Details:

Journal Title:
Journal of Geophysical Research: Atmospheres
Personal Author:
Wood, Robert ; Stemmler, Jayson D. ; Rémillard, Jasmine ; Jefferson, Anne
Wood, Robert ; Stemmler, Jayson D. ; Rémillard, Jasmine ; Jefferson, Anne Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research) ; CIRES (Cooperative Institute for Research in Environmental Sciences)
OAR (Oceanic and Atmospheric Research) ; CIRES (Cooperative Institute for Research in Environmental Sciences) Less -
Description:
A 20 month cloud condensation nucleus concentration (N-CCN) data set from Graciosa Island (39 degrees N, 28 degrees 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 N-CCN < 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-November. 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 (N-d) at Graciosa, but liquid water path (LWP) during low-CCN events was not systematically different from that at other times. Satellite N-d and LWP estimates from MODIS collocated with Lagrangian back trajectories show systematically lower N-d 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.
Source:
Journal of Geophysical Research-Atmospheres, 122(2), 1203-1223.
DOI:
https://doi.org/10.1002/2016jd025557
Document Type:
Journal Article
Rights Information:
Other
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:40c4a761978beecd4092e8df4adcb18c849c4e29928b1e450d4fe074852b006f
Download URL:
https://repository.library.noaa.gov/view/noaa/18325/noaa_18325_DS1.pdf
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