Research on Atmospheric Diffusion Condition Parameters Based on Wind Profile Radar
To harness the benefits derived from the high spatial and temporal resolution of vertically continuous wind profile radar observations and exploit its capacity for monitoring atmospheric diffusion conditions during pollution events,this paper calculates parameters such as vertical wind shear,divergence,vorticity,and boundary layer ventilation by utilising 13 sets of wind profile radar data in Hebei Province.The computations are based on the principles of atmospheric dynamics and the dynamic conditions inversion algorithm.By comparing the results with sounding data and analysing them in conjunction with near-surface PM2.5 concentration,the four parameter algorithms are examined.The results show that the variations and characteristics of the inversion products are reasonably represented,effectively reflecting the evolution of atmospheric pollution conditions.However,due to disparities in resolution and detection methods among different observational datasets,substantial discrepancies exist in the results derived from various datasets.Therefore,it is imperative to maintain data consistency when conducting analyses.Taking the regional PM2.5 pollution event in Hebei from 9 to 11 November 2022 as an example,through multi-site joint application,the evolution characteristics of the four products in this process indicate the following:during the pollution accumulation process,vertical wind shear below 3 km decreased from the diagonal to the lower right corner,with most values below 5 m/(s·km).Vorticity and divergence values were mostly within 20 × 10-5 s-1,and less than 15 × 10-5 s-1for distances below the 950 hPa isobaric surface,indicating a stable meteorological situation.Boundary layer ventilation was less than 3000 m2/s.Before the pollutant dispersal,vertical wind shear increased to above 10 m/(s.km)throughout the entire layer.The region with wind shear greater than 10 m/(s.km)between 2-3 km height and 0-1 km above the ground showed the strongest sensitivity to pollutant dispersion.Vorticity and divergence above the 850 hPa isobaric surface first increased to above 30 × 10-5 s-1,and when vorticity and divergence above 20 × 10-5 s-1 extended within the boundary layer,the near-surface PM2.5 concentration rapidly decreased.When boundary layer ventilation reached 4000 m2/s,pollutant concentrations met the standards.The values at downstream stations increased significantly with a noticeable delay along the cold air transmission path,thus multi-station joint analysis could be used for pollution dispersion forecasts at downstream sites.By comparing with the data of airborne sounding and near-surface wind field,the wind profile data had obvious advantages of high temporal and spatial resolution.However,these parameters exclusively responded to atmospheric dynamic conditions and did not account for the evolving principles governing the weather system.The application was most effective when used in conjunction with the prevailing circulation patterns and the diagnostic analysis of the weather system.
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