Annual and diurnal african biomass burning temporal dynamics

Abstract

Abstract. Africa is the single largest continental source of biomass burning emissions. Here we conduct the first analysis of one full year of geostationary active fire detections and fire radiative power data recorded over Africa at 15-min temporal interval and a 3 km sub-satellite spatial resolution by the Spinning Enhanced Visible and Infrared Imager (SE-VIRI) imaging radiometer onboard the Meteosat-8 satellite. We use these data to provide new insights into the rates and totals of open biomass burning over Africa, particularly into the extremely strong seasonal and diurnal cycles that exist across the continent. We estimate peak daily biomass combustion totals to be 9 and 6 million tonnes of fuel per day in the northern and southern hemispheres respectively, and total fuel consumption between February 2004 and January 2005 is estimated to be at least 855 million tonnes. Analysis is carried out with regard to fire pixel temporal persistence, and we note that the majority of African fires are detected only once in consecutive 15 min imaging slots. An investigation of the variability of the diurnal fire cycle is carried out with respect to 20 different land cover types, and whilst differences are noted between land covers, the fire diurnal cycle characteristics for most land cover type are very similar in both African hemispheres. We compare the Fire Radiative Power (FRP) derived biomass combustion estimates to burned-areas, both at the scale of individual fires and over the entire continent at a 1-degree scale. Fuel consumption estimates are found to be less than 2 kg/m 2 for all land cover types noted to be subject to significant fire activity, and for savanna grasslands where literature values are commonly reported the FRP-derived median fuel consumption estimate of 300 g/m 2 is well within commonly quoted values. Meteosatderived FRP data of the type presented here is now available freely to interested users continuously and in near realtime for Africa, Europe and parts of South America via the EUMETSAT (European Organisation for the Exploitation of

Global and regional estimates of warm cloud droplet number concentration based on 13 years of AQUA-MODIS observations

“…Peak anthropogenic biomass burning does not coincide with the height of the dry season, but does coincide with the middle of the burning season over the northern parts of Angola, the Democratic Republic of Congo, and Zambia, where savannah fires are often lit in July/August well before the peak of the dry season (Le Page et al, 2010). This picture is substantiated by individual fire counts based on geostationary satellite observations, which also shows peak fire activity around July/August, with peak burning of about 6 Tg per day in July (Roberts et al, 2009). In contrast, in the eastern part of South Africa and Mozambique as well as northern Namibia, the middle of the fire season is shifted toward September.…”

AERONET-based models of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

“…The most likely reasons include additional ageing (examination of HYSPLIT back-trajectories for these cases suggests the air masses left the African continent ∼ 5 days before arriving at Ascension Island) and the possibility that properties of the freshly emitted aerosol are different from those near Mongu. Some air masses reaching Ascension Island pass over parts of Africa north of Mongu, which are more heavily forested (Roberts et al, 2009;Adams et al, 2012), and could lead to different typical optical properties compared to savannah burning (Ward et al, 1996;Reid et al, 2005b). Unfortunately, there are no AERONET sites in this part of Africa.…”

“…Although AERONET contains several long-term sites in the Sahel, the peak season for biomass burning there (November-February) coincides with strong dust activity, such that the aerosol is normally a mixture of biomass burning smoke and dust (Pandithurai et al, 2001;Roberts et al, 2009). Johnson et al (2008) and Eck et al (2010) found cases where these smoke aerosols were highly absorbing, with midvisible SSA as low as 0.76, although the more common cases of mixed smoke and dust in this region are less absorbing.…”

A review of approaches to estimate wildfire plume injection height within large-scale atmospheric chemical transport models

“…Since the initial trigger of plume rise is the heat released by the casual fire, InjH are strongly influenced by fire diurnal cycles (Roberts et al, 2009). This leads to lower nocturnal InjH which are amplified by the combination of nighttime stable atmosphere and lower PBL (Sofiev et al, 2013).…”