Transport of smoke from Canadian forest fires to the surface near Washington, D.C.: Injection height, entrainment, and optical properties (original) (raw)
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Smoke and pollutants from Canadian forest fires were transported over the northeastern United States in July 2002. Lidar observations at the NASA Goddard Space Flight Center show the smoke from these fires arriving in an elevated plume that was subsequently mixed to the surface. Trajectory and three-dimensional model calculations confirm the' origin of the smoke and show that it mixed to the surface after it was intercepted by the turbulent planetary boundary layer. Modeled smoke optical properties agreed well with aircraft and remote sensing observations provided coagulation of smoke particles was accounted for in the model. Our results have important implications for the long-range transport of pollutants and their subsequent entrainment to the surface, as well as the evolving optical properties of smoke from boreal forest fires.
Transport of Canadian forest fire smoke over the UK as observed by lidar
Atmospheric Chemistry and Physics
Layers of aerosol at heights between 2 and 11 km were observed with Raman lidars in the UK between 23 and 31 May 2016. A network of these lidars, supported by ceilometer observations, is used to map the extent of the aerosol and its optical properties. Space-borne lidar profiles show that the aerosol originated from forest fires over western Canada around 17 May, and indeed the aerosol properties-weak volume depolarisation (< 5 %) and a lidar ratio at 355 nm in the range 35-65 sr-were consistent with longrange transport of forest fire smoke. The event was unusual in its persistence-the smoke plume was drawn into an atmospheric block that kept it above northwestern Europe for 9 days. Lidar observations show how the smoke layers became optically thinner during this period, but the lidar ratio and aerosol depolarisation showed little change. The results demonstrate the value of a dense network of observations for tracking forest fire smoke, and show how the dispersion of smoke in the free troposphere leads to the emergence of discrete thin layers in the far field. They also show how atmospheric blocking can keep a smoke plume in the same geographic area for over a week.
Smoke injection heights from fires in North America: analysis of 5 years of satellite observations
Atmospheric Chemistry and Physics, 2010
We analyze an extensive record of aerosol smoke plume heights derived from observations over North America for the fire seasons of 2002 and 2004-2007 made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument on board the NASA Earth Observing System Terra satellite. We characterize the magnitude and variability of smoke plume heights for various biomes, and assess the contribution of local atmospheric and fire conditions to this variability. Plume heights are highly variable, ranging from a few hundred meters up to 5000 m above the terrain at the Terra overpass time (11:00-14:00 local time). The largest plumes are found over the boreal region (median values of ∼850 m height, 24 km length and 940 m thickness), whereas the smallest plumes are found over cropland and grassland fires in the contiguous US (median values of ∼530 m height, 12 km length and 550-640 m thickness). The analysis of plume heights in combination with assimilated meteorological observations from the NASA Goddard Earth Observing System indicates that a significant fraction (4-12%) of plumes from fires are injected above the boundary layer (BL), consistent with earlier results for Alaska and the Yukon Territories during summer 2004. Most of the plumes located above the BL (>83%) are trapped within stable atmospheric layers. We find a correlation between plume height and the MODerate resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) thermal anomalies associated with each plume. Smoke plumes located in the free troposphere Correspondence to: M. Val Martin (mvalmart@seas.harvard.edu) (FT) exhibit larger FRP values (1620-1640 MW) than those remaining within the BL (174-465 MW). Plumes located in the FT without a stable layer reach higher altitudes and are more spread-out vertically than those associated with distinct stable layers (2490 m height and 2790 m thickness versus 1880 m height and 1800 m thickness). The MISR plume climatology exhibits a well-defined seasonal cycle of plume heights in boreal and temperate biomes, with greater heights during June-July. MODIS FRP measurements indicate that larger summertime heights are the result of higher fire intensity, likely due to more severe fire weather during these months. This work demonstrates the significant effect of fire intensity and atmospheric structure on the ultimate rise of fire emissions, and underlines the importance of considering such physical processes in modeling smoke dispersion.
Atmospheric Chemistry and Physics, 2011
Forest fires in Northern California and Oregon were responsible for two significant regional scale aerosol transport events observed in southern British Columbia during summer 2008. A combination of ground based (CORALNet) and satellite (CALIPSO) lidar, sunphotometry and high altitude chemistry observations permitted unprecedented characterization of forest fire plume height and mixing as well as description of optical properties and physicochemistry of the aerosol. In southwestern BC, lidar observations show the smoke to be mixed through a layer extending to 5-6 km a.g.l. where the aerosol was confined by an elevated inversion in both cases. Depolarization ratios for a trans-Pacific dust event (providing a basis for comparison) and the two smoke events were consistent with observations of dust and smoke events elsewhere and permit discrimination of aerosol events in the region. Based on sunphotometry, the Aerosol Optical Thicknesses (AOT) reached maxima of
Atmospheric Environment, 2012
Forest-fire and biomass burning often inject large amounts of smoke aerosols into the atmosphere, which play important roles in climate radiation and air quality. In this study, the combined observations of smoke plumes from a ground-based multi-wavelength lidar, sun/sky radiometer and MODIS and CALIOP satellites are presented. We focus in particular on one representative event (the Idaho-Montana forest fire on August 14-15, 2007) to retrieve aerosol plumes optical characteristics and track their intra-continent transport. Multi-wavelength extinction profiles of aerosol plumes are first derived by constraining lidar profiles with sunphotometer-measured column aerosol optical depth (AOD), and then Angstrom exponents are obtained to discriminate smoke plumes from cloud and dust particles. Long-distance transport and origins of smoke plumes are illustrated by satellite MODIS/Aqua, Calipso/CALIOP imageries and NOAA/HYSPLIT air backward trajectory analysis. Importantly, we show that aloft smoke plumes may mix downward into the planetary boundary layer (PBL) and potentially result in the increase of surface PM2.5 concentrations and that these mixings are a major factor in pollution enhancement during the summer when the PBL is more convective allowing for enhanced mixing.
Radiative and cloud microphysical effects of forest fire smoke over North America and Siberia
Aerosol affects climate both through direct radiative effects and by indirect effects on cloud development. Absorbing aerosols have additional influence on the vertical temperature profile of the atmospheric column. Forest fire smoke contributes roughly half of the global absorbing aerosol, with most of the unsupervised burning occurring in the forests of Canada and Siberia. Radiative effects of smoke are studied for the case of a Canadian smoke plume that blanketed the U.S. mid-Atlantic seaboard. Optical properties derived from aircraft in situ measurements demonstrate that the smoke formed a layer with a base 2 km above the surface, and absorptive heating in this layer could have strengthened and maintained the subsidence inversion responsible for the layer structure. An optical model of the smoke formed from a blend of aircraft and AERONET measurements allows retrieval of the smoke aerosol by satellite, so that comparisons are possible to measurements made by any instrument in th...
2008
We analyze an extensive record of aerosol smoke plume heights derived from observations over North America for the fire seasons of 2002 and 2004-2007 made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument on board the NASA Earth Observing System Terra satellite. We characterize the magnitude and variability of smoke plume heights for various biomes, and assess the contribution of local atmospheric and fire conditions to this variability. Plume heights are highly variable, ranging from a few hundred meters up to 5000 m above the terrain at the Terra overpass time (11:00-14:00 local time). The largest plumes are found over the boreal region (median values of ∼850 m height, 24 km length and 940 m thickness), whereas the smallest plumes are found over cropland and grassland fires in the contiguous US (median values of ∼530 m height, 12 km length and 550-640 m thickness). The analysis of plume heights in combination with assimilated meteorological observations from the NASA Goddard Earth Observing System indicates that a significant fraction (4-12%) of plumes from fires are injected above the boundary layer (BL), consistent with earlier results for Alaska and the Yukon Territories during summer 2004. Most of the plumes located above the BL (>83%) are trapped within stable atmospheric layers. We find a correlation between plume height and the MODerate resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) thermal anomalies associated with each plume. Smoke plumes located in the free troposphere Correspondence to: M. Val Martin (mvalmart@seas.harvard.edu) (FT) exhibit larger FRP values (1620-1640 MW) than those remaining within the BL (174-465 MW). Plumes located in the FT without a stable layer reach higher altitudes and are more spread-out vertically than those associated with distinct stable layers (2490 m height and 2790 m thickness versus 1880 m height and 1800 m thickness). The MISR plume climatology exhibits a well-defined seasonal cycle of plume heights in boreal and temperate biomes, with greater heights during June-July. MODIS FRP measurements indicate that larger summertime heights are the result of higher fire intensity, likely due to more severe fire weather during these months. This work demonstrates the significant effect of fire intensity and atmospheric structure on the ultimate rise of fire emissions, and underlines the importance of considering such physical processes in modeling smoke dispersion.
2004
During early July 2002, dense smoke from a number of large forest fires in central Quebec Province was transported south by prevailing winds into the New England and Mid-Atlantic states. Given the high concentrations of smoke, strong flows from the north, and relative absence of other emissions in that direction, this event provides a unique opportunity to evaluate impacts of nearly pure wood smoke at multiple monitoring sites in the Northeast. Continuous measurements of PM 2.5 mass from State and Federal monitoring programs and light scattering from (a few) IMPROVE nephelometers and (many) ASOS forward scatter meters reveal highly complex spatial and temporal patterns of smoke impacts at the surface on July 6-8, 2002. Maximum observed 24-hour smoke impacts at most US surface sites occurred on July 7 th , which was coincidently a routine filter sampling day for the IMPROVE, STN and FRM (fine mass-only) networks. Combining the continuous PM, light scattering and filter-based chemical data provides insights into the chemical and physical features of the smoke during this "event of opportunity".