Five satellite sensor study of the rapid decline of wildfire smoke in the stratosphere

Smoke from Western North American wildfires reached the stratosphere in large amounts in August 2017. Limb-oriented satellite-based sensors are commonly used for studies of wildfire aerosol injected into the stratosphere (OMPS-LP (Ozone Mapping and Profiler Suite Limb Profiler) and SAGE III/ISS (Stratospheric Aerosol and Gas Experiment III on the International Space Station)). We find that these methods are inadequate for studies the first 1–2 months after such a strong fire event due to event termination (“saturation”). The nadir-viewing lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) is less affected due to shorter path in the smoke, and, further, provides means that we could use to develop a method to correct for strong attenuation of the signal. After the initial phase, the aerosol optical depth (AOD) from OMPS-LP and CALOP show very good agreement above the 380 K isentrope, whereas the OMPS-LP tends to produce higher AOD than CALIOP in the lowermost stratosphere (LMS), probably due to reduced sensitivity at altitudes below 17 km. Time series from CALIOP of attenuation-corrected stratospheric AOD of wildfire smoke show an exponential decline during the first month after the fire, which coincides with highly significant changes in the wildfire aerosol optical properties. The AOD decline is verified by the evolution of the smoke layer composition, comparing the aerosol scattering ratio (CALIOP) to the water vapor concentration from MLS (Microwave Limb Sounder). Initially the stratospheric wildfire smoke AOD is comparable with the most important volcanic eruptions during the last 25 years. Wildfire aerosol declines much faster, 80–90 % of the AOD is removed with a half-life of approximately 10 days. We hypothesize that this dramatic decline is caused by photolytic loss. This process is rarely observed in the atmosphere. However, in the stratosphere this process can be studied with practically no influence from wet deposition, in contrast to the troposphere where this is the main removal path of sub-micron aerosol particles. Despite the loss, the aerosol particles from wildfire smoke in the stratosphere are relevant for the climate.

High-resolution smoke forecasting for the 2018 Camp Fire in California

Smoke from the 2018 Camp Fire in Northern California blanketed a large part of the region for two weeks, creating poor air quality in the “unhealthy” range for millions of people. The NOAA Global System Laboratory’s HRRR-Smoke model was operating experimentally in real time during the Camp Fire. Here, output from the HRRR-Smoke model is compared to surface observations of PM2.5 from AQS and PurpleAir sensors as well as satellite observation data. The HRRR-Smoke model grid at 3-km resolution successfully simulated the evolution of the plume during the initial phase of the fire (8-10 November 2018). Stereoscopic satellite plume height retrievals were used to compare with model output (for the first time, to the authors’ knowledge), showing that HRRR-Smoke is able to represent the complex 3D distribution of the smoke plume over complex terrain. On 15-16 November, HRRR-Smoke was able to capture the intensification of PM2.5 pollution due to a high pressure system and subsidence that trapped smoke close to the surface; however, HRRR-Smoke later underpredicted PM2.5 levels due to likely underestimates of the fire radiative power (FRP) derived from satellite observations. The intensity of the Camp Fire smoke event and the resulting pollution during the stagnation episodes make it an excellent test case for HRRR-Smoke in predicting PM2.5 levels, which were so high from this single fire event that the usual anthropogenic pollution sources became insignificant. The HRRR-Smoke model was implemented operationally at NOAA/NCEP in December 2020, now providing essential support for smoke forecasting as the impact of US wildfires continues to increase in scope and magnitude.

Exploring the inorganic composition of the Asian Tropopause Aerosol Layer using medium-duration balloon flights

Satellite observations have revealed an enhanced aerosol layer near the tropopause over Asia during the summer monsoon, called the Asian Tropopause Aerosol Layer (ATAL). In this work, aerosol particles in the ATAL were collected with a balloon-borne impactor near the tropopause region over India, using extended duration balloon flights, in summer 2017 and winter 2018. Their chemical composition was further investigated by quantitative analysis using offline ion chromatography. Nitrate (NO3−) and nitrite (NO2−) were found to be the dominant ions in the collected aerosols with values ranging between 87–343 ng/m3 STP during the summer campaign. In contrast, sulfate (SO42−) levels were found above the detection limit (> 10 ng/m3 STP) only in winter. In addition, we determined the origin of the air masses sampled during the flights through analysis of back trajectories along with convective influence. The results obtained therein were put into a context of large-scale transport and aerosol distribution with GEOS-Chem chemical transport model simulations. The first flight of summer 2017 which sampled air mass within the Asian monsoon anticyclone (AMA), influenced by convection over Western China, was associated with particle size radius (0.05–2 μm). In contrast, the second flight sampled air mass at the edge of the AMA associated with larger particle size radius (> 2 μm) with higher nitrite concentration. The sampled air masses in winter 2018 were likely affected by smoke from the Pacific Northwest fire event in Canada, which occurred 7 months prior to our campaign, leading to concentration enhancements of SO42− and Ca2+. Overall, our results suggest that nitrogen-containing particles represent a large fraction of aerosols populating the ATAL, in agreement with the results from aircraft measurements during the StratoClim campaign. Furthermore, GEOS-Chem model simulations suggest that lightning NOx emissions had a significant impact on the production of nitrate aerosols sampled during the summer 2017.

Fire Performance of Fly Ash-Based Geopolymer Concrete: Effect of Burning Temperature

Geopolymer concrete (GEO) is a cementless concrete produced from the reaction of an aluminosilica-rich material, in particular, fly ash, with an alkaline solution, which can either be sodium or potassium-based. In light of the potential of fly ash-based GPC as an alternative to Ordinary Portland Cement (OPC)-based concrete as a green building material, an investigation on the fire performance of GEO, in comparison to OPC-based concrete, is essential. The results of an experimental study on the fire performance of fly ash-based GEO that was subjected to a flame test using a methane burner torch, after 28 days of curing, to simulate a real fire event, are presented. Concrete specimens were exposed to a fire flame at 500 °C and 1200 °C for two hours and subsequently cooled to the ambient temperature, prior to testing. Visual inspection was performed on the specimens to observe for any cracking, spalling and change in colour. Losses of mass and residual compressive strength were measured. The results were compared with those of OPC-based reference specimens. The findings revealed that, in contrast to OPC-based concrete, the strength of GPC increased when exposed to fire at 500 °C. GEO also suffered a smaller loss of mass as compared to OPC-based concrete due to the smaller amount of loss in moisture from burning. It was also observed that no spalling had occurred on the GEO, with less cracking on the exposed surface in relation to OPC-based concrete, hence indicating that the structural integrity of GEO was successfully maintained.

Hybrid Architectural Network Implementation to Realize a Fire Evacuation Path with 2.4 GHz Zigbee and LoRa

The Internet of Things (IoT) is playing a significant role in realizing real monitoring. In fire safety and evacuation, early fire event detection using IoT-enabled sensors may help to control and minimize further consequences of the fire accident. In this study, we propose a hybrid architecture based on 2.4 GHz Zigbee and long-range (LoRa) for real-time fire detection, monitoring, and assisting in the safe evacuation of the building. The architecture comprises five different components, namely: end device, evacuation path display controller, safety operation controller, vision node, and gateway. The end device and vision node provide real-time sensory data and visuals that provide details of fire occurrence. The evacuation path display controller and the safety operation controller based on the 2.4 GHz Zigbee receive data from the end device and make the decision accordingly. In addition, a Zigbee simulation is performed on the OPNET simulator to analyze the network parameters such as throughput, retransmission attempts, medium access (MAC) queue size and queue delay, and packet delivery ratio (PDR). The evaluation metrics of link budget and ToA of LoRa are also calculated by varying the code rate and spreading factor. To realize the proposed architecture, customization of hardware is carried out with the development of hardware prototypes. Dijkstra’s shortest path algorithm is implemented in the evacuation path display controller to provide the shortest evacuation path during a fire incident. The hardware of the system is implemented in real-time, and the system provides real-time sensor data along with the evacuation path.

Mixed Reality Maps to help convey disaster information

In safe and industrialized nations most people have only been sporadically in contact with disaster information. But nevertheless, suitable cartographic products are needed to support first aid responders and help teams trying to save as many lives as possible in disaster events. The spatial information on which these teams have to rely on are currently maps without any interactivity and flexibility which was detected by a requirements analysis asking stakeholders working in the field of disaster management. Based on this analysis a tabletop mixed reality application was developed. Within the application two case study scenarios were integrated. Both scenarios together showed the flexibility of the mixed reality approach for representing disaster information in a suitable and feasible way. The first scenario illustrates a large fire event as well as several additional information sources which can assist response and management teams in various directions. The second scenario displays an earthquake event visualizing damaged and destroyed houses and streets. This scenario as well integrates many different information sources and spans from small scale area visualizations to large scale indoor maps for highlighting e.g. injured people in distinct rooms or floors. The resulting application was evaluated by experts. First the application was presented and explained to the experts. Afterwards the experts were asked in a structured interview how they would evaluate the usability and willingness to use such an application in real scenarios. The experts were impressed by the available possibilities in representing and integrating disaster information via the tabletop mixed reality approach yet mentioned that a head mounted device compared to a smartphone would be more beneficial in practice.

The impact of sustainability on fire safety

<p>There is a growing demand for building green buildings that are perceived to have benefits environmentally through promoting recycling, energy efficiency and efficient use of resources. The green movement has also led to innovative technologies that are focused on reducing cost. However, the fire safety industry has concerns with the use of certain technologies that create passages for smoke and fire to spread such as passive ventilation or materials that can burn severely and release large amount of toxins. The benefit of this research is to determine which features are high risk and are commonly used. The aim of this research is to investigate whether sustainable or green features have an influence on fire safety in commercial buildings and determine which feature or features would have the most significant implications for building safety in regards to tenability. A detailed investigation was done on passive ventilation such as double skin facade and the thesis also briefly discusses other green features and their implications. There were two methods used to collect data. The first was a qualitative study done through sending out surveys to fire engineers to rate and rank the most significant features that have negative implications for fire safety in reference to the New Zealand Building Code Fire Safety Section criteria and objectives. Then, a one hour interview was carried out to determine the reason behind the engineers’ choice and their perceptions. The results from the surveys and the interviews were that double skin facade and atrium were ranked the most significant. The surveys established double skin facade has the highest ranking in terms of the worst feature, and the fire engineers reinforced that double skin facade needs to be studied as there is not enough research that have gone into this feature. While atrium issues are known and mitigation measures are well developed. A subsequent analysis for only double skin facade is conducted using Fire Dynamics Simulator (FDS) because little literature is found in regards to fire safety and double skin facade. FDS was used to simulate 14 small models and 2 large models for the best and worst scenarios of DSF. Each of the 14 models, one to three parameters are changed as part of the sensitivity study to determine which parameter have the most and least effect on fire safety in term of Carbon Monoxide (CO) and visibility. The issues the engineers raised and the mitigation measures were modelled, because the engineers had stated their opinions not facts. The output results from FDS illustrated that it is essential that the system shuts off in a fire event to prevent smoke spread to upper floors, which is the same mitigation measure that were emphasised at the interviews.</p>

The impact of sustainability on fire safety

<p>There is a growing demand for building green buildings that are perceived to have benefits environmentally through promoting recycling, energy efficiency and efficient use of resources. The green movement has also led to innovative technologies that are focused on reducing cost. However, the fire safety industry has concerns with the use of certain technologies that create passages for smoke and fire to spread such as passive ventilation or materials that can burn severely and release large amount of toxins. The benefit of this research is to determine which features are high risk and are commonly used. The aim of this research is to investigate whether sustainable or green features have an influence on fire safety in commercial buildings and determine which feature or features would have the most significant implications for building safety in regards to tenability. A detailed investigation was done on passive ventilation such as double skin facade and the thesis also briefly discusses other green features and their implications. There were two methods used to collect data. The first was a qualitative study done through sending out surveys to fire engineers to rate and rank the most significant features that have negative implications for fire safety in reference to the New Zealand Building Code Fire Safety Section criteria and objectives. Then, a one hour interview was carried out to determine the reason behind the engineers’ choice and their perceptions. The results from the surveys and the interviews were that double skin facade and atrium were ranked the most significant. The surveys established double skin facade has the highest ranking in terms of the worst feature, and the fire engineers reinforced that double skin facade needs to be studied as there is not enough research that have gone into this feature. While atrium issues are known and mitigation measures are well developed. A subsequent analysis for only double skin facade is conducted using Fire Dynamics Simulator (FDS) because little literature is found in regards to fire safety and double skin facade. FDS was used to simulate 14 small models and 2 large models for the best and worst scenarios of DSF. Each of the 14 models, one to three parameters are changed as part of the sensitivity study to determine which parameter have the most and least effect on fire safety in term of Carbon Monoxide (CO) and visibility. The issues the engineers raised and the mitigation measures were modelled, because the engineers had stated their opinions not facts. The output results from FDS illustrated that it is essential that the system shuts off in a fire event to prevent smoke spread to upper floors, which is the same mitigation measure that were emphasised at the interviews.</p>

Fire and water: contaminants and clearance following uncontrolled fires

There is a growing body of evidence surrounding the implications of uncontrolled bushfires and wildfires on water. This topic has importance from an ecological perspective, and significance for human health as it has consequences for drinking water quality and supply. Against the backdrop of climate change, it is especially important to holistically understand the impact of fire on water. This review took a systematic approach to establish a comprehensive overview of the changes occurring in freshwater systems following uncontrolled wildfires and bushfires. Screening of 16,551 results obtained from Web of Science, PubMed, and MEDLINE resulted in 111 manuscripts suitable for inclusion. The impact of fire across a wide range of water quality indicators either relative to pre-fire measurements or reference sites was examined qualitatively (increase/decrease) and where possible quantitatively (% change or difference). Factors included biomass, indicator species and species diversity, metals, nutrients, salts, polycyclic aromatic hydrocarbons, particulates and turbidity, pH, conductivity, temperature, and water course morphology. Evidence focused largely on short to medium term impacts (e.g. within 2 years of the fire event), with only a subset of studies reporting on longer term changes in response to fire. We found that bushfire has acute and long-lasting effects on water in terms of physical (e.g. decreased suspended particle size), chemical (e.g. increased nutrient concentration), and biological (e.g. decreased species diversity) characteristics. There was also evidence of resilience and recovery. We urge future work to consider measures that will fulfil both environmental and human health considerations, to allow more integrated insight into the impacts of fire on water.

Impacts of a single fire event on large, old trees in a grass-invaded arid river system

Background Large old trees are keystone structures of terrestrial ecosystems that provide unique habitat resources for wildlife. Their widespread decline worldwide has serious implications for biodiversity and ecosystem integrity. In arid regions, large trees are relatively uncommon and often restricted to areas with elevated soil moisture and nutrients. Introduced grasses, now pervasive in many dryland environments, also thrive in such areas and are promoting more frequent and intense fire, potentially threatening the persistence of large trees. Here we report on the impact of a single wildfire on large river red gums (Eucalyptus camaldulensis Dehnh.) in arid riparian woodland invaded by buffel grass (Cenchrus ciliaris L.), a serious invader of desert ecosystems worldwide. In 2018, 266 trees with > 80 cm equivalent trunk diameter were mapped at six sites to provide a ‘pre-fire’ baseline. Within a year, the sites were impacted by a large, unprecedented wildfire that burnt an area of 660 km2 ha in 15 days. Sites were resurveyed in February 2019 to assess the fate of the trees. Reference to fire severity, calculated from remote-sensed imagery, is provided for additional context. Results In total, 67 trees, 27% of all large trees at the sites were destroyed. If trees in unburnt patches are excluded, 54% of trees exposed to the fire were destroyed and the remainder lost on average 79% of their canopy. Conclusions This severe detrimental effect of a single fire, on trees estimated to be centuries old, is indicative of tree-loss occurring across remote arid Australia in habitats where fire is now fuelled predominantly by invasive grasses. Large volumes of novel grass fuels along creeklines in combination with extreme weather events were major factors driving the spread, extent and impacts of the wildfire we report on and are causing a shift from relatively uncommon and predictable, rainfall-dependent large wildfires to large, severe fires that can occur anytime. We predict further decline in the abundance of large trees from similar fires will occur widely throughout arid Australia over the next decade with substantial long-term impacts on multiple species. New strategies are urgently required to manage fire in invaded arid ecosystems to better protect large trees and the critical resources they provide.