nasa-gesdisc/es-publications-researchareas huggingface dataset:
Tracing devastating fires in Portugal to a snow archive in the Swiss (2020)

Abstract. Recent large wildfires, such as those in Portugal in
2017, have devastating impacts on societies, economy, ecosystems and
environments. However, wildfires are a natural phenomenon, which has been
exacerbated by land use during the past millennia. Ice cores are one of the
archives preserving information on fire occurrences over these timescales. A
difficulty is that emission sensitivity of ice cores is often unknown, which
constitutes a source of uncertainty in the interpretation of such archives.
Information from specific and well-documented case studies is therefore
useful to better understand the spatial representation of ice-core burning
records. The wildfires near Pedrogao Grande in central Portugal in
2017 provided a test bed to link a fire event to its footprint left in a
high-alpine snowpack considered a surrogate for high-alpine ice-core sites.
Here, we (1) analysed black carbon (BC) and microscopic charcoal particles
deposited in the snowpack close to the high-alpine research station
Jungfraujoch in the Swiss Alps; (2) calculated backward trajectories based
on ERA-Interim reanalysis data and simulated the transport of these
carbonaceous particles using a global aerosol-climate model; and (3)
analysed the fire spread, its spatial and temporal extent, and its
intensity with remote-sensing (e.g. MODIS) Active Fire and Burned Area products. According to modelled emissions of the FINN v1.6 database, the
fire emitted a total amount of 203.5 t BC from a total burned area of 501 km2 as observed on the basis of satellite fire products. Backward
trajectories unambiguously linked a peak of atmospheric-equivalent BC
observed at the Jungfraujoch research station on 22 June  with
elevated levels until 25 June  with the highly intensive fires in
Portugal. The atmospheric signal is in correspondence with an outstanding
peak in microscopic charcoal observed in the snow layer, depositing nearly
as many charcoal particles as during an average year in other ice archives.
In contrast to charcoal, the amount of atmospheric BC deposited during the
fire episode was minor due to a lack of precipitation. Simulations with a
global aerosol-climate model suggest that the observed microscopic
charcoal particles originated from the fires in Portugal and that their
contribution to the BC signal in snow was negligible. Our study revealed
that microscopic charcoal can be transported over long distances (1500 km)
and that snow and ice archives are much more sensitive to distant events
than sedimentary archives, for which the signal is dominated by local fires.
The findings are important for future ice-core studies as they document
that, for BC as a fire tracer, the signal preservation depends on precipitation.
Single events, like this example, might not be preserved due to unfavourable
meteorological conditions.

Research areas: Wildfires, Cryospheric Indicators
The 2018 fire season in North America as seen by TROPOMI: aerosol layer height intercomparisons and evaluation of model-derived plume heights (2020)

Abstract. Before the launch of the TROPOspheric Monitoring Instrument (TROPOMI), only two other satellite instruments were able to observe aerosol plume heights globally, the Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The TROPOMI aerosol layer height is a potential game changer, since it has daily global coverage, and the aerosol layer height retrieval is available in near real time. The aerosol layer height can be useful for aviation and air quality alerts, as well as for improving air quality forecasting related to wildfires. Here, TROPOMI's aerosol layer height product is evaluated with MISR and CALIOP observations for wildfire plumes in North America for the 2018 fire season (June to August). Further, observing system simulation experiments were performed to interpret the fundamental differences between the different products. The results show that MISR and TROPOMI are, in theory, very close for aerosol profiles with single plumes. For more complex profiles with multiple plumes, however, different plume heights are retrieved; the MISR plume height represents the top layer, and the plume height retrieved with TROPOMI tends to have an average altitude of several plume layers. The comparison between TROPOMI and MISR plume heights shows that, on average, the TROPOMI aerosol layer heights are lower, by approximately 600 m, compared to MISR, which is likely due to the different measurement techniques. From the comparison to CALIOP, our results show that the TROPOMI aerosol layer height is more accurate over dark surfaces, for thicker plumes, and plumes between approximately 1 and 4.5 km. MISR and TROPOMI are further used to evaluate the plume height of Environment and Climate Change Canada's operational forecasting system FireWork with fire plume injection height estimates from the Canadian Forest Fire Emissions Prediction System (CFFEPS). The modelled plume heights are similar compared to the satellite observations but tend to be slightly higher with average differences of 270580 and 60320 m compared to TROPOMI and MISR, respectively.

Research areas: Wildfires
Relationship between Fire Events and Land Use Changes in the State of São Paulo, Brazil (2021)

This study investigated the land use and land cover changes in the state of Sao Paulo, Brazil, for the period of 2002 through 2017, to determine if forested areas were burned or converted to other land uses, to analyze the use of fire as a catalyst and mechanism for land cover change, and to determine if there was a relationship between land use changes and gross domestic product (GDP). MapBiomas classifications and MODIS data were analyzed using the Google Earth Engine. The results of the analysis found that there were minimal changes in the forested areas in Sao Paulo during the study period; however, there was a 5% increase in natural forest and a 75% increase in planted forest cover. On the other hand, there was a 128% increase in sugarcane, and nearly a 50% decrease in pasture land coverage, suggesting that land was converted from pasture to more profitable agricultural land. Finally, there was a strong positive correlation (r = 0.96) between the increase in sugarcane and the GDP, and a negative correlation between the frequency of fire events and economic production (r = 0.62). Overall, there was a decline in fire events in Sao Paulo, with fire events occurring in less than 2% of the total observed land area by 2017. This overall declining trend in fire events are likely the direct result of increases in green harvest methods, which prevent the need for pre-harvest burning.

Research areas: Wildfires, Habitat Conversion/Fragmentation
Agricultural fires in the southeastern US during SEAC⁴RS: Emissions of trace gases and particles and evolution of ozone, reactive nitrogen, and organic aerosol (2016)

Emissions from 15 agricultural fires in the southeastern U.S. were measured from the NASA DC8 research aircraft during the summer 2013 Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. This study reports a detailed set of emission factors (EFs) for 25 trace gases and 6 fine particle species. The chemical evolution of the primary emissions in seven plumes was examined in detail for ~1.2 h. A Lagrangian plume crosssection model was used to simulate the evolution of ozone (O3), reactive nitrogen species, and organic aerosol (OA). Observed EFs are generally consistent with previous measurements of crop residue burning, but the fires studied here emitted high amounts of SO2 and fine particles, especially primary OA and chloride. Filterbased measurements of aerosol light absorption implied that brown carbon (BrC) was ubiquitous in the plumes. In aged plumes, rapid production of O3, peroxyacetyl nitrate (PAN), and nitrate was observed with O3/CO, PAN/NOy, and nitrate/NOy reaching ~0.1, ~0.3, and ~0.3. For five selected cases, the model reasonably simulated O3 formation but underestimated PAN formation. No significant evolution of OA mass or BrC absorption was observed. However, a consistent increase in oxygentocarbon (O/C) ratios of OA indicated that OA oxidation in the agricultural fire plumes was much faster than in urban and forest fire plumes. Finally, total annual SO2, NOx , and CO emissions from agricultural fires in Arkansas, Louisiana, Mississippi, and Missouri were estimated (within a factor of ~2) to be equivalent to ~2% SO2 from coal combustion and ~1% NOx and ~9% CO from mobile sources.

Research areas: Environmental Impacts
Post-wildfire denudation assessed from compositional features of river sediments (Central Portugal) (2020)

The wildfires of 2017 were responsible for vegetation clearance in a wide area of central Portugal, leaving the weathering profiles more exposed to erosive action. In the present research, suspended loads from a set of catchment areas affected by these fires with diverse geological and orographic features were periodically sampled to evaluate spatial and seasonal variability in sediment production. Bulk mineralogy reflected the geology of the source areas, but displayed high variability even for a single sampling site, which can be partially linked to the grain-size control on sediment composition. Clay mineralogy provided a better picture of the denudation at catchment scale. The predominance of detrital illite with low I5/I10 (ratio of the intensities at 5 A (002) and 10 A (001)) indicated very shallow weathering profiles. Chlorite was usually the second most common mineral, more common in metasedimentary-derived sediments, whilst kaolinite was detected only in less steep catchment areas with a predominance of granitic basement rocks or where previous-cycle depositional units are also present. Year-long shifts in clay assemblages were attributed to different spatial patterns of denudation. A depletion of kaolinite occurred in sampling sites mainly sourced by granitoids. An opposite trend was observed where areas with Meso-Cenozoic deposits, less affected by the wildfires than those with basement units, occupy significant proportions of the drainage basins. This trend was ascribed to the wearing out of the weathering profiles covering the basement. Regolith denudation was also testified by a progressive decrease in I5/I10. Shifts in clay mineralogy linked with progressive surface denudation were found to be limited in areas with shallow soils, but may complicate any paleoenvironmental reconstructions based on sediment composition when more evolved weathering profiles have been eroded.

Research areas: Wildfires, Land Surface/Agriculture Indicators
Assessing the accuracy of remotely sensed fire datasets across the southwestern Mediterranean Basin (2021)

Abstract. Recently, many remote-sensing datasets providing features of individual fire events from gridded global burned area products have been released. Although very promising, these datasets still lack a quantitative estimate of their accuracy with respect to historical ground-based fire datasets. Here, we compared three state-of-the-art remote-sensing datasets (RSDs; Fire Atlas, FRY, and GlobFire) with a harmonized ground-based dataset (GBD) compiled by fire agencies monitoring systems across the southwestern Mediterranean Basin (20052015). We assessed the agreement between the RSDs and the GBD with respect to both burned area (BA) and number of fires (NF). RSDs and the GBD were aggregated at monthly and 0.25 resolutions, considering different individual fire size thresholds ranging from 1 to 500 ha. Our results show that all datasets were highly correlated in terms of monthly BA and NF, but RSDs severely underestimated both (by 38 % and 96 %, respectively) when considering all fires > 1 ha. The agreement between RSDs and the GBD was strongly dependent on individual fire size and strengthened when increasing the fire size threshold, with fires > 100 ha denoting a higher correlation and much lower error (BA 10 %; NF 35 %). The agreement was also higher during the warm season (May to October) in particular across the regions with greater fire activity such as the northern Iberian Peninsula. The Fire Atlas displayed a slightly better performance with a lower relative error, although uncertainty in the gridded BA product largely outpaced uncertainties across the RSDs. Overall, our findings suggest a reasonable agreement between RSDs and the GBD for fires larger than 100 ha, but care is needed when examining smaller fires at regional scales.

Research areas: Wildfires
Emissions mitigation opportunities for savanna countries from early dry season fire management (2018)

Savanna fires produce significant emissions globally, but if managed effectively could provide an important mitigation opportunity, particularly in African least developed countries. Here we show global opportunities for emissions reductions through early dry season burning for 37 countries including: 29 countries in Africa (69.1 MtCO2-e yr1), six countries in South America (13.3 MtCO2-e yr1), and Australia and Papua New Guinea (6.9 MtCO2-e yr1). Emissions reduction estimates are based on the successful approach developed in Australia to reduce emissions from savanna fires using global-scale, remotely sensed estimates of monthly emissions. Importantly, 20 least developed countries in Africa account for 74% of the mitigation potential (60.2 MtCO2-e yr1). More than 1.02 million km2 of savanna dominated protected areas within these countries could be used as pilot sites to test and advance a regional approach to mitigation efforts for savanna fires in Africa. Potential versus actual abatement opportunities are discussed.

Research areas: Wildfires, Habitat Conversion/Fragmentation
Patterns of ecosystem structure and wildfire carbon combustion across six ecoregions of the North American boreal forest (2020)

Increases in fire frequency, extent, and severity are expected to strongly impact the structure and function of boreal forest ecosystems. An important function of the boreal forest is its ability to sequester and store carbon (C). Increasing disturbance from wildfires, emitting large amounts of C to the atmosphere, may create a positive feedback to climate warming. Variation in ecosystem structure and function throughout the boreal forest is important for predicting the effects of climate warming and changing fire regimes on C dynamics. In this study, we compiled data on soil characteristics, stand structure, pre-fire C pools, C loss from fire, and the potential drivers of these C metrics from 527 sites distributed across six ecoregions of North Americas western boreal forests. We assessed structural and functional differences between these fire-prone ecoregions using data from 417 recently burned sites (20042015) and estimated ecoregion-specific relationships between soil characteristics and depth from 167 of these sites plus an additional 110 sites (27 burned, 83 unburned). We found that northern boreal ecoregions were generally older, stored and emitted proportionally more belowground than aboveground C, and exhibited lower rates of C accumulation over time than southern ecoregions. We present ecoregion-specific estimates of depth-wise soil characteristics that are important for predicting C combustion from fire. As climate continues to warm and disturbance from wildfires increases, the C dynamics of these fire-prone ecoregions are likely to change with significant implications for the global C cycle and its feedbacks to climate change.

Research areas: Wildfires, Ecosystems
Radiative and microphysical responses of clouds to an anomalous increase in fire particles over the Maritime Continent in 2015 (2022)

Abstract. The year of 2015 was an extremely dry year for Southeast Asia where the direct impact of a strong El Nino was in play. As a result of this dryness and the relative lack of rainfall, an extraordinary quantity of aerosol particles from biomass burning remained in the atmosphere over the Maritime Continent during the fire season. This study uses the Weather Research and Forecasting model coupled with Chemistry to understand the impacts of these fire particles on cloud microphysics and radiation during the peak biomass burning season in September. Our simulations, one with fire particles and the other without them, cover the entire Maritime Continent region at a cloud-resolving resolution (4 km) for the entire month of September in 2015. The comparison of the simulations shows a clear sign of precipitation enhancement by fire particles through microphysical effects; smaller cloud droplets remain longer in the atmosphere to later form ice crystals, and/or they are more easily collected by ice-phase hydrometeors in comparison to droplets under no fire influences. As a result, the mass of ice-phase hydrometeors increases in the simulation with fire particles, and so does rainfall. On the other hand, the aerosol radiative effect weakly counteracts the invigoration of convection. Clouds are more reflective in the simulation with fire particles as ice mass increases. Combined with the direct scattering of sunlight by aerosols, the simulation with fire particles shows higher albedo over the simulation domain on average. The simulated response of clouds to fire particles in our simulations clearly differs from what was presented by two previous studies that modeled aerosolcloud interaction in years with different phases of El NinoSouthern Oscillation (ENSO), suggesting a further need for an investigation on the possible modulation of fireaerosolconvection interaction by ENSO.

Research areas: Wildfires, Atmospheric/Ocean Indicators
Fuel availability not fire weather controls boreal wildfire severity and carbon emissions (2020)

Carbon (C) emissions from wildfires are a key terrestrialatmosphere interaction that influences global atmospheric composition and climate. Positive feedbacks between climate warming and boreal wildfires are predicted based on top-down controls of fire weather and climate, but C emissions from boreal fires may also depend on bottom-up controls of fuel availability related to edaphic controls and overstory tree composition. Here we synthesized data from 417 field sites spanning six ecoregions in the northwestern North American boreal forest and assessed the network of interactions among potential bottom-up and top-down drivers of C emissions. Our results indicate that C emissions are more strongly driven by fuel availability than by fire weather, highlighting the importance of fine-scale drainage conditions, overstory tree species composition and fuel accumulation rates for predicting total C emissions. By implication, climate change-induced modification of fuels needs to be considered for accurately predicting future C emissions from boreal wildfires.

Research areas: Wildfires, Atmospheric/Ocean Indicators
Ranking of Basin-Scale Factors Affecting Metal Concentrations in River Sediment (2022)

River sediments often contain potentially harmful pollutants such as metals. Much research has been conducted to identify factors involved in sediment concentrations of metals. While most metal pollution studies focus on smaller scales, it has been shown that basin-scale parameters are powerful predictors of river water quality. The present study focused on basin-scale factors of metal concentrations in river sediments. The study was performed on the contiguous USA using Random Forest (R.F.) to analyze the importance of different factors of the metal pollution potential of river sediments and evaluate the possibility of assessing this potential from basin characteristics. Results indicated that the most important factors belonged to the groups Geology, Dams, and Land cover. Rock characteristics (contents of K2O, CaO, and SiO2) and reservoir drainage area were strong factors. Vegetation indices were more important than land cover types. The response of different metals to basin-scale factors varied greatly. The R.F. models performed well with prediction errors of 16.5% to 28.1%, showing that basin-scale parameters hold sufficient information for predicting potential metal concentrations. The results contribute to research and policymaking dependent on understanding large-scale factors of metal pollution.

Research areas: Water Quality
Mega-dams and extreme rainfall: Disentangling the drivers of extensive (2021)

Extreme weather events and the presence of mega-hydroelectric dams, when combined, present an emerging threat to natural habitats in the Amazon region. To understand the magnitude of these impacts, we used remote sensing data to assess forest loss in areas affected by the extreme 2014 flood in the entire Madeira River basin, the location of two mega-dams. In addition, forest plots (26 ha) were monitored between 2011 and 2015 (14,328 trees) in order to evaluate changes in tree mortality, aboveground biomass (AGB), species composition and community structure around the Jirau reservoir (distance between plots varies from 1 to 80 km). We showed that the mega-dams were the main driver of tree mortality in Madeira basin forests after the 2014 extreme flood. Forest loss in the areas surrounding the reservoirs was 56 km
              2
              in Santo Antonio, 190 km
              2
              in Jirau (7.49.2% of the forest cover before flooding), and 79.9% above that predicted in environmental impact assessments. We also show that climatic anomalies, albeit with much smaller impact than that created by the mega-dams, resulted in forest loss along different Madeira sub-basins not affected by dams (34173 km
              2
              ; 0.51.7%). The impact of flooding was greater in
              varzea
              and transitional forests, resulting in high rates of tree mortality (88100%), AGB decrease (89100%), and reduction of species richness (78100%). Conversely,
              campinarana
              forests were more flood-tolerant with a slight decrease in species richness (6%) and similar AGB after flooding. Taking together satellite and field measurements, we estimate that the 2014 flood event in the Madeira basin resulted in 8.8112.47  10
              6
              tons of dead biomass. Environmental impact studies required for environmental licensing of mega-dams by governmental agencies should consider the increasing trend of climatic anomalies and the high vulnerability of different habitats to minimize the serious impacts of dams on Amazonian biodiversity and carbon stocks.

Research areas: Floods, Habitat Conversion/Fragmentation