Fires In Alaska Research Articles

Evaluating the Alaska Blocking Index as an indicator of wildfire potential in Alaska's central eastern interior

AbstractIncreased Arctic air temperatures and evaporative fluxes have coincided with more frequent and destructive high‐latitude wildfires. Arctic fires impact ecosystems and people, especially at the community‐level by degrading air quality, destroying agriculture, and threatening life and property. Central Eastern Interior (CEI) Alaska is one such region that has recently experienced the effects of wildfire activity related to warming air temperatures. To improve our ability to identify fire weather events and assess their potential for extreme outbreaks at actionable lead times relevant to fire weather forecasters and managers, new metrics and approaches need to be established and applied toward understanding the physical mechanisms underlying such wildland fire characteristics. Our study uses a new, regional atmospheric circulation metric, the Alaska Blocking Index (ABI), to describe midtropospheric air pressure around Alaska, which is subsequently related to CEI fire weather conditions at the Predictive Service Area (PSA) scale in climatological and extreme events frameworks. Of note, during years of high fire activity, Build‐Up Index (BUI) values tend to be anomalously high during the duff and drought phases across the CEI PSAs, though comparatively lower BUI values are still associated with high fire activity in the Tanana Zone‐South (AK03S) PSA. Likewise, extreme BUI values are strongly tied to high ABI values and well‐defined upper‐air ridging circulation patterns in the duff and drought periods. The statistical skill of mean daily ABI values in the 6–10 day period preceding extreme duff period BUI values is modest (τ2 > 14%) in the Upper Yukon Valley (AK02) PSA, a hotbed of wildland fire activity. Extremes in ABI and CEI BUI often occur in tandem, yielding regional predictability of upper‐air weather patterns and extremes and underlying surface weather conditions, by statistical and/or dynamical forecast models, imperative for local community and governmental organizations to effectively manage and allocate Alaska's fire weather resources.

Prehospital Care Standards in the Federal Wildland Fire Service

Abstract Objective Defining the role of federal wildland firefighters (WFF) in the context of emergency medical services (EMS) is a gap in the literature. Our work highlights the importance of standardizing and enhancing the EMS capabilities of federal WFF for their own occupational safety and well-being, while emphasizing their potential for responding to all disasters and providing medical safety net in rural communities. Methods A comprehensive academic literature review on the topic returned one non-peer reviewed manuscript. Study members analyzed National Wildfire Coordinating Group (NWCG) EMS policy to assess current EMS standards within the WFF service. Results The study reveals a lack of standardized, comprehensive support for EMS capabilities among federal WFF, despite need for their expertise in wide-ranging emergency situations. There are few incentives for individuals to obtain and maintain EMS certification. Various innovations, such as the Alaska Fire Medic Program and the BLM Operational Medical Support Program, are potential models for improving EMS across the entire NWCG. Conclusions To enhance the safety, professionalization, and efficiency of WFF, the NWCG should consider standardizing EMS guidelines, especially in providing consistent support for medical certifications. EMS certified WFF could contribute to nationwide disaster response capabilities if supported by NWCG.

Anomalous Selective Absorption of Smoke Aerosol during Forest Fires in Alaska in July–August 2019

Anomalous Selective Absorption of Smoke Aerosol during Forest Fires in Alaska in July–August 2019

Anomalous Selective Absorption of Smoke Aerosol during Forest Fires in Alaska in July–August 2019

According to the monitoring data of the optical and microphysical characteristics of smoke aerosol at AERONET stations during forest fires in the summer of 2019 in Alaska, anomalous selective absorption of smoke aerosol was detected in the visible and near infrared spectral range from 440 to 1020 nm. With anomalous selective absorption, the imaginary part of the refractive index of smoke aerosol reached 0.315 at a wavelength of 1020 nm. A power-law approximation of the spectral dependence of the imaginary part of the refractive index with an exponent from 0.26 to 2.35 is proposed. It is shown that for anomalous selective absorption, power-law approximations of the spectral dependences of the aerosol optical extinction and absorption depths are applicable with an Angstrom exponent from 0.96 to 1.65 for the aerosol optical extinction depth and from 0.97 to –0.89 for the aerosol optical absorption depth, which reached 0.72. Single scattering albedo varied from 0.62 to 0.96. In the size distribution of smoke aerosol particles with anomalous selective absorption, the fine fraction of particles of condensation origin dominated. The similarity of the fraction of particles distinguished by anomalous selective absorption with the fraction of tar balls detected by electron microscopy in smoke aerosol, which, apparently, arise during the condensation of terpenes and their oxygen-containing derivatives, is noted.

Mental health during wildfires in Southcentral Alaska: An assessment of community-derived mental health categories, interventions, and implementation considerations

Previous studies have linked wildfires to a range of adverse mental health outcomes, but there has been limited research on the mental health impacts of wildfire in Alaska, an area undergoing rapid environmental change. We used a multi-level qualitative approach to identify mental health and psychosocial problems, coping, existing support, and gaps in support among communities who were affected by the Swan Lake and McKinley fires in Alaska in 2019. We recruited 39 community members from Anchorage and the Kenai Peninsula to participate in free list interviews, a community ranking workshop, and in-depth interviews, and we recruited 12 professional key informants including wildland firefighters, mental health providers, community advocates, policy makers, and public health professionals to participate in in-depth interviews and a discussion-based workshop. There were several locally-defined categories of mental health issues identified in relation to wildfires in southcentral Alaska in 2019. Key informants who work in the region identified a package of communications-related interventions as being the most impactful and actionable support for wildfire-related mental health concerns. Additional highly rated mental health supports centered around leadership acknowledging the connection between wildfire and mental health, connecting community members to formal or informal systems of mental health care, enhancing the emergency shelter system, and providing crises debriefing during wildfire evacuations. The results of this study can be utilized to facilitate implementation of prevention and response activities to support mental health resilience during wildfires in Alaska and other wildfire-affected regions.

Fuel Loads and Plant Traits as Community‐Level Predictors of Emergent Properties of Vulnerability and Resilience to a Changing Fire Regime in Black Spruce Forests of Boreal Alaska

AbstractBlack spruce forest communities in boreal Alaska have undergone self‐replacement succession following low‐to‐moderate severity fires for thousands of years. However, recent intensification of interior Alaska's fire regime, particularly deeper burning of the soil organic layer, is leading to shifts to deciduous‐dominated successional pathways, resulting in many socioecological consequences. Both fuel load quantity and quality (or “burnability”) influence black spruce plant communities' potential to burn. Even relatively low fuel loads, such as those seen in black spruce forest understory, can be highly influential drivers of fire behavior due to their high flammability. Additionally, black spruce community self‐replacement following fire can be largely attributed to the suite of functional and life history traits possessed by the species dominating these communities. We used fuel load (quantity and quality) and amount of within‐population plant trait variation (coefficient of variation; CV) as community‐level emergent properties to investigate black spruce forest vulnerability and resilience to a changing fire regime across the landscape. Our burn severity potential index (BSPI), calculated from fuel load quantity and quality measurements, indicates that drier, higher elevation stands with thicker active layers were the most vulnerable to fire‐induced vegetation shifts under a changing fire regime. Forest resilience to fire‐induced vegetation shift, represented by higher CV, was negatively associated with BSPI and greatest in ecoregions dominated by lowland black spruce forests. Together, these analyses provide critical information for determining the likelihood of stand‐replacing shifts in dominant vegetation following fire and for implementing appropriate ecosystem management practices.

A Potential Framework for Allocating National Park Service Budgets

The US Department of Interior, including the National Park Service (NPS), has interest in developing a national fire budgeting process that reflects and promotes program (fuels and preparedness) efficiencies while being transparent, fair, stable, and predictable. A systematic approach should have the potential to operate at all scales (national, regional, and park). To accomplish these objectives, the research introduced a Budgeting Analysis that can be integrated into the STARFire (Strategic budgeting and planning system for wildland fire). The approach used is known as the “gradient method” reflecting the concept that budgets are allocated based on proportionate performance. Using the gradient method, budget increments were allocated to fuels and preparedness programs to improve return on investment (ROI). Three-dimensional performance surfaces were generated for each of the parks in the NPS’s Alaska Fire Management Zone and a gradient was fit to each surface. The individual park gradients were then used to allocate the zone budget increments to the parks and in turn, to the park’s fuels and preparedness programs. These allocations were then summed up to illustrate regional and park level allocations and allocations by program. The results show how a full range of budget increments can be allocated from the zone to each individual park and to each park’s program. The process and the allocations are repeatable and defensible while meeting the NPS budgeting criteria. They also address the concerns expressed by the US Government Accountability Office and reflect the objectives of the Cohesive Strategy. In the current study, we demonstrate a pragmatic example of implementing this method.

The Impacts of Climate and Wildfire on Ecosystem Gross Primary Productivity in Alaska

AbstractThe increase in wildfire occurrence and severity seen over the past decades in the boreal and Arctic biomes is expected to continue in the future in response to rapid climate change in this region. Recent studies documented positive trends in gross primary productivity (GPP) for Arctic boreal biomes driven by warming, but it is unclear how GPP trends are affected by wildfires. Here, we used satellite vegetation observations and environmental data with a diagnostic GPP model to analyze recovery from large fires in Alaska over the period 2000–2019. We confirmed earlier findings that warmer‐than‐average years provide favorable climate conditions for vegetation growth, leading to a GPP increase of 1 Tg C yr−1, contributed mainly from enhanced productivity in the early growing season. However, higher temperatures increase the risk of wildfire occurrence leading to direct carbon loss over a period of 1–3 years. While mortality related to severe wildfires reduce ecosystem productivity, post‐fire productivity in moderately burned areas shows a significant positive trend. The rapid GPP recovery following fires reported here might be favorable for maintaining the region's net carbon sink, but wildfires can indirectly promote the release of long‐term stored carbon in the permafrost. With the projected increase in severity and frequency of wildfires in the future, we expect a reduction of GPP and therefore amplification of climate warming in this region.

Overwintering fires in boreal forests.

Forest fires are usually viewed within the context of a single fire season, in which weather conditions and fuel supply can combine to create conditions favourable for fire ignition-usually by lightning or human activity-and spread1-3. But some fires exhibit 'overwintering' behaviour, in which they smoulder through the non-fire season and flare up in the subsequent spring4,5. In boreal (northern) forests, deep organic soils favourable for smouldering6, along with accelerated climate warming7, may present unusually favourable conditions for overwintering. However, the extent of overwintering in boreal forests and the underlying factors influencing this behaviour remain unclear. Here we show that overwintering fires in boreal forests are associated with hot summers generating large fire years and deep burning into organic soils, conditions that have become more frequent in our study areas in recent decades. Our results are based on an algorithm with which we detect overwintering fires in Alaska, USA, and the Northwest Territories, Canada, using field and remote sensing datasets. Between 2002 and 2018, overwintering fires were responsible for 0.8 per cent of the total burned area; however, in one year this amounted to 38 per cent. The spatiotemporal predictability of overwintering fires could be used by fire management agencies to facilitate early detection, which may result in reduced carbon emissions and firefighting costs.

MODIS Sensor Capability to Burned Area Mapping-Assessment of Performance and Improvements Provided by the Latest Standard Products in Boreal Regions.

This paper presents an accuracy assessment of the main global scale Burned Area (BA) products, derived from daily images of the Moderate-Resolution Imaging Spectroradiometer (MODIS) Fire_CCI 5.1 and MCD64A1 C6, as well as the previous versions of both products (Fire_CCI 4.1 and MCD45A1 C5). The exercise was conducted on the boreal region of Alaska during the period 2000–2017. All the BA polygons registered by the Alaska Fire Service were used as reference data. Both new versions doubled the annual BA estimate compared to the previous versions (66% for Fire_CCI 5.1 versus 35% for v4.1, and 63% for MCD64A1 C6 versus 28% for C5), reducing the omission error (OE) by almost one half (39% versus 67% for Fire_CCI and 48% versus 74% for MCD) and slightly increasing the commission error (CE) (7.5% versus 7% for Fire_CCI and 18% versus 7% for MCD). The Fire_CCI 5.1 product (CE = 7.5%, OE = 39%) presented the best results in terms of positional accuracy with respect to MCD64A1 C6 (CE = 18%, OE = 48%). These results suggest that Fire_CCI 5.1 could be suitable for those users who employ BA standard products in geoinformatics analysis techniques for wildfire management, especially in Boreal regions. The Pareto boundary analysis, performed on an annual basis, showed that there is still a potential theoretical capacity to improve the MODIS sensor-based BA algorithms.

Making the Transition from Science Delivery to Knowledge Coproduction in Boundary Spanning: A Case Study of the Alaska Fire Science Consortium

Abstract Boundary organizations facilitate two-way, sustained interaction and communication between research and practitioner spheres, deliver existing science, and develop new, actionable scientific information to address emerging social–ecological questions applicable to decision-making. There is an increasing emphasis on the role of boundary organizations in facilitating knowledge coproduction, which is collaborative research with end users to develop actionable scientific information for decision-making. However, a deeper understanding of how boundary organizations and knowledge coproduction work in practice is needed. This paper examines the Alaska Fire Science Consortium (AFSC), a boundary organization focused on fire science and management in Alaska that is working to address climate impacts on wildfire. A case study approach was used to assess AFSC activities over time. AFSC’s boundary spanning involves a continuum of outputs and activities, but their overall trajectory has involved a deliberate transition from an emphasis on science delivery to knowledge coproduction. Key factors that facilitated this transition included a receptive and engaged audience, built-in evaluation and learning, subject matter expertise and complementarity, and embeddedness in the target audience communities. Recommendations for boundary organizations wishing to develop knowledge coproduction capacity include knowing your audience, employing trusted experts in boundary spanning, and engaging in frequent self-evaluation to inform change over time.

Boreal forest vegetation and fuel conditions 12 years after the 2004 Taylor Complex fires in Alaska, USA

BackgroundFire has historically been a primary control on succession and vegetation dynamics in boreal systems, although modern changing climate is potentially increasing fire size and frequency. Large, often remote fires necessitate large-scale estimates of fire effects and consequences, often using Landsat satellite-derived dNBR (differenced Normalized Burn Ratio) to estimate burn severity. However, few studies have examined long-term field measures of ecosystem condition in relation to dNBR severity classes in boreal Alaska, USA. The goals of this study were: 1) assess changes in dominant vegetation at plots resampled one and 12 years post fire; 2) use dNBR classes to characterize vegetation and downed woody fuels 12 years post fire; and 3) characterize the relationship between biophysical, topographic, and remotely sensed characteristics (e.g., moss and duff depth, canopy cover, elevation, aspect, dNBR) and understory species assemblages 12 years post fire.ResultsUnderstory species richness doubled (from 39 to 73) between 2005 and 2016; some common species increased in cover over time (e.g., Ledum groenlandicum Oeder) while others decreased (e.g., Hylocomium splendens [Hedw.] Schimp.). In 2016, live and dead tree densities, tall shrub cover, and 1- and 100-h woody fuels were significantly different among dNBR classes; moss and duff depth, canopy cover, and spruce seedling density were not. Elevation and aspect significantly influenced tall shrub cover, hardwood sapling density, and downed woody fuel loads. Understory plant communities differed between unburned and all burn classes, as well as between low and high dNBR severity. Ordination analysis showed that overstory (e.g., live tree density), understory (e.g., moss depth, woody fuel loading), and site (elevation, aspect, dNBR) significantly influences understory species assemblages.ConclusionRemeasured sites (sampled one and 12 years post fire) showed recruitment of new understory species and differing, diverse responses to burning by several common plant species. In 2016, low-severity burned sites had generally the highest woody fuel loading, which may increase risk of repeated surface burning, although the reduction in live tree density would still result in decreased fire risk and behavior. Understory community composition correlated with multiple biotic and abiotic factors, including moss depth, canopy cover, elevation, aspect, and dNBR. Overall, our findings can improve landscape-level predictions of ecosystem condition following fire based on dNBR.

Detecting high and low-intensity fires in Alaska using VIIRS I-band data: An improved operational approach for high latitudes

Fire products from Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) imagery provide timely information for wildfire detection, monitoring, and characterization at the global scale. However, in Alaskan boreal forest fires, their lower effectiveness in detecting residual fire once the high-intensity fire front has passed limits their practical use for regional or local fire management decisions. Using data acquired during Alaska's 2016 fire season, we analyzed the performance of the MODIS-based MOD14/MYD14, and the more recent VIIRS I-band active fire products. A comparison with the fire perimeter and properties data published by the Alaska Interagency Coordination Center (AICC) shows that both MODIS and VIIRS fire products successfully detect all fires larger than approximately 200–300ha. For fires smaller than this threshold, the VIIRS I-band product offers higher detection likelihood. To map burn areas containing both low- and high-intensity active fire, we developed the VIIRS I-band Fire Detection Algorithm for High Latitudes (VIFDAHL). We apply this algorithm to regions of known Alaskan boreal forest fires and validate it using events mapped by fire management agencies and detected on closely-timed Landsat imagery. We find that for Alaska, an example of a high-latitude region, VIFDAHL more accurately captures the fire spread, can differentiate well between low- and high-intensity fires, and can detect 30–90% more fire pixels compared to the MODIS and VIIRS global fire products.

Moose alter the rate but not the trajectory of forest canopy succession after low and high severity fire in Alaska

Mammalian herbivory on palatable trees affects tree growth, forest composition, and forest succession. Antecedent effects of herbivores can be identified through remnants of dead stems and altered tree morphology as well as changes in tree ring patterns and growth. Increases in fire severity, particularly surface fuel combustion, in the boreal forest of western North America can cause a shift in the successional trajectory from coniferous to deciduous dominated forests, which may alter plant–animal interactions. We measured height and tree ring growth of the two dominant canopy tree species, trembling aspen (Populus tremuloides Michx.) and black spruce (Picea mariana (Mill.) BSP), in sites that experienced stand-replacing fire with deep versus shallow surface fuel combustion 20years ago. We also classified individual trees into a category of browsing damage based on external features and morphology. We hypothesized the effects of browsing to be contingent on fire severity. Using linear mixed effect models, we investigated the main and interactive effects of fire severity and browsing intensity on aspen growth. We also developed tree ring chronologies to test for growth releases in aspen and black spruce.Effects of moose browsing on aspen growth depended on fire severity (surface fuel combustion), with negative effects in high severity sites and no effects in low severity sites. Spruce growth showed no direct or indirect browsing effects, indicating moose have not altered the potential for spruce to reach the forest canopy. Aspen in severely burned sites showed abrupt growth releases in tree rings corresponding to changes in herbivore pressure and density. Height-growth projections indicated that moose slowed the rate of aspen growth and canopy dominance in severely burned areas by ten years, through repeated stunting of apical growth in aspen, without affecting the initial trajectory to an aspen-dominated canopy. Lightly burned areas, with their larger proportion of spruce biomass, slower aspen growth, and reduced browsing pressure during the first 20years after fire, will likely provide accessible aspen forage until >50years post-fire as sites return to spruce dominance. Heterogeneously burned forests could thus sustain high rates of available moose forage for a much longer period than previously reported. Our study highlights the importance of including fire severity when considering the impacts of large herbivores on tree growth and forest structure.

An Assessment of the Role of Anthropogenic Climate Change in the Alaska Fire Season of 2015

An Assessment of the Role of Anthropogenic Climate Change in the Alaska Fire Season of 2015

Synoptic-scale fire weather conditions in Alaska

Recent concurrent widespread fires in Alaska are evaluated to assess their associated synoptic-scale weather conditions. Several periods of high fire activity from 2003 to 2015 were identified using Moderate Resolution Imaging Spectroradiometer (MODIS) hotspot data by considering the number of daily hotspots and their continuity. Fire weather conditions during the top six periods of high fire activity in the fire years of 2004, 2005, 2009, and 2015 were analyzed using upper level (500 hPa) and near surface level (1000 hPa) atmospheric reanalysis data. The top four fire-periods occurred under similar unique high-pressure fire weather conditions related to Rossby wave breaking (RWB). Following the ignition of wildfires, fire weather conditions related to RWB events typically result in two hotspot peaks occurring before and after high-pressure systems move from south to north across Alaska. A ridge in the Gulf of Alaska resulted in southwesterly wind during the first hotspot peak. After the high-pressure system moved north under RWB conditions, the Beaufort Sea High developed and resulted in relatively strong easterly wind in Interior Alaska and a second (largest) hotspot peak during each fire period. Low-pressure-related fire weather conditions occurring under cyclogenesis in the Arctic also resulted in high fire activity under southwesterly wind with a single large hot-spot peak.

Daily burned area and carbon emissions from boreal fires in Alaska

Abstract. Boreal fires burn into carbon-rich organic soils, thereby releasing large quantities of trace gases and aerosols that influence atmospheric composition and climate. To better understand the factors regulating boreal fire emissions, we developed a statistical model of carbon consumption by fire for Alaska with a spatial resolution of 450 m and a temporal resolution of 1 day. We used the model to estimate variability in carbon emissions between 2001 and 2012. Daily burned area was mapped using imagery from the Moderate Resolution Imaging Spectroradiometer combined with perimeters from the Alaska Large Fire Database. Carbon consumption was calibrated using available field measurements from black spruce forests in Alaska. We built two nonlinear multiplicative models to separately predict above- and belowground carbon consumption by fire in response to environmental variables including elevation, day of burning within the fire season, pre-fire tree cover and the differenced normalized burn ratio (dNBR). Higher belowground carbon consumption occurred later in the season and for mid-elevation forests. Topographic slope and aspect did not improve performance of the belowground carbon consumption model. Aboveground and belowground carbon consumption also increased as a function of tree cover and the dNBR, suggesting a causal link between the processes regulating these two components of carbon consumption. Between 2001 and 2012, the median carbon consumption was 2.54 kg C m-2. Burning in land-cover types other than black spruce was considerable and was associated with lower levels of carbon consumption than for pure black spruce stands. Carbon consumption originated primarily from the belowground fraction (median = 2.32 kg C m-2 for all cover types and 2.67 kg C m-2 for pure black spruce stands). Total carbon emissions varied considerably from year to year, with the highest emissions occurring during 2004 (69 Tg C), 2005 (46 Tg C), 2009 (26 Tg C), and 2002 (17 Tg C) and a mean of 15 Tg C year-1 between 2001 and 2012. Mean uncertainty of carbon consumption for the domain, expressed as 1 standard deviation (SD), was 0.50 kg C m-2. Uncertainties in the multiplicative regression model used to estimate belowground consumption in black spruce stands and the land-cover classification were primary contributors to uncertainty estimates. Our analysis highlights the importance of accounting for the spatial heterogeneity of fuels and combustion when extrapolating emissions in space and time, and the need for of additional field campaigns to increase the density of observations as a function of tree cover and other environmental variables influencing consumption. The daily emissions time series from the Alaskan Fire Emissions Database (AKFED) presented here creates new opportunities to study environmental controls on daily fire dynamics, optimize boreal fire emissions in biogeochemical models, and quantify potential feedbacks from changing fire regimes.

Recent Changes in Annual Area Burned in Interior Alaska: The Impact of Fire Management

Abstract The Alaskan boreal forest is characterized by frequent extensive wildfires whose spatial extent has been mapped for the past 70 years. Simple predictions based on this record indicate that area burned will increase as a response to climate warming in Alaska. However, two additional factors have affected the area burned in this time record: the Pacific decadal oscillation (PDO) switched from cool and moist to warm and dry in the late 1970s and the Alaska Fire Service instituted a fire suppression policy in the late 1980s. In this paper a geographic information system (GIS) is used in combination with statistical analyses to reevaluate the changes in area burned through time in Alaska considering both the influence of the PDO and fire management. The authors found that the area burned has increased since the PDO switch and that fire management drastically decreased the area burned in highly suppressed zones. However, the temporal analysis of this study shows that the area burned is increasing more rapidly in suppressed zones than in the unsuppressed zone since the late 1980s. These results indicate that fire policies as well as regional climate patterns are important as large-scale controls on fires over time and across the Alaskan boreal forest.

Investigating impacts of forest fires in Alaska and western Canada on regional weather over the northeastern United States using CAM5 global simulations to constrain transport to a WRF-Chem regional domain

An aerosol-enabled globally driven regional modeling system has been developed by coupling the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) with the Weather Research and Forecasting model with chemistry (WRF-Chem). In this modeling system, aerosol-enabled CAM5, a state-of-the-art global climate model is downscaled to provide coherent meteorological and chemical boundary conditions for regional WRF-Chem simulations. Aerosol particle emissions originating outside the WRF-Chem domain can be a potentially important nonlocal aerosol source. As a test case, the potential impacts of nonlocal forest fire aerosols on regional precipitation and radiation were investigated over the northeastern United States during the summer of 2004. During this period, forest fires in Alaska and western Canada lofted aerosol particles into the midtroposphere, which were advected across the United States. WRF-Chem simulations that included nonlocal biomass burning aerosols had domain-mean aerosol optical depths that were nearly three times higher than those without, which reduced peak downwelling domain-mean shortwave radiation at the surface by ~25 W m-2. In this classic twin experiment design, adding nonlocal fire plume led to near-surface cooling and changes in cloud vertical distribution, while variations in domain-mean cloud liquid water path were negligible. The higher aerosol concentrations in the simulation with the fire plume resulted in a ~10% reduction in domain-mean precipitation coincident with an ~8% decrease in domain-mean CAPE. A suite of simulations was also conducted to explore sensitivities of meteorological feedbacks to the ratio of black carbon to total plume aerosols, as well as to overall plume concentrations. Results from this ensemble revealed that plume-induced near-surface cooling and CAPE reduction occur in a wide range of conditions. The response of moist convection was very complex because of strong thermodynamic internal variability. Key Points Nonlocal fire emissions resulted in ~10% precipitation reduction Nonlocal fire emissions reduced peak surface shortwave radiation at by 25 W m-2 An aerosol-enabled globally driven regional modeling system is developed ©2014. American Geophysical Union. All Rights Reserved.

Burned Area Mapping in the North American Boreal Forest Using Terra-MODIS LTDR (2001–2011): A Comparison with the MCD45A1, MCD64A1 and BA GEOLAND-2 Products

An algorithm based on a Bayesian network classifier was adapted to produce 10-day burned area (BA) maps from the Long Term Data Record Version 3 (LTDR) at a spatial resolution of 0.05° (~5 km) for the North American boreal region from 2001 to 2011. The modified algorithm used the Brightness Temperature channel from the Moderate Resolution Imaging Spectroradiometer (MODIS) band 31 T31 (11.03 μm) instead of the Advanced Very High Resolution Radiometer (AVHRR) band T3 (3.75 μm). The accuracy of the BA-LTDR, the Collection 5.1 MODIS Burned Area (MCD45A1), the MODIS Collection 5.1 Direct Broadcast Monthly Burned Area (MCD64A1) and the Burned Area GEOLAND-2 (BA GEOLAND-2) products was assessed using reference data from the Alaska Fire Service (AFS) and the Canadian Forest Service National Fire Database (CFSNFD). The linear regression analysis of the burned area percentages of the MCD64A1 product using 40 km × 40 km grids versus the reference data for the years from 2001 to 2011 showed an agreement of R2 = 0.84 and a slope = 0.76, while the BA-LTDR showed an agreement of R2 = 0.75 and a slope = 0.69. These results represent an improvement over the MCD45A1 product, which showed an agreement of R2 = 0.67 and a slope = 0.42. The MCD64A1, BA-LTDR and MCD45A1 products underestimated the total burned area in the study region, whereas the BA GEOLAND-2 product overestimated it by approximately five-fold, with an agreement of R2 = 0.05. Despite MCD64A1 showing the best overall results, the BA-LTDR product proved to be an alternative for mapping burned areas in the North American boreal forest region compared with the other global BA products, even those with higher spatial/spectral resolution.