In this work, we proceed to an optical and microphysical analysis of the observations reversed by the MODIS, SeaWiFS, MISR and OMI sensors with the aim of proposing the best-adapted airborne sensor for better monitori...In this work, we proceed to an optical and microphysical analysis of the observations reversed by the MODIS, SeaWiFS, MISR and OMI sensors with the aim of proposing the best-adapted airborne sensor for better monitoring of aerosols in Burkina Faso. To this end, a comparison of AOD between satellite observations and in situ measurements at the Ouagadougou site reveals an underestimation of AERONET AOD except for OMI which overestimates them. Also, an inter-comparison done based on the linear regression line representation shows the correlation between the aerosol models incorporated in the airborne sensor inversion algorithms and the aerosol population probed. This can be seen through the correlation coefficients R which are 0.84, 0.64, 0.55 and 0.054 for MODIS, SeaWiFS, MISR and OMI respectively. Furthermore, an optical analysis of aerosols in Burkina Faso by the MODIS sensor from 2001 to 2016 indicates a large spatial and temporal variability of particles strongly dominated by desert dust. This is corroborated by the annual and seasonal cycles of the AOD at 550 nm and the Angström coefficient measured in the spectral range between 412 nm and 470 nm. A zoom on a few sites chosen according to the three climatic zones confirms the majority presence of mineral aerosols in Burkina Faso, whose maxima are observed in spring and summer.展开更多
This paper deals with the characterization of aerosols in the Sahelian zone, particularly in Burkina Faso based on MODIS observations and in situ measurements of the AERONET network on the Ouagadougou site (12.2&#...This paper deals with the characterization of aerosols in the Sahelian zone, particularly in Burkina Faso based on MODIS observations and in situ measurements of the AERONET network on the Ouagadougou site (12.2°N, 1.4°W). Thus, a seasonal spatial distribution of aerosols made over the period from 2001 to 2016 gives a very great variability of aerosols in Burkina Faso, whose maxima are encountered in Spring, characterized by winds from the North East. This seasonality of aerosols is also shown by the annual cycles of optical, radiative and microphysical parameters measured by AERONET between 1999 and 2006. Moreover, an analysis of these parameters shows the prevalence of mineral dusts characterized by low values of the Angstrom coefficient (α440-870 0.9) and the cooling noticed in the bottom of atmosphere (BOA) and at the top of the atmosphere (TOA). Also, the climatology of the volume size distribution of aerosols shows a very great variability of particles in terms of size influenced by the thin and coarse pattern where most sizes are between 1 and 10 μm.展开更多
This paper deals with the climatology of aerosols in West Africa based on satellite and in situ measurements between 2001 and 2016 and covers four sites in the Sahelian zone. There are indeed Banizoumbou (13.541&d...This paper deals with the climatology of aerosols in West Africa based on satellite and in situ measurements between 2001 and 2016 and covers four sites in the Sahelian zone. There are indeed Banizoumbou (13.541°N, 02.665°E), Cinzana (13.278°N, 05.934°W), Dakar (14.394°N, 16.959°W) and Ouagadougou (12.20°N, 1.40°W) located respectively in Niger, Mali, Senegal and Burkina Faso. Thus, an intercomparison between the satellite observations and the in situ measurements shows a good correlation between MODIS and AERONET with a correlation coefficient R = 0.86 at Cinzana, R = 0.85 at Banizounbou, R = 0.84 at Ouagadougou and a low correlation coefficient R = 0.66 calculated on the Dakar site. Like MODIS, SeaWiFS shows a very good correspondence with measurements of the ground photometer especially for Banizoumbou (R = 0.89), Cinzana (R = 0.88) and Dakar (R = 0.75) followed by a low correlation coefficient calculated on the Ouagadougou site (R = 0.64). The performance of these airborne sensors is also corroborated by the calculation of root mean square error (RMSE) and the mean absolute error (MAE). Following this validation, a climatological analysis based on aerosol optical depth (AOD) shows the seasonality of aerosols in West Africa strongly influenced by the climate dynamics illustrated by the MERRA model reanalysis. This seasonal spatial distribution of aerosols justifies the temporal variability of the particles observed at the different sites in the Sahel. In addition, a combined analysis of AOD and Angstrom coefficient indicates the aerosol period in the Sahel in spring (March-April-May) and summer (June-July-August). However, these aerosols are strongly dominated by desert dust whose main sources are located north in the Sahara and Sahel.展开更多
文摘In this work, we proceed to an optical and microphysical analysis of the observations reversed by the MODIS, SeaWiFS, MISR and OMI sensors with the aim of proposing the best-adapted airborne sensor for better monitoring of aerosols in Burkina Faso. To this end, a comparison of AOD between satellite observations and in situ measurements at the Ouagadougou site reveals an underestimation of AERONET AOD except for OMI which overestimates them. Also, an inter-comparison done based on the linear regression line representation shows the correlation between the aerosol models incorporated in the airborne sensor inversion algorithms and the aerosol population probed. This can be seen through the correlation coefficients R which are 0.84, 0.64, 0.55 and 0.054 for MODIS, SeaWiFS, MISR and OMI respectively. Furthermore, an optical analysis of aerosols in Burkina Faso by the MODIS sensor from 2001 to 2016 indicates a large spatial and temporal variability of particles strongly dominated by desert dust. This is corroborated by the annual and seasonal cycles of the AOD at 550 nm and the Angström coefficient measured in the spectral range between 412 nm and 470 nm. A zoom on a few sites chosen according to the three climatic zones confirms the majority presence of mineral aerosols in Burkina Faso, whose maxima are observed in spring and summer.
文摘This paper deals with the characterization of aerosols in the Sahelian zone, particularly in Burkina Faso based on MODIS observations and in situ measurements of the AERONET network on the Ouagadougou site (12.2°N, 1.4°W). Thus, a seasonal spatial distribution of aerosols made over the period from 2001 to 2016 gives a very great variability of aerosols in Burkina Faso, whose maxima are encountered in Spring, characterized by winds from the North East. This seasonality of aerosols is also shown by the annual cycles of optical, radiative and microphysical parameters measured by AERONET between 1999 and 2006. Moreover, an analysis of these parameters shows the prevalence of mineral dusts characterized by low values of the Angstrom coefficient (α440-870 0.9) and the cooling noticed in the bottom of atmosphere (BOA) and at the top of the atmosphere (TOA). Also, the climatology of the volume size distribution of aerosols shows a very great variability of particles in terms of size influenced by the thin and coarse pattern where most sizes are between 1 and 10 μm.
文摘This paper deals with the climatology of aerosols in West Africa based on satellite and in situ measurements between 2001 and 2016 and covers four sites in the Sahelian zone. There are indeed Banizoumbou (13.541°N, 02.665°E), Cinzana (13.278°N, 05.934°W), Dakar (14.394°N, 16.959°W) and Ouagadougou (12.20°N, 1.40°W) located respectively in Niger, Mali, Senegal and Burkina Faso. Thus, an intercomparison between the satellite observations and the in situ measurements shows a good correlation between MODIS and AERONET with a correlation coefficient R = 0.86 at Cinzana, R = 0.85 at Banizounbou, R = 0.84 at Ouagadougou and a low correlation coefficient R = 0.66 calculated on the Dakar site. Like MODIS, SeaWiFS shows a very good correspondence with measurements of the ground photometer especially for Banizoumbou (R = 0.89), Cinzana (R = 0.88) and Dakar (R = 0.75) followed by a low correlation coefficient calculated on the Ouagadougou site (R = 0.64). The performance of these airborne sensors is also corroborated by the calculation of root mean square error (RMSE) and the mean absolute error (MAE). Following this validation, a climatological analysis based on aerosol optical depth (AOD) shows the seasonality of aerosols in West Africa strongly influenced by the climate dynamics illustrated by the MERRA model reanalysis. This seasonal spatial distribution of aerosols justifies the temporal variability of the particles observed at the different sites in the Sahel. In addition, a combined analysis of AOD and Angstrom coefficient indicates the aerosol period in the Sahel in spring (March-April-May) and summer (June-July-August). However, these aerosols are strongly dominated by desert dust whose main sources are located north in the Sahara and Sahel.
