On the effect of wind speed on submicron sea salt mass concentrations and source fluxes
Worsnop, Douglas R.
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Ovadnevaite, Jurgita; Ceburnis, Darius; Canagaratna, Manjula; Berresheim, Harald; Bialek, Jakub; Martucci, Giovanni; Worsnop, Douglas R. O'Dowd, Colin (2012). On the effect of wind speed on submicron sea salt mass concentrations and source fluxes. Journal of Geophysical Research: Atmospheres 117 ,
A High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was evaluated for its ability to quantify submicron sea salt mass concentrations. The evaluation included both laboratory and field studies. Quantification of the sea salt signal in the HR-ToF-AMS was achieved by taking the (NaCl+)-Na-23-Cl-35 ion as a surrogate for sea salt and then identifying a calibration scaling factor through a comparison with mono-disperse laboratory generated sea salt aerosol. Ambient sea salt concentrations calculated using this method agreed well with those obtained by ion chromatography of filter samples, following a 1: 1 regression slope and a correlation coefficient R = 0.93. A key advantage of this AMS-based method is that it allows for high time resolution measurements of sea salt (5 min) along with the speciation of other chemical compounds, including primary organics contributing to sea spray. The high-time resolution sea salt measurement capability enabled the quantification of sea salt mass in both increasing and decreasing wind speed regimes up to 26 m s(-1). A mass flux source function was also derived and found to have a power law wind speed dependency with an exponent of 3.1 for increasing winds and 2.3 for decreasing winds. Comparison of the mass flux relationship in this study suggests that previous schemes based on the Monahan whitecap-wind speed approach significantly over-estimate the submicron mass flux. Both the whitecap-wind speed component and the differential whitecap-aerosol productivity component of the source flux function contribute toward the over-estimation.