Forest Fire Emissions Research Articles

Tropospheric emission spectrometer (TES) and atmospheric chemistry experiment (ACE) measurements of tropospheric chemistry in tropical southeast Asia during a moderate El Niño in 2006

High spectral resolution Fourier transform spectrometer (FTS) measurements of tropospheric carbon monoxide (CO) distributions show mixing ratios over Indonesia during October 2006 of ∼200 ppbv (10 −9 per unit volume) in the middle troposphere. The elevated emissions were caused by intense and widespread Indonesian peat and forest fire emissions elevated compared to other years by the impact of a moderate El Niño/Soutern Oscillation (ENSO) event, which delayed that year's monsoon season and produced very dry conditions. Moderate resolution imaging spectrometer (MODIS) fire counts, atmospheric chemistry experiment (ACE) measurements of elevated mixing ratios of fire emission products and near infrared extinction, and back trajectory calculations for a sample measurement location near the time of maximum emissions provide additional evidence that the elevated 2006 emissions resulted primarily from the Indonesia fires. Lower CO mixing ratios measured by ACE and fewer MODIS fire counts in Indonesia during October 2005 indicate lower emissions than during 2006. Coincident profiles from the ACE agree within the uncertainties with those from the tropospheric emission spectrometer (TES) for pressure ranges and time periods with good TES sensitivity after accounting for its lower vertical sensitivity compared with the ACE FTS.

Transport of forest fire emissions from Alaska and the Yukon Territory to Nova Scotia during summer 2004

Emissions from forest fires in Alaska and the Yukon Territory were observed at Chebogue Point, Nova Scotia (43.7°N, 66.1°W), between 11 and 13 July 2004. Smoke aerosols were first detected in the free troposphere by a Raman lidar and extended up to 8 km altitude. The plume was not evident at the surface until the second day, when increases in CO, acetonitrile (CH3CN), benzene, and aerosol mass concentrations were observed by in situ instrumentation. Enhancement ratios for each species relative to CO agreed with the range of values from other measurements of the same plume. The surface aerosols had an elevated black carbon fraction relative to both CO and organic matter, and the ratio of black to organic carbon was higher than what is typically observed in fresh smoke. The emissions were tracked back to Alaska and the Yukon Territory using aerosol optical depth measurements from the Aqua MODIS satellite instrument, and the transport was reconstructed using the GEOS‐Chem and FLEXPART atmospheric models. The analysis suggests that aerosols were injected into the atmosphere in proportion to CO and that aerosol removal processes were weak during the 7 to 9 day transit time in the free troposphere. Transport of the tracers to the ground was strongly connected to synoptic‐scale features in the surface meteorology.

Trace gas and particulate emissions from the 2003 southern California wildfires

In October 2003, thirteen major wildfires in southern California burned more than 300,000 hectares of mainly chaparral biome. High‐precision in situ trace gas and particle measurements of the wildfire plumes in La Jolla, California, showed a high degree of correlation among carbon dioxide (CO2), methane (CH4), nonmethane hydrocarbons, and methyl halide mixing ratios, as well as with particle number concentrations (10–300 nm and 500–2500 nm aerodynamic diameter). Aerosol time‐of‐flight mass spectrometry of individual aerosol particles (50–2500 nm range) showed that 70–85% had typical biomass burning signatures (levoglucosan coupled with potassium). Only 5–18% of particles in the 50–300 nm range had vehicle signatures. Molar trace gas enhancement ratios (ERs) versus ethane and CO2 were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N2O and CH3CCl3 versus CO2 were determined, but correlations were poor. No significant CH2Cl2 or CHCl3 emissions were detected. CO2 emissions from the nearby Cedar fire were estimated both with a simple Lagrangian atmospheric transport model and a burned area approach and extrapolated to 11 Tg CO2 for the total burned area in southern California. Total CO2, CH4, C2‐hydrocarbons, benzene, toluene, methyl chloride, methyl iodide, and PM2.5 emissions were ∼0.2–3.5% of yearly global extratropical forest fire emissions and more than 28% of CH4, C6H6, and PM2.5 2003 San Diego and South Coast Air Basins anthropogenic emissions. Particle distributions and single particle chemistry are discussed. PM2.5 considerably exceeded the EPA short‐term exposure limit.

Chemical composition observed over the mid‐Atlantic and the detection of pollution signatures far from source regions

The atmospheric composition of the central North Atlantic region has been sampled using the FAAM BAe146 instrumented aircraft during the Intercontinental Transport of Ozone and Precursors (ITOP) campaign, part of the wider International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). This paper presents an overview of the ITOP campaign. Between late July and early August 2004, twelve flights comprising 72 hours of measurement were made in a region from approximately 20 to 40°W and 33 to 47°N centered on Faial Island, Azores, ranging in altitude from 50 to 9000 m. The vertical profiles of O3 and CO are consistent with previous observations made in this region during 1997 and our knowledge of the seasonal cycles within the region. A cluster analysis technique is used to partition the data set into air mass types with distinct chemical signatures. Six clusters provide a suitable balance between cluster generality and specificity. The clusters are labeled as biomass burning, low level outflow, upper level outflow, moist lower troposphere, marine and upper troposphere. During this summer, boreal forest fire emissions from Alaska and northern Canada were found to provide a major perturbation of tropospheric composition in CO, PAN, organic compounds and aerosol. Anthropogenic influenced air from the continental boundary layer of the USA was clearly observed running above the marine boundary layer right across the mid‐Atlantic, retaining high pollution levels in VOCs and sulfate aerosol. Upper level outflow events were found to have far lower sulfate aerosol, resulting from washout on ascent, but much higher PAN associated with the colder temperatures. Lagrangian links with flights of other aircraft over the USA and Europe show that such signatures are maintained many days downwind of emission regions. Some other features of the data set are highlighted, including the strong perturbations to many VOCs and OVOCs in this remote region.

Arctic haze: current trends and knowledge gaps

Trend analyses were performed on several indicators of Arctic haze using data from sites located in the North American, Norwegian, Finnish and Russian Arctic for the spring months of March and April. Concentrations of nonseasalt (nss) SO 4 = in the Canadian, Norwegian and Finnish Arctic were found to have decreased by 30–70% from the early 1990s to present. The magnitude of the decrease depended on location. The trend in nss SO 4 = at Barrow, Alaska from 1997 to present, is unclear. Measurements at Barrow of light scattering by aerosols show a decrease of about 50% between the early 1980s and the mid-1990s for both March and April. Restricting the analysis to the more recent period of 1997 to present indicates an increase in scattering of about 50% during March. Aerosol NO 3 - measured at Alert, Canada has increased by about 50% between the early 1990s and 2003. Nss K + and light absorption, indicators of forest fires, have a seasonal maximum during the winter and spring and minimum during the summer and fall at both Alert and Barrow. Based on these data, the impact of summertime forest fire emissions on low-altitude surface sites within the Arctic is relatively small compared to winter/spring emissions. Key uncertainties about the impact of long range transport of pollution to the Arctic remain including the certainty of the recent detected trends; sources, transport and trends of soot; and radiative effects due to complex interactions between aerosols, clouds and radiation in the Arctic. DOI: 10.1111/j.1600-0889.2006.00238.x

Arctic haze: current trends and knowledge gaps

Trend analyses were performed on several indicators of Arctic haze using data from sites located in the North American, Norwegian, Finnish and Russian Arctic for the spring months of March and April. Concentrations of nonseasalt (nss) SO4= in the Canadian, Norwegian and Finnish Arctic were found to have decreased by 30–70% from the early 1990s to present. The magnitude of the decrease depended on location. The trend in nss SO4= at Barrow, Alaska from 1997 to present, is unclear. Measurements at Barrow of light scattering by aerosols show a decrease of about 50% between the early 1980s and the mid-1990s for both March and April. Restricting the analysis to the more recent period of 1997 to present indicates an increase in scattering of about 50% during March. Aerosol NO3- measured at Alert, Canada has increased by about 50% between the early 1990s and 2003. Nss K+ and light absorption, indicators of forest fires, have a seasonal maximum during the winter and spring and minimum during the summer and fall at both Alert and Barrow. Based on these data, the impact of summertime forest fire emissions on low-altitude surface sites within the Arctic is relatively small compared to winter/spring emissions. Key uncertainties about the impact of long range transport of pollution to the Arctic remain including the certainty of the recent detected trends; sources, transport and trends of soot; and radiative effects due to complex interactions between aerosols, clouds and radiation in the Arctic.

Biomass burning and anthropogenic sources of CO over New England in the summer 2004

During the summer of 2004 large wildfires were burning in Alaska and Canada, and part of the emissions were transported toward the northeast United States, where they were measured during the NEAQS‐ITCT 2k4 (New England Air Quality Study–Intercontinental Transport and Chemical Transformation) study on board the NOAA WP‐3 aircraft and the NOAA research vessel Ronald H. Brown. Using acetonitrile and chloroform as tracers the biomass burning and the anthropogenic fraction of the carbon monoxide (CO) enhancement are determined. As much as 30% of the measured enhancement is attributed to the forest fires in Alaska and Canada transported into the region, and 70% is attributed to the urban emissions of mainly New York and Boston. On some days the forest fire emissions were mixed down to the surface and dominated the CO enhancement. The results compare well with the FLEXPART transport model, indicating that the total emissions during the measurement campaign for biomass burning might be about 22 Tg. The total U.S. anthropogenic CO sources used in FLEXPART are 25 Tg. FLEXPART model, using the U.S. EPA NEI‐99 data, overpredicts the CO mixing ratio around Boston and New York in 2004 by about 50%.

Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada

The NOAA WP‐3 aircraft intercepted aged forest fire plumes from Alaska and western Canada during several flights of the NEAQS‐ITCT 2k4 mission in 2004. Measurements of acetonitrile (CH3CN) indicated that the air masses had been influenced by biomass burning. The locations of the plume intercepts were well described using emissions estimates and calculations with the transport model FLEXPART. The best description of the data was generally obtained when FLEXPART injected the forest fire emissions to high altitudes in the model. The observed plumes were generally drier than the surrounding air masses at the same altitude, suggesting that the fire plumes had been processed by clouds and that moisture had been removed by precipitation. Different degrees of photochemical processing of the plumes were determined from the measurements of aromatic VOCs. The removal of aromatic VOCs was slow considering the transport times estimated from the FLEXPART model. This suggests that the average OH levels were low during the transport, which may be explained by the low humidity and high concentrations of carbon monoxide and other pollutants. In contrast with previous work, no strong secondary production of acetone, methanol and acetic acid is inferred from the measurements. A clear case of removal of submicron particle volume and acetic acid due to precipitation scavenging was observed.

A case study of pyro-convection using transport model and remote sensing data

Abstract. Summer 2004 saw severe forest fires in Alaska and the Yukon Territory that were mostly triggered by lightning strikes. The area burned (>2.7×106 ha) in the year 2004 was the highest on record to date in Alaska. Pollutant emissions from the fires lead to violation of federal standards for air quality in Fairbanks. This paper studies deep convection events that occurred in the burning regions at the end of June 2004. The convection was likely enhanced by the strong forest fire activity (so-called pyro-convection) and penetrated into the lower stratosphere, up to about 3 km above the tropopause. Emissions from the fires did not only perturb the UT/LS locally, but also regionally. POAM data at the approximate location of Edmonton (53.5° N, 113.5° W) show that the UT/LS aerosol extinction was enhanced by a factor of 4 relative to unperturbed conditions. Simulations with the particle dispersion model FLEXPART with the deep convective transport scheme turned on showed transport of forest fire emissions into the stratosphere, in qualitatively good agreement with the enhancements seen in the POAM data. A corresponding simulation with the deep convection scheme turned off did not result in such deep vertical transport. Lidar measurements at Wisconsin on 30 June also show the presence of substantial aerosol loading in the UT/LS, up to about 13 km. In fact, the FLEXPART results suggest that this aerosol plume originated from the Yukon Territory on 25 June.

Measurements of trace gas emissions from Australian forest fires and correlations with coincident measurements of aerosol optical depth

We present vertically integrated measurements of C2H2, C2H4, C2H6, HCOOH, CO, H2CO, HCN and NH3 through smoke plumes from Australian forest fires measured by ground‐based solar absorption spectroscopy. The column amounts of these gases are highly correlated with simultaneous, colocated measurements of aerosol optical depth, providing a potential method of mapping biomass‐burning emissions using satellite measurements of aerosol optical depth. We have calculated emission ratios relative to CO for the trace gases using aerosol optical depth as a proxy for CO and converted to emission factors by using an average emission factor for CO from literature measurements of extratropical forest fires. The results show that Australian forest fire emissions are broadly similar to those from other geographical regions except for comparatively low emissions of C2H6.

Tracking changes in carbon monoxide budget over Europe between 1995 and 2000

The variation in carbon monoxide (CO) mixing ratio is of primary interest since it affects the atmospheric abundance of several trace gases, like methane, via extensive chemical feedback mechanisms. From the mid-1990s the global annual average mixing ratio of CO varied by about ±0–1% yr −1 while in 1998 a great pulse of CO emission increased the global CO concentration through mid-1999 by 16% over the background level. This surplus was primarily caused by heavy forest fires in several regions of the world. Our study was performed to reveal the potential causes of changes in the European CO budget and mixing ratio between 1995 and 2000 using a simple tropospheric box model. The primary anthropogenic emission from fossil fuel combustion and industrial processes in Europe showed a fairly constant annual decrease of about 4% yr −1 between 1995 and 2000, while the secondary anthropogenic CO source strength was reduced at a rate of about 3% yr −1. This decrease was partly balanced by sporadic pulses of European forest fire emissions. In spite of the reduction in the sources the region remained a net CO producer. The incremental change in the global CO budget caused by European sources was about 47.2±15.2 Tg CO yr −1 on average. The output of the model was validated against available observational data, both in absolute terms and with respect to the seasonal variation of the CO mixing ratio. The model revealed that the downward tendency of CO mixing ratios in Europe was temporarily offset by the contribution of large-scale forest fires in the northern hemisphere through long-range atmospheric transport.

On the significance of atmospheric CO2 growth rate anomalies in 2002–2003

We examine the facts behind the growth rate of atmospheric CO2 in 2002 and 2003. Observations show consecutive increases of greater than 2 parts per million (ppmv) per year for the first time on the Mauna Loa record (which extends back to 1958). We use a statistical regression to show that increasing anthropogenic emissions and El Niño activity are able to account for variations in the CO2 growth rate at Mauna Loa, aside from the anomalously low growth rates of 1992 and 1993 following the Pinatubo volcanic eruption, and the anomalously high growth rate of 2003. Increased forest fires in the northern hemisphere, consistent with remote‐sensing and carbon monoxide measurements, seem likely to have contributed significantly to the 2003 anomaly. We hypothesise that the hot and dry Eurasian summer of 2003 led to an increase in forest fire emissions from Siberia, and may also have directly suppressed land‐carbon uptake. Insofar as the 2003 Eurasian summer may have been a symptom of anthropogenic climate change, it is possible that the 2003 CO2 growth rate anomaly is the first evidence of a positive climate‐carbon cycle feedback.

Modeling of Combined Aerosol and Photooxidant Processes in the Mediterranean Area

The combined UAM-AERO/RAMS modeling system has been applied to study the dynamics of photochemical gaseous species and particulate matter processes in the eastern Mediterranean area between the Greek mainland and the island of Crete. In particular, the modeling system is applied to simulate atmospheric conditions for two periods, i.e., 13-16 July 2000 and 26-30 July 2000. The spatial and temporal distributions of both gaseous and particulate matter pollutants have been extensively studied together with the identification of major emission sources in the area. New pre-processors were developed for the UAM-AERO model for evaluating detailed emission inventories for biogenic compounds, resuspended dust and sea salt. Comparison of the modeling results with measured data was performed and satisfactory agreement was found for a number of gaseous species. However, the model underestimates the PM10 measured concentrations during summer. This is mainly due to the considerable underestimation of particulate matter emissions and in particular dust resuspension, the effect of forest fire emissions and the contribution of Saharan dust episodes.

Boreal forest fires in 1997 and 1998: a seasonal comparison using transport model simulations and measurement data

Abstract. Forest fire emissions have a strong impact on the concentrations of trace gases and aerosols in the atmosphere. In order to quantify the influence of boreal forest fire emissions on the atmospheric composition, the fire seasons of 1997 and 1998 are compared in this paper. Fire activity in 1998 was very strong, especially over Canada and Eastern Siberia, whereas it was much weaker in 1997. According to burned area estimates the burning in 1998 was more than six times as intense as in 1997. Based on hot spot locations derived from ATSR (Along Track Scanning Radiometer) data and official burned area data, fire emissions were estimated and their transport was simulated with a Lagrangian tracer transport model. Siberian and Canadian forest fire tracers were distinguished to investigate the transport of both separately. The fire emissions were transported even over intercontinental distances. Due to the El Niño induced meteorological situation, transport from Siberia to Canada was enhanced in 1998. Siberian fire emissions were transported towards Canada and contributed concentrations more than twice as high as those due to Canada's own CO emissions by fires. In 1998 both tracers arrive at higher latitudes over Europe, which is due to a higher North Atlantic Oscillation (NAO) index in 1998. The simulated emission plumes are compared to CMDL (Climate Monitoring and Diagnostics Laboratory) CO2 and CO data, Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) data and Global Ozone Monitoring Experiment (GOME) tropospheric NO2 and HCHO columns. All the data show clearly enhanced signals during the burning season of 1998 compared to 1997. The results of the model simulation are in good agreement with ground-based as well as satellite-based measurements.

A backward modeling study of intercontinental pollution transport using aircraft measurements

In this paper we present simulations with a Lagrangian particle dispersion model to study the intercontinental transport of pollution from North America during an aircraft measurement campaign over Europe. The model was used for both the flight planning and a detailed source analysis after the campaign, which is described here with examples from two episodes. Forward calculations of emission tracers from North America, Europe, and Asia were made in order to understand the transport processes. Both episodes were preceded by stagnant conditions over North America, leading to the accumulation of pollutants in the North American boundary layer. Both anthropogenic sources and, to a lesser extent, forest fire emissions contributed to this pollution, which was then exported by warm conveyor belts to the middle and upper troposphere, where it was transported rapidly to Europe. Concentrations of many trace gases (CO, NOy, CO2, acetone, and several volatile organic compounds; O3 in one case) and of ambient atmospheric ions measured aboard the research aircraft were clearly enhanced in the pollution plumes compared to the conditions outside the plumes. Backward simulations with the particle model were introduced as an indispensable tool for a more detailed analysis of the plume's source region. They make trajectory analyses (which, to date, were mainly used to interpret aircraft measurement data) obsolete. Using an emission inventory, we could decompose the tracer mixing ratios at the receptors (i.e., along the flight tracks) into contributions from every grid cell of the inventory. For both plumes we found that emission sources contributing to the tracer concentrations over Europe were distributed over large areas in North America. In one case, sources in California, Texas, and Florida contributed almost equally, and smaller contributions were also made by other sources located between the Yucatan Peninsula and Canada. In the other case, sources in eastern North America, including moderate contributions from forest fires, were most important. The plume's maximum was mainly caused by anthropogenic emissions from the New York area. To our knowledge, this is the first case reported where a pollution plume from a megacity was reliably detected over another continent.

Fire science for rainforests.

Forest fires are growing in size and frequency across the tropics. Continually eroding fragmented forest edges, they are unintended ecological disturbances that transcend deforestation to degrade vast regions of standing forest, diminishing ecosystem services and the economic potential of these natural resources. Affecting the health of millions, net forest fire emissions may have released carbon equivalent to 41% of worldwide fossil fuel use in 1997-98. Episodically more severe during El Niño events, pan-tropical forest fires will increase as more damaged, less fire-resistant, forests cover the landscape. Here I discuss the current state of tropical fire science and make recommendations for advancement.

Emissions of carbon dioxide, carbon monoxide, and methane from boreal forest fires in 1998

The global boreal forest region experienced some 17.9 million ha of fire in 1998, which could be the highest level of the decade. Through the analysis of fire statistics from North America and satellite data from Russia, semimonthly estimates of area burned for five different regions in the boreal forest were generated and used to estimate total carbon release and CO2, CO, and CH4emissions. Different levels of biomass, as well as different biomass categories, were considered for each of the five different regions (including peatlands in the Russian Far East and steppes in Siberia), as were different levels of fraction of biomass (carbon) consumed during fires. Finally, two levels of flaming versus smoldering combustion were considered in the model. Boreal forest fire emissions for 1998 were estimated to be 290–383 Tg of total carbon, 828–1103 Tg of CO2, 88–128 Tg of CO, and 2.9–4.7 Tg of CH4. The higher estimate represents 8.9% of total global carbon emissions from biomass burning, 13.8% of global fire CO emissions, and 12.4% of global fire CH4emissions. Russian fires accounted for 71% of the total emissions, with the remainder (29%) from fires in North America. Assumptions regarding the level of smoldering versus flaming generally resulted in small (<4%) variations into the emissions estimates, although in two cases, these variations were higher (6% and 12%). We estimated that peatland fires in the Russian Far East contributed up to 40 Tg of carbon to the atmosphere in the fall of 1998. The combined seasonal CO emissions from forest and peatland fires in Russia are consistent with anomalously high atmospheric CO measurements collected at Point Barrow, Alaska.

Transport of boreal forest fire emissions from Canada to Europe

In August 1998, severe forest fires occurred in many parts of Canada, especially in the Northwest Territories. In the week from August 5 to 11, more than 1000 different fires burned >1 × 106 ha of boreal forest, the highest 1‐week sum ever reported throughout the 1990s. In this study we can unambigously show for the first time that these fires caused pronounced large‐scale haze layers above Europe and that they influenced concentrations of carbon monoxide and other trace gases at the surface station Mace Head in Ireland over a period of weeks. Transport took place across several thousands of kilometers. An example of such an event, in which a pronounced aerosol layer was observed at an altitude of 3–6 km over Germany during August 1998, is investigated in detail. Backward trajectories ending at the measured aerosol layer are calculated and shown to have their origin in the forest fire region. Simulations with a particle dispersion model reveal how a substantial amount of forest fire emissions was transported across the Atlantic. The resulting aerosol lamina over Europe is captured well by the model. In addition, the model demonstrates that the forest fire emissions polluted large regions over Europe during the second half of August 1998. Surface measurements at Mace Head are compared to the model results for an anthropogenic and a forest fire carbon monoxide tracer, respectively. While wet deposition removed considerable amounts of aerosol during its transport, forest fire carbon monoxide reached Europe in copious amounts. It is estimated that during August 1998, 32%, 10%, and 58% of the carbon monoxide enhancement over the background level at Mace Head were caused by European and North American anthropogenic emissions and forest fire emissions, respectively.

PM 2.5 chemical source profiles for vehicle exhaust, vegetative burning, geological material, and coal burning in Northwestern Colorado during 1995

PM 2.5 (particles with aerodynamic diameters less than 2.5 μm) chemical source profiles applicable to speciated emissions inventories and receptor model source apportionment are reported for geological material, motor vehicle exhaust, residential coal (RCC) and wood combustion (RWC), forest fires, geothermal hot springs; and coal-fired power generation units from northwestern Colorado during 1995. Fuels and combustion conditions are similar to those of other communities of the inland western US. Coal-fired power station profiles differed substantially between different units using similar coals, with the major difference being lack of selenium in emissions from the only unit that was equipped with a dry limestone sulfur dioxide (SO 2) scrubber. SO 2 abundances relative to fine particle mass emissions in power plant emissions were seven to nine times higher than hydrogen sulfide (H 2S) abundances from geothermal springs, and one to two orders of magnitude higher than SO 2 abundances in RCC emissions, implying that the SO 2 abundance is an important marker for primary particle contributions of non-aged coal-fired power station contributions. The sum of organic and elemental carbon ranged from 1% to 10% of fine particle mass in coal-fired power plant emissions, from 5% to 10% in geological material, >50% in forest fire emissions, >60% in RWC emissions, and >95% in RCC and vehicle exhaust emissions. Water-soluble potassium (K +) was most abundant in vegetative burning profiles. K +/K ratios ranged from 0.1 in geological material profiles to 0.9 in vegetative burning emissions, confirming previous observations that soluble potassium is a good marker for vegetative burning.

X-ray fluorescence method in analyzing forest fire emission elements

Composition of aerosols from large taiga forest fires was investigated using an X-ray fluorescence method that involves excitation of the characteristic spectrum by synchrotron radiation. Emissions were sampled directly from the convection column with the help of various instruments (including an impactor) mounted on a helicopter. We compared the results of the study with literature data.