A Long-Term Record of Aerosol Optical Depth from TOMS Observations and Comparison to AERONET Measurements

Observations of backscattered near-ultraviolet radiation from the Total Ozone Mapping Spectrometer (TOMS) on board the Nimbus-7 (1979‐92) and the Earth Probe (mid-1996 to present) satellites have been used to derive a long-term record of aerosol optical depth over oceans and continents. The retrieval technique applied to the TOMS data makes use of two unique advantages of near-UV remote sensing not available in the visible or nearIR: 1) low reflectivity of all land surface types (including the normally bright deserts in the visible), which makes possible aerosol retrieval over the continents; and 2) large sensitivity to aerosol types that absorb in the UV, allowing the clear separation of carbonaceous and mineral aerosols from purely scattering particles such as sulfate and sea salt aerosols. The near-UV method of aerosol characterization is validated by comparison with Aerosol Robotic Network (AERONET) ground-based observations. TOMS retrievals of aerosol optical depth over land areas (1996‐2000) are shown to agree reasonably well with AERONET sun photometer observations for a variety of environments characterized by different aerosol types, such as carbonaceous aerosols from biomass burning, desert dust aerosols, and sulfate aerosols. In most cases the TOMS-derived optical depths of UV-absorbing aerosols are within 30% of the AERONET observations, while nonabsorbing optical depths agree to within 20%. The results presented here constitute the first long-term nearly global climatology of aerosol optical depth over both land and water surfaces, extending the observations of aerosol optical depth to regions and times (1979 to present) not accessible to ground-based observations.

[1]  D. Tanré,et al.  Remote Sensing of Tropospheric Aerosols from Space: Past, Present, and Future. , 1999 .

[2]  P. Bhartia,et al.  Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation , 1998 .

[3]  E. M. Patterson,et al.  Complex Index of Refraction Between 300 and 700 nm for Saharan Aerosols , 1977 .

[4]  M. Chin,et al.  Sources and distributions of dust aerosols simulated with the GOCART model , 2001 .

[5]  Jay R. Herman,et al.  Aerosol properties from EP-TOMS near UV observations , 2002 .

[6]  C. Tropea,et al.  Light Scattering from Small Particles , 2003 .

[7]  Ina Tegen,et al.  A comparison of seasonal and interannual variability of soil dust aerosols over the Atlantic Ocean as inferred by the TOMS AI and AVHRR AOT retrievals , 2001 .

[8]  P. Bhartia,et al.  Impact of tropospheric aerosol absorption on ozone retrieval from backscattered ultraviolet measurements , 1999 .

[9]  I. Sokolik,et al.  Complex refractive index of atmospheric dust aerosols , 1993 .

[10]  T. Eck,et al.  Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols , 1999 .

[11]  H. Gordon,et al.  Remote sensing of ocean color and aerosol properties: resolving the issue of aerosol absorption. , 1997, Applied optics.

[12]  Manuel Arbelo,et al.  Relationship between errors in AVHRR‐derived sea surface temperature and the TOMS aerosol index , 2001 .

[13]  Jay R. Herman,et al.  Earth surface reflectivity climatology at 340–380 nm from TOMS data , 1997 .

[14]  Glen Jaross,et al.  Earth probe total ozone mapping spectrometer (TOMS): data products user's guide , 1998 .

[15]  T. Nakajima,et al.  A use of two‐channel radiances for an aerosol characterization from space , 1998 .

[16]  Michael D. King,et al.  A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements , 2000 .

[17]  O. Torres,et al.  Biomass burning smoke measured using backscattered ultraviolet radiation: SCAR‐B and Brazilian smoke interannual variability , 1998 .

[18]  H. V. Hulst.  Light Scattering by Small Particles , 1957 .

[19]  A. da Silva,et al.  Quantification of dust-forced heating of the lower troposphere , 1998, Nature.

[20]  James B. Kerr,et al.  Satellite estimation of spectral surface UV irradiance in the presence of tropospheric aerosols , 1998 .

[21]  Ina Tegen,et al.  Climate Response to Soil Dust Aerosols , 1998 .

[22]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[23]  Jay R. Herman,et al.  Distribution of UV radiation at the Earth's surface from TOMS-measured UV-backscattered radiances , 1999 .

[24]  O. Torres,et al.  ENVIRONMENTAL CHARACTERIZATION OF GLOBAL SOURCES OF ATMOSPHERIC SOIL DUST IDENTIFIED WITH THE NIMBUS 7 TOTAL OZONE MAPPING SPECTROMETER (TOMS) ABSORBING AEROSOL PRODUCT , 2002 .

[25]  T. I. Quickenden,et al.  Visible and near-ultraviolet absorption spectrum of liquid water. , 1999, Applied optics.

[26]  P. Bhartia,et al.  Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) Data Products User`s Guide , 1993 .

[27]  G. Stenchikov,et al.  The impact of aerosols on solar ultraviolet radiation and photochemical smog. , 1997, Science.

[28]  J. R. Herman,et al.  UV 380 NM Reflectivity of the Earth's Surface , 2001 .

[29]  A. Lacis,et al.  Aerosol retrievals over the ocean by use of channels 1 and 2 AVHRR data: sensitivity analysis and preliminary results. , 1999, Applied optics.

[30]  J. Lelieveld,et al.  Role of mineral aerosol as a reactive surface in the global troposphere , 1996 .

[31]  G. S. Kent,et al.  LITE and SAGE II measurements of aerosols in the southern hemisphere upper troposphere , 1998 .

[32]  Paul Ginoux,et al.  Environmental Characterization of Global Sources of Atmospheric Soil Dust Identified with the NIMBUS-7 TOMS Absorbing Aerosol Product , 2001 .

[33]  Alexander Ignatov,et al.  Development, validation, and potential enhancements to the second‐generation operational aerosol product at the National Environmental Satellite, Data, and Information Service of the National Oceanic and Atmospheric Administration , 1997 .

[34]  P. Bhartia,et al.  Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data , 1997 .