HR: 16:05h
AN: A54A-01 INVITED     [Abstracts]
TI: Aerosol over the Indian Ocean: Observations from INDOEX 1999
AU: * Clarke, A D
EM: tclarke@soest.hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology, 1000 Pope Rd., Honolulu, HI 96822
AB: The Indian Ocean Experiment (INDOEX) measurements during February-March 1999 on land, sea and in the air provided complementary assessment of chemical, physical and optical properties of the aerosol haze over the Indian Ocean (IO). Regional characterization from different platforms resulted in differences linked to variability in time and space and emphasizes the need to combine such efforts with coordinated satellite and modeling studies able to characterize large-scale regional structure and variability. In general, different platforms showed greater variability in extensive aerosol characteristics than intensive properties due to differing sampling locations and strategies. For aerosol intensive properties, the measured ratios of chemical species were found to exhibit larger differences than properties of the size distribution or aerosol optical properties. Even so, at moderate to high haze concentrations with, various approaches to determine the aerosol mass scattering efficiency (MSE) at 33% relative humidity converged on values of about 3.8 m2g-1, providing a firm constraint upon the description and modeling of typical haze optical properties over the IO. Dust influences were generally small during INDOEX and confined to the northwest IO and sea-salt was usually low due to low winds resulting in submicron pollution dominating the IO aerosol optical properties. Pollutant emissions from western India were generally confined to the marine boundary layer (MBL) and decreased in concentration during advection to the ITCZ, apparently due to horizontal divergence and entrainment of cleaner air aloft. At times, enhanced pollution layers above the MBL lofted from central India or SE Asia made large contributions to aerosol optical depth (AOD) and often had enhanced biomass burning signatures. Aerosol cloud interactions were evident. Evaluations of chemical, microphysical and optical properties across platforms and comparisons to column AOD indicate that confirming "closure" to better than about 20% will require significant improvements in techniques, calibration procedures and comparison efforts.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0360 Radiation: transmission and scattering
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005