Global impact of smoke aerosols from landscape fires on climate and the Hadley circulation

Tosca, M. G.; Randerson, James T.; Zender, Charles S.

doi:10.5194/acp-13-5227-2013

Cited by 150 publications

(182 citation statements)

References 77 publications

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“…In contrast, the switch from GFAS to AEROCOM emissions introduces a regional surface RF of 2-5 W m −2 in large parts of topical Africa, South America and also boreal North America. Tosca et al (2013) compared a simulation based on GFEDv3 wildfire emissions to a zero wildfire-emission control run to estimate the net change in surface shortwave fluxes in the community Earth system model (CESM). The authors only considered a prescribed wildfire emission release at the surface.…”

Section: Radiative Forcingmentioning

confidence: 99%

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

et al. 2015

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Abstract. Wildfires represent a major source for aerosols impacting atmospheric radiation, atmospheric chemistry and cloud micro-physical properties. Previous case studies indicated that the height of the aerosol-radiation interaction may crucially affect atmospheric radiation, but the sensitivity to emission heights has been examined with only a few models and is still uncertain. In this study we use the general circulation model ECHAM6 extended by the aerosol module HAM2 to investigate the impact of wildfire emission heights on atmospheric long-range transport, black carbon (BC) concentrations and atmospheric radiation. We simulate the wildfire aerosol release using either various versions of a semiempirical plume height parametrization or prescribed standard emission heights in ECHAM6-HAM2. Extreme scenarios of near-surface or free-tropospheric-only injections provide lower and upper constraints on the emission height climate impact. We find relative changes in mean global atmospheric BC burden of up to 7.9 ± 4.4 % caused by average changes in emission heights of 1.5-3.5 km. Regionally, changes in BC burden exceed 30-40 % in the major biomass burning regions. The model evaluation of aerosol optical thickness (AOT) against Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol RObotic NETwork (AERONET) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations indicates that the implementation of a plume height parametrization slightly reduces the ECHAM6-HAM2 biases regionally, but on the global scale these improvements in model performance are small. For prescribed emission release at the surface, wildfire emissions entail a total sky top-of-atmosphere (TOA) radiative forcing (RF) of −0.16 ± 0.06 W m −2 . The application of a plume height parametrization which agrees reasonably well with observations introduces a slightly stronger negative TOA RF of −0.20 ± 0.07 W m −2 . The standard ECHAM6-HAM2 model in which 25 % of the wildfire emissions are injected into the free troposphere (FT) and 75 % into the planetary boundary layer (PBL), leads to a TOA RF of −0.24 ± 0.06 W m −2 . Overall, we conclude that simple plume height parametrizations provide sufficient representations of emission heights for global climate modeling. Significant improvements in aerosol wildfire modeling likely depend on better emission inventories and aerosol process modeling rather than on improved emission height parametrizations.

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Section: Radiative Forcingmentioning

confidence: 99%

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

et al. 2015

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“…Using WRFChem model over South America, Wu et al (2011) showed that BBA suppressed the diurnal amplitude of convection by about 11 %, decreasing clouds (consistent with Cook and Highwood, 2004) and precipitation in the afternoon but increasing them at night. Using the Community Atmosphere Model version 5 (CAM5), Tosca et al (2013) found that BBA increased global mean AODs by 10 %, increased tropospheric heating and decreased global surface temperature by 0.13±0.01 • C. This resulted in a weakening of the Hadley circulation, causing small reductions in global precipitation but with larger reductions near the Equator.…”

Section: Introductionmentioning

confidence: 99%

“…Landscape fires occur due to both natural and anthropogenic activities, such as forest fires, agricultural crop residue burning, deliberate burning of savannah grasslands and deforestation for agricultural purposes. South America accounts for an estimated 15 % of global fire emissions of carbon from landscape fires and open biomass burning (van der Werf et al, 2010), with regional hotspots of fire activity around the edges of Amazonia. The Amazon region experiences a large number of fires each dry season (August-October).…”

Section: Introductionmentioning

confidence: 99%

“…The majority of fires worldwide occur in tropical countries (Crutzen and Andreae, 1990;van der Werf et al, 2010) and the tropics play a particularly pivotal role in tropospheric chemistry (Crutzen and Zimmermann, 1991). Landscape fires occur due to both natural and anthropogenic activities, such as forest fires, agricultural crop residue burning, deliberate burning of savannah grasslands and deforestation for agricultural purposes.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of Amazonia biomass burning aerosols assessed from short-range weather forecasts

et al. 2015

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Abstract. The direct radiative impacts of biomass burning aerosols (BBA) on meteorology are investigated using shortrange forecasts from the Met Office Unified Model (MetUM) over South America during the South American Biomass Burning Analysis (SAMBBA). The impacts are evaluated using a set of three simulations: (i) no aerosols, (ii) with monthly mean aerosol climatologies and (iii) with prognostic aerosols modelled using the Coupled Large-scale Aerosol Simulator for Studies In Climate (CLASSIC) scheme. Comparison with observations show that the prognostic CLAS-SIC scheme provides the best representation of BBA. The impacts of BBA are quantified over central and southern Amazonia from the first and second day of 2-day forecasts during 14 September-3 October 2012. On average, during the first day of the forecast, including prognostic BBA reduces the clear-sky net radiation at the surface by 15 ± 1 W m −2 and reduces net top-of-atmosphere (TOA) radiation by 8 ± 1 W m −2 , with a direct atmospheric warming of 7 ± 1 W m −2 . BBA-induced reductions in all-sky radiation are smaller in magnitude: 9.0 ± 1 W m −2 at the surface and 4.0 ± 1 W m −2 at TOA. In this modelling study the BBA therefore exert an overall cooling influence on the Earthatmosphere system, although some levels of the atmosphere are directly warmed by the absorption of solar radiation. Due to the reduction of net radiative flux at the surface, the mean 2 m air temperature is reduced by around 0.1 ± 0.02 • C. The BBA also cools the boundary layer (BL) but warms air above by around 0.2 • C due to the absorption of shortwave radiation. The overall impact is to reduce the BL depth by around 19 ± 8 m. These differences in heating lead to a more anticyclonic circulation at 700 hPa, with winds changing by around 0.6 m s −1 . Inclusion of climatological or prognostic BBA in the MetUM makes a small but significant improvement in forecasts of temperature and relative humidity, but improvements were small compare with model error and the relative increase in forecast skill from the prognostic aerosol simulation over the aerosol climatology was also small. Locally, on a 150 km scale, changes in precipitation reach around 4 mm day −1 due to changes in the location of convection. Over Amazonia, including BBA in the simulation led to fewer rain events that were more intense. This change may be linked to the BBA changing the vertical profile of stability in the lower atmosphere. The localised changes in rainfall tend to average out to give a 5 % (0.06 mm day −1 ) decrease in total precipitation over the Amazonian region (except on day 2 with prognostic BBA). The change in water budget from BBA is, however, dominated by decreased evapotranspiration from the reduced net surface fluxes (0.2 to 0.3 mm day −1 ), since this term is larger than the corresponding changes in precipitation and water vapour convergence.

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“…Specifically, a modelling study suggested that the Hadley Cell circulation can be weakened due to the heating of the atmosphere and cooling of the surface that smoke aerosols cause in the tropics, with large precipitation reductions near the equator offset by smaller increases north and south of it [86]. The area of study of fire effects on circulation and precipitation on large scales is very much at its infancy and requires a lot more investigation in future research.…”

Section: Effects On Radiative Forcing and Climatementioning

confidence: 99%

Fire Influences on Atmospheric Composition, Air Quality and Climate

Voulgarakis

Field

2015

Curr Pollution Rep

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Fires impact atmospheric composition through their emissions, which range from long-lived gases to shortlived gases and aerosols. Effects are typically larger in the tropics and boreal regions but can also be substantial in highly populated areas in the northern mid-latitudes. In all regions, fire can impact air quality and health. Similarly, its effect on large-scale atmospheric processes, including regional and global atmospheric chemistry and climate forcing, can be substantial, but this remains largely unexplored. The impacts are primarily realised in the boundary layer and lower free troposphere but can also be noticeable in upper troposphere/lower stratosphere (UT/LS) region, for the most intense fires. In this review, we summarise the recent literature on findings related to fire impact on atmospheric composition, air quality and climate. We explore both observational and modelling approaches and present information on key regions and on the globe as a whole. We also discuss the current and future directions in this area of research, focusing on the major advances in emission estimates, the emerging efforts to include fire as a component in Earth system modelling and the use of modelling to assess health impacts of fire emissions.

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Global impact of smoke aerosols from landscape fires on climate and the Hadley circulation

Cited by 150 publications

References 77 publications

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

Impacts of Amazonia biomass burning aerosols assessed from short-range weather forecasts

Fire Influences on Atmospheric Composition, Air Quality and Climate

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