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Lanzhou University (2022)

Vertical Distribution and Radiative Effects of Absorbing Aerosols in A Typical City in the Semi-arid Region of Northwest China

关勖

Titre : Vertical Distribution and Radiative Effects of Absorbing Aerosols in A Typical City in the Semi-arid Region of Northwest China

Auteur : 关勖

Grade : Doctoral Dissertation 2022

Université : Lanzhou University

Résumé partiel
Atmospheric aerosols are provided with the ability to absorb and scatter solar radiation and affect the radiation balance of the Earth-atmosphere system directly or indirectly through aerosol-radiation and aerosol-cloud interactions.Absorbing aerosols can heat the atmosphere by absorbing solar radiation,causing complex and important effects on the boundary layer processes,the weather and climate,and have long been one of the hot issues for research in atmospheric science.However,given shortcomings in both their observations and simulations,there are still large uncertainties in the assessment of aerosol radiation effects,with the simulation capability of numerical atmospheric models limited by difficulties in quantifying its key role.Absorbing aerosols and their vertical distribution play a crucial role in accurately quantifying their direct radiative effects.It is consequently of great scientific value to carry out research on their optical properties and vertical distribution so as to accurately calculate the aerosol radiative forcing.Arid and semi-arid regions in China,mainly in the western part,account for about 40%of the total land area,and are considerably sensitive to the response of global climate change,while climate change in these regions places essential and profound effects on water resources,agriculture,ecological environment and extreme weather.The role played by absorbing aerosols in air pollution and aerosol radiative forcing is particularly highlighted in Lanzhou,a typical city in the semi-arid region of northwest China featured by its strong radiation,heavy pollution and complex sources of absorbing aerosols.First,the contributions of different types of absorbing aerosols to the aerosol absorption coefficients and the changes of aerosol absorption under different levels of fine mode particulate matter(PM2.5)pollution were analyzed by virtue of comprehensive observations of aerosol physicochemical properties from November 2019 to November 2020 at the Lanzhou Atmospheric Component Super Monitoring Station(LACMS).Then,to obtain the boundary layer and aerosol vertical sounding datasets with high spatial and temporal resolution,and to deeply analyze the characteristics and influencing factors of aerosol absorption properties and vertical distribution,a tethered air-boat integrated sounding experiment was conducted at the Semi-Arid Climate and Environment Observatory of Lanzhou University(SACOL)in the winter of 2018 and 2019.Finally,the vertical distributions of the observed aerosol parameters are input into the SBDART radiative transfer model to calculate the vertical profile of radiative heating rate and radiative forcing,through which,more realistic aerosol radiative heating rate and direct radiative forcing are obtained,the uncertainty in the calculation of aerosol radiative effects is reduced,and the key role of absorptive aerosols is quantified.

Mots clés : Absorbing aerosols ;optical properties ;single scattering albedo ;vertical distribution ;radiation effects ;

Présentation (CNKI)

Page publiée le 15 octobre 2022