Seasonal Variations in High Arctic Free Tropospheric Aerosols Over Ny‐Ålesund, Svalbard, Observed by Ground‐Based Lidar. Issue 21 (12th November 2018)

• Record Type: Journal Article
• Authors: Shibata, T.; Shiraishi, K.; Shiobara, M.; Iwasaki, S.; Takano, T.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 21(2018)
• Page Start: 12, 353
• Page End: 12, 367
• Publication Date: 2018-11-12
• Subjects: high Arctic -- free troposphere -- aerosols -- seasonal variations -- lidar; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2018JD028973
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Free tropospheric aerosols over the high Arctic were observed by lidar for about 4 years from March 2014 at Ny‐Ålesund (78.9°N, 11.9°E). Vertical profiles of aerosol backscattering coefficients at two wavelengths, 532 and 1, 064 nm, and depolarization ratio at one wavelength, 532 nm, are derived from these observations. The aerosol backscattering coefficient, the particle depolarization ratio, and the color ratio (the ratio of the backscattering coefficients at the two wavelengths) are roughly proportional to mass concentration, nonsphericity, and size of the aerosol particles, respectively. The aerosol backscattering coefficients indicate that monthly averaged concentration of aerosols was largest in the lowest free troposphere at about 1 km in altitude and was an order of magnitude less at an about 10 km in altitude and that the concentration of aerosols was highest from late spring to summer and lowest from late summer to fall. The depolarization ratio was less than a few percent in the troposphere during the four observed years. The depolarization ratio and the color ratio were greatest from winter to spring and smallest from summer to fall. The maxima in the monthly averaged nonsphericity and size precede the maxima in the monthly averaged concentration by a few months, indicating a seasonal change in the morphology or the characteristics of the aerosol particles. The small particle depolarization ratio of less than a few percent is consistent with previous findings that Arctic free tropospheric aerosol particles in spring are composed of a mixture of liquid phase sulfate and soot particles. Key Points: The aerosol concentration in the free troposphere was highest in late spring and summer and lowest in late summer and fall The aerosol particle depolarization ratio in the free troposphere was largest in winter and spring and smallest in summer The values of the particle depolarization ratio are consistent with a previously found mixture of liquid phase sulfate and soot particles