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Investigation of Aerosol Optical Depth (AOD) and Ångström Exponent over the Desert Region of Northwestern China Based on Measurements from the China Aerosol Remote Sensing Network (CARSNET)

Category: Optical/Radiative Properties and Remote Sensing

Volume: 15 | Issue: 5 | Pages: 2024-2036
DOI: 10.4209/aaqr.2014.12.0326
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Jie Yu1,2, Huizheng Che 2,3, Quanliang Chen1, Xiangao Xia4,5, Hujia Zhao6, Hong Wang2, Yaqiang Wang2, Xiaoye Zhang2, Guangyu Shi7

  • 1 Plateau Atmospheric and Environment Key Laboratory of Sichuan Province, College of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China
  • 2 Key Laboratory for Atmospheric Chemistry, Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, CMA, Beijing 100081, China
  • 3 Jiangsu Collaborative Innovation Center of Climate Change, Nanjing, 210093, China
  • 4 Laboratory for Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 5 Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China
  • 6 Institute of Atmospheric Environment, China Meteorological Administration, Shenyang 110016, China
  • 7 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China

Highlights

AOD of northwestern China (NWC) was investigated from CARSNET observation.
Different AOD variations were found over rural and urban sites of NWC.
Both mineral dust and anthropogenic aerosols contribute the AOD variation over NWC.


Abstract

Aerosols at ten sites in northwestern China are classified in this study: (1) by using the aerosol optical depth (AOD), the Ångström exponent (α) and the Ångström exponent difference (δα); and (2) by using the total means of AOD440nm and α. The seasonal variations of the AOD and α show that the maximum AODs occur in spring, except at Urumqi and Lanzhou. The seasonal mean α values are lower than 0.80 in all four seasons at Tazhong, Hotan, Hami, Ejina, Dunhuang, Minqin, and Jiuquan, but higher than 0.80 in winter at Urumqi, Lanzhou and Yinchuan. The first classification method shows that coarse mode particles are found at all ten sites, but that fine mode growth only happens at Urumqi, Lanzhou, and Yinchuan. The relationship between AOD440nm and α show that α smaller than 0.80 decrease with increasing AOD440nm at all ten sites. Aerosols are classified into four types (Type I–IV) according to the total mean τ440 (τ̅440) and total mean Ångström exponent () of each site. Aerosols with a τ440 smaller than τ̅440, but greater than or equal to (τ440τ̅440; α) are classified as Type I; aerosols with τ440 ≥ τ̅440 and α are Type II; those with τ440 < and α < are Type III; and those with τ440 ≥ τ̅440 and α < are Type IV. The second aerosol classification method shows that Type I and Type III aerosols are the most common at all ten sites. Type II aerosols are the least at Tazhong and Hotan, but are the most common at Urumqi, Lanzhou, and Yinchuan. On the contrary, Type IV aerosols are the most common at Tazhong and Hotan, but are the least common at Urumqi, Lanzhou and Yinchuan.

Keywords

Aerosol optical depth (AOD) Ångström exponent Aerosol classification Northwestern China


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