Continuous day and night aerosol optical depth observations in the Arctic between 1991 and 1999

Abstract

[1] Ground-based measurements of total aerosol optical depth (AOD), e.g., tropospheric and stratospheric aerosol, have been established at the Koldewey station in Ny-Å lesund, Spitzbergen (Norway, 78.95°N, 11.93°E), since 1991. The basic instrumentation is a multichannel photometer using sunlight. New instruments have been developed to extend the measurement period to polar night. The new instruments are a Sun and Moon photometer (1995) and a star photometer (1996). The instruments and applied methods for aerosol optical depth retrieval for Sun, Moon, and star measurements are briefly discussed. The year-round measurements made it possible to study in detail the interannual and seasonal variations of total AOD in the Arctic. The seasonal variation and the long-term trend of tropospheric aerosol optical depth are discussed, taking into account the stratospheric AOD measured by the Stratospheric Aerosol and Gas Experiment (SAGE II). The lowest tropospheric aerosol optical depth values occur in late summer and fall. Each year, strong Arctic haze events were recorded not only during spring but also in late winter as the first star photometer measurements clearly show. Five-day backward trajectories were used to analyze possible sources for high tropospheric AOD. Elevated tropospheric aerosol optical depth appears for northeasterly, easterly, or westerly winds. Finally, the long-term changes of tropospheric AOD have been assessed. A small positive trend of the tropospheric aerosol optical depth is found for the vicinity of Spitzbergen during the measurement period.

An update on polar aerosol optical properties using POLAR-AOD and other measurements performed during the International Polar Year

“…3 that the Gaussian curve centred at AOD(500 nm) ¼ 0.045 shows (i) a right wing with 10% half-width at AOD(500 nm) ¼ 0.08, giving a statistical indication that the summer BG values of AOD(500 nm) should all be smaller than 0.08, and (ii) a long-tailed right wing, which is presumably given by the relatively high number of FFS particle transport episodes occurring in the Svalbard region. The estimate of a threshold value of 0.08 for the BG aerosol cases agrees very well with the evaluations of AOD(532 nm) performed by Herber et al (2002), who found a mean summer value of AOD ¼ 0.046 AE 0.012 at this wavelength, with more than 90% of the AOD(532 nm) measurements ranging between 0.022 and 0.070 during summer. On the basis of these evaluations, it was decided to assume a threshold value of 0.08 to distinguish the summer BG values of AOD(500 nm) from the summer values affected by FFS extinction.…”

Springtime Arctic aerosol: Smoke versus haze, a case study for March 2008

“…drschulz.com/cnt/) was used. These instruments are able to measure aerosol optical depth (AOD or s A ) at 17 wavelengths l in the range of 350 nme1050 mm (Herber et al, 2002). The AOD is calculated by eqn.…”

Interpretation of Arctic aerosol properties using cluster analysis applied to observations in the Svalbard area

“…This is in agreement with cluster 3 of the ASTAR database. The determined mean values for cluster 2 are in the range of AOD measurements reported from other authors for high Arctic aerosol loadings (Shaw, 1975;Freud, 1983;Dutton et al, 1989;Leiterer et al, 1992;Herber et al, 2002;Eneroth et al, 2003).…”

“…First, an 11-yr observation record of integrated aerosol optical depth (AOD) from 1991 to 2001 from a sun photometer (polar day) and a star photometer (polar night) at Ny-Ålesund (78 • 55 N, 11 • 53 E) and second, the 3-yr data record of the scattering coefficient from Zeppelin Mountain (78 • 54 N, 11 • 53 E). The AOD measurements are described in detail in Herber et al (2002) and were provided as daily mean values. The scattering coefficients were averaged to daily mean Abbreviations: IN, integrating nephelometer; OPC, optical particle counter; DMPS, differential mobility particle sizer; PSAP, particle soot/absorption photometer; RH, relative humidity; PNC, particle number concentration.…”

“…Some long-term records of Arctic aerosol properties are available (e.g. Bodhaine and Dutton, 1993;Polissar et al, 1999;Herber et al, 2002;Quinn et al, 2002).…”