Abstract
The atmospheric boundary layer (ABL), an atmospheric region near the Earth’s surface, is affected by surface forcing and is important for studying air quality, climate, and weather forecasts. In this study, long-term urban nocturnal boundary layers (NBLs) were estimated by an elastic backscatter light detection and ranging (LiDAR) with various methods in Wuhan (30.5° N, 114.4° E), a city in Central China. This study aims to explore two ABL research topics: (1) the relationship between NBL height (NBLH) and near-surface parameters (e.g., sensible heat flux, temperature, wind speed, and relative humidity) to elucidate meteorological processes governing NBL variability; and (2) the influence of NBLH variations in surface particulate matter (PM) in Wuhan. We analyzed the nocturnal ABL-dilution/ABL-accumulation effect on surface particle concentration by using a typical case. A long-term analysis was then performed from 5 December 2012–17 June 2016. Results reveal that the seasonal averages of nocturnal (from 20:00 to 05:00 next day, Chinese standard time) NBLHs are 386 ± 161 m in spring, 473 ± 154 m in summer, 383 ± 137 m in autumn, and 309 ± 94 m in winter. The seasonal variations in NBLH, AOD, and PM2.5 display a deep (shallow) seasonal mean NBL, consistent with a small (larger) seasonal mean PM2.5 near the surface. Seasonal variability of NBLH is partly linearly correlated with sensible heat flux at the surface (R = 0.72). Linear regression analyses between NBLH and other parameters show the following: (1) the positive correlation (R = 0.68) between NBLH and surface temperature indicates high (low) NBLH corresponding to warm (cool) conditions; (2) the slight positive correlation (R = 0.52) between NBLH and surface relative humidity in Wuhan; and (3) the weak positive correlation (R = 0.38) between NBLH and wind speed inside the NBL may imply that the latter is not an important direct driver that governs the seasonal variability of NBLH.
Highlights
The atmospheric boundary layer (ABL), an atmospheric region near the Earth’s surface, is affected by surface forcing, ranging from 100 m to a few kilometers and plays an important role in the exchange of matter and energy between the surface and the free atmosphere [1]
Conditions; (2) the slight positive correlation (R = 0.52) between NBL height (NBLH) and surface relative humidity in Wuhan; and (3) the weak positive correlation (R = 0.38) between NBLH and wind speed inside the nocturnal boundary layers (NBLs) may imply that the latter is not an important direct driver that governs the seasonal variability of NBLH
We present a long-term analysis on the variability of main parameters of the NBLH diurnal cycle
Summary
The atmospheric boundary layer (ABL), an atmospheric region near the Earth’s surface, is affected by surface forcing, ranging from 100 m to a few kilometers and plays an important role in the exchange of matter and energy between the surface and the free atmosphere [1]. The top of the boundary layer exhibits a blocking effect on surface pollutant dispersion, resulting in high concentrations of near-surface contaminants [2,3,4]. An accurate study of the ABL height on diurnal, seasonal, Int. J. Res. Public Health 2016, 13, 1071; doi:10.3390/ijerph13111071 www.mdpi.com/journal/ijerph
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