Exceptional Emissions of NH3 and HCOOH in the 2010 Russian Wildfires

EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmos. Chem. Phys., 13, 4171–4181, 2013 Atmospheric Atmospheric www.atmos-chem-phys.net/13/4171/2013/ doi:10.5194/acp-13-4171-2013 Chemistry Chemistry © Author(s) 2013. CC Attribution 3.0 License. and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Exceptional emissions of NH3 and HCOOH in the 2010 Russian Open Access wildfires Biogeosciences Biogeosciences Discussions Y. R’Honi1, L. Clarisse1, C. Clerbaux1,2, D. Hurtmans1, V. Duflot1, S. Turquety3, Y. Ngadi1, and P.-F. Coheur1 1Spectroscopie de l’Atmosphere,` Chimie Quantique et Photophysique, Universite´ Libre de Bruxelles (U.L.B.), Brussels, Open Access Belgium Open Access 2UPMC Univ. Paris 06, Universite´ Versailles St.-Quentin, CNRS/INSU, LATMOS-IPSL, Paris, France Climate 3UPMC Univ. Paris 06, CNRS/INSU, LMD-IPSL, Paris, France Climate of the Past of the Past Correspondence to: Y. R’Honi ([email protected]) Discussions Open Access Received: 25 October 2012 – Published in Atmos. Chem. Phys. Discuss.: 7 December 2012 Open Access Revised: 18 March 2013 – Accepted: 22 March 2013 – Published: 18 April 2013 Earth System Earth System Dynamics Dynamics Abstract. In July 2010, several hundred forest and peat fires 2011), but uncertainties remain due to the lack of measure- Discussions broke out across central Russia during its hottest summer ments over larger areas or periods; this is particularly true for on record. Here, we analyze these wildfires using observa- the total emission of reactive species. Open Access Open Access tions of the Infrared Atmospheric Sounding Interferometer The polar orbiting InfraredGeoscientific Atmospheric Sounding Inter- Geoscientific (IASI). Carbon monoxide (CO), ammonia (NH3) and formic ferometer (IASI), whichInstrumentation measures globally the Earth’s out- Instrumentation acid (HCOOH) total columns are presented for the year 2010. going infrared radiation atMethods a high spectral and resolution and Methods and Maximum total columns were found to be one order (for CO low instrumental noise (Clerbaux et al., 2009), is an excel- Data Systems Data Systems and HCOOH) and two orders (for NH3) of magnitude larger lent tool for observing and analyzing trace gas emissions than typical background values. The temporal evolution of from strong fire events (Coheur et al., 2009; Turquety et al., Discussions Open Access Open Access NH3 and HCOOH enhancement ratios relative to CO are 2009; Clarisse et al., 2011). Its potential to monitor CO (car- Geoscientific presented. Evidence of secondary formation of HCOOH is bon monoxide) from vegetationGeoscientific burning has frequently been Model Development found, with enhancement ratios exceeding reported emission used. MeasurementsModel of other Development fire emission products, such as ratios in fresh plumes. We estimate the total emitted masses NH3 (ammonia) or volatile organic compounds, have in con- Discussions for the period July–August 2010 over the center of western trast not much been exploited. Such measurements can di- Open Access Russia; they are 19–33 Tg (CO), 0.7–2.6 Tg (NH3) and 0.9– rectly improve our knowledge of fire emissionsOpen Access and fluxes. 3.9 Tg (HCOOH). For NH3 and HCOOH, these quantities These currently rely onHydrology the remote sensing and of fire counts Hydrology and are comparable to what is emitted in the course of a whole (e.g. Kasischke et al., 2003) and fire radiation power (e.g. year by all extratropical forest fires. Wooster et al., 2005), withEarth application System of tabulated average Earth System values of emission factors. HereSciences we study simultaneous CO, Sciences NH3 and HCOOH (formic acid) fire emissions in the 2010 Discussions Open Access Russian fires. It is the first time that such a largeOpen Access spatial- 1 Introduction and temporal-scale case study for a fire event is undertaken Ocean Science for NH3 and HCOOH.Ocean IASI CO Science observations of these fires Biomass burning is a major source of atmospheric trace gases (Yurganov et al., 2011; Krol et al., 2012) are used to test our Discussions and aerosols (Crutzen and Andreae, 1990). Boreal forest fires methodology and for the calculation of enhancement ratios. contribute significantly to these emissions and are also im- We use total columns of NH3 and CO from the FORLI (Fast- Open Access portant as they can severely affect air quality in populated Optimal Estimation Retrievals on Layers for IASI)Open Access near-real- regions of the Northern Hemisphere (Langmann et al. (2009) time retrieval software (Hurtmans et al., 2012) and a retrieval Solid Earth and references therein). Many laboratory, field and aircraft scheme based on brightness temperatureSolid Earth difference between studies have been conducted to characterize the composi- a perturbed and a reference channel (BTD) for HCOOH Discussions tion of fire plumes (Andreae and Merlet, 2001; Akagi et al., Open Access Open Access Published by Copernicus Publications on behalf of the European Geosciences Union. The Cryosphere The Cryosphere Discussions 4172 Y. R’Honi et al.: Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires

(Razavi et al., 2011). Only the daytime data, which are more marize our findings, in particular on the magnitude of the sensitive to surface concentrations, have been used. In ad- exceptional HCOOH and NH3 emissions. dition, NH3 and HCOOH are retrieved only when enough spectral information is available (see Sect. 5). Formic acid is an important volatile organic compound in 2 Distributions and time series of total columns the atmosphere; but uncertainties in its global budget remain large (Stavrakou et al., 2011). The majority is photochem- Average total columns of CO, NH3 and HCOOH are shown ically produced from non-methane hydrocarbons. It is also in Fig. 1 over Europe and Asia in grid cells of 0.5◦ × 0.5◦, released directly in the atmosphere from terrestrial vegeta- from 27 July (corresponding to the first IASI observation of tion and biomass burning, for which the total (primary) emis- the fire plumes) to 27 August (a few days after the end of the sions account for 1–4 Tg yr−1 (Paulot et al., 2011; Stavrakou fires) of 2010. There are some differences between the spatial et al., 2011). NH3 is the most important base in the atmo- extents of CO, NH3 and HCOOH. These can be explained sphere and is released primarily from agriculture (76 %), by differences in lifetime (see Sect. 4), but also by the fact ◦ natural sources (19 %) and fossil fuel burning (5 %). Natu- that we have a more limited sensitivity above 55 N for NH3 ral fires only account for 4 % of the total emissions totaling and HCOOH related to thermal contrast (see Sect. 5). Note 5–15 Tg yr−1 (European Commission, Joint Research Cen- also that the red box in Fig. 1, extending in the area of 40– tre (JRC)/Netherlands Environmental Assessment Agency 75◦ N and 30–150◦ N, is the same area as the one considered (PBL), 2011). in the study of Yurganov et al. (2011). This choice was made During the summer of 2010, central European Russia intentionally to facilitate the comparison of our results to that endured the driest and hottest July ever recorded. Witte earlier study. et al. (2011) reported anomalously high temperatures (35– Very high total columns were observed during the event 41 ◦C, compared to average temperatures of 15–20 ◦C usu- for the three species. Figure 2a shows the temporal evolution ally observed in the summer season) and low relative humid- of the retrieved total column maximums during a two month ity (9–25 %) from mid-June to mid-August 2010, from ra- period that includes the fires (1 July to 1 September 2010) diosonde measurements in western Russia. The intense heat in the area corresponding to the red box in Fig. 1; Fig. 2b and drought wave initiated hundreds of wildfires in Euro- shows the mean total columns for the year 2010 covering pean Russia and burned forests, grasslands, croplands, fields the same area. In Fig. 2a one sees a significant increase of and urbanized areas across a massive region around Moscow total columns at the end of July, which corresponds to the (Shvidenko et al., 2011), severely affecting the air quality beginning of the fires (more precisely on 27 July) reaching (Elansky et al., 2011a,b; Fokeeva et al., 2011; Konovalov a maximum emission on 2, 10 and 15 August respectively et al., 2011; Zvyaginstev et al., 2011; Golitsyn et al., 2012). for CO, HCOOH and NH3. For NH3 the maximum columns The unusual magnitude of the event was revealed for instance have been observed close to the sources, at around 500 km by high values of the fire radiative power, which reached southeast of Moscow. For CO and HCOOH these were ob- 19 000 MW close to Moscow (Witte et al., 2011); this is served somewhat further, at around 1000 km southeast of 400 times more than what is observed on average in Rus- Moscow. These values are 40 times (for CO and HCOOH) sia (Wooster and Zhang, 2004). Along this, large emissions and more than 300 times (for NH3) higher than the typical of aerosols and trace gases such as CO, tropospheric nitro- background values which were calculated as the mean of the gen oxides (NO2), ozone (O3) and formaldehyde (HCHO) daily minimum columns measured with IASI before the fire have been reported, using measurements from a variety of period (from 1–26 July). satellite sounders (Konovalov et al., 2011; Yurganov et al., As the BTD retrieval method of HCOOH was not designed 2011; Chubarova et al., 2012; Huijnen et al., 2012; Krol et al., for such exceptional columns, we have performed indepen- 2012). dent optimal estimation retrievals (OEM) to verify these re- In the next section we present the CO, NH3 and HCOOH sults. Since these are time consuming they were applied only total column maximums observed within a 2 month period (1 over a small area (54–57◦ N and 47–54◦ N) and for a few July to 1 September) in the summer of 2010, and the mean days (from 27 July to 10 August 2010). The OEM retrievals total columns for these species for the year 2010 over the yield total columns which are on average a factor two smaller area 40–75◦ N and 30–150◦ N. Section 3 presents the calcu- than the BTDs retrievals (around 1.5 for columns higher lation and temporal evolution of the enhancement ratios of than 5 × 1016 molec cm−2 and 2.3 for columns lower than 16 −2 NH3 and HCOOH relative to CO. In Sect. 4, we calculate the 5×10 molec cm ). The observed differences between the total masses and the extra burden due to fires, the fluxes in two retrieval approaches could point to limitations of the Tg day−1, as well as the total emitted masses over the entire BTD retrieval method for this specific event. On the other burning period. The issues of surface sensitivity, the related hand also OEM retrievals are prone to errors (including the measurement uncertainties and how they affect the presented important smoothing errors when the sensitivity is low). The results are briefly discussed in Sect. 5. In Sect. 6 we sum- discrepancy clearly shows the difficulty in the measuring accurate concentrations for this species. As far as we know,

Atmos. Chem. Phys., 13, 4171–4181, 2013 www.atmos-chem-phys.net/13/4171/2013/ Y. R’Honi et al.: Exceptional emissions of NH and HCOOH in the 2010 Russian wildﬁres 4173 Y. R’Honi et al.: Exceptional emissions of NH3 3 and HCOOH in the 2010 Russian wildﬁres 3

18 x 10 80 5 CO 70 4

60 3

50 2

40 1

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NH 12 70 3 10

60 8

50 6

4 40 2

30 0 0 50 100 150 16 x 10 80 8 HCOOH 7 70 6

60 5 4

50 3

2 40 1 30 0 0 50 100 150

Fig. 1. IASI morningFig. observations 1. IASI morning observationsof the 2010 of the Russian 2010 Russian wildﬁres wildﬁres plumes. plumes. The The 3 panels 3 panels show the show mean theCO, meanNH3 and CO,HCOOH NH3totaland columns HCOOH total columns −2 ◦ ◦ in molec cm−2, in gridin molec cells cm of, in0.5 grid◦ × cells0.5 of◦ 0.5for× one0.5 for month, one month, from from 27 July July 27 to to August 27 August 27 of 2010. 2010.

agreement with recent studies of Yurganov et al. (2011), with the increase in spring of agricultural activities (for NH3) Witte et al. (2011) and Mielonen et al. (2012) which reported (Clarisse et al., 2009) and plant growth (for HCOOH). The there have been no independent measurements of formic acid with the increase in spring of agricultural activities (for NH3) mean values between 2 and 4 1018 molec cm−2 in differ- seasonality in HCOOH seen by IASI here is in a goodagree- in the Russian fires,ent so areas that around we Moscow. cannot resolveThe higher this than uncertainty average CO to- ment(Clarisse with those et reported al., 2009 by Grutter) and et plant al. (2010) growth in the (for up- HCOOH). The at this stage. However,180 tal columns in what observed follows above Central it is important Russia between to Januarykeep 190 perseasonality troposphere as in observed HCOOH by MIPAS. seen byAs explained IASI here above, is in a good agree- in mind that all HCOOHand June 2010 columns (Fig. 2b) and are derived due to the quantities usual seasonality (en- of thement lack with of retrieved thoseHCOOH reportedcolumns by Grutter in autumn et and al. win-(2010) in the upper that species, maybe intensified in springtime by the transport ter is due to too low thermal contrasts, not exceeding the 5K hancement ratios,of total fire plumes masses from and outside fluxes) the studied are possibly region (Parrington over- thresholdtroposphere for the conditional as observed retrievals. by MIPAS (Michelson Interferome- estimated by a factoret al., 1.5 2012). to Similarly, 2.3. the progressive increase in NH3 and ter for Passive Atmospheric Sounding). As explained above, The maximum185 HCOOH observedfrom March columns to thestart of ofboth the fires HCOOH can be explained and the lack of retrieved HCOOH columns in autumn and win- NH3 quickly return to typical background values after Au- ter is due to too low thermal contrasts, not exceeding the 5K gust 20. This decrease is especially pronounced for NH3, threshold for the conditional retrievals. which is the shortest-lived species of the three. The mean CO total columns, presented here (Fig. 2b), are in good agreement with recent studies of Yurganov et al. (2011), Witte 3 Enhancement ratios et al. (2011) and Mielonen et al. (2012), which reported mean values between 2 and 4 × 1018 molec cm−2 in differ- Fires emit trace gases in amounts that depend on the spe- ent areas around Moscow. The higher than average CO to- cific fire conditions and source material. A useful parame- tal columns observed above central Russia between January ter to quantify trace gas emissions from fires is the emission and June 2010 (Fig. 2b) are due to the usual seasonality of factor, which is the amount of emitted species per amount that species, maybe intensified in springtime by the transport of dry fuel (in g kg−1)(Reid et al., 2009). Emission fac- of fire plumes from outside the studied region (Parrington tors are measured both in situ (e.g. Delmas et al., 1995; et al., 2012). Similarly, the progressive increase in NH3 and Yokelson et al., 1999) and in laboratories (Andreae et al., HCOOH from March to the start of the fires can be explained 1988; Koppmann et al., 2005). Large compilations of emission factors, grouped in different source types, can be found www.atmos-chem-phys.net/13/4171/2013/ Atmos. Chem. Phys., 13, 4171–4181, 2013 41744 Y. R’Honi Y.R’Honietal.:Exceptionalemissionsof et al.: Exceptional emissions of NHNH3 3andand HCOOHHCOOH in the 2010 2010 Russian Russian wildfires wildfires

8.0x10

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0.0 X

1/1 1/2 1/3 1/4 1/5 1/6 1/7 1/8 1/9 1/10 1/11 1/12

Dates of 2010

Fig. 2. (a) Temporal evolution of CO (black), NH3 (red) and HCOOH (blue) total column maximums betweenst 1 July andst 1 September Fig. 2. a. Temporal evolution of CO (black), NH◦ 3 (red) and◦HCOOH (blue) total column maximums between 1 July and 1 September 2010. (b) Mean total column over the area 40–75◦ ◦ N, 30–150◦ ◦ N for CO, NH3 and HCOOH, for the year 2010. Only retrievals with spectral 2010. b. Mean total column over the area 40−7 -75 N, 30 -150−6 E for−2CO−,1NH3 and HCOOH, for the year 2010. Only retrievals with spectral residual root-mean-square less than 3 × 10−7 and 3 ×−106 W2 m −sr1 m for CO and NH3, respectively, were considered here. residual root-mean-square less than 3 10 and 3 10 (W/m sr m ) for CO and NH3 respectively were considered here.

in Andreae and Merlet (2001) and Akagi et al. (2011). A re- rather high columns of CO (>4 × 1018 molec cm−2), likely 3 Enhancement ratios pair ([X],[CO]), while an average enhancement ratio can be lated parameter is the emission ratio of a trace gas X, which correspond to aged air masses. For this day of 5 August, the estimated from the slope of the linear regression ∆X vs. is the ratio of emitted molecules of X over the number of calculated enhancement ratios are 0.032 for NH and 0.021 Fires emit trace gases in amounts that depend on the specific ∆CO (Coheur et al., 2009). 3 emitted molecules of a target species such as CO, used here- for HCOOH. Enhancement ratios are calculated similarly for fire conditions and source material. A useful parameter to Enhancement ratios for the Russian fires are shown in after.quantify Emission trace ratios gas emissions can be calculated from fires from is the emission emission factors fac- each day and the corresponding time evolution from 27 July 205 Fig. 3 over the area defined above. Figure 3a shows an exam- bytor, multiplying which is thewith amount the ratio of of emitted the molar species masses per amountMCO/MX of. to 24 August is shown in Fig. 3b. Only NH3 total columns ple of the enhancement ratio’s−6 calculation.−2 −1 The scatter plots Indry fresh fuel plumes, (in g kg the−1) emission (Reid et ratio al., 2009). can be Emission estimated factors from with RMS less than 3 × 10 W m sr m are considered of total columns of NH3 (with RMS (Root Mean Square) less theare ratio measured of concentrations, both in situ (e.g. the so-called Delmas et enhancement al. (1995); Yokel- ratio here. For− NH6 3 enhancement2 −1 ratios start around 0.010 on the than 3 10 (W/(m sr m )) and HCOOH vs. CO on Au- (Goode et al., 2000): 27 July and reach a maximum of 0.052 on 10 August when son et al. (1999)) and in laboratories (Andreae et al., 1988; gust 5 is presented here. The high correlations (correlation Koppmann et al., 2005). Large compilations of emission fac- NH3 total columns are largest (Fig. 2b). After that, the en- [ ] − [ ] 210 coefficients of 0.75) are indicative of the common emission 1tors,X groupedX smoke in differentX ambient source types, can be found in An- hancement ratio decreases gradually, pointing to a decrease = . (1) source for the three species. The series of low NH3 columns 1CO [CO] − [CO] dreae and Merletsmoke (2001) andambient Akagi et al. (2011). A related (in<10 fire16 activitymolec cmand− a2) return in Fig. to 3a, background which are CO associated columns. with Less parameter is the emission ratio of a trace gas X, which is pronounced variations of the enhancement18 ratio are−2 found for As the plume ages, the enhancement ratios will typically rather high columns of CO (>4 10 molec cm ), likely the ratio of emitted molecules of X over the number of emit- correspondHCOOH. to aged air masses. For this day of August 5, the decreaseted molecules for species of a target with species a lifetime such shorter as CO,than used hereafter.CO. The As the 2010 Russian fires are associated with the burning 215 calculated enhancement ratios are 0.032 for NH3 and 0.021 timeEmission evolution ratios of can the be enhancement calculated from ratio emission therefore factors gives in- by of both peat lands (accounting for 30 % of emitted CO, Kono- sight into the chemical loss processes within the plume (Xiao for HCOOH. Enhancement ratios are calculated similarly multiplying with the ratio of the molar masses MCO/MX. forvalov each et dayal., 2011 and the) and corresponding other types of time vegetation, evolution it from is difficult July etIn al. fresh, 2007 plumes,). When the a lotemission of observations ratio can be are estimated available, from the 27to tocompare August24 the is results shown to in aFig. single 3b. Only emissionNH3 total ratio. columns We find, enhancementthe ratio of concentrations, ratios can be calculated the so-called for each enhancement measurement ratio −6 2 −1 withhowever, RMS that less forthan NH 3 103 the(W/(m range ofsrm values)) are measured considered from pair(Goode ([X],[CO]), et al., 2000): while an average enhancement ratio can be 220 here.IASI For(0.010–0.052)NH3 enhancement is consistent ratios with start the around values 0.010 reported on the in estimated from the slope of the linear regression 1X vs 1CO − 27theth literature,of July and which reach average a maximum 0.033 of for 0.052 extratropical on the 10th forestof (Coheur et al., 2009∆X). [X]smoke [X]ambient = (1) Augustfires, 0.035 when forNH boreal3 total forest columns fires are and largest 0.097 (Fig. for 2.b). peat Af-lands Enhancement∆ ratiosCO for[CO the]smoke Russian−[CO]ambient fires are shown in ter(Akagi that, et the al. enhancement, 2011). ratio decreases gradually, pointing Fig. 3 over the area defined above. Figure 3a shows an ex- to aFor decrease HCOOH, in fire the activity calculated and enhancementa return to background ratios varyCO be- 195 ampleAs of the the plume enhancement ages, the enhancement ratio’s calculation. ratios will The typically scatter decrease for species with a lifetime shorter than CO. The 225 columns.tween 0.010 Less and pronounced 0.032 and variations are much of larger the enhancement than the emission ra- plots of total columns of NH3 (with RMS (root mean square) tioratios are reported found for inHCOOHAkagi et. al. (2011), which are 2.7 × 10−3, time evolution× − of6 the enhancement−2 −1 ratio therefore gives in- less than 3 10 W m sr m and HCOOH vs CO on 5 2.7 × 10−3 and 1.8 × 10−3 respectively for typical Boreal, Augustsight into is presented the chemical here. loss The processes high correlations within the plume (correlation (Xiao As the 2010 Russian fires are associated with the burn- et al., 2007). When a lot of observations are available, the ingextratropical of both peat and lands peat (accounting forests fire emissions.for 30% of The emitted difference, coefficients of 0.75) are indicative of the common emission CO 200 enhancement ratios can be calculated for each measurement Konovalovbetween these et al. emission (2011)) and ratios other and types our calculatedof vegetation, enhance- it is source for the three species. The series of low NH3 columns ment ratios points toward a significant secondary formation (<1016 molec cm−2) in Fig. 3a, which are associated with

Atmos. Chem. Phys., 13, 4171–4181, 2013 www.atmos-chem-phys.net/13/4171/2013/ Y.Y. R’Honi R’Honi et et al.: al.: Exceptional emissions emissions of ofNH NH3 3andandHCOOH HCOOHin in the the 2010 2010 Russian Russian wildﬁres wildﬁres 4175 5

NH 05 August of 2010

3 )

-2 (a) HCOOH

molec cm 17

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R = 0.75, = 21.5 10 3.7 10

-3 -4

R = 0.76, = 32.2 10 4.2 10

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0 2 4 6 8 10 12 14 16 18 20

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[CO] (10 molec cm )

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NH HCOOH

3 50

40 1000 x ] 30

[ 20 ]

10 X [

26/7 29/7 1/8 4/8 7/8 10/8 13/8 16/8 19/8 22/8

Dates of 2010

Fig. 3. (a) Scatter plot of NH and HCOOH total columns vs CO total columns for 5 August 2010. Linear regressions are plotted for both NH3 HCOOH CO th speciesFig. 3. asa. red Scatter and blue plot lines, of respectively.3 and Thetotal values columns for the vs.resultingtotal slopes columns and their for errors 5 August are given of 2010. in the Linear figure, regressions along with are the plotted correlation for coefficientboth speciesR. as(b) redTemporal and blue evolution lines, respectively. of the enhancement The values ratiosfor the of NH resultingand HCOOHslopes and relative their errors to CO, are calculated given in the as the figu slopesre, along of the with linear the 3 NH HCOOH CO regressionscorrelation from coefficient 27 July R. to b. 24 Temporal August, evolution in the region of the 40–75 enha◦ncementN and 30–90 ratios◦ ofN. The3 errorand bars are therelative corresponding to , calculated slopes errors. as the slopes of the linear regressions from July 27 to August 24, in the region 40◦-75◦N and 30◦-90◦E. The error bars are the corresponding slopes errors.

of HCOOH. Such a secondary production has been reported 0.005, but these observations are made in the upper tropo- 230 difficult to compare the results to a single emission ratio. We 255 Section 2, OEM retrievals of formic acid yield columns about in a number of studies. Increases in the emission ratios by a sphere and further downwind of the fires (Coheur et al., 2007; find, however, that for NH3 the range of values measured a factor two lower; corresponding enhancement ratios could factor of 2–2.5 in 2.5 h were found in an Alaskan fire (Goode Tereszchuk et al., 2011, 2012). More observations and fur- from IASI (0.010–0.052) is consistent with the values re- therefore also be a factor two lower. The total averaged en- et al., 2000); a factor of 5.5 in less than a day in a Brazil- ther research is needed to understand the conditions in which ported in the literature, which average 0.033 for extratropical hancement ratio found for all the HCOOH OEM retrievals ian fire (Yokelson et al., 2007); a factor of 2.5 in an hour secondary formation of HCOOH is important. Also note that forest fires, 0.035 for boreal forest fires and 0.097 for peat equals 0.011. This is still a factor five larger than the tabu- (Yokelson et al., 2009) in Mexico and, finally, by a factor of a more general interpretation of the enhancement ratios mea- 235 lands (Akagi et al., 2011). 260 lated emission ratios given by Akagi et al. (2011). There- 7.34 in 4.5 h in a Californian fire (Akagi et al., 2012). The sured by IASI is hampered by the continuous emission, pro- For HCOOH, the calculated enhancement ratios vary before even in this scenario, there is evidence of secondary large values found for the enhancement ratios of formic acid duction and complex transport patterns: the buildup of CO tween 0.010 and 0.032 and are much larger than the emission formation of formic acid and interestingly this 0.011 value are unlikely to be due to an underestimation of the CO− total during the entire burning period could in particular mean that ratios reported in Akagi et al. (2011) which are 2.7 10 3, 2.7 is in good agreement with Goode et al. (2000) and Yokel- column,− which has− been shown to be consistent with correla- the real emission ratios are still higher than our reported en- 10 3 and 1.8 10 3 respectively for typical Boreal, extratrop- son et al. (2007) who observed enhancementratios (corrected tive measurements in various validation studies (e.g. George hancement ratios. 240 ical and peat forests fire emissions. The difference between 265 for spectroscopy -see interactive comment of Yokelson et al. et al., 2009, Kerzenmacher et al., 2012). As mentioned in As a general comment, determination of enhancement ra- these emission ratios and our calculated enhancement ratios (2013)) in downwind plumes from forest fires in the range Sect. 2, OEM retrievals of formic acid yield columns about a tios from nadir observations is not ideal since there are differ- points toward a significant secondary formation of HCOOH. of ∼ 0.011–0.014. Recent reported values of enhancement factorSuch of a twosecondary lower; productioncorresponding has enhancement been reported ratios in a could num- encesratios both from in occultation the vertical measurements profile of the are different generally species below and thereforeber of studies. also be Increases a factor of in twothe emission lower. The ratios total by averaged a factor in0.005, the vertical but these sensitivity observations of the measurements, are made in the which upper will tro- af- enhancement ratio found for all the HCOOH OEM retrievals fect the retrieved enhancement ratios. Uncertainties related to 245 of 2-2.5 in 2.5 hours were found in an Alaskan fire (Goode 270 posphere and further downwind of the fires (Coheur et al. equalset al., 0.011. 2000); This a factor is still 5.5 a factorin less of than five a larger day in than a Brazilian the tab- limited(2007); sensitivity Tereszchuk of et the al. boundary (2011, 2012)). layer only More partially observations cancel ulatedfire (Yokelson emission et ratios al., 2007); given by a factorAkagi 2.5 et inal. an(2011 hour). (Yokel- There- eachand further other out. research is needed to understand the conditions in foreson even et al., in 2009) this scenario, in Mexico there and is evidencefinally a factor of secondary 7.34 in for- 4.5 which secondary formation of HCOOH is important. Also mationhours inof a formic Californian acid and fire interestingly (Akagi et al., this 2012). 0.011 The value large is note that a more general interpretation of the enhancement 4 Total mass 250 invalues good found agreement for the with enhancementGoode et al. ratios(2000 of) formic and Yokelson acid are 275 ratios measured by IASI is hampered by the continuousemis- et al. (2007) who observed enhancement ratios (corrected for sion, production and complex transport patterns: the buildup unlikely to be due to an underestimation of the CO total col- Daily observed total masses, TM , of species X have been spectroscopy – see interactive comment of Yokelson et al., of CO during the entire burningX period could in particular umn, which has been shown to be consistent with correla- calculated here as follows: 2013tive) measurements in downwind in plumes various from validation forest studies fires in (e.g. the Geor rangege mean that the real emission ratios are still higher than our ∼ ofet al.0.011–0.014. (2009), Kerzenmacher Recent reported et al. (2012)). values ofAs enhancement mentioned in reportedM enhancementXCXS ratios. ratios from occultation measurements are generally below TMX = , (2) Na

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-1

Burden, Tg Total M asses, Tg Emissions, Tg day

10 = 7 days 1.8 36

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34 2

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26 CO

0.6

1/1 1/3 1/5 1/7 1/9 1/11 29/6 14/7 29/7 13/8 28/8 12/9 27/9 29/6 14/7 29/7 13/8 28/8 12/9 27/9

0.06

0.04

0.16

Observed = 6 h

0.05 Smoothed = 12 h 0.14

= 24 h Background

1 0.03 0.12

0.04

0.10

3 0.03

0.02 0.08 NH

0.06

0.02

0.01 0.04

0.01

0.02

0.00 0.00 0.00

1/1 1/3 1/5 1/7 1/9 1/11 29/6 14/7 29/7 13/8 28/8 12/9 27/9 29/6 14/7 29/7 13/8 28/8 12/9 27/9

0.40 0.20

0.7

= 2 days

0.35

= 4 days 0.6

= 10 days 0.30 0.15

0.5

0.25

0.4

0.20 0.10

0.3 0.15 HCOOH

0.10 0.05

0.2

0.05

0.1

0.00 0.00

1/1 1/3 1/5 1/7 1/9 1/11 29/6 14/7 29/7 13/8 28/8 12/9 27/9 29/6 14/7 29/7 13/8 28/8 12/9 27/9

Dates of 2010

◦ ◦ Fig. 4. Left: total CO, NH3 and HCOOH masses in Tg (black dots and line) over the area 40–75 N, 30–150 N for CO and HCOOH and ◦ ◦CO NH HCOOH ◦ ◦ ◦ ◦ CO HCOOH 40–75Fig. 4. Left:N, 30–90 total N for, NH3 3and. The red linesmasses are the in smoothed Tg (black total dots massesand line) in over 10 day the intervals; area 40 -75 theN, blue 30 lines-150 areE totalfor massesand representativeand ◦ ◦ ◦ ◦ NH of40 background-75 N, 30 -90 concentrations.E for 3. Middle: The redextra lines areCO, the NH smoothed3 and HCOOH total masses smoothed in 10-day burden interv in Tgals; from the bluefires lines obtained are total by subtracting masses representative background valuesof background from the concentrations. total masses. Right: Middle: fluxes extra inCO Tg day, NH−13 respectivelyand HCOOH ofsmoothed NH and burden HCOOH in Tgcalculated from fires by obtained Eq. (3). by subtracting background −1 3 values from the total masses. Right: Fluxes in Tg day respectively of NH3 and HCOOH calculated by equation 3.

−1 where MX is the molar mass of X (in g mol ), CX is the lution of the total masses for the year 2010 (in black: daily 280 meanAs columna general retrieved comment, from determination IASI daytime of enhancement observations ra-(in 4values; Total in Mass red: smoothed). The total masses reach in mid- tios from− nadir2 observations is not ideal since there are differ- molec cm , see Fig. 2b), Na is the Avogadro number and S August maximums of 36.1 Tg for CO, ∼ 0.06 Tg for NH3 Daily observed total masses TMX of species X have been representsences both a in defined the vertical surface profile area. of For the CO different and HCOOH species an thed and 0.70 Tg for HCOOH. The latter should be considered calculated here as follows: latterin the corresponds vertical sensitivity to the red of the rectangle measurements identified which in Fig. will 1 and af- with care, with lower values for HCOOH, considering the fect the retrieved enhancement17 2 ratios. Uncertainties related S is estimated at 2.75 × 10 cm . For NH3, S is a smaller area possible overestimation of totalMX columnsCX – see Sect. 2. 285 to limited◦ sensitivity of◦ the boundary layer only partially can- TMX = (2) (40–75 N and 30–90 N) and this is justified by the fact that After having calculated the dailyNa total masses over the cel each other out. (Fast Optimal Retrievals on Layers for IASI) FORLI-NH3 is area of interest it is possible to estimate the− total1 emissions a conditional retrieval method, as discussed previously, and whereby makingMX is some the molarextra assumptions. mass of X (in Here g mol we follow), CX anis the ap- that the short lifetime of this species prevents its long-range meanproach column similar retrieved to that of fromYurganov IASI daytime et al. ( observations2011). In a first (in −2 S transport. Figure 4 shows, in the left panel, the daily evo-290 molecstep we cm estimate, see Fig. the 2b), daily Na totalis the mass Avogadro due to number the fires and (the represents a defined surface area. For CO and HCOOH the

Atmos. Chem. Phys., 13, 4171–4181, 2013 www.atmos-chem-phys.net/13/4171/2013/ Y. R’Honi et al.: Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildﬁres 4177

Table 1. Comparative analysis of total emissions of CO, NH3 and HCOOH from current and previous studies of the 2010 Russian wildﬁres.

CO NH3 HCOOH Comment Max. daily emission (Tg day−1) Fokeeva et al. (2011) 1.2–1.4 – – AIRS-MOPITT, standard Fokeeva et al. (2011) 2.3–2.4 – – AIRS-MOPITT, adjusted Yurganov et al. (2011) 1.5 – – IASI-OE, standard Yurganov et al. (2011) 2.1–2.2 – – Estimate from 3 different sounders (IASI, AIRS and MOPITT), adjusted This study 1.41–1.87 0.04–0.15 0.07–0.19 IASI-OE standard Total emitted (Tg) Fokeeva et al. (2011) 19–26 – – AIRS-MOPITT, standard Fokeeva et al. (2011) 36–42 – – AIRS-MOPITT, adjusted Fokeeva et al. (2011) 12–14 – – MODIS, inventory method Huijnen et al. (2012) 12.2 – – MODIS, inventory method (GFASv1.0) Konovalov et al. (2011) 9.7 – – MODIS, inverse modeling Krol et al. (2012) 20–25 – – IASI, inverse modeling Yurganov et al. (2011) 26.2 – – IASI-OE, standard Yurganov et al. (2011) 34–40 – – Estimate from 3 different sounders (IASI, AIRS and MOPITT), adjusted This study 19–33 0.7–2.6 0.9–3.9 IASI-OE standard so-called burden) by subtracting total mass background val- culate also for these species the fluxes for a range of different ues. The background values (Fig. 4 left panel in blue) were lifetimes. This approach allows to conservatively estimate a obtained by smoothing the minimum of the total masses ob- range of total emissions compatible with the IASI measure- served in 10 day intervals. The resulting burden are plotted ments. For HCOOH, we use 2, 4 and 10 days following its in the middle panel in Fig. 4. Maximum burden are calcu- global estimated lifetime of 3–4 days (see Stavrakou et al. lated at around 10 Tg for CO, 0.04 Tg for NH3 and 0.37 Tg (2011) and references therein). For NH3, we use lifetimes of for HCOOH. A 10 Tg of CO burden represents more than 6, 12 and 24 h as its lifetime ranges typically from a couple 85 % of total annual anthropogenic emissions in that region of hours to days (Dentener and Crutzen, 1994; Asman et al., (Konovalov et al., 2011) and the NH3 and HCOOH maxi- 1998; Aneja et al., 2001). The right column in Fig. 4 shows mum values reported here account alone for 5 and 20 % of the time evolution of the (smoothed) fluxes in Tg day−1 of the total annual emissions from extratropical forest fires (An- these species for these various lifetimes, from 29 June to 27 dreae and Merlet, 2001). It should be noted though that for September 2010. The maximum values calculated this way HCOOH the values in Andreae and Merlet (2001) represent are 1.41–1.87 Tg day−1, 0.04–0.08–0.16 Tg day−1 and 0.07– −1 primary emissions only. 0.11–0.19 Tg day for CO, NH3 and HCOOH respectively, From the burden we can calculate emission fluxes (in with the larger values logically for the smaller values of τeff. Tg day−1) assuming a simple box model and first order loss Finally, total emissions were estimated from these fluxes be- terms (Jacob, 1999): tween 25 July and 31 August 2010 and are 19–33 Tg (CO), 0.7–2.6 Tg (NH3) and 0.9–3.9 Tg (HCOOH). For NH3 and B − B e−t/τeff = i+1 i HCOOH, this is comparable to what is normally emitted in Ei+1(X) −t/τ . (3) τeff(1 − e eff ) the course of a whole year by all extratropical forest fires (Galloway et al., 2004; Stavrakou et al., 2011). However for Here, E and B are respectively the flux and the burden on i i HCOOH, it is important to keep in mind the possible over- day i, t is time between two observations (here one day) and estimation (by a factor 1.5–2.3) of the BTD retrievals men- τ is the effective lifetime of the species X. This lifetime eff tioned in Sect. 2. term includes chemical losses, but also losses due to trans- Several estimates of total emitted CO have been reported port outside the considered area. Here, we assume that all in the literature for the 2010 Russian fires, and these have burden are due to the Russian fires and neglect potential in- been summarized in Table 1. These include on the one hand flow of excess columns. The calculation thus depends exclu- estimates derived from CO measurements from the infrared sively on the effective lifetime, τ , of the species. Following eff sounders IASI, AIRS (Atmospheric Infrared Sounder) and estimates of the CO effective lifetime given in Yurganov et al. MOPITT (Measurements of Pollution in the Troposphere) (2011), the daily fluxes for CO have been estimated using (sometimes coupled with an atmospheric transport model), two values of τ –namely, 7 and 15 days. As we do not have eff and on the other hand estimates derived from MODIS (Mod- accurate knowledge of the effective lifetime of HCOOH and erate Resolution Imaging Spectroradiometer) fire radiative NH3, especially not in such an extraordinary event, we cal- www.atmos-chem-phys.net/13/4171/2013/ Atmos. Chem. Phys., 13, 4171–4181, 2013 4178 Y. R’Honi et al.: Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires power measurements. In the studies of Yurganov et al. (2011) retrievals as compared to ground-based measurements close and Fokeeva et al. (2011), who use direct CO measurements, to Moscow. However, as our total mass estimate is in excel- allowance is made for the limited sensitivity of infrared in- lent agreement with a more sophisticated inverse modelling struments to boundary layer concentrations by adding an approach of Krol et al. (2012), we do not expect a consistent offset estimated from the difference between satellite and low bias of the retrieved CO columns. ground based measurements, rather than making use of av- Retrieval errors for ammonia are larger than for CO, be- eraging kernels, like is done in the study of Krol et al. (2012) cause of smaller signal-to-noise ratios and larger dependence (see below). For these studies the labels “standard” and “ad- on thermal contrast. Here, NH3 was conditionally retrieved justed” indicate whether adjustments were made. from IASI spectra, on the basis of a firm spectral signature There is a large scatter in the data, both for the maxi- (which depends on both the total column of NH3 and the mum daily emissions (1.2–2.4 Tg) and the total emitted CO thermal contrast). While we obtain less measurements in this (10–40 Tg). The standard estimates from CO measurements way, the measurements that are retained have limited depen- found in Yurganov et al. (2011) (26.2 Tg) and Fokeeva et al. dence on the a priori column (low smoothing error). An esti- (2011) (19–26 Tg) agree well with our estimates (19–33 Tg). mate of the error for NH3 in the case of extreme conditions as This is not surprising as all three studies use similar ap- those reported here is outside the scope of this paper, as collo- proaches. Their adjusted values, with enhanced boundary cated in situ measurements are the only way to assess it. For layer concentrations are about 40 % higher. The total emis- agricultural pollution in the boundary layer a retrieval error sions reported here also agree well with the values 20–25 Tg of 30–50 % for the total column has been estimated (Clarisse given in Krol et al. (2012) and obtained using inverse mod- et al., 2010). The selection criteria might lead to an under- eling of IASI CO data. As they take into account IASI’s sen- estimate of the total burden and mass of NH3 (see Sect. 4). sitivity to the boundary layer using averaging kernels this is Finally, the retrieval of HCOOH relies on conversion from somehow surprising but points to a possible overcorrection BTDs and is also dependent on the thermal contrast. As in in the papers of Yurganov et al. (2011) and Fokeeva et al. Razavi et al. (2011), we have restricted retrieval to observa- (2011). Differences and potential sources of errors are dis- tions with a thermal contrast above 5 K. Razavi et al. (2011) cussed in detail in Krol et al. (2012). The wide scatter in estimate average uncertainties to be about 60 % for such con- the data is evidence of the difficulty in estimating total emit- ditions. Independent OEM retrievals performed here indicate ted masses from satellite data. For CO our approach gives a possible overestimation of a factor two. a rather large but realistic range of values, and gives confi- Systematic errors on the total columns will propagate to dence to our methodology. Likewise, for NH3 and HCOOH, the calculation of the enhancement ratios and the emissions. we have taken several possible effective lifetimes, as to ob- However, random retrieval errors will cancel each other out tain a range of reasonable values for the total emissions. in the calculation of total masses as this involves integration We can calculate effective emission ratios using the me- of many total columns over a large area. dian estimates of the total emissions. Assuming a total CO emission of 26 Tg we obtain for NH3 an emission ratio of 0.082. This is naturally larger than the observed enhancement 6 Conclusions ratios 0.010–0.055. For HCOOH an average emission ratio of 0.047 is found, also higher than the observed enhancement The fires that occurred in Russia during the summer 2010 ratios (0.020–0.030 for the most active period). emitted important quantities of trace gases and aerosols for almost a month. In this work, we focused on three trace gases–namely, CO, NH3 and HCOOH. We presented total 5 Discussion columns (maximum and mean) from IASI observations for 2010. We have calculated enhancement ratios of HCOOH The sensitivity of IASI to lower tropospheric concentrations and NH3 relative to CO for each day and reported their time of CO, NH3 and HCOOH depends heavily on the surface– evolution during the fire period. For NH3, the enhancement atmospheric temperature difference, the so-called thermal ratios were shown to be in good agreement with tabulated contrast (Clarisse et al., 2010; Razavi et al., 2011). Day- values of emission ratios, while for HCOOH our reported time observations typically have a larger thermal contrast values are an order of magnitude larger. Even if we con- than night-time observations and are the preferred overpass sider an overestimation by a factor of two due to the retrieval to study these species. FORLI CO retrievals have on aver- method, there is still a difference of a factor of five, sup- age a retrieval error below 10–15 % (Hurtmans et al., 2012). porting evidence of rapid secondary formation of HCOOH in However, the total error can be much larger such as in the the plumes. For both species the maximum enhancement ra- case of strong fires (George et al., 2009), especially when tios were found around mid-August, where the total columns there is limited sensitivity to the boundary layer. As we have are largest. In addition, we have calculated total masses and mentioned in Sect. 4, Yurganov et al. (2011) and Fokeeva the burden from fires for each day, as well as fluxes using et al. (2011) found large underestimates in CO total column assumptions on the species lifetimes. For CO, the results

Atmos. Chem. Phys., 13, 4171–4181, 2013 www.atmos-chem-phys.net/13/4171/2013/ Y. R’Honi et al.: Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires 4179 obtained are comparable to previous work. For NH3 and lagoons, Atmos. Environ., 35, 1949–1958, doi:10.1016/S1352- HCOOH, these are the first values reported. They are of the 2310(00)00547-1, 2001. order of 0.1 Tg day−1 depending on the choice of reference Asman, W. A. H., Sutton, M. A., and Schjørring, J. K.: Ammo- lifetime. When integrated over the entire fire period (July– nia: emission, atmospheric transport and deposition, New Phy- August 2010), the emission fluxes translate to a total emitted tol., 139, 27–48, doi:10.1046/j.1469-8137.1998.00180.x, 1998. mass of 19–33 Tg for CO, 0.7–2.6 Tg for NH and 0.9–3.9 Tg Chubarova, N., Nezval’, Ye., Sviridenkov, I., Smirnov, A., and 3 Slutsker, I.: Smoke aerosol and its radiative effects during ex- for HCOOH. For all these species, there is a significant con- treme fire event over Central Russia in summer 2010, Atmos. tribution to the yearly global emission. For instance, this is Meas. Tech., 5, 557–568, doi:10.5194/amt-5-557-2012, 2012. for NH3 and HCOOH comparable to what is emitted in a year Clarisse, L., Clerbaux, C., Dentener, F., Hurtmans, D., and Coheur, by all extratropical forest fires. This study also highlights the P.-F.: Global ammonia distribution derived from infrared satellite difficulty in retrieving HCOOH from nadir observations. observations, Nature Geos., doi:10.1038/NGEO551, 2009. Clarisse, L., Shephard, M. W., Dentener, F., Hurtmans, D., Cady- Pereira, K., Karagulian, F., Damme, M. V., Clerbaux, C., and Acknowledgements. IASI has been developed and built under the Coheur, P.-F.: Satellite monitoring of ammonia: A case study responsibility of the Centre National d’Etudes´ Spatiales (CNES, of the San Joaquin Valley, J. Geophys. Res., 115, D13302, France). It is flown on board the Metop satellites as part of the doi:10.1029/2009JD013291, 2010. EUMETSAT Polar System. The IASI L1 data are received through Clarisse, L., R’Honi, Y., Coheur, P.-F., Hurtmans, D., and Clerbaux, the EUMETCast near real-time data distribution service. Part of C.: Thermal infrared nadir observations of 24 atmospheric gases, the work on CO benefits from the activities undertaken within the Geophys. Res. L., 38, L10802, doi:10.1029/2011GL047271, O3SAF and supported by EUMETSAT. The research in Belgium 2011. was funded by the F.R.S.-FNRS, the Belgian State Federal Office Clerbaux, C., Boynard, A., Clarisse, L., George, M., Hadji-Lazaro, for Scientific, Technical and Cultural Affairs and the European J., Herbin, H., Hurtmans, D., Pommier, M., Razavi, A., Turquety, Space Agency (ESA-Prodex arrangements). Financial support by S., Wespes, C., and Coheur, P.-F.: Monitoring of atmospheric the “Actions de Recherche Concertees”´ (Communaute´ Française composition using the thermal infrared IASI/MetOp sounder, At- de Belgique) is also acknowledged. L. Clarisse and P.-F. Coheur mos. Chem. Phys., 9, 6041–6054, doi:10.5194/acp-9-6041-2009, are respectively Postdoctoral Researcher and Research Associate 2009. (Chercheur Qualifie)´ with F.R.S.-FNRS. C. Clerbaux and S. Tur- Coheur, P.-F., Herbin, H., Clerbaux, C., Hurtmans, D., Wespes, C., quety are grateful to CNES for scientific collaboration and financial Carleer, M., Turquety, S., Rinsland, C. P., Remedios, J., Hauglus- support. Y. R’Honi is grateful to the “Fonds pour la Formation a` la taine, D., Boone, C. D., and Bernath, P. 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