Continuous vertical aerosol profiling with a multi-wavelength Raman polarization lidar over the Pearl River Delta, China

Abstract. A dataset of particle optical properties of the highly polluted atmosphere over the Pearl River Delta (PRD), Guangzhou, China, is presented in this paper. The data were derived from the measurements of a multi-wavelength Raman and depolarization lidar PollyXT and a co-located AERONET sun photometer. The measurement campaign was conducted from November 2011 to mid-June 2012. These are the first Raman lidar measurements in the PRD that lasted for several months. A mean value of aerosol optical depth (AOD) of 0.54 ± 0.33 was observed by the sun photometer at 500 nm in the polluted atmosphere over this megacity for the whole measurement period. The lidar profiles frequently show lofted aerosol layers, which reach altitudes of up to 2 to 3 km and, especially during the spring season, up to 5 km. These layers contain between 12 and 56 % of the total AOD, with the highest values in spring. The aerosol types in these lofted layers are classified by their optical properties. The observed lidar ratio values range from 30 to 80 sr with a mean value of 48.0 ± 10.7 sr at 532 nm. The linear particle depolarization ratio at 532 nm lies mostly below 5 %, with a mean value of 3.6 ± 3.7 %. The majority of the Angstrom exponents lie between 0.5 and 1.5, indicating a mixture of fine- and coarse-mode aerosols. These results reveal that mostly urban pollution particles mixed with particles produced from biomass and industrial burning are present in the atmosphere above the Pearl River Delta. Trajectory analyses show that these pollution mixtures arise mainly from local and regional sources.

[1]  A. Ansmann,et al.  Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. , 1992, Applied optics.

[2]  V. Freudenthaler,et al.  Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006 , 2009 .

[3]  R. Steven Nerem,et al.  The 2011 La Niña: So strong, the oceans fell , 2012 .

[4]  F. G. Fernald.  Analysis of atmospheric lidar observations: some comments. , 1984, Applied optics.

[5]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[6]  Albert Ansmann,et al.  The automated multiwavelength Raman polarization and water-vapor lidar PollyXT: The neXT generation , 2016 .

[7]  A. Ansmann,et al.  Middle East versus Saharan dust extinction-to-backscatter ratios , 2015 .

[8]  Nobuo Sugimoto,et al.  Continuous Observations of Aerosol Profiles with a Two-Wavelength Mie-Scattering Lidar in Guangzhou in PRD2006 , 2009 .

[9]  N. Sugimoto,et al.  Vertical distribution of water-soluble, sea salt, and dust aerosols in the planetary boundary layer estimated from two-wavelength backscatter and one-wavelength polarization lidar measurements in Guangzhou and Beijing, China , 2010 .

[10]  Charles A. Trepte,et al.  Comparison of CALIPSO aerosol optical depth retrievals to AERONET measurements, and a climatology for the lidar ratio of dust , 2012 .

[11]  V. Freudenthaler,et al.  Towards an aerosol classification scheme for future EarthCARE lidar observations and implications for research needs , 2015 .

[12]  Xiuji Zhou,et al.  Long-term trend of visibility and its characterizations in the Pearl River Delta (PRD) region, China , 2008 .

[13]  O. Dubovik,et al.  Variability of aerosol and spectral lidar and backscatter and extinction ratios of key aerosol types derived from selected Aerosol Robotic Network locations , 2005 .

[14]  Albert Ansmann,et al.  Particle backscatter, extinction, and lidar ratio profiling with Raman lidar in south and north China. , 2007, Applied optics.

[15]  Albert Ansmann,et al.  High aerosol load over the Pearl River Delta, China, observed with Raman lidar and Sun photometer , 2005 .

[16]  Zhaoyan Liu,et al.  Seasonal Characteristics of Spherical Aerosol Distribution in Eastern Asia: Integrated Analysis Using Ground/Space-Based Lidars and a Chemical Transport Model , 2011 .

[17]  D. Althausen,et al.  Aerosol optical properties observed by combined Raman‐elastic backscatter lidar in winter 2009 in Pearl River Delta, south China , 2014 .

[18]  Kengo Iokibe,et al.  Ground‐based network observation of Asian dust events of April 1998 in east Asia , 2001 .

[19]  R. Engelmann,et al.  An overview of the first decade of Polly NET : an emerging network of automated Raman-polarization lidars for continuous aerosol profiling , 2016 .

[20]  J. Klett.  Stable analytical inversion solution for processing lidar returns. , 1981, Applied optics.

[21]  Riko Oki,et al.  The EarthCARE Satellite: The Next Step Forward in Global Measurements of Clouds, Aerosols, Precipitation, and Radiation , 2015 .

[22]  Zhanqing Li,et al.  Seasonal variations in aerosol optical properties over China , 2008 .

[23]  A. Ansmann,et al.  Aerosol-type-dependent lidar ratios observed with Raman lidar , 2007 .

[24]  Albert Ansmann,et al.  Portable Raman Lidar Polly XT for Automated Profiling of Aerosol Backscatter, Extinction, and Depolarization , 2009 .

[25]  Y. H. Zhang,et al.  Strong particle light absorption over the Pearl River Delta (south China) and Beijing (north China) determined from combined Raman lidar and Sun photometer observations , 2006 .

[26]  C. Chan,et al.  Air pollution in mega cities in China , 2008 .

[27]  R. Draxler,et al.  NOAA’s HYSPLIT Atmospheric Transport and Dispersion Modeling System , 2015 .

[28]  Zhengqiang Li,et al.  Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements , 2009 .