Abstract
Reynolds stress anisotropy is estimated from the stress spheroids, based on 20 Hz ultrasonic anemometer measurements, performed in the coastal area of northern France, over a 1.5-year long period. Size and shape variation (i.e., prolate, oblate, disk, rod, etc.) of stress spheroids are used for the characterization of energy redistribution by turbulent eddies. The sea-breeze (SB) events were identified using a change in wind direction from seaward (SWD) to landward (LWD) during the day time. We found that the LWD wind creates more turbulent anisotropic states than SWD wind. The prolate-shaped stress spheroids correspond to small-scale turbulence observed during LWD wind, while oblate spheroids are found during SWD winds. Moreover, it was found that during LWD winds, large turbulence kinetic energy (TKE) in the flow field produces large stress spheroids. On the contrary, during SWD winds, a smaller level of TKE is responsible for small-size stress spheroid formation. The average volume of the corresponding Reynolds stress spheroids during the LWD is 13% larger than that of during SWD wind.
Highlights
Meteorological phenomena affect the air quality within the industrial and urban areas near the shoreline [1,2,3]
Injection of humid cold air from the maritime boundary layer into the ascending inland air leads to the generation of convective clouds, which can be a cause of strong thunderstorms and convective precipitation [6]
Baker et al [7] revealed that SB-initiated precipitation in a coastal area affects the surrounding air quality
Summary
Meteorological phenomena (such as sea-breeze and nocturnal low-level jets) affect the air quality within the industrial and urban areas near the shoreline [1,2,3]. A shift in wind direction from offshore to onshore was identified from an alteration of the sign of SB component (SBC) from negative to positive as: SBC = U × sin(0 − W ), where W is the wind direction and U is the horizontal wind speed [1,22] (zero angle corresponds to the wind direction from the north with po3siotfi1v3e values measured clockwise). A rapid change in wind direction, speed, and temperature during the SB days may create a difference in turbulence within the lower troposphere in the coastal regions. We have distinguished SWD and LWD during the SB days and performed an estimation of turbulence parameters for these two stages of wind
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