Canadian Forest Fires Research Articles

Rapid response of stream dissolved phosphorus concentrations to wildfire smoke

Wildfires can produce large plumes of smoke that are transported across vast distances, altering nutrient cycling of undisturbed watersheds exposed downwind. To date, wildfire smoke influence on stream biogeochemical signatures remains an important knowledge gap. Here we evaluate the impacts of wildfire smoke on phosphorus (P) biogeochemical cycling in a temperate watershed in the Finger Lakes Region of Central New York located downwind from record setting Canadian forest fires during the summer of 2023. Daily sampling of stream and rainwaters was conducted over the 2 month smoke period, generating a robust geochemical dataset. Stream dissolved P showed high sensitivity to smoke events, attaining concentrations 2–3 × greater than the pre-smoke period. Subsequent rain events after smoke deposition were identified as a potentially important factor in magnitude and timing of dissolved P responses. These findings demonstrate the capacity for wildfire smoke to trigger rapid, observable changes to stream P chemistry.

Carbon emissions from the 2023 Canadian wildfires

The 2023 Canadian forest fires have been extreme in scale and intensity with more than seven times the average annual area burned compared to the previous four decades1. Here, we quantify the carbon emissions from these fires from May to September 2023 on the basis of inverse modelling of satellite carbon monoxide observations. We find that the magnitude of the carbon emissions is 647 TgC (570–727 TgC), comparable to the annual fossil fuel emissions of large nations, with only India, China and the USA releasing more carbon per year2. We find that widespread hot–dry weather was a principal driver of fire spread, with 2023 being the warmest and driest year since at least 19803. Although temperatures were extreme relative to the historical record, climate projections indicate that these temperatures are likely to be typical during the 2050s, even under a moderate climate mitigation scenario (shared socioeconomic pathway, SSP 2–4.5)4. Such conditions are likely to drive increased fire activity and suppress carbon uptake by Canadian forests, adding to concerns about the long-term durability of these forests as a carbon sink5–8.

Changes in aerosol properties at the El Arenosillo site in Southern Europe as a result of the 2023 Canadian forest fires

From the beginning of May 2023 to the end of August 2023, the Northern Hemisphere experienced significant wildfire activity with the most widespread fires occurring in Canada. Forest fires in Canada destroyed more than 15.6 million hectares of forests. These wildfires worsened air quality across the region and other parts of the world. The smoke reached southern Europe by the end of June 2023. To better understand the consequences of such forest fires far from the site of origin, aerosol optical, microphysical and radiative properties were analyzed during this event for southern Europe using data from the Visible Infrared Imaging Radiometer Suite (VIIRS), TROPOspheric Monitoring Instrument (TROPOMI), and Aerosol Robotic Network (AERONET). TROPOMI aerosol index (AI) and the carbon monoxide (CO) product confirm that the smoke originated directly from these forest fires. AERONET data from the El Arenosillo site in southern Spain showed maximum aerosol optical depth (AOD) values on June 27 reached 2.36. Data on Angstrom Exponent (AE), aerosol volume size distribution (VSD), single scattering albedo (SSA), fine mode fraction (FMF), volume particle concentration, effective radius (REff), absorption AOD (AAOD), extinction AE (EAE) and absorption AE (AAE) showed that fine-mode particles with carbonaceous aerosols contribution predominated in the atmosphere above the El Arenosillo site. Direct aerosol radiative forcing (DARF) at the top (DARFTOA) and bottom of atmosphere (DARFBOA) were −103.1 and −198.93 Wm−2, respectively. The atmospheric aerosol radiative forcing (DARFATM) was found to be 95.83 Wm−2 and with a heating rate 2.69 K day−1, which indicates the resulting warming of the atmosphere.

Using the Weather Index Classification System for Canadian Forest Fires over the Al-Jabal Al-Akhdar in Libya

Using the Weather Index Classification System for Canadian Forest Fires over the Al-Jabal Al-Akhdar in Libya

Tracking Carbon Dioxide with Lagrangian Transport Simulations: Case Study of Canadian Forest Fires in May 2021

The large amounts of greenhouse gases, such as carbon dioxide, produced by severe forest fires not only seriously affect the ecosystems in the area where the fires occur but also cause a greenhouse effect that has a profound impact on the natural environment in other parts of the world. Numerical simulations of greenhouse gas transport processes are often affected by uncertainties in the location and timing of the emission sources and local meteorological conditions, and it is difficult to obtain accurate and credible predictions by combining remote sensing satellite data with given meteorological forecasts or reanalyses. To study the regional transport processes and impacts of greenhouse gases produced by sudden large-scale forest fires, this study applies the Lagrangian particle dispersion model Massive-Parallel Trajectory Calculations (MPTRAC) to conduct forward simulations of the CO2 transport process of greenhouse gases emitted from forest fires in the central region of Saskatchewan, Canada, during the period of 17 May to 25 May 2021. The simulation results are validated with the Orbiting Carbon Observatory-2 Goddard Earth Observing System (OCO-2 GEOS) Level 3 daily gridded CO2 product over the study area. In order to leverage the high computational costs of the numerical simulations of the model, we implement the forward simulations on the Tianhe-2 supercomputer platform and the JUWELS HPC system, which greatly improves the computational efficiency through parallel computation and makes near-real-time predictions of atmospheric transport processes feasible.

Canadian forest fires, Icelandic volcanoes and increased local dust observed in six shallow Greenland firn cores

Abstract. Greenland ice cores provide information about past climate. Few impurity records covering the past 2 decades exist from Greenland. Here we present results from six firn cores obtained during a 426 km long northern Greenland traverse made in 2015 between the NEEM and the EGRIP deep-drilling stations situated on the western side and eastern side of the Greenland ice sheet, respectively. The cores (9 to 14 m long) are analyzed for chemical impurities and cover time spans of 18 to 53 years (±3 years) depending on local snow accumulation that decreases from west to east. The high temporal resolution allows for annual layers and seasons to be resolved. Insoluble dust, ammonium, and calcium concentrations in the six firn cores overlap, and the seasonal cycles are also similar in timing and magnitude across sites, while peroxide (H2O2) and conductivity both have spatial variations, H2O2 driven by the accumulation pattern, and conductivity likely influenced by sea salt. Overall, we determine a rather constant dust flux over the period, but in the data from recent years (1998–2015) we identify an increase in large dust particles that we ascribe to an activation of local Greenland sources. We observe an expected increase in acidity and conductivity in the mid-1970s as a result of anthropogenic emissions, followed by a decrease due to mitigation. Several volcanic horizons identified in the conductivity and acidity records can be associated with eruptions in Iceland and in the Barents Sea region. From a composite ammonium record we obtain a robust forest fire proxy associated primarily with Canadian forest fires (R=0.49).

Microwave Limb Sounder (MLS) observations of biomass burning products in the stratosphere from Canadian forest fires in August 2017

Abstract. Forest fires in British Columbia in August 2017 caused a pyrocumulonimbus event that injected a polluted air mass into the lower stratosphere. The Microwave Limb Sounder (MLS) on the Aura satellite first observed the polluted air mass on 14 August 2017 and continued to observe it for 60 d (100 d in water vapour). We estimate the mass of CO injected into the stratosphere to be 2400 Gg. Events in which a fire injects its burning products directly into the stratosphere are rare: this is the third of four such events in the 16 years since the launch of Aura, the second largest of the four events, and the only one in the Northern Hemisphere. The other three events occurred in Australia in December 2006, February 2009 and from December 2019 to January 2020. Unlike the 2006 and 2009 events, but like the 2019–2020 event, the polluted air mass described here had a clearly elevated water vapour content: between 2.5 and 5 times greater than that in the surrounding atmosphere. We describe the evolution of the polluted air mass, showing that it rose to an altitude of about 24 km (31 hPa) and divided into several identifiable parts. In addition to CO and H2O, we observe enhanced amounts of HCN, CH3CN, CH3Cl and CH3OH with mixing ratios in the range to be expected from a variety of measurements in other biomass burning plumes. We use back trajectories and plume-dispersion modelling to demonstrate that the pollutants observed by MLS originated in the British Columbia fires, the likeliest source being at 53.2∘ N, 121.8∘ W at 05:20 UTC on 13 August 2017.

On the phenomenon of the blue sun

Abstract. This study examines the cause of the blue colour of the sun as observed after the eruption of Krakatao in 1883 as well as other volcanic eruptions or massive forest fire events. Aerosol particles, e.g. volcanic ash or products of biomass burning, are believed to be able to modify the spectral distribution of transmitted solar radiation making it appear blue or green to a human observer. Previous studies already showed that narrow aerosol particle size distributions with radii on the order of about 500 nm can lead to anomalous scattering; i.e. scattering cross sections increasing with increasing wavelength in the visible spectral range. In this work we treat the effect of Rayleigh scattering on the shape of the transmitted solar spectrum correctly employing radiative transfer (RT) simulations with the SCIATRAN RT-model. The colour associated with solar transmission spectra is determined based on the CIE (International Commission on Illumination) colour matching functions and CIE chromaticity values. It is shown that a blue sun can be simulated for aerosol optical depths (at 550 nm) of about τ=0.5 (or higher) if Rayleigh scattering is taken into account. Without considering Rayleigh scattering – as in most of the previous studies – a blue sun is in principle produced with aerosol optical depths as low as about τ=0.1 (at 550 nm) if the aerosol particle size distribution is chosen to maximize anomalous scattering in the visible spectral range. It is demonstrated that Rayleigh scattering – as expected – has a strong impact on the transmission spectrum, particularly at low solar-elevation angles, and needs to be considered for a correct determination of the perceived colour of the sun. We also test the hypothesis that the blue sun after the eruption of Krakatao was caused by large abundances of water vapour in the atmosphere, as proposed in earlier studies. In addition, we present a case study on a particularly noteworthy blue sun event in the past, i.e. the one related to the large Canadian forest fires in September 1950.

Polycyclic aromatic compounds (PACs) in the Canadian environment: Sources and emissions.

Twenty-five years after the first look at polycyclic aromatic compounds (PACs) in Canada, this article presents current knowledge on Canadian PAC emission sources. The analysis is based on national inventories (the National Pollutant Release Inventory (NPRI) and the Air Pollutant Emissions Inventory (APEI)), an analysis of Canadian forest fires, and several air quality model-ready emissions inventories. Nationally, forest fires continue to dominate PAC emissions in Canada, however there is uncertainty in these estimates. Though forest fire data show a steady average in the total annual area burned historically, an upward trend has developed recently. Non-industrial sources (home firewood burning, mobile sources) are estimated to be the second largest contributor (∼6-8 times lower than forest fires) and show moderate decreases (25%-65%) in the last decades. Industrial point sources (aluminum production, iron/steel manufacturing) are yet a smaller contributor and have seen considerable reductions (90%+) in recent decades. Fugitive emissions from other industrial sources (e.g. disposals by the non-conventional oil extraction and wastewater sectors, respectively) remain a gap in our understanding of total PAC emissions in Canada. Emerging concerns about previously unrecognized sources such as coal tar-sealed pavement run-off, climate change are discussed elsewhere in this special issue. Results affirm that observations at the annual/national scale are not always reflective of regional/local or finer temporal scales. When determining which sources contribute most to human and ecosystem exposure in various contexts, examination at regional and local scales is needed. There is uncertainty overall in emissions data stemming in part from various accuracy issues, limitations in the scope of the various inventories, and inventory gaps, among others.

Effects of Climate Change on Canadian Forest Fires

This study aimed to determine the effects of climate change on forest fire trends in Canada by measuring correlations between weather conditions, and the frequencies and sizes of forest fires. Upon identifying the correlations, a model was created to understand future forest fire trends in order to prevent the increasing occurrences of forest fires, and to devise solutions to reduce their damages. The data obtained from the Canadian National Fire Database was modeled with a linear regression to predict and correlate weather conditions with future forest fire trends. It was concluded that temperature and wind speed correlated positively with forest fire frequency and size, while precipitation presented a negative correlation. To reduce the harmful effects of forest fires, cloud seeding can be used to create more precipitation, and wind farms can be built to lower wind speeds and attract lightning. However, more research and stricter policies directly targeting climate change is a necessity when it comes to decreasing forest fire trends and improving longterm security.

Temporal variations in optical and microphysical properties of mineral dust and biomass burning aerosol derived from daytime Raman lidar observations over Warsaw, Poland

In July 2013, favorable weather conditions caused a severe events of advection of biomass burning particles of Canadian forest fires to Europe. The smoke layers were widely observed, especially in Western Europe. An unusual atmospheric aerosol composition was measured at the EARLINET site in Warsaw, Central Poland, during a short event that occurred between 11 and 21 UTC on 10th July 2013. Additionally to the smoke layer, mineral dust was detected in a separate layer. The long-range dust transport pathway followed an uncommon way; originating in Western Sahara, passing above middle Atlantic, and circulating over British Islands, prior to its arrival to Poland. An effective radius of 560 nm was obtained for Saharan dust over Warsaw. This relatively small effective radius is likely due to the long time of the transport. The aerosol-polarization-Raman PollyXT-UW lidar was used for a successful daytime Raman retrieval of the aerosol optical properties at selected times during this short event. The aerosol vertical structure during the inflow over Warsaw in terms of optical properties and depolarization was analyzed, indicating clear distinction of the layers. The microphysical properties were inverted from the lidar derived optical data for selected ranges as representing the smoke and the mineral dust. For smoke, the effective radius was in the range of 0.29–0.36 μm and the complex refractive index 1.36 + 0.008i, on average. For dust, the values of 0.33–0.56 μm and 1.56 + 0.004i were obtained. An evolution of the aerosol composition over Warsaw during the day was analyzed.

Quantifying black carbon deposition over the Greenland ice sheet from forest fires in Canada

AbstractBlack carbon (BC) concentrations observed in 22 snowpits sampled in the northwest sector of the Greenland ice sheet in April 2014 have allowed us to identify a strong and widespread BC aerosol deposition event, which was dated to have accumulated in the pits from two snow storms between 27 July and 2 August 2013. This event comprises a significant portion (57% on average across all pits) of total BC deposition over 10 months (July 2013 to April 2014). Here we link this deposition event to forest fires burning in Canada during summer 2013 using modeling and remote sensing tools. Aerosols were detected by both the Cloud‐Aerosol Lidar with Orthogonal Polarization (on board CALIPSO) and Moderate Resolution Imaging Spectroradiometer (Aqua) instruments during transport between Canada and Greenland. We use high‐resolution regional chemical transport modeling (WRF‐Chem) combined with high‐resolution fire emissions (FINNv1.5) to study aerosol emissions, transport, and deposition during this event. The model captures the timing of the BC deposition event and shows that fires in Canada were the main source of deposited BC. However, the model underpredicts BC deposition compared to measurements at all sites by a factor of 2–100. Underprediction of modeled BC deposition originates from uncertainties in fire emissions and model treatment of wet removal of aerosols. Improvements in model descriptions of precipitation scavenging and emissions from wildfires are needed to correctly predict deposition, which is critical for determining the climate impacts of aerosols that originate from fires.

Characteristics of stratospheric aerosol from data of lidar measurements over Obninsk in 2012–2015

Lidar polarization measurements of stratospheric aerosol were performed over Obninsk in 2012–2015. In all, over 300 altitude profiles of the aerosol backscattering coefficient at a wavelength of 532 nm in the altitude interval from 10 to 40 km were obtained. Overall, the measured aerosol backscattering characteristics are close to the known background values. During spring 2013, an elevated content of spherical-type aerosol was noted in the tropopause region, seemingly associated with sedimentation of aerosol structures formed during the fall of the Chelyabinsk meteorite. In July 2014 and 2015, layers of increased aerosol scattering were observed in the altitude interval from 10 to 15 km, associated with transcontinental transport of aerosol from Canadian forest fires. Integrated backscattering and extinction characteristics are estimated for the lower (from tropopause level to 15 km) and middle (from 15 to 30 km) stratospheric layers. It is found that the contribution of the lower layer to these optical characteristics is 1.8 and 1.6 times larger than the contribution of the middle layer.

Canadian Forest Fires and the Effects of Long-Range Transboundary Air Pollution on Hospitalizations among the Elderly.

In July 2002, lightning strikes ignited over 250 fires in Quebec, Canada, destroying over one million hectares of forest. The smoke plume generated from the fires had a major impact on air quality across the east coast of the U.S. Using data from the Medicare National Claims History File and the U.S. Environmental Protection Agency (EPA) National air pollution monitoring network, we evaluated the health impact of smoke exposure on 5.9 million elderly people (ages 65+) in the Medicare population in 81 counties in 11 northeastern and Mid-Atlantic States of the US. We estimated differences in the exposure to ambient PM2.5-airborne particulate matter with aerodynamic diameter of ≤2.5 μm-concentrations and hospitalizations for cardiovascular, pulmonary and injury outcomes, before and during the smoke episode. We found that there was an associated 49.6% (95% confidence interval (CI), 29.8, 72.3) and 64.9% (95% CI, 44.3-88.5) increase rate of hospitalization for respiratory and cardiovascular diagnoses, respectively, when the smoke plume was present compared to before the smoke plume had arrived. Our study suggests that rapid increases in PM2.5 concentrations resulting from wildfire smoke can impact the health of elderly populations thousands of kilometers removed from the fires.

Characterization of atmospheric aerosols for a long range transport of biomass burning particles from Canadian forest fires over the southern Iberian Peninsula in July 2013

espanolEste trabajo presenta la caracterizacion, durante un evento especial de transporte a gran distancia, de particulas de combustion de biomasa, procedentes de incendios forestales en Canada. El evento se detecto entre el 11 y el 17 de julio de 2013 en la estacion de EARLINET en Granada (37.16° N, 3.61° W, 680 snm), asi como en otras estaciones de EARLINET. Para su caracterizacion se han usado diferentes tecnicas, incluyendo activas/pasivas y terrestres/por satelite. En particular, el estudio implico el procesado de senales lidar tanto elasticas como Raman, y datos de fotometro solar de la red AERONET. Ademas se han usado modelos como HYSPLIT, NAAPS y BSC-DREAM8b para investigar el comportamiento de las plumas de aerosol a escala sinoptica. Los resultados destacan la presencia de una estructura con multiples capas que muestran un exponente de Angstrom de coeficiente de retrodispersion alto (aproximadamente 2) y una despolarizacion lineal de particulas muy baja (menos de 0.04) en las capas a 5-6 km (snm) de altura, lo que indica que son particulas considerablemente pequenas y esfericas. Durante el periodo mas intenso, el 14 de julio, se detectaron valores del coeficiente de retrodispersion de hasta 2.9×10ˉ⁶ (m sr) ˉ¹ para 532 nm. EnglishThis work presents the characterization of aerosols during a special episode of long-range transported biomass burning particles from Canadian forest fires. This event was detected at the EARLINET Granada station (37.16° N, 3.61° W, 680 m asl) from 11ᵗʰ to 17ᵗʰ July 2013, and also over other EARLINET stations. Different techniques, covering active/passive and ground based/satellite ones, have been used. In particular, the study has involved processing of both Raman and elastic lidar signals and sun-photometer AERONET data. Furthermore, modeling tools as HYSPLIT, NAAPS and BSC-DREAM8b have been used to understand the synoptic behavior of the aerosol plumes. The results highlight the presence of a multilayered structure showing large backscatter-related Angstrom Exponent (around 2) and very low particle linear depolarization (less than 0.04) at layers around 5-6 km (asl) which means considerably small and spherical particles. During the strongest period, on 14ᵗʰ July, aerosol backscatter values up to 2.9×10ˉ⁶ (m sr) ˉ¹ at 532 nm were detected in this layer.

A methodology for investigating trends in changes in the timing of the fire season with applications to lightning-caused forest fires in Alberta and Ontario, Canada

Lightning-caused fires account for approximately 45% of ignitions and 80% of area burned by forest fires in Canada. Investigating the seasonality of these fires and the extent to which it may be changing over time is of interest to both fire managers and researchers. In this project, we develop flexible models for describing the temporal variation in the risk of lightning-caused fires. Generalized additive models are first used to obtain smooth estimates of fire risk by Julian day for each year. Inverse calculations are then employed to obtain point and interval estimates of the start and end of the fire season annually; these are defined by the crossing of fire risk thresholds. Finally, permutation-based methods are used to test for significant linear trends in the start and end of the fire season. This methodology is applied to historical forest fire records in Alberta, Canada, and the western and eastern subregions of Ontario, Canada. Our results suggest significant changes to both the start and end of the fire season in Alberta and a significant change to the end of the fire season in western and eastern Ontario.

Impacts of the Canadian Forest Fires on Atmospheric Mercury and Carbonaceous Particles in Northern New York

The impact of Canadian forest fires in Quebec on May 31, 2010 on PM(2.5), carbonaceous species, and atmospheric mercury species was observed at three rural sites in northern New York. The results were compared with previous studies during a 2002 Quebec forest fire episode. MODIS satellite images showed transport of forest fire smoke from southern Quebec, Canada to northern New York on May 31, 2010. Back-trajectories were consistent with this regional transport. During the forest fire event, as much as an 18-fold increase in PM(2.5) concentration was observed. The concentrations of episode-related OC, EC, BC, UVBC, and their difference (Delta-C), reactive gaseous mercury (RGM), and particle-bound mercury (PBM) were also significantly higher than those under normal conditions, suggesting a high impact of Canadian forest fire emissions on air quality in northern New York. PBM, RGM, and Delta-C are all emitted from forest fires. The correlation coefficient between Delta-C and other carbonaceous species may serve as an indicator of forest fire smoke. Given the marked changes in PBM, it may serve as a more useful tracer of forest fires over distances of several hundred kilometers relative to GEM. However, the Delta-C concentration changes are more readily measured.

A Markov Chain Monte Carlo approach to joint simulation of regional areas burned annually in Canadian forest fires

A simulation of regional and national forest carbon balance in Canada requires, due to regional correlations, a joint simulation of areas burned ( BA) in regional fires. Regional correlations of BA are largely determined by concurrent years of relatively large ( LF) and small fires ( SF). A binary Markov Chain Monte Carlo procedure (MCMC) is constructed for forecasting regional LF( SF) status on an annual basis. For each forecast year the regional BA-value is obtained by a random draw from region-specific empirical quantile functions for LF and SF years. In the MCMC the conditional likelihood of a regional allocation of nLF* LF-years is maximized; whereby nLF* is drawn from a distribution fitted to LF( SF) classified data of area burned in 29 Canadian forest fire regions between 1959 and 1999. Regional allocation is governed by region-specific autologistic functions. MCMC results confirmed regional and national means and variances while regional correlations were generally somewhat lower than in the data.

Future emissions from Canadian boreal forest fires

New estimates of greenhouse gas emissions from Canadian forest fires were calculated based on a revised model for fuel consumption, using both the fire fuel load and the Drought Code of the Canadian Forest Fire Weather Index System. This model was applied to future climate scenarios of 2×CO2 and 3×CO2 environments using the Canadian Global Climate Model. Total forest floor fuel consumption for six boreal ecozones was estimated at 60, 80, and 117 Tg dry biomass for the 1×CO2, 2×CO2, and 3×CO2 scenarios, respectively. These ecozones cover the boreal and taiga regions and account for about 86% of the total fire consumption for Canada. Almost all of the increase in fuel consumption for future climates is caused by an increase in the area burned. The effect of more severe fuel consumption density (kilograms of fuel consumed per square metre) is relatively small, ranging from 0% to 18%, depending on the ecozone. The emissions of greenhouse gases from all Canadian fires are estimated to increase from about 162 Tg·year–1 of CO2 equivalent in the 1×CO2 scenario to 313 Tg·year–1 of CO2 equivalent in the 3×CO2 scenario, including contributions from CO2, CH4, and N2O.

Evidence of the cloud lifetime effect from wildfire‐induced thunderstorms

A case study is presented of pyro‐cumulonimbi (pyroCbs) forming over Canadian forest fires. Cloud‐top ice effective radius values of these pyroCbs are significantly smaller than are those within surrounding convection. The smoke provides a massive source of cloud condensation nuclei (CCN), resulting in smaller cloud droplets which freeze homogeneously at temperatures around −40°C and produce very small ice crystals. It is also shown that the pyroCb anvils persist 6–12 hours longer than convectively‐generated cirrus anvils from nearby convection. This provides evidence for the so‐called cloud lifetime effect, an aerosol indirect effect identified by the most recent Intergovernmental Panel on Climate Change (IPCC) report.