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.

Graphical abstract

摘要

基于2014年夏季地基观测数据分析了华北平原忻州郊区站点辐射和气溶胶特性。结果表明, 晴空和云天条件下的长波辐射最大值和最小值分别出现在地方时17:00 (392.6 W m⁻²) 和06:00 (360.0 W m⁻²); 总辐射, 直接辐射, 散射辐射, 光合有效辐射, 紫外A和紫外B辐射最大值出现在~13:00。气溶胶粒径呈双峰结构, 粗细模态峰值分别为~5微米和0.1–0.2微米。气溶胶光学厚度大于0.4 (400 nm) 时主要为黑碳覆盖粗粒子类型气溶胶 (85.7%), 使得气溶胶单次散射反照率 (0.81) 低于华北平原其他测站典型值 (~0.90); 消光和吸收埃斯特朗指数平均值分别为1.14 ± 0.15和0.58 ± 0.28; 地表气溶胶直接辐射强迫瞬时平均值为−138.9 ± 33.0 W m⁻²。

KEYWORDS:

• Radiation
• aerosols
• suburban site
• North China Plain

关键词:

• 辐射
• 气溶胶
• 郊区站点
• 华北平原

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key R&D Program of China [grant number 2017YFA0603504] and the National Natural Science Foundation of China [grant number 41875183].