Winter to summer monsoon variation of aerosol optical depth over the tropical Indian Ocean

[1] The northern Indian Ocean undergoes a major transition from anthropogenic aerosols during the northeasterly winter monsoon season to mineral dust and sea salt during the southwest summer monsoon. The former is dominated by low-level transport from south and southeast Asia, while the latter results from low to mid tropospheric transport from the African continent and the Arabian Peninsula. During the winter monsoon, low-level transport from the Indian subcontinent and neighboring nations is particularly important. This paper uses 5 years of satellite-derived aerosol optical depths (AODs) to document the large seasonal variations in AODs modulated by the monsoons. In situ data are used to develop and validate the procedure we employ to derive visible AODs from the radiances observed by the advanced very high resolution radiometer (AVHRR) onboard polar-orbiting satellites. Monthly mean AOD over the Arabian Sea displays a clear annual cycle with a maximum (0.60 ± 0.10) in July and a minimum (0.20 ± 0.05) in January. The summer monsoon maximum is due both to the southwest winds bringing dust from the Horn of Africa over the Arabian Sea and mid tropospheric transport of dust from the Arabian Peninsula. Such long-range transports also lead to aerosol loading south of the equator. We also show that the Indonesia forest fires during the 1997 El Nino led to a large increase in AOD over most of the equatorial Indian Ocean.

[1]  W. Munk,et al.  Measurement of the Roughness of the Sea Surface from Photographs of the Sun’s Glitter , 1954 .

[2]  S. Duntley.  Detection of ocean chlorophyll from earth orbit , 1972 .

[3]  H. Gordon,et al.  Clear water radiances for atmospheric correction of coastal zone color scanner imagery. , 1981, Applied optics.

[4]  Didier Tanré,et al.  Estimation of Saharan aerosol optical thickness from blurring effects in thematic mapper data , 1988 .

[5]  R. Saunders,et al.  An improved method for detecting clear sky and cloudy radiances from AVHRR data , 1988 .

[6]  S. Ackerman,et al.  Surface weather observations of atmospheric dust over the southwest summer monsoon region , 1989 .

[7]  N. Che,et al.  Survey of radiometric calibration results and methods for visible and near infrared channels of NOAA-7, -9, and -11 AVHRRs , 1992 .

[8]  T. Rixen,et al.  Seasonality and interannual variability of particle fluxes to the deep Arabian sea , 1993 .

[9]  B. Holben,et al.  Calibration of the AVHRR visible and near-IR bands by atmospheric scattering, ocean glint and desert reflection , 1993 .

[10]  Yoram J. Kaufman,et al.  Size distribution and scattering phase function of aerosol particles retrieved from sky brightness measurements , 1994 .

[11]  Menghua Wang,et al.  Retrieval of water-leaving radiance and aerosol optical thickness over the oceans with SeaWiFS: a preliminary algorithm. , 1994, Applied optics.

[12]  C. Rao,et al.  Inter-satellite calibration linkages for the visible and near-infared channels of the Advanced Very High Resolution Radiometer on the NOAA-7, -9, and -11 spacecraft , 1995 .

[13]  Cloud Detection using AVHRR Data. , 1996 .

[14]  N. Loeb.  In-flight calibration of NOAA AVHRR visible and near-IR bands over Greenland and Antarctica , 1997 .

[15]  Larry L. Stowe,et al.  Characterization of tropospheric aerosols over the oceans with the NOAA advanced very high resolution radiometer optical thickness operational product , 1997 .

[16]  H. Fukushima,et al.  Asian dust aerosol: Optical effect on satellite ocean color signal and a scheme of its correction , 1997 .

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

[18]  K. Moorthy,et al.  Investigations of marine aerosols over the tropical Indian Ocean , 1997 .

[19]  V. Ramanathan,et al.  Direct observations of aerosol radiative forcing over the tropical Indian Ocean during the January-F , 1998 .

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

[21]  P. Koepke,et al.  Optical Properties of Aerosols and Clouds: The Software Package OPAC , 1998 .

[22]  T. N. Krishnamurti,et al.  Aerosol and pollutant transport and their impact on radiative forcing over the tropical Indian Ocean during the January February 1996 pre-INDOEX cruise , 1998 .

[23]  I. Tegen,et al.  A general circulation model study on the interannual variability of soil dust aerosol , 1998 .

[24]  C. Rao,et al.  Revised post-launch calibration of the visible and near-infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-14 spacecraft , 1999 .

[25]  Jim Aiken,et al.  The atmospheric correction of water colour and the quantitative retrieval of suspended particulate matter in Case II waters: Application to MERIS , 1999 .

[26]  Irina N. Sokolik,et al.  Incorporation of mineralogical composition into models of the radiative properties of mineral aerosol from UV to IR wavelengths , 1999 .

[27]  S. K. Satheesh,et al.  A model for the natural and anthropogenic aerosols over the tropical Indian Ocean derived from Indian Ocean Experiment data , 1999 .

[28]  V. Ramanathan,et al.  Regional aerosol distribution and its long‐range transport over the Indian Ocean , 2000 .

[29]  Quirine M. Ketterings,et al.  Soil Color as an Indicator of Slash‐and‐Burn Fire Severity and Soil Fertility in Sumatra, Indonesia , 2000 .

[30]  Emilio Chuvieco,et al.  Remote Sensing of Forest Fires , 2000 .

[31]  J. Lelieveld,et al.  The Indian Ocean Experiment: Widespread Air Pollution from South and Southeast Asia , 2001, Science.

[32]  B. Holben,et al.  Baseline maritime aerosol: Methodology to Derive the optical thickness and scattering properties , 2001 .

[33]  W. R. Tahnk.  INDOEX Aerosol Optical Depths and Radiative Forcing Derived from AVHRR , 2001 .

[34]  Glenn E. Shaw,et al.  Indian Ocean Experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze , 2001 .

[35]  T. Eck,et al.  Variability of Absorption and Optical Properties of Key Aerosol Types Observed in Worldwide Locations , 2002 .