Properties of summer radiation and aerosols at Xinzhou, a suburban site on the North China Plain

Abstract

The properties of summer radiation and aerosols were studied at Xinzhou, a suburban site on the North China Plain (NCP) by using ground-based measurements in 2014. The radiation detections under clear and cloudy skies showed that longwave radiation presented a sigmate pattern, with a maximum of 392.6 W m−2 at 1700 local standard time (LST) associated with the cloud radiative forcing, and a minimum of 360.0 W m−2 at 0600 LST when the lowest surface temperature (17.1°C) occurred. Solar radiation, including global, direct, diffuse, photosynthetically active, ultraviolet-A, and ultraviolet-B, exhibited a single peak at ~1300 LST. A bimodal size distribution, with fine mode aerosols showing a peak between 0.1 and 0.2 μm and coarse mode aerosols showing a peak at ~5 μm, was observed at Xinzhou. The dominant aerosol type was black carbon coating on coarse particles (85.7%) for the cases with aerosol optical depth at 400 nm (AOD) greater than 0.4, leading to a lower single scattering albedo (0.81) than the typical value (~0.90) at the other stations on the NCP. The mean values of EAE and AAE (extinction and absorption Ångström exponent, respectively) were 1.14 ± 0.15 and 0.58 ± 0.28 for the aerosol measurements. The average of instantaneous aerosol direct radiative forcing at the bottom of the atmosphere was −138.9 ± 33.0 W m−2 for the cases with AOD > 0.4. The results in this study are expected to improve understanding at suburban sites on the NCP of aerosol properties and their impacts on regional radiation budgets.

Keywords

• radiation
• aerosols
• suburban site
• north china plain