Upload
kita
View
48
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Observations of an Atmospheric Chemical Equator and its Implications for the Tropical Warm Pool Region. - PowerPoint PPT Presentation
Citation preview
Observations of an Atmospheric Chemical
Equator and its Implications for the
Tropical Warm Pool Region
Jacqueline F. Hamilton1, Grant Allen2, Nicola M. Watson1, James D. Lee1, Julie E. Saxton1, Alastair C. Lewis1, Geraint Vaughan2, Keith N. Bower2, Michael J. Flynn2, Jonathon Crosier2, Glenn D. Carver3, Neil R.P. Harris3,
Robert J. Parker4, John J. Remedios4, Nigel A.D. Richards5
1Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.2School of Earth, Atmospheric and Environmental Science, Sackville St Building, Sackville St, University of
Manchester, Manchester, M60 1QD, UK. 3Chemistry Department, University of Cambridge, Cambridge, CB2 1TN, UK.
4Earth Observation Science, Space Research Centre, Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK.
5Institute for Atmospheric Science, School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
J. Geophys. Res., 113, D20313, doi:10.1029/2008JD009940, (2008).
Overview• Flight tracks• Meteorology• Results
– Chemical characteristics – Trajectory analysis and biomass burning
• Comparison with Satellite and Model data
• Conclusions• Acknowledgements
• 2 measurement periods– Pre-monsoon (October – December 2005)– Monsoonal (January – March 2006)
• Monsoon period was composed of a number of different meteorological conditions– Active monsoon– Inactive monsoon– Break Period – with intense “Hector” storms over
Tiwi islands
Strong Westerly wind in Darwin, inhibited local convectionFlew north looking for the boundary between northern and southern hemispheric air.
Introduce the generic term “Chemical Equator” to describe a
defined boundary between tropospheric air of northern and
southern hemispheric origin• Generally associated with the Inter-Tropical
Convergence Zone (ITCZ)• ITCZ is a low pressure region circling the globe where
the trade winds associated with the Hadley circulation in NH and SH meet
• Characterised by rapid vertical uplift and heavy rainfall• Provide a meteorological barrier to cross equatorial flow
in the troposphere – exchange times around 6 months
Previous Studies of Chemical Equators• There have been a number of studies of the
characteristics on either side of the chemical equators associated with the ITCZ using aircraft
• Chemical Equators (CE) separates polluted NH from the pristine SH
• Differences in chemical signatures on each side dependant on location. Carbon Monoxide (CO) can be used as a tracer for transport of pollution– PEM-TROPICS B – CO 6-15 ppb higher N of ITCZ– INDOEX – average CO was 49 ppb at 5 º S and 175 ppb at 5 ºN
• Ship measurements during INDOEX showed factor of 3-4 increase in CO crossing the ITCZ
• Transition was found to be sharp – over the course of a day.
Chemical Equator • Difficult to sample across the ITCZ in aircraft as it is a
highly convective region• ITCZ is a complex system – can break down and reform• A boundary between air with NH and SH chemical
signatures does not have to be associated with the ITCZ– Chemical Equator
• Chemical and aerosol data collected across a chemical equator using the Dornier during ACTIVE will be presented– High time resolution measurements of CO, O3 and aerosol
properties across the boundary– Lower-time resolution measurements of VOCs and CFCs give
averaged profiles on either side of the boundary
Flight Tracks• Flights part of ACTIVE – Dornier Survey
Flights– SD019 – 30th January 2006– SD022 – 3rd February 2006SD019 SD022
MeteorologySD019 30th Jan SD022 3rd Feb
MTSAT Infrared images 14:03 local
ECMWF Mean Sea level pressure and 10 m winds 15:30 local
Results – Time Series
CO O3
Aerosol
AMS
10
30
50
70
90
110
130
150
170
14:09:36 14:52:48 15:36:00 16:19:12 17:02:24 17:45:36 18:28:48
CO
(ppb
), A
lt/20
(m)
-2
8
18
28
38
48
58
68
Ozone (ppb)
COAltitude/20Ozone
10
30
50
70
90
110
130
150
170
14:38:24 15:21:36 16:04:48 16:48:00 17:31:12 18:14:24
CO
(ppb
), Al
t/20
(m)
-2
8
18
28
38
48
Ozone (ppb)
COAltitude/20Ozone
0
50
100
150
200
250
300
14:38:24 15:21:36 16:04:48 16:48:00 17:31:12 18:14:24
Grim
m, A
SP
, FS
SP
*10
(Par
ticle
s cm
-3)
0
200
400
600
800
1000
1200
1400
1600
1800
2000
CP
C (P
articles cm-3)
GRIMMASPFSSP*10CPC
-1
0
1
2
3
4
5
6
7
8
14:38:24 15:21:36 16:04:48 16:48:00 17:31:12 18:14:24
Time Local (Darwin)
Mas
s Lo
adin
g (m
g m
-3)
SULPHATEORGANICNITRATE
0
20
40
60
80
100
120
140
160
14:09:36 14:52:48 15:36:00 16:19:12 17:02:24 17:45:36 18:28:48G
rim
m,
AS
P, F
SS
P*1
0 (
Pa
rtic
les
cm-3
)
0
500
1000
1500
2000
2500
3000
3500
4000
CP
C (P
article
s cm-3)
GRIMMASPFSSP*10CPC
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
14:09:36 14:52:48 15:36:00 16:19:12 17:02:24 17:45:36 18:28:48
Time Local (Darwin)
Mas
s Lo
adin
g (
g m
-3)
SULPHATEORGANICNITRATE
Time Local (Darwin) Time Local (Darwin)
Mas
s Lo
adin
g (
g m
-3)
Mas
s Lo
adin
g (
g m
-3)
Grim
m, A
SP, F
SSP*
10 (P
artic
les
cm-3)
Grim
m, A
SP, F
SSP*
10 (P
artic
les
cm-3
)CO
(ppb
), Al
t/20
(m)
CO (p
pb),
Alt/2
0 (m
)
Ozone (ppb)
Ozone (ppb)
CPC (Particles cm
-3)
CPC
(Particles cm-3)
SD019 SD022
CO and Ozone• CO is an ideal tracer for transport of pollution sources
– Photo-chemically produced via oxidation of CH4 and VOCs– Direct emission from incomplete combustion sources
(biomass/fossil)• Ozone – by-product of VOC oxidation in presence of NOx.• Coloured flight path by CO (40-150ppb). Transition at chemical
equator is sharp (CO 40 to 165 ppb within 50 km)
ChemicalEquator
ChemicalEquator
SD019
SD022
Air Mass Origin
Coloured by CO40 ppb blue-160 ppb red
5 day back trajectory10 day back trajectory
Back trajectories calculated along the flight track using NOAA’s HYSPLIT model
CO and Ozone• Using trajectory analysis have separated the data according to
hemispheric origin (over the previous five days)
• Definite correlation between CO and O3 in NH air in SD022. Not as clear in SD019.
• Ratio of O3:CO in polluted NH air was 0.16.• Similar to INDOEX – polluted air masses from India 0.14-0.16 • SE Asia biomass burning plumes – 0.12-0.2 Stehr et al., JGR-Atmos., 107, 19, 2002.
Kondo et al., JGR-Atmos, 109, 2004
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
0 20 40 60 80 100 120 140 160 180 200
CO (ppb)
Ozo
ne (p
pb)
Originated in NHOriginated in SH
y = 0.166x + 7.7424R2 = 0.4509
y = -0.0965x + 24.742R2 = 0.0285
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0 20 40 60 80 100 120 140 160 180 200
CO (ppb)
Ozo
ne (p
pb)
Orginating in NHOrginating in SHLinear (Orginating in NH)Linear (Orginating in SH)
SD019 SD022
Gas phase organics• Collected air samples onto absorbent tubes during flights and analysed using gas chromatography with time of flight mass
spectrometry. • 5 minute sample time – 15 tubes per flight.• Typical SH background concentrations determined using other flights under similar met conditions. (AD018 and SD020/21 –
Survey flights to Alice Springs) • Average VOC concentration determined for samples collected when air originated in NH.
• Elevated aromatic concentrations indicate a larger anthropogenic pollution source north of the chemical equator. Tracers for fossil fuel burning and transportation (i.e. evaporations from petrol stations)
• Also seen with other petroleum markers e.g. alkanesSH air (ppt) NH air (ppt) SH air (ppt) NH air (ppt)
ethyl benzene 5.2 60.0 4-ethyl toluene 2.3 17.0m + p xylene 15.9 73.6 1,3,5-trimethyl benzene 3.3 28.5o -xylene 5.3 47.7 1,2,4-trimethyl benzene 5.9 37.5propyl benzene 1.6 30.5 1,2,3-trimethyl benzene 2.2 19.7isopropyl benzene 0.6 10.5 nonane 17.5 75.33-ethyltoluene 1.7 9.3
Biomass burning• The Moderate Resolution Imaging Spectroradiometer
(MODIS) onboard the Terra and Aqua Satellites can be used to detect thermal anomalies including fire occurrence
• Data obtained from http://landweb.nascom.nasa.gov/cgi-bin/browse/browse.cgi
Extensive fires burning in North Sumatara and SE Asia (Thailand)
Elevated pollutant levels are a result ofBIOMASS BURNING
ANDHIGHER BACKGROUND IN N. HEMISPHERE
Weekly mean upper troposphere MLS Cloud Filtered CO profile (ppbv) at approximately 215 mbar (29 January – 4 February 2006)
Evidence for uplift in convection?
Comparison to Satellite dataThe chemical equator can clearly been seen in the Western Pacific region in the TES data
The change in magnitude is not as great as in the in-situ measurements - due to averaging over an 11-day time period to obtain sufficient satellite coverage - averaging over the vertical column (approximately 5 km) and the higher tangent altitude of TES observations (mid-troposphere).
TES CO profile (ppbv) at approximately 600 mbar (25 January – 5 February 2006)
Modelling of Chemical equator• CO modelled using p-TOMCAT chemical transport
model, using ECMWF operational analyses.• Models chemistry, emissions, boundary layer mixing
and convective parameterisation were switched off– Advecting passive tracers only – features which
develop are due to forcing from analysed winds
Horizontal resolution (0.75 x 0.75 degrees)31 Vertical levels up to 10hPaHigh-resolution model initialised from lower resolution
run (that included all the model’s processes) at 1st January 2006.
Modelling of Chemical equatorHorizontal (830mb) Vertical (130 E)
SD01930/01/2006
SD02203/02/2006
The famous plot!!!
The Press!!
• Some of the weirder titles– 'Chemical equator' protects Antarctica's
clean air – There's A 'Chemical Equator' - And We're On
The Wrong Side Of It– Discovered: Nature Segregates Dirty, Rich
Nations From Clean, Poor World
Appeared in Nature, New Scientist, National Geographic, Discovery Channel, MSNBC, Fox
Conclusions and Implications• Evidence of a chemical equator was investigated using a
comprehensive combination of chemical and meteorological tools and techniques, over a broad range of spatial and temporal scales, using the expertise of a large team of international scientists
• Transition was very sharp indicating inhibited inter-hemispheric mixing– CHEMICAL EQUATOR
• The effect of the CE is amplified by the landphoon to the south transporting very clean air from the Southern Ocean and extensive biomass burning in Sumatra and SE Asia to the north.
• In both flights, the air north of the chemical equator is highly polluted (CO, Ozone, aerosols and aromatic VOCs).
• Back trajectory analysis indicates that this polluted air has travelled to the chemical equator through a highly active convective region.
• Aircraft measurements indicate that deep convection in the TWP is an important mechanism (via rapid vertical transport) for injecting large quantities of highly polluted air to the upper troposphere.
• Comparison with satellite and model data indicates air lofted in the TWP may be highly polluted.
Acknowledgements• Thanks go to the rest of the ACTIVE team who took part,
particularly those whose data has been used
• Thanks to the pilots of the Dornier and staff at the Airborne Remote Sensing Facility (ARSF)
• Thanks to the collaborative projects SCOUT-O3 and TWP-ICE and the Australian Bureau of Meteorology. Satellite data and Met analysis are courtesy of TWP-ICE and BoM.
• Jonathan Jiang at JPL for MLS plots and the TES science team at JPL
• Fire count data was obtained from the World Fire Atlas project, the Data User Element of the European Space Agency, and plotted by Manasvi Panchal.