Observation of wind shear during evening transition and an estimation of submicron aerosol concentrations in Beijing using a Doppler wind lidar |
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| Authors: | Yong Chen Junling An Xiquan Wang Yele Sun Zifa Wang Jing Duan |
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| Affiliation: | 1.State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing,China;2.Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment,Chinese Academy of Sciences,Xiamen,China;3.Chinese Academy of Meteorological Sciences,Beijing,China |
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| Abstract: | The wind speed and direction measured over six months by a Doppler wind lidar (Windcube-8) were compared with wind cup anemometers mounted on the 325-m Beijing meteorological tower (BMT). Five mountain–plain wind cases characterized by wind direction shear were selected based on the high-frequency (1.1 s) wind profile of the Windcube-8 and analyzed with 1-h mesoscale surface weather charts. Also analyzed was the relationship between in-situ PM1 (aerodynamic diameter ≤ 1 μm) concentrations measured at 260 m on BMT and the carrier-to-noise ratio (CNR) of the co-located Windcube-8. The results showed that the 10-min averaged wind speed and direction were highly correlated (R = 0.96–0.99) at three matched levels (80, 140, and 200 m). The evening transition duration was 1–3 h, with an average wind speed of 1 m s–1 at 80 m above the ground. In addition, there was a zero horizontal-wind-speed zone along the wind direction shear line, and in one case, the wind speed was characterized by a Kelvin–Helmholtz gravity wave. The variability of the PM1 concentrations was captured by the CNR of the Windcube-8 in a fair weather period without the long-range transport of dust. |
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