Impact of fires on surface albedo dynamics over the African continent

[1] The seasonal variation analysis of a land surface albedo data set derived from 1-year Meteosat observations reveals the high sensitivity of albedo to anthropogenic biomass burning activities during the dry season. At the beginning of this season, a rapid decrease of albedo is observed over fire-prone areas. These low albedo values last during the entire dry season, increasing slowly at the end of this season. This paper focuses on a quantitative estimation of biomass burning impact on albedo seasonal variations. To this end, a conceptual method is proposed to detect pixels whose albedo seasonal cycle is affected by biomass burning. The performance of this approach is evaluated over the central Africa region, where the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) field campaign took place in November 1996. Our results compare favorably with maps of fire-affected areas derived from NOAA advanced very high resolution radiometer (AVHRR) observations. When applied over the entire African continent, the Northern Hemisphere appears much more affected by fire-induced albedo decrease than the Southern Hemisphere. At a regional scale, Northern Hemisphere fires are responsible for a relative decrease of the albedo as large as 25% with respect to nonburnt areas. The amplitude of this large-scale darkening phenomenon might locally affect the wind regime and associated rainfall.

[1]  B. Hinton,et al.  An investigation of surface albedo variations during the recent Sahel drought , 1979 .

[2]  Yves M. Govaerts,et al.  The role of Bright Desert Regions in shaping North African climate , 2001 .

[3]  J. Levine Biomass Burning: Its History, Use, and Distribution and Its Impact on Environmental Quality and Global Climate , 1991 .

[4]  R. Scholes,et al.  An African Savanna: Synthesis of the Nylsvley Study. , 1993 .

[5]  H. Rahman,et al.  Coupled surface-atmosphere reflectance (CSAR) model: 2. Semiempirical surface model usable with NOAA advanced very high resolution radiometer data , 1993 .

[6]  G. Dedieu,et al.  Radiation exchanges above West African moist savannas: Seasonal patterns and comparison with a GCM simulation , 1994 .

[7]  B. Pinty,et al.  GEMI: a non-linear index to monitor global vegetation from satellites , 1992, Vegetatio.

[8]  D. Diner,et al.  Surface albedo retrieval from Meteosat: 1. Theory , 2000 .

[9]  F. White The vegetation of Africa : a descriptive memoir to accompany the Unesco/AETFAT/UNSO vegetation map of Africa , 1985 .

[10]  W. R. Cofer,et al.  Seasonal distribution of African savanna fires , 1992, Nature.

[11]  C. Tucker,et al.  Enhancement of Interdecadal Climate Variability in the Sahel by Vegetation Interaction. , 1999, Science.

[12]  W. Cramer,et al.  The IIASA database for mean monthly values of temperature , 1991 .

[13]  D. Diner,et al.  Surface albedo retrieval from Meteosat: 2. Applications , 2000 .

[14]  J. C. Price,et al.  Land surface temperature measurements from the split window channels of the NOAA 7 Advanced Very High Resolution Radiometer , 1984 .

[15]  Edward Dwyer,et al.  Satellite monitoring of vegetation fires for EXPRESSO: Outline of activity and relative importance of the study area in the global picture of biomass burning , 1999 .

[16]  Daniela Stroppiana,et al.  Satellite monitoring of fire in the EXPRESSO study area during the 1996 dry season experiment: Active fires, burnt area, and atmospheric emissions , 1999 .

[17]  M. Latif,et al.  Vegetation feedback on Sahelian rainfall variability in a coupled climate-land-vegetation model , 2001 .

[18]  S. Nicholson,et al.  Contrasting Conditions of Surface Water Balance in Wet Years and Dry Years as a Possible Land Surface-Atmosphere Feedback Mechanism in the West African Sahel , 1994 .

[19]  J. Leonard,et al.  The Vegetation of Africa , 1984 .

[20]  João M. N. Silva,et al.  Evaluating the performance of multitemporal image compositing algorithms for burned area analysis , 2003 .

[21]  G. Tyndall,et al.  Patterns in volatile organic compound emissions along a savanna‐rainforest gradient in central Africa , 1998 .

[22]  Piers J. Sellers,et al.  A Global Climatology of Albedo, Roughness Length and Stomatal Resistance for Atmospheric General Circulation Models as Represented by the Simple Biosphere Model (SiB) , 1989 .

[23]  J. Lacaux,et al.  Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO): An Overview , 1999 .

[24]  Nadine Gobron,et al.  Do man-made fires affect Earth's surface reflectance at continental scales? , 2000 .

[25]  Jose M. Cardoso Pereira,et al.  An assessment of vegetation fire in Africa (1981–1991): Burned areas, burned biomass, and atmospheric emissions , 1999 .

[26]  Guiling Wang,et al.  Role of vegetation dynamics in enhancing the low‐frequency variability of the Sahel rainfall , 2000 .

[27]  J. Charney Dynamics of deserts and drought in the Sahel , 1975 .

[28]  Pietro Ceccato,et al.  A contextual algorithm for AVHRR fire detection , 1996 .

[29]  S. I. Rasool,et al.  Surface albedo and the Sahel drought , 1984, Nature.

[30]  Christopher O. Justice,et al.  The Miombo Network: Framework for a Terrestrial Transect Study of Land-Use and Land-Cover Change in the Miombo Ecosystems of Central Africa , 1997 .

[31]  Yongkang Xue,et al.  The Influence of Land Surface Properties on Sahel Climate. Part 1: Desertification , 1993 .

[32]  P. Barbosa,et al.  An Algorithm for Extracting Burned Areas from Time Series of AVHRR GAC Data Applied at a Continental Scale , 1999 .

[33]  Y. Govaerts Correction of the Meteosat-5 and -6 radiometer solar channel spectral response with the Meteosat-7 sensor spectral characteristics , 1999 .