Below-Cloud Aerosol Scavenging by Different-Intensity Rains in Beijing City
- 16 Downloads
Below-cloud aerosol scavenging process by precipitation is important for cleaning the polluted aerosols in the atmosphere, and is also a main process for acid rain formation. However, the related physical mechanism has not been well documented and clarified yet. In this paper, we investigated the below-cloud PM2.5 (particulate matter with aerodynamic diameter being 2.5 μm or less) scavenging by different-intensity rains under polluted conditions characterized by high PM2.5 concentrations, based on in-situ measurements from March 2014 to July 2016 in Beijing city. It was found that relatively more intense rainfall events were more efficient in removing the polluted aerosols in the atmosphere. The mean PM2.5 scavenging ratio and its standard deviation (SD) were 5.1% ± 25.7%, 38.5% ± 29.0%, and 50.6% ± 21.2% for light, moderate, and heavy rain events, respectively. We further found that the key impact factors on below-cloud PM2.5 scavenging ratio for light rain events were rain duration and wind speed rather than raindrop size distribution. However, the impacts of rain duration and wind speed on scavenging ratio were not important for moderate and heavy rain events. To our knowledge, this is the first statistical result about the effects of rain intensity, rain duration, and raindrop size distribution on below-cloud scavenging in China.
Key wordsPM2.5 below-cloud scavenging rain intensity impact factors
Unable to display preview. Download preview PDF.
The authors highly appreciate the constructive comments from the Editor and two anonymous reviewers.
- American Meteorological Society, cited 2019: “Rain”. Glossary of Meteorology. Available online at https://doi.org/glossary.ametsoc.org/wiki/Rain.
- Bae, S. Y., C. H. Jung, and Y. P. Kim, 2006: Development and evaluation of an expression for polydisperse particle scavenging coefficient for the below-cloud scavenging as a function of rain intensity using the moment method. J. Aerosol Sci., 37: 1507–1519, doi: 10.1016/j.jaerosci.2006.02.003.CrossRefGoogle Scholar
- Bloemink, H. I., and E. Lanzinger, 2005: Precipitation type from the Thies disdrometer. Technical Conference on Meteorological and Environmental Instruments and Methods of Observation. Bucharest, Romania: WMO, 1–7.Google Scholar
- Guo, L. H., 2016: Haze and health. Natl. Sci. Rev., 3: 412–413, doi: 10.1093/nsr/nww071.Google Scholar
- Pruppacher, H. R., and J. D. Klett, 1997: Microphysics of Clouds and Precipitation. Kluwer Academic, Dordrecht, 720–730.Google Scholar
- Qian, Y., D. P. Kaiser, L. R. Leung, et al., 2006: More frequent cloud-free sky and less surface solar radiation in China from 1955 to 2000. Geophys. Res. Lett., 33, L01812, doi: 10.1029/2005gl024586.Google Scholar
- Quérel, A., P. Lemaitre, M. Monier, et al., 2014a: An experiment to measure raindrop collection efficiencies: Influence of rear capture. Atmos. Meas. Tech., 7: 1321–1330, doi: 10.5194/amt-7-1321-2014.Google Scholar
- Quérel, A., M. Monier, A. I. Flossmann, et al., 2014b: The importance of new collection efficiency values including the effect of rear capture for the below-cloud scavenging of aerosol particles. Atmos. Res., 142: 57–66, doi: 10.1016/j.atmosres. 2013.06.008.Google Scholar
- Seinfeld, J. H., and S. N. Pandis, 2006: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. Wiley & Sons, Hoboken, NJ, 932 pp.Google Scholar
- Wang, X., L. Zhang, and M. D. Moran, 2011: On the discrepancies between theoretical and measured below-cloud particle scavenging coefficients for rain—a numerical investigation using a detailed one-dimensional cloud microphysics model. Atmos. Chem. Phys., 11: 11859–11866, doi: 10.5194/acp-11-11859-2011.CrossRefGoogle Scholar