Remote Measurement of Energy and Carbon Flux From Wildfires in Brazil

Abstract

Temperature, intensity, spread, and dimensions of fires burning in tropical savanna and slashed tropical forest in central Brazil were measured for the first time by remote sensing with an infrared imaging spectrometer that was designed to accommodate the high radiances of wildland fires. Furthermore, the first in situ airborne measurements of sensible heat and carbon fluxes in fire plumes were combined with remote measurements of flame properties to provide consistent remote-sensing-based estimators of these fluxes. These estimators provide a means to determine rates of fuel consumption and carbon emission to the atmosphere by wildland fires as required for assessments of fire impacts on regional air pollution or global emissions of greenhouse gases. Observed fires developed complex fire-line geometry and thermal structure, even as average whole-fire temperatures varied little. Flame temperatures sometimes exceeded 1600 K along the leading edge of actively spreading fire lines, yet Ͼ90% of the radiant energy from observed fires was associated with temperatures of 830-1440 K. Fire in a partially slashed forest encompassed a high-intensity flaming front and a trailing reach of residual combustion extending 400 m. Fire fronts in tropical savanna typically formed with little depth and a high proportion of their radiant flux density associated with high temperatures due to low levels of residual combustion. Measured fires had such low and variable radiance compared with that of a blackbody of comparable temperature as to preclude the use of fire radiance at a single wavelength as a measure of fire intensity or temperature. One-half of the radiant flux density from a measured savanna fire was associated with values of a combined emissivity-fractional-area parameter Ͻ0.091 m 2 /m 2 ; for a slash fire this fraction was associated with values Ͻ0.37 m 2 /m 2 . Observations reported here show wildland fires to be so complex and dynamic as to require frequent high-resolution measurements over their course and duration in order to specify their effects in the environment; an understanding of global fire impacts may require such measurements over a large sample of individual fires.

Including the sub-grid scale plume rise of vegetation fires in low resolution atmospheric transport models

“…Using the carbon flux estimated by the authors, the mean heat flux from the fires was about 28 kW m −2 . Riggan et al (2004) describe temperature, vertical velocity, sensible heat and radiative fluxes, among other properties in plumes from typical vegetation fires on September 1992 in Brazil, using remote sensing. Airborne measurements at 200 m a.g.l.…”

Controle De Qualidade Posicional Em Dados Espaciais Utilizando Feições Lineares

“…Em relação ao espalhamento do fogo pela amostra, na amostra seca ele acontece em torno de 20 segundos, com a elevação rápida da FRP, que chega a atingir 0,005 MW. Para a amostra úmida, o espalhamento do fogo demora a ocorrer, e começa a elevar a FRP somente após 32 segundos depois do início do processo de combustão, com FRP máxima correspondente a 0,0028 MW em 110 segundos, pois a presença de umidade na vegetação influencia diretamente na redução da FRP, situação também encontrada por Riggan et al (2004).…”

Impact of including the plume rise of vegetation fires in numerical simulations of associated atmospheric pollutants

“…The heat flux from biomass burning is highly variable, and mainly related to the fuel load, fuel water content, and weather conditions. Based on several published data sets [Miranda et al, 1993;Carvalho et al, 1995Carvalho et al, , 2001Ferguson et al, 2000;Ward et al, 1992;Riggan et al, 2004] all possible classes of vegetation burning were aggregated into three main types: tropical forest, woody savanna and grassland; then for each type a lower and upper heat flux limit was estimated (Table 1). For tropical forest, the estimated lower and upper limit was 30 and 80 kW m…”