Deposition velocity of ultrafine particles measured with the Eddy‐Correlation Method over the Nansen Ice Sheet (Antarctica)

Abstract

[1] This work reports an analysis of the concentration, size distribution, and deposition velocity of atmospheric particles over snow and iced surfaces on the Nansen Ice Sheet (Antarctica). Measurements were performed using the eddy-correlation method at a remote site during the XXII Italian expedition of the National Research Program in Antarctica (PNRA) in 2006. The measurement system was based on a condensation particle counter (CPC) able to measure particles down to 9 nm in diameter with a 50% efficiency and a Differential Mobility Particle Sizer for evaluating particle size distributions from 11 to 521 nm diameter in 39 channels. A method based on postprocessing with digital filters was developed to take into account the effect of the slow time response of the CPC. The average number concentration was 1338 cm −3 (median, 978 cm; interquartile range, 435-1854 cm −3). Higher concentrations were observed at low wind velocities. Results gave an average deposition velocity of 0.47 mm/s (median, 0.19 mm/s; interquartile range, −0.21 −0.88 mm/s). Deposition increased with the friction velocity and was on average 0.86 mm/s during katabatic wind characterized by velocities higher than 4 m/s. Observed size distributions generally presented two distinct modes, the first at approximately 15-20 nm and the second (representing on average 70% of the total particles) at 60-70 nm. Under strong-wind conditions, the second mode dominated the average size distribution.

Evaluation of five dry particle deposition parameterizations for incorporation into atmospheric transport models

“…Over ice/snow surface, the results suggest that the ZH14 is the most accurate parameterization, and PZ10 is the least accurate. Qualitatively, this finding is consistent with Petroff and Zhang (2010), who reported that their model significantly underestimated the measured deposition velocities over ice/snow surface for the following studies: Ibrahim et al (1983), Duan et al (1988), Nilsson and Rannik (2001), and Contini et al (2010), which were also investigated in the present study. We also note that the Z01 parameterization overestimated the measured V d from the aforementioned studies.…”

“…We note that the studies by Möller and Schumann (1970) and Sehmel et al (1974) were conducted in the wind tunnels, and thus the observed deposition does not necessarily reflect deposition under natural conditions. Particle deposition measurements on ice/snow pack were collected from eight studies: Ibrahim et al (1983), Duan et al (1988), Nilsson and Rannik (2001), Gronlund et al (2002), Contini et al (2010), Held et al (2011a, b), and Donateo and Contini (2014). The parameterizations were fed using reported values of particle properties (diameter and density), meteorological conditions (stability parameter, temperature, wind speed, etc.…”

“…Two studies over snow (Ibrahim et al, 1983;and Duan et al, 1988) and six studies over ice surfaces (Nilsson and Rannik, 2001;Gronlund et al, 2002;Contini et al, 2010;Held et al, 2011a, b;and Donateo and Contini, 2014) were used to evaluate the accuracy of the four parameterizations (Z01, PZ10, KS12, and ZH14) for smooth surfaces. The ZS14 parameterization was not included here because it does not allow prediction of deposition over ice/snow surfaces.…”

Evaluation of factors controlling long-range transport of black carbon to the Arctic

“…As a result, v d is calculated to be 0.15-0.6 cm s −1 globally, which is much larger than the observed v d over ice or snow surfaces (typically 0.02-0.06 cm s −1 , under different atmospheric stabilities) [Duan et al, 1988;Nilsson and Rannik, 2001;Gallagher et al, 2002;Contini et al, 2010]. To better constrain model results with observations, g is increased to 1200 over snow or ice surfaces.…”

Case Study of Particle Number Fluxes and Size Distributions during Nucleation Events in Southeastern Italy in the Summer

“…This value was obtained in ten repeated laboratory experiments measuring the complete eddy-covariance flux system response to a concentration step, and the variability observed in these experiments was used to evaluate the uncertainty. This response time proved sufficient to measure concentration fluctuations at frequencies that typically made a substantial contribution to the vertical turbulent fluxes of particles [23,36,37]. However, the high frequency undersampling generates an error on F N that needs to be corrected.…”