Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

Vertical Distributions of Aerosol Optical Properties during Haze and Floating Dust Weather in Shanghai

A comparative study on the vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai was conducted based on the data obtained from a micro pulse lidar.There was a distinct difference in layer thickness and extinction coefficient under the two types of weather conditions.Aerosols were concentrated below 1 km and the aerosol extinction coefficients ranged from 0.25 to 1.50km^（-1） on haze days.In contrast,aerosols with smaller extinction coefficients（0.20 0.35 km^（-1）） accumulated mainly from the surface to 2 km on floating dust days.The seasonal variations of extinction and aerosol optical depth（AOD） for both haze and floating dust cases were similar greatest in winter,smaller in spring,and smallest in autumn.More than 85%of the aerosols appeared in the atmosphere below 1 km during severe haze and floating dust weather.The diurnal variation of the extinction coefficient of haze exhibited a bimodal shape with two peaks in the morning or at noon,and at nightfall,respectively.The aerosol extinction coefficient gradually increased throughout the day during floating dust weather.Case studies showed that haze aerosols were generated from the surface and then lifted up,but floating dust aerosols were transported vertically from higher altitude to the surface.The AOD during floating dust weather was higher than that during haze.The boundary layer was more stable during haze than during floating dust weather.

MAX-DOAS observation in the midlatitude marine boundary layer: Influences of typhoon forced air mass

As a passive remote sensing technique,MAX-DOAS method was widely used to investigate the vertical profiles of aerosol and trace gases in the lower troposphere.However,the measurements for midlatitude marine boundary layer are rarely reported,especially during the storm weather system.In this study,the MAX-DOAS was used to retrieve the aerosol,HCHO and NO_(2) vertical distribution at Huaniao Island of East China Sea in summer 2018,during which a strong tropical cyclone developed and passed through the measurement site.The observed aerosol optical depth(AOD),HCHO-and NO_(2)-VCDs(Vertical Column Density)were in the range of 0.19-0.97,(2.57-12.27)×10^(15) molec/cm^(2),(1.24-4.71)×10^(15) molec/cm^(2),which is much higher than remote ocean area due to the short distance to continent.The vertically resolved aerosol extinction coefficient(AEC),HCHO and NO_(2) presented the decline trend with the increase of height.After the typhoon passing through,the distribution of high levels of aerosol and HCHO stretched to about 1 kmand the abundances of the bottom layer were found as double higher than before,reaching 0.51 km^(−1) and 2.44 ppbv,while NO_(2) was still constrained within about 300 m with 2.59 ppbv in the bottom layer.The impacts of typhoon process forced air mass were also observed at the suburban site in Shanghai in view of both the aerosol extinction and chemical components.The different changes on air quality associated with typhoon and its mechanism in two different environments:coastal island and coastal city are worthy of further investigation as it frequent occurred in East Asia during summer and fall.