Biomass Smoke Aerosol:Spatial and Temporal Pattern over the US

October 2005rhusar@me.wustl.edu

Estimation of Smoke Mass

• The estimation of smoke mass from speciated aerosol data has eluded full quantification for many years

• CIRA, Poirot and others have • While full quantification is still not in hand, a proposed

approximate approach yields reasonably consistent results

• The smoke quantification consists of two steps:– Step 1: Carbon apportionment into Smoke and NonSmoke parts– Step 2: Applying factors to turn OCSmoke and OCNonSmoke into

Mass

Smoke Quantification using Chemical Data

– Step 1: Carbon apportionment into Smoke and NonSmoke partsCarbon (OC & EC) is assumed to have only two forms: smoke and non-smoke

OC = OCS (Smoke) + OCNS (NonSmoke)EC = ECS (Smoke) + ECNS (NonSmoke)

In each form, the EC/OC ratio is assumed to be constantECS/OCS = rs (In smoke, EC/OC ratio rs =0.08)ECNS/OCNS = rns (In non-smoke, EC/OC ratio rns = 0.4)

With thes four equations, the value of the four unknowns can be calcualted OCS = (rns*OC –EC)/(rns-rs) = (0.4*OC – EC)/0.32OCNS = OC-OCSECS = 0.088*OCSECNS = 0.4*OCNS

– Step2: Apply a factor to turn OC into MassThe smoke and non-smoke OC is scaled by a factor to estimate the mass

OCSmokeMass = OCS*1.5OCNonSmokeMass = OCNS*2.4

Smoke Excess OC – EC Calibration of Smoke Composition

• Smoke (excess) PM25, EC and OC yields calibration• Ratios for Kansas, Big Bend and Quebec smoke are similar• Good news for OC apportionment

PM25

ECOC

Smoke:EC/OC = 0.08PM25/OC = 1.5

EC/OC Ratio

OC–EC Non-Smoke Calibration by Iteration

• Non-smoke ratios are more difficult• EC/OC of about 0.2-0.4 is reasonable• Outside this range is not

EC/OC Non-Smoke = 0.15 EC/OC Non-Smoke = 0.2

EC/OC Non-Smoke = 1EC/OC Non-Smoke = 0.4

Negative Smoke – not Possible Maybe??

Maybe?? Too little non-smoke too much smoke

Smoke OC

Non Smoke OC

Measured and Reconstructed PM25 Mass

• Regional ‘calibration’ constants we applied to OC and Soil

OCS, OCNS and PM25 Seasonal PatternAverage over 2000-2004 period

PM25Mass

OCS Smoke

OCNS NonSmoke

Day of Year

Mexican Smoke

Agricultural Smoke

Urban NonSmoke Carbon

OC Smoke Spatial Pattern

Dec Jan Feb

Sep Oct Nov

Mar Apr May

Jun Jul Aug

EC NonSmoke

Dec Jan Feb

Sep Oct Nov

Mar Apr May

Jun Jul Aug

PM2.5 (blue) and ‘SmokeMass’ (red)

Smoke Events

Kansas Ag Smoke

Example OC ‘Smoke’ Events

Smoke Events

Seasonality of OC

Percentiles

• IMPROVE/STN Inconsistencies Not shown here

Great Smoky Mtn:

Episodic OC in the Fall season

Chattanooga::

Elevated and Persistent OC

GRSM Seasonal Pattern of Percentiles

PM25

OC

SO4

Soil

Episodic

Episodic

OC in Fall dominates episodicity - Smoke Organics?

Monthly Maps of Fire Pixels

• Fire pixels are necessary but not sufficient• Some Fire pixels produce more smoke aerosol than others …by at least factor of 5

NOAA HMS – S. Falke

Jan Feb Mar Apr

AugJun JulMay

Sep Oct Nov Dec

Smoke

Kansas Ag Smoke

No Smoke

Summary

• Developments (CIRA, Poirot, others) • OC and EC can be reasonably apportioned between Smoke

and NonSmoke components

• The reconstructed mass can be matched to the measured PM25

Problems of OC Apportionment

• Need to incorporate biogenic OC!• IMPROVE and STN OC don’t match

• Some coefficients may need regional/seasonal calibration