Abstract. We describe and begin to evaluate a parameterization to include the vertical transport of hot gases and particles emitted from biomass burning in low resolution atmosphericchemistry transport models. This sub-grid transport mechanism is simulated by embedding a 1-D cloud-resolving model with appropriate lower boundary conditions in each column of the 3-D host model. Through assimilation of remote sensing fire products, we recognize which columns have fires. Using a land use dataset appropriate fire properties are selected. The host model provides the environmental conditions, allowing the plume rise to be simulated explicitly. The derived height of the plume is then used in the source emission field of the host model to determine the effective injection height, releasing the material emitted during the flaming phase at this height. Model results are compared with CO aircraft profiles from an Amazon basin field campaign and with satellite data, showing the huge impact that this mechanism has on model performance. We also show the relative role of each main vertical transport mechanisms, shallow and deep moist convection and the pyro-convection (dry or moist) induced by vegetation fires, on the distribution of biomass burning CO emissions in the troposphere.

An impressive amount of evidence supports the proposal of Alvarez et al. that the Cretaceous era was ended abruptly by the impact of a comet or asteroid. The recent discovery of an apparently global soot layer at the Cretaceous/Tertiary boundary indicates that global wildfires were somehow ignited by the impact. Here we show that the thermal radiation produced by the ballistic re-entry of ejecta condensed from the vapour plume of the impact could have increased the global radiation flux by factors of 50 to 150 times the solar input for periods ranging from one to several hours. This great increase in thermal radiation may have been responsible for the ignition of global wildfires, as well as having deleterious effects on unprotected animal life.

We describe the results of 357 experimental fires conducted in an environmentally controlled large wind tunnel. The fires were burned over a range of particle sizes, fuel bed depths, packing ratios, moisture contents and windspeeds. We find that spread rate decreases with moisture content in a way which depends on the fuel type and diameter. It decreases as the square root of the packing ratio. Fuel bed depth has little elfect on spread rate, and fuel diameter has significant effect only for diameters above I mm. The relationship between rate of spread and windspeed is virtually linear.We develop a predictive model for rate of-spread based on energy transfer considerations and the laboratory results. Other laboratory-based models for spread rate are compared with our model, and tested against the laboratory data. The other models have forms similar to ours, but do not predict our data well. Our model predicts well the spread rates for fires burned in windspeeds below 3 mlsec in other laboratories. The scale of the experiments and the similarity of the dependence on windspeed to that found in the field indicate that a field model may be developed from the laboratory model with relatively few modifications.

Abstract. Vegetation fires emit hot gases and particles which are rapidly transported upward by the positive buoyancy generated by the combustion process. In general, the final vertical height that the smoke plumes reach is controlled by the thermodynamic stability of the atmospheric environment and the surface heat flux released by the fire. However, the presence of a strong horizontal wind can enhance the lateral entrainment and induce additional drag, particularly for small fires, impacting the smoke injection height. In this paper, we revisit the parameterization of the vertical transport of hot gases and particles emitted from vegetation fires, described in Freitas et al. (2007), to include the effects of environmental wind on transport and dilution of the smoke plume at its scale. This process is quantitatively represented by introducing an additional entrainment term to account for organized inflow of a mass of cooler and drier ambient air into the plume and its drag by momentum transfer. An extended set of equations including the horizontal motion of the plume and the additional increase of the plume radius is solved to simulate the time evolution of the plume rise and the smoke injection height. One-dimensional (1-D) model results are presented for two deforestation fires in the Amazon basin with sizes of 10 and 50 ha under calm and windy atmospheric environments. The results are compared to corresponding simulations generated by the complex non- The 1-D model may thus be used in field situations where extensive computing facilities are not available, especially under conditions for which several optional cases must be studied.

This study presents spatially and temporally resolved measurements of air temperatures and radiant energy fluxes in a boreal forest crown fire. Measurements were collected 3.1, 6.2, 9.2, 12.3, and 13.8 m above the ground surface. Peak air temperatures exceeded 1330 °C, and maximum radiant energy fluxes occurred in the upper third of the forest stand and reached 290 kW·m–2. Average radiant flux from the flames across all experiments was found to be approximately 200 kW·m–2. Measured temperatures showed some variation with vertical height in the canopy. Equivalent radiometric temperatures calculated from radiant heat flux measurements exceeded thermocouple-based temperatures for all but the 10-m height, indicating that fire intensity estimates based on thermocouple measurements alone may result in underestimation of actual radiant intensity. The data indicate that the radiative energy penetration distance is significantly longer in the forest canopy than in the lower levels of the forest stand.

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Abstract. We revisit the parameterization of the vertical transport of hot gases and particles emitted from biomass burning, described in Freitas et al. (2007), to include the effects of environmental wind on transport and dilution of the smoke plume at the cloud scale. Typically, the final vertical height that the smoke plumes reach is controlled by the thermodynamic stability of the atmospheric environment and the surface heat flux released by the fire. However, the presence of a strong horizontal wind can enhance the lateral entrainment and induce additional drag, particularly for small fires, impacting the smoke injection height. This process is quantitatively represented by introducing an additional entrainment term to account for organized inflow of a mass of cooler and drier ambient air into the plume and its drag by momentum transfer. An extended set of equations including the horizontal motion of the plume and the additional increase of the plume radius is solved to explicitly simulate the time evolution of the plume rise with the additional mass and momentum. One-dimensional (1-D) model results are presented for two deforestation fires in the Amazon basin with sizes of 10 and 50 ha under calm and windy atmospheric environments. The results are compared to corresponding simulations generated by the complex non-hydrostatic three dimensional (3-D) Active Tracer High resolution Atmospheric Model (ATHAM). We show that the 1-D model results compare well with the full 3-D simulations. The 1-D model may thus be used in field situations where extensive computing facilities are not available, especially under conditions for which several optional cases must be studied.