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