High altitude plume
Nucle ation region
4
4
2
6
DMA 40 deg
OP C 40 deg
800
4
Eleva ted sp region
600
400
200
2
2
1000
Biomass plume (Afric a?)
dN/dlogDp
6
Altitude (km)
Palt (km)
6
Inversion
0
0.01
0.1
Dp ( m)
0
0
0
500
1000
1500
3
CN co ncent ration (#/cm )
2000
Tahitian Pl ume-No OPC data
0
20
40
60
80
O3 concentration ( ppbv)
100
0.01
0.10
Dp (m)
10.0
1
10
Variability of Aerosol Size Distributions
PEM Tropics, Flt10
dN
/dlo
gD
p
b
,m
e
r
su
s
e
Pr
600
Tahiti
1000
SPCZ
0.01
Di
am
et
er
,u
m
Diverg.Easterlies
ITCZ
0.1
Hawaii
• 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.
Number Concentration is Enhanced in FT as the
Result of New Particles Production.
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).
Above 3 km
Below 3 km
2500
-3
2000
p<12nm), cm
DCN (3nm<D
2000
1500
-110
-120
-130
1000
500
0 20
-140
ITCZ
10
0
-10
Latitude
-150
SPCZ
-20
-160
-30
Longitude
1500
-110
-120
-130
1000
500
-140
-150
0 20
10
0
-10
Latitude
-20
-160
-30
Longitude
p<12nm), cm
DCN (3nm<D
-3
2500
Zonal Structure of MBL Aerosol Size Distributions
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.
The modulations in MBL aerosol
number distributions in passing
through the key Pacific
meteorological zones.
Covert et al.
FT / MBL exchange and size distributions
in the equatorial Pacific
An example of a sharp transition to aged
MBL equatorial region aerosol upon
passing through SPCZ region with strong
convection.
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).
-3
-1
dN/dlogDp, cm
800
12
600
400
Divergent Easterlies
dN/dlogDp, cm
-3
dN/dLogDp, cm
-3
800 -- 1000
400 -- 800
200 -- 400
100 -- 200
0 -- 100
B
Divergent Easterlies
ITCZ
9
200
-6
Transition
0
SPCZ
800
SPCZ and ITCZ
C
600
400
-12
dN/dlogDp, cm
-3
-9
0.1
Latitude
Latitude
0.01
6
Vert.Profile
MBL
3
800.0 -- 1000
600.0 -- 800.0
400.0 -- 600.0
200.0 -- 400.0
0 -- 200.0
ITCZ
200
A
SPCZ
0
0.005
0.03
0.135
Dp, 
0.55
0.01
0.1
Diam, 
Inversion
Inversion
FT
2
4
10
Altitude, km
MBL
50
Dp, nm
120
FT / MBL exchange and size distributions
in the equatorial Pacific (cont.)
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 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 e r o s o l s iz e d is tr ib u tio n ,
d N /d lo g D
333
a.
RH, %
6
30 60 90
RH
AmbTemp
1600 -- 2400
800.0 -- 1600
400.0 -- 800.0
400.0 -- 400.0
0 -- 400.0
0 -- 0
Altitude, km
4
332
346
b.
Day of Y ear
0
344
325
2
c.
MBL
0
-10 0 10 20
T, deg
10
40
Dp, nm
80
323
10
24
50
Dp, nm
108
261
Some Aerosol Optical and Microphysical
Properties of Aerosol Plumes over South Pacific
NOTE: sp  =550 nm & ap  =565 nm
1.0x10
8.0x10
4.0x10
-6
sub-m sp (1/m)
6.0x10
-6
-7
4.0x10
y-int.=-3.54x10 (1/m)
slope=0.242
-6
2
R =0.890
2.0x10
-5
F18
F17
F12
F18
F17
F12
3.0x10
ap (1/m)
Scattering vs.
absorption
coefficients
suggest a
typical single
scattering
albedo of 0.81
-5
-6
2.0x10
1.0x10
-5
-5
-7
-5
y-int.=-5.67x10 (1/m)
 = sp/( sp+ ap)=1/(1+slope)
=0.81
6
slope=7.51x10 (1/m)
2
R =0.998
0.0
0.0
0.0
1.0x10
-5
2.0x10
-5
3.0x10
-5
4.0x10
-5
5.0x10
0
-5
 sp (1/m)
2
3
4
3
5
3
sub-m unheated V (m /cm )
1.5
1.0x10
F18
F17
F12
8.0x10
-5
Light absorption
and refractory
volume are
related with
values
indicative of a
soot carbon
core
F18
F17
F12
-6
3
sub-m ref. V (m /cm )
1.0
3
3
3
y-int.=-0.03 ( m /cm )
slope=0.26
ap (1/m)
Submicrometer
total and
refractory (soot)
volume are
related for these
plumes
indicating
similar
refractory
fraction in
aerosol
1
2
R =0.980
0.5
6.0x10
4.0x10
-6
-6
-7
2.0x10
y-int.=-3.34x10 (1/m)
-6
6
slope=7.33x10 (1/m)
2
R =0.910
0.0
0.0
0
1
2
3
4
3
3
sub-m unheated V (m /cm )
5
0.0
0.5
1.0
3
1.5
3
sub-m ref. V (m /cm )
Submicrometer
scattering and
volume are
strongly linear
indicating a
similar particle
size
independent
of
concentration
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