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Influence of Ambient Relative Humidity on Seasonal Trends of the Scattering Enhancement Factor for Aerosols in Chiba, Japan

Category: Optical/Radiative Properties and Remote Sensing

Article In Press
DOI: 10.4209/aaqr.2018.07.0267
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Nofel Lagrosas 1,2, Gerry Bagtasa3, Naohiro Manago1, Hiroaki Kuze1

  • 1 Center for Environmental Remote Sensing (CEReS), Chiba University, Chiba 263-8522, Japan
  • 2 Manila Observatory, Ateneo de Manila University Campus, Quezon City 1108, Philippines
  • 3 Institute of Environmental Science and Meteorology, University of the Philippines Diliman, Quezon City 1101, Philippines

Highlights

  • Monthly trends of ambient f(RH) are determined from ground instruments.
  • Monthly ambient f(RH) values with RH are modeled.
  • Ambient f(RH) measurements are higher than f(RH) values from sampling measurements.
  • Scattering enhancement ratios from dusts have low response to RH.

Abstract

In this study, we used ground instruments, namely, a visibility meter, an integrating nephelometer, an aethalometer, a lidar, and a weather monitor, to measure the scattering enhancement factor, f(RH), which quantifies the effect of ambient relative humidity (RH) on aerosol light-scattering, and to generate a model of its annual variation in the city of Chiba, Japan. First, the f(RH) values were calculated with chemical analysis data. Second, visibility-meter and aethalometer data were used to model the monthly trends of f(RH) at 550 nm. The f(RH) values were higher during summer than during the other three seasons, which can be attributed to the general pattern of the regional climatology as well as the loading of different particle types into the lower troposphere. Third, the f(RH) values at 532 nm were obtained from lidar and aethalometer measurements. Low and constant f(RH) values were observed during November, whereas higher and increasing f(RH) values were observed during May. Also, dust events during March 2015 showed decreasing f(RH) with increasing RH .

Keywords

Scattering enhancement factor Relative humidity Scattering coefficient Dust aerosol Angström coefficient


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