Geoscience Reference
In-Depth Information
Major sources of NO
x
are attributed to anthropogenic activities (e.g. high tem-
perature combustion processes), biomass burning (intentional and accidental), soil
microbial production, and lightning strikes (Lee et al.
1997
).
Since the launch of the Global Ozone Monitoring Experiment (GOME) on board
ESA
s European Remote Sensing (ERS)-2 satellite (Burrows et al.
1999
), NO
2
total
and tropospheric vertical columns have been retrieved from nadir measurements by
applying the Differential Optical Absorption Spectroscopy (DOAS) method, intro-
duced by Perner and Platt (
1979
). The GOME-2 on board the Meteorological Oper-
ational (MetOp) satellites is an improved version of GOME (Callies et al.
2004
) and
was launched in October 2006 (MetOp-A) and in September 2012 (MetOp-B).
Large vegetation
'
fires, which are known to occur every single month on our
planet, emit large amounts of trace species into the atmosphere, among them NO
x
.
During the combustion process, nitrogen (N) present in the fuel is converted in part
into oxides and N present in amino acids is converted to NO. However, NO
x
may
also result from the reaction of molecular nitrogen (N
2
) with O
2
at very high
temperatures (Andreae and Merlet
2001
).
Fire radiative power (FRP) is a parameter describing the radiant component of
energy release from a
ed in the infrared spectral range (Kaufman
et al.
1998
). First analyses of satellite-based FRP measurements have indicated clear
spatio-temporal differences in the energy radiated by active
fire and is quanti
res (Wooster and Zhang
2004
). Moreover, Wooster et al. (
2005
) have found proportionality between FRP and
the combustion rate, which quantitatively links FRP to dry matter combustion rate.
Emission factors (EFs) of NO
x
are used in bottom-up emission inventories for
the translation of biomass burned into trace gas emissions (e.g. van der Werf et al.
2010
; Kaiser et al.
2012
). These parameters have been mainly derived from labo-
ratory-controlled combustion experiments and
field measurements (Andreae and
Merlet
2001
; Akagi et al.
2011
).
Recently, satellite measurements of NO
2
have been used for the evaluation of
fire emission rates (FERs) and EFs of NO
x
for different biomes and regions (Mebust
and Cohen
2013
; Castellanos et al.
2014
; Schreier et al.
2014a
,
b
). These studies
provide an important complementary collection of EFs for the community.
In this study, the satellite-based estimation of FERs and EFs of NO
x
is dem-
onstrated in a summarized form and EFs of NO
x
as obtained from GOME-2
measurements are presented for the major land cover types burned.
2 Data and Methods
2.1 Satellite Measurements of TVC NO
2
As in most recent studies, the retrieval of tropospheric NO
2
vertical columns (TVC
NO
2
) from the GOME-2 measurements is achieved in four steps.
In the
first step, the trace gas concentration integrated along the light path (slant
column density or SCD) is determined by applying the Differential Optical
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