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Lanzhou University (2012)

Measurements of Aerosol Radiative Properties Over Semi-arid Region of the Loess Plateau

周碧; Zhou Bi

Titre : Measurements of Aerosol Radiative Properties Over Semi-arid Region of the Loess Plateau

Auteur : 周碧; Zhou Bi

Grade : Doctoral Dissertation 2012

Université : Lanzhou University

Résumé partiel
Atmospheric aerosol, as a crucial composition of atmosphere affects regional and global climate change through its direct, indirect, and semi-direct radiative effects modulation of the surface and atmospheric radiation budgets.It is a key factor of aerosol radiative forces as working on climate change, and also for climate change’s uncertainty. The largest uncertainty of aerosol radiative effect has also been lack of fully understanding its space and temporal distribution, physical, and optical characteristics. The semi-arid region of the Loess Plateau with especial underlying surface is a transition area from arid to semi-wet region, and its climate is extremely vulnerable. However, only a few observatories are operating in the region, resulting in a lack of measurement and analysis of aerosol. The long continuous measurement of aerosol from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) can provide significant scientific support for understanding the space and temporal distribution, physical, and optical characteristics of aerosol in this region, and also provide basic theoretical proof for deeply knowing aerosol radiative effect and globle climate change.The vertical distribution and temporal evolution of aerosol over the semi-arid region of the Loess Plateau are analyzed by using the data of the Mie scattering lidar (CE-370-2) and the dual-wavelength polarization lidar (L2S-SM II) from SACOL. Then the properties of concentration and size of aerosol, PM10concentration, airflow path, and the relationship between PM10concentration and meteorological elements are presented based on the measurements of particle sizer (APS-3321)and PM10particulate monitor (TEOM RP1400a) combining with the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT-4) model and National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis project data (2.5°×2.5°).Finally, using Mie theory in combination with the data of the number concentration size distribution of aerosol and the measurement of the nephelometer, the distributions of aerosol scattering coefficient with particle size in dust process and coal combustion period are calculated and analysed. Some valuable results are retrieved. The main results are as follows.(1)Using the observational data of the lidar (CE-370-2) since2006to2011,the results from the retrieval show that aerosol optical depth (AOD) during March to May and November to December is larger, and AOD during June to October is small. AOD in springtime is the largest with the value of0.42, and AODs in winter and fall are larger with the values of0.36and0.30respectively. AOD in summer is the least with the value of0.21.The analysis of frequency shows that AOD mostly ranges0.3around, and has significant seasonal differences. Aerosol in this region mostly distributes below2km, and has absolute dominance below1km. In daytime, aerosol extinction coefficient within the lowest troposphere (below2.0km) is large, and that in nighttime is small. The vertical distribution height of aerosol in summer is the highest, next in fall, and the height in winter is very low. In dust processes, aerosol mostly distributes below3km, and in strong dust events, aerosol can penetrate up to6km or more than6km.The temporal evolution trend of dust AOD is similar to that of PM10mass concentration, and their correlation coefficient is0.75. AOD (ranging from0.2to0.5) in coal combustion period is lager than that of background (ranging from0.08to0.15), and its diurnal variation presents dual-peaks structure, aerosol mostly distributing below1km.(2) The polarization lidar system can distinctly distinguish aerosol and cloud, and roughly identify ice cloud, water cloud and mixed cloud, based on the measurement of dual-wavelength polarization lidar (L2S-SM II).

Mots clés : Lidar; Aerosol; Optical depth; Extinction coefficient; Depolarization ratio; sizedistribution; Gaussian distribution;

Présentation (CNKI)

Page publiée le 12 septembre 2014, mise à jour le 11 janvier 2018