 |
| Titel |
Quantifying pyroconvective injection heights using observations of fire energy: sensitivity of spaceborne observations of carbon monoxide |
| VerfasserIn |
S. Gonzi, P. I. Palmer, R. Paugam, M. Wooster, M. N. Deeter |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 8 ; Nr. 15, no. 8 (2015-04-29), S.4339-4355 |
| Datensatznummer |
250119668
|
| Publikation (Nr.) |
 copernicus.org/acp-15-4339-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| We use observations of active fire area and fire radiative power (FRP) from
the NASA Moderate Resolution Imaging Spectroradiometers (MODIS),
together with a parameterized plume rise model, to estimate biomass
burning injection heights during 2006. We use these injection heights
in the GEOS-Chem (Goddard Earth Observing System Chemistry) atmospheric chemistry transport model to vertically
distribute biomass burning emissions of carbon monoxide (CO) and to
study the resulting atmospheric distribution.
For 2006, we use over half a million FRP and fire area observations as
input to the plume rise model. We find that convective heat fluxes
and active fire area typically lie in the range of 1–100 kW m−2
and 0.001–100 ha, respectively, although in rare circumstances the
convective heat flux can exceed 500 kW m−2. The resulting injection
heights have a skewed probability distribution with approximately
80% of the injections remaining within the local boundary layer (BL),
with occasional injection height exceeding 8 km.
We do not find a strong correlation between the FRP-inferred surface
convective heat flux and the resulting injection height, with
environmental conditions often acting as a barrier to rapid vertical
mixing even where the convective heat flux and active fire area are
large. We also do not find a robust relationship between the
underlying burnt vegetation type and the injection height.
We find that CO columns calculated using the MODIS-inferred injection
height (MODIS-INJ) are typically −9 to +6%
different to the control
calculation in which emissions are emitted into the BL,
with differences typically largest over the point of emission.
After applying MOPITT (Measurement of Pollution in the Troposphere) v5 scene-dependent averaging kernels we find
that we are much less sensitive to our choice of injection height
profile. The differences between the MOPITT and the model CO columns
(max bias ~ 50%), due largely to uncertainties in emission
inventories, are much larger than those introduced by the injection heights.
We show that including a realistic diurnal variation in FRP (peaking
in the afternoon) or accounting for subgrid-scale emission errors does
not alter our main conclusions.
Finally, we use a Bayesian maximum a posteriori approach constrained by
MOPITT CO profiles to estimate the CO emissions but because of the
inherent bias between model and MOPITT we find little impact on the
resulting emission estimates.
Studying the role of pyroconvection in the distribution of gases and
particles in the atmosphere using global MOPITT CO observations (or
any current spaceborne measurement of the atmosphere) is still
associated with large errors, with the exception of a small subset of
large fires and favourable environmental conditions, which will
consequently lead to a bias in any analysis on a global scale. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|