Bernadette Chatenet

Bio: Bernadette Chatenet is an academic researcher from University of Paris. The author has contributed to research in topics: Aerosol & Mineral dust. The author has an hindex of 30, co-authored 43 publications receiving 5687 citations. Previous affiliations of Bernadette Chatenet include Centre national de la recherche scientifique & Institut de recherche pour le développement.

An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET

Abstract: Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented.

Columnar aerosol optical properties at AERONET sites in central eastern Asia and aerosol transport to the tropical mid‐Pacific

Abstract: [1] The column-integrated optical properties of aerosol in the central eastern region of Asia and midtropical Pacific were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites in these regions. Characterization of aerosol properties in the Asian region is important due to the rapid growth of both population and economic activity, with associated increases in fossil fuel combustion, and the possible regional and global climatic impacts of related aerosol emissions. Multiyear monitoring over the complete annual cycle at sites in China, Mongolia, South Korea, and Japan suggest spring and/or summer maximum in aerosol optical depth (τa) and a winter minimum; however, more monitoring is needed to establish accurate climatologies. The annual cycle of Angstrom wavelength exponent (α) showed a springtime minimum associated with dust storm activity; however, the monthly mean α440–870 was >0.8 even for the peak dust season at eastern Asian sites suggesting that fine mode pollution aerosol emitted from population centers in eastern Asia dominates the monthly aerosol optical influence even in spring as pollution aerosol mixes with coarse mode dust originating in western source regions. Aerosol optical depth peaks in spring in the tropical mid-Pacific Ocean associated with seasonal shifts in atmospheric transport from Asia, and ∼35% of the springtime τa500 enhancement occurs at altitudes above 3.4 km. For predominately fine mode aerosol pollution cases, the average midvisible (∼550 nm) single scattering albedo (ω0) at two continental urban sites in China averaged ∼0.89, while it was significantly higher, ∼0.93, at two relatively rural coastal sites in South Korea and Japan. Differences in fine mode absorption between these regions may result from a combination of factors including aerosol aging during transport, relative humidity differences, sea salt at coastal sites, and fuel type and combustion differences in the two regions. For cases where τa was predominately coarse mode dust aerosol in the spring of 2001, the absorption was greater in eastern Asia compared to the source regions, with ω0 at Dunhuang, China (near to the major Taklamakan dust source), ∼0.04 higher than at Beijing at all wavelengths, and Anmyon, South Korea, showing an intermediate level of absorption. Possible reasons for differences in dust absorption magnitude include interactions between dust and fine mode pollution aerosol and also variability of dust optical properties from different source regions in China and Mongolia.

Comparisons of the TOMS aerosol index with Sun-photometer aerosol optical thickness: Results and applications

Abstract: A nearly 20-year global data set (1979–1994 and 1996 to the present) of tropospheric absorbing aerosols has been developed from total ozone mapping spectrometer (TOMS) backscattered radiance measurements in the range from 331 to 380 nm. The occurrence of aerosols is derived directly from measured backscattered radiances and is represented by a quantity known as the aerosol index. Previous theoretical model simulations have demonstrated that the aerosol index depends on aerosol optical thickness (AOT), single scattering albedo, and aerosol height and that the AOT can be determined provided that the microphysical properties and height of aerosols are known. In this paper we show that the TOMS aerosol index measurements are linearly proportional to the AOT derived independently from ground-based Sun-photometer instruments over regions of biomass burning and regions covered by African dust. We also show how this linear relationship can be used to directly convert the aerosol index into AOT for smoke and dust aerosols for the regions near the Sun-photometer sites and how information about aerosol height can be inferred from the results. Finally, we apply this method to the TOMS data over the last two decades and find a significant increase in the amount of biomass burning smoke in the African savanna regions during the 1990s in addition to the more obvious increase in South America.

Origins of African dust transported over the northeastern tropical Atlantic

Abstract: On the basis of 3 years of daily measurements of mineral dust concentrations at Sal Island (Cape Verde), this study focuses on the origin of the dust transported over the northeastern tropical Atlantic during the dusty season (October to April). Using backward trajectories, we have identified three different sectors of origin of the transported dust, covering the Sahara (north/west and central/south) and the Sahel regions. Time variations of the dust transport from these different areas can be explained by the seasonal shift of the subtropical high-pressure center. A geochemical approach highlights that the calcium amount and the Si/Al ratio of the transported dust differ according to these source regions, in relation to their respective soil compositions.

An additional low layer transport of Sahelian and Saharan dust over the north-eastern Tropical Atlantic

Abstract: Mineral dust concentrations have been measured from a monitoring aerosol station set up at Sal, Cape Verde Island between December 1991 and December 1994 in order to assess the transport process of African dust over the North-eastern Tropical Atlantic. These measurements indicate a pronounced seasonal pattern, with maximum dust concentrations observed during winter. A meteorological analysis shows that the transport of dust occurs at low altitudes, in the trade winds layer, during this season. Large quantities of dust are carried out of North-western Africa, in particular from the Sahel at these altitudes. Such process could constitute the major supply of atmospheric mineral matter to the surface sea water of the Eastern Atlantic.

Emission of trace gases and aerosols from biomass burning

Abstract: A large body of information on emissions from the various types of biomass burning has been accumulated over the past decade, to a large extent as a result of International Geosphere-Biosphere Programme/International Global Atmospheric Chemistry research activities. Yet this information has not been readily accessible to the atmospheric chemistry community because it was scattered over a large number of publications and reported in numerous different units and reference systems. We have critically evaluated the presently available data and integrated these into a consistent format. On the basis of this analysis we present a set of emission factors for a large variety of species emitted from biomass fires. Where data were not available, we have proposed estimates based on appropriate extrapolation techniques. We have derived global estimates of pyrogenic emissions for important species emitted by the various types of biomass burning and compared our estimates with results from inverse modeling studies.

Global and regional climate changes due to black carbon

Abstract: Black carbon in soot is an efficient absorbing agent of solar irradiation that is preferentially emitted in the tropics and can form atmospheric brown clouds in mixture with other aerosols. These factors combine to make black carbon emissions the second most important contribution to anthropogenic climate warming, after carbon dioxide emissions.

Environmental characterization of global sources of atmospheric soil dust identified with the nimbus 7 total ozone mapping spectrometer (toms) absorbing aerosol product

Abstract: [1] We use the Total Ozone Mapping Spectrometer (TOMS) sensor on the Nimbus 7 satellite to map the global distribution of major atmospheric dust sources with the goal of identifying common environmental characteristics The largest and most persistent sources are located in the Northern Hemisphere, mainly in a broad “dust belt” that extends from the west coast of North Africa, over the Middle East, Central and South Asia, to China There is remarkably little large-scale dust activity outside this region In particular, the Southern Hemisphere is devoid of major dust activity Dust sources, regardless of size or strength, can usually be associated with topographical lows located in arid regions with annual rainfall under 200–250 mm Although the source regions themselves are arid or hyperarid, the action of water is evident from the presence of ephemeral streams, rivers, lakes, and playas Most major sources have been intermittently flooded through the Quaternary as evidenced by deep alluvial deposits Many sources are associated with areas where human impacts are well documented, eg, the Caspian and Aral Seas, Tigris-Euphrates River Basin, southwestern North America, and the loess lands in China Nonetheless, the largest and most active sources are located in truly remote areas where there is little or no human activity Thus, on a global scale, dust mobilization appears to be dominated by natural sources Dust activity is extremely sensitive to many environmental parameters The identification of major sources will enable us to focus on critical regions and to characterize emission rates in response to environmental conditions With such knowledge we will be better able to improve global dust models and to assess the effects of climate change on emissions in the future It will also facilitate the interpretation of the paleoclimate record based on dust contained in ocean sediments and ice cores

Variability of Absorption and Optical Properties of Key Aerosol Types Observed in Worldwide Locations

Abstract: Aerosol radiative forcing is a critical, though variable and uncertain, component of the global climate. Yet climate models rely on sparse information of the aerosol optical properties. In situ measurements, though important in many respects, seldom provide measurements of the undisturbed aerosol in the entire atmospheric column. Here, 8 yr of worldwide distributed data from the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations. Established procedures for maintaining and calibrating the global network of radiometers, cloud screening, and inversion techniques allow for a consistent retrieval of the optical properties of aerosol in locations with varying emission sources and conditions. The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property driving aerosol climate forcing, for desert dust, biomass burning, urban‐industrial, and marine aerosols. Moreover, significant variability of the absorption for the same aerosol type appearing due to different meteorological and source characteristics as well as different emission characteristics are observed. It is expected that this aerosol characterization will help refine aerosol optical models and reduce uncertainties in satellite observations of the global aerosol and in modeling aerosol impacts on climate.