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Published March 27, 2017 | Published
Journal Article Open

Relationships Between Giant Sea Salt Particles and Clouds Inferred from Aircraft Physicochemical Data


This study uses airborne data from multiple field campaigns off the California coast to determine the extent to which a size distribution parameter and a cloud water chemical measurement can capture the effect of giant cloud condensation nuclei (GCCN), specifically sea salt, on marine stratocumulus cloud properties. The two GCCN proxy variables, near-surface particle number concentration for diameters > 5 µm and cloud water chloride concentration, are significantly correlated (95% confidence) with each other, and both exhibit expected relationships with other parameters (e.g., surface wind) that typically coincide with sea salt emissions. Factors influencing the relationship between these two GCCN proxy measurements include precipitation rate (R) and the standard deviation of the sub-cloud vertical velocity owing likely to scavenging effects and improved mixing/transport of sea salt to cloud base, respectively. When comparing twelve pairs of high and low chloride cloud cases (at fixed liquid water path and cloud drop number concentration), the average drop spectra for high chloride cases exhibit enhanced drop number at diameters exceeding 20 µm, especially above 30 µm. In addition, high chloride cases coincide with enhanced mean columnar R and negative values of precipitation susceptibility. The difference in drop effective radius between high and low chloride conditions decreases with height in cloud, suggesting that some GCCN-produced rain drops precipitate before reaching cloud tops. The sign of cloud responses (i.e., R) to perturbations in giant sea salt particle concentration, as evaluated from MERRA-2 reanalysis data, is consistent with the aircraft data.

Additional Information

© 2017 American Geophysical Union. Accepted manuscript online: 8 March 2017; Manuscript Accepted: 2 March 2017; Manuscript Revised: 1 March 2017; Manuscript Received: 30 September 2016. All data and results are available from the corresponding author (armin@email.arizona.edu). This work was funded by NASA grant NNX14AM02G and Office of Naval Research grants N00014-10-1-0811, N00014-11-1-0783, N00014-10-1-0200, N00014-04-1-0118, and N00014-16-1-2567. We acknowledge Daniel Rosenfeld and two anonymous reviewers for helpful comments.

Attached Files

Published - Dadashazar_et_al-2017-Journal_of_Geophysical_Research-_Atmospheres.pdf



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