Publication Abstracts

Wood et al. 2017

Wood, R., J.D. Stemmler, J. Rémillard, and A. Jefferson, 2017: Low CCN concentration air masses over the eastern North Atlantic: Seasonality, meteorology and drivers. J. Geophys. Res. Atmos., 122, no. 2, 1203-1223, doi:10.1002/2016JD025557.

A 20 month cloud condensation nucleus concentration (NCCN) dataset from Graciosa Island (39°N, 28°W) in the remote North Atlantic is used to characterize air masses with low cloud condensation nuclei (CCN) concentrations. Low-CCN events are defined as 6 h periods with mean NCCN < 20 cm-3 (0.1% supersaturation). A total of 47 low-CCN events are identified. Surface, satellite, and reanalysis data are used to explore the meteorological and cloud context for low-CCN air masses. Low-CCN events occur in all seasons, but their frequency was 3 times higher in December-May than during June-Noember. Composites show that many of the low-CCN events had a common meteorological basis that involves southerly low-level flow and rather low wind speeds at Graciosa. Anomalously low pressure is situated to the west of Graciosa during these events, but back trajectories and lagged SLP composites indicate that low-CCN air masses often originate as cold air outbreaks to the north and west of Graciosa. Low-CCN events were associated with low cloud droplet concentrations (Nd) at Graciosa, but liquid water path (LWP) during low-CCN events was not systematically different from that at other times. Satellite Nd and LWP estimates from MODIS collocated with Lagrangian back-trajectories show systematically lower Nd and higher LWP several days prior to arrival at Graciosa, consistent with the hypothesis that observed low-CCN air masses are often formed by coalescence scavenging in thick warm clouds, often in cold air outbreaks.

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BibTeX Citation

@article{wo01100l,
  author={Wood, R. and Stemmler, J. D. and Rémillard, J. and Jefferson, A.},
  title={Low CCN concentration air masses over the eastern North Atlantic: Seasonality, meteorology and drivers},
  year={2017},
  journal={J. Geophys. Res. Atmos.},
  volume={122},
  number={2},
  pages={1203--1223},
  doi={10.1002/2016JD025557},
}

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RIS Citation

TY  - JOUR
ID  - wo01100l
AU  - Wood, R.
AU  - Stemmler, J. D.
AU  - Rémillard, J.
AU  - Jefferson, A.
PY  - 2017
TI  - Low CCN concentration air masses over the eastern North Atlantic: Seasonality, meteorology and drivers
JA  - J. Geophys. Res. Atmos.
VL  - 122
IS  - 2
SP  - 1203
EP  - 1223
DO  - 10.1002/2016JD025557
ER  -

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