Measurements of Asian dust optical properties over the Yellow Sea of China by shipboard and ground‐based photometers, along with satellite remote sensing: A case study of the passage of a frontal system during April 2006

摘要

Aerosol optical properties were measured by a POM‐01 MarkII Sun and sky photometer onboard the Dongfanghong Number 2 Research Ship on the Yellow Sea of China during the passage of a cold front surrounded by airborne dust that originated in Mongolia between 21 and 24 April 2006. The aerosol size distributions in clean marine environment were dominated by an accumulate mode with radius of 0.15 μ m and a coarse mode with radius of 4.5 μ m. The mean aerosol optical depth (AOD) and Ångström exponent were 0.26 and 1.26, respectively. In the frontal zone the aerosol size distribution was dominated by an accumulate mode with radius of 0.25 μ m and two coarse modes with radii of 1.69 and 7.73 μ m, and the AOD and Ångström exponent were 2.46 and 0.84, respectively. In the nonfrontal dust conditions, the concentration of coarse modes with radii of 2.5 μ m increased to a maximum of 0.3 μ m 3 / μ m 2 , and the mean AOD and Ångström exponent were 0.70 and 0.30, respectively. Aerosol Robotic Network (AERONET) observations combined with shipboard measurements reveal the decreasing concentration of dust aerosol during its transport from continent to Japan. The spatial distribution of dust aerosol was studied using the Aqua/Moderate Resolution Imaging Spectroradiometer (MODIS) and Aura/Ozone Monitoring Instrument (OMI) products. On 22 April, for frontal dust, their AOD and UV aerosol index (UVAI) increased with decreasing distance to the frontal line, peaked with values of 4.36 and 5.21 in the frontal zone, and decreased rapidly with increasing distance off the frontal line. On 23 April, nonfrontal dust showed the lower AOD and UVAI with peak values of 2.0 and 2.7, respectively.