OMI NO2 observations of boreal forest fires
Nicolas Bousserez, Randall V. Martin, Lok Lamsal,
and the ARCTAS team
Dalhousie University Halifax, Nova Scotia
ARCTAS experiment Spring/Summer 2008
Summer phase (June, 18 - July, 13)
Boreal forest fires over center Canada
DC-8 measurements:
NOx concentrations
Aerosols optical properties
Boreal fires emissions over ‘Alberta’ domain
OMI (DOMINO KNMI) NO2 tropospheric columns
MODIS Aerosol Optical Depth (AOD)
MODIS fire pixels
ARCTAS summer phase averaged NO2 and AOD tropospheric columns
Summer Phase (18/06 to 13/07)
Tropospheric AOD NO2 Tropospheric Columns
GEOS-Chem v8-01-01
Modifications:
- David Streets 2006 emissions over SE Asia & China
- FLAMBE daily biomass burning emissions GEOS-5 Metfields
Horizontal Grid: 2º lat x 2.5º lon
Vertical Grid: Reduced 47 layers
Bias in GC
GC
DC-8
NO2 (pptV)
Ext
inct
ion
coef
ficie
nt (5
50nm
) (M
m-1
)
-DC-8 criteria:
HCN > 500 pptV NOx/NOy > 40%
-GC criteria:
CObb > 90% Total CO (sensitivity runs)
Impact of aerosols and GC NO2 profiles on NO2 retrievals?
AMF with explicit aerosols and clouds correction (LIDORT model)
GEOS-Chem provides NO2 profiles (shape factor) and aerosol optical properties (scattering weights calculation)
Ωv = Ωs / AMF
Shape factor Scattering weights
Ωs = Slant Column Ωv = Vertical Column AMF = Air Mass Factor
AMF Aerosol Correction Factor ~ + 7.5 %
AMF Shape Factor Correction Factor ~ - 35 %
Shape factor impact dominates
AMF/AMFw/o aerosols
AMF/AMFw/o bb emissions
SSA
Mostly Scattering Aerosols
DC-8
GC
Single Scattering Albedo(SSA)
DC-8 GC
KNMI (DOMINO) KNMI_gc
(w/ GC profiles)
Correction over boreal fires: NO2 KNMI_GC ~ 2*NO2 KNMI
BB criteria: data points close to MODIS
hot spot pixels (r < 10 km)
NO2
AO
D (M
OD
IS)
OMI NO2 / GCstd NO2
AM
F co
rrec
ted
/ AM
F st
anda
rd
Linear relationship between AMF correction factor and OMI NO2/GCstd NO2 ratio?
Real-time correction to measured NO2 columns over boreal fires areas
In practice, exclude data when AMFcorrected/AMFstandard < 0.2
OMI NO2 - GCstd NO2 > 0.5 x GCstd NO2 r = -0.68 y = -0.10 x + 0.76 nb pts = 11