Open AccessParticle fluxes and condensational uptake over sea ice during COBRA
Author(s) -
Whitehead J. D.,
Dorsey J. R.,
Gallagher M. W.,
Flynn M. J.,
McFiggans G.,
Carpenter L. J.
Publication year - 2012
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2012jd017798
Subject(s) - atmospheric sciences , particle size , environmental science , cloud condensation nuclei , particle (ecology) , particle number , flux (metallurgy) , mass flux , range (aeronautics) , wind speed , aerosol , physics , meteorology , chemistry , materials science , mechanics , geology , oceanography , thermodynamics , volume (thermodynamics) , composite material , organic chemistry
Particle fluxes were measured over sea ice at Hudson Bay, Canada, during the COBRA experiment in February and March, 2008. Eddy covariance particle fluxes were measured using a condensation particle counter and an ultrasonic anemometer on a 2.5 m mast on the sea ice. After applying appropriate corrections and filtering, the mean net deposition velocity was 0.12 ± 0.11 mm s −1 for particles measured with a CPC 3776 (lower size threshold, D p 50 = 2.5 nm) and was at the detection limit of the measurement system. No evidence of nucleation events was seen. Two optical particle counters (at heights 0.2 and 1.35 m on the mast) allowed size segregated fluxes of particles in the accumulation and coarse mode diameter range 0.3–20 μ m to be derived using the aerodynamic flux gradient method. Strong net emission fluxes were observed around midday, 3rd March, when winds increased to around 10 m s −1 , suggesting ice particle resuspension. The fluxes during this period had a significant influence on the derived condensational loss rate to the available particle surfaces, k t . Number fluxes were greatest in the smallest size channels, while the largest sizes dominated the mass flux. Number fluxes also increased with wind speed, and this relationship was strongest for the smaller sizes. Particle mass size distributions showed an enhanced mode around 400 nm (dry size). Values of k t were well approximated by the molecular regime and were found to be much smaller and less variable than values derived for marine air.