Optical properties and size distribution of dust aerosols over the Tengger Desert in Northern China

A field experiment was performed during 1 April–30 September 2001 in the southeast Tengger Desert in Northern China to measure the solar radiant flux by a solar direct radiometer and a multi-wavelength sun-photometer. The observation and research results are as follows. On fine days, dust aerosols attenuate the direct solar radiant flux by 2.6–47.0%, with an average of 16.9%. On dusty days, dust aerosols attenuate the direct solar radiant flux by 10–90%, with an average of 38%. The mean atmospheric turbidity for broadband (300–4000 nm) flux is 0.26 for fine days and 0.74 for dusty days. Under the typical background, floating dust, and dust storm weather conditions, the aerosol optical depths (AODs; at 550 nm) are about 0.1, 0.9, and 2.0, and the Ångström exponents are about 2.0, 0.38, and −0.24, respectively. The mean AOD of the examples is 0.66, and 0.87 for the Ångström exponents. On dusty days, the aerosol number concentration is 2–10 times higher than that on fine days. The aerosol size distribution is a multi-normal distribution during dusty conditions, while the aerosol size distribution is a logarithmic normal distribution during fine weather.