Pyro-convective smoke plume observed at ~10 km over British Columbia, June 2004

Vertical transport of surface fire emissions observed from space

Siegfried Gonzi, Paul Palmer

Fires are an integral part of many natural ecosystemsPlant responses post-fire include:•Increased productivity•Increased flowering •Fire stimulated seed release and dispersal •Improved germination

US Fire Administration

Estimates of Global emissions from Biomass burning

Biomass burning (Tg Element/yr)

All Sources (Tg Element/yr)

Biomass burning (%)

CO2 3500 8700 40

O3* 420 1100 38

CO 350 1100 32

NMHC 24 100 24

NOx 8.5 40 21

CH4 38 380 10

EC 19 22 86

Quantifying the perturbation of fires on contemporary climate

Given the importance of fires in climate we want to answer 4 simple first-order questions about fire:

1.Where?

2.When?

3.How big?

4.How high?

We have been able to infer biomass burning characteristics for more than a

decade

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For the Along-Track Scanning Radiometer (ATSR), 1995-present:

Fire “hot spots” are determined using the 3.7 m channel. Fitted radiant temperatures greater than a threshold are labelled as fire.

Given the importance of fires in climate we want to answer 4 simple first-order questions about fire:

1.Where?

2.When?

3.How big?

4.How high?

Polar-orbiting satellites have sufficient coverage to infer information about variability on timescales from diurnal to year-to-year

5-years of Terra MODIS data (11/00 – 10/05)

Firecounts have disadvantages

There are a number of technical problems with the data but more importantly, these data do not tell you

1)about the intensity of the fire

2)about the emissions from the fire

Given the importance of fires in climate we want to answer 4 simple first-order questions about fire:

1.Where?

2.When?

3.How big?

4.How high?

Bottom-up emission estimates

M = A x B x a x b

Grams of dry matter burned per year

Total land area burned annually

The average organic matter per unit area

Fraction of above ground biomass relative average biomass B

Burning efficiency of the above ground biomass

Emission factors for flaming and smouldering fires

Space-borne observations of trace gases released by fires

Forward model H

Inverse model

Observations y

Emissions xBB

BF

Top-down methodology

)]([ aobs

ap H xyKxx

Posterior Prior Gain matrix

Observations

Forward model

ap PKHP )( 1

)( aobs H xy

Top-down emission estimates based on inverse model calculations or process-

based models

GFEDv2 CO Emissions for JJASO 2006 [g CO/m2]

Given the importance of fires in climate we want to answer 4 simple first-order questions about fire:

1.Where?

2.When?

3.How big?

4.How high?

MOPITT CO column data, c/o Edwards et al, 2006

Estimating injection heights of biomass burning plumes

•Atmospheric transport of fire emission depends on the height at which emissions are injected into the atmosphere

•Transport models typically assume fire emissions only in the first few kms but observations show that emissions can reach mid-high troposphere (5-10km)

Injection height Smoke entrained

in mean flow

Injection height is a complex function of fuel loading, overlying meteorology, etc

Multi-angle Imaging SpectroRadiometer- MISR

9 view angles at Earth surface: nadir to 70.5º forward and backward

4 bands at each angle:446, 558, 672, 866 nm

Continuous pole-to-pole coverage on orbit dayside

400-km swath9 day coverage at equator2 day coverage at poles

Overpass around local noon time in high and mid- latitudes

275 m - 1.1 km sampling

In orbit aboard Terra since December 1999

Stereographic projection provides information about fire smoke aerosol height layer

5-30% smoke emissions are injected above the North American boundary layer

(2002-2007)

Kahn et al, [2008]

Distribution of MISR heights-PBL for smoke plumes

2004Alaska-Yukon

Kahn et al, GRL, 2008

We use CO as a tracer for incomplete combustion

We use cloud-free data from two instruments aboard the NASA Aura spacecraft (left):

Tropospheric Emission Spectrometer (TES)

Microwave Limb Sounder (MLS)

Over burning scenes, together they are sensitive to changes in CO from the lower troposphere to the upper troposphere/lower stratosphere

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We develop the traditional surface emission inverse

problemBoth sides describe the sensitivity of the measured quantity y to changes in surface emissions e

We estimate emitted CO mass in five regions from 0 – 15 km.

During June-October 2006 we use 1785 TES profiles (672 colocated with MLS)

Omitting gory details, only 2-3% of retrievals failed.

Define an injection height as the maximum height at which:

1)Posterior uncertainty is smaller than prior by 50%

2)Posterior mass is higher than the prior mass

33% pass this criterion; remaining 67% assume boundary layer injection

•We estimate an injection height of greater than 10 km (recall we estimate mass over large vertical regions)

•Posterior CO mass increased by 50% due to biomass burning.

(Limited) evaluation of our product: Indonesia, October 2006

2 = cloud 3 = aerosol

Level of neutral buoyancy = 138 hPa

Nearby radiosonde

Disproportionate impact of large fires: Cctrl-Cptb

Longitude [deg]

Boreal (42-67oN)Tropics (0-30oS)

Pre

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re [

hPa]

Concluding remarks

•In terms of climate, there is a lot we don’t know about fires.

•The height at which emissions are injected influence transport of surface air pollutants (BORTAS)

•Injections above the boundary layer is relatively rare but results in disproportionate perturbations.

•Key challenge: to combine Bayesian inference and CFD approaches to develop robust predictive models.