Post Cold Frontal Clouds at the ARM Eastern North Atlantic Site: An Examination of the Relationship Between Large-Scale Environment and Low-Level Cloud Properties

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Naud, Catherine M., Booth, James F., Lamraoui, Fayçal
• Language: unknown
• Published: 2021
• Subjects: 58 GEOSCIENCES; North Atlantic
• Online Access: http://www.osti.gov/servlets/purl/1594074; https://www.osti.gov/biblio/1594074; https://doi.org/10.1029/2018JD029015

Using cloud and environment observations from the Atmospheric Radiation Measurement program Eastern North Atlantic site and an automated cold front detection routine, cloud properties in post-cold front (PCF) periods are examined and compared to similar conditions of subsidence (non-PCF). PCF periods exhibit stronger subsidence and wind speed than non-PCF periods, with weaker inversions and stronger surface temperature contrasts. Low-level clouds are predominant and are found to have higher cloud-base and top heights, colder cloud-top temperature, as well as greater vertical extent and liquid water path during PCF than non-PCF periods. The environmental metric that is best correlated with cloud boundaries for both PCF and non-PCF periods is the difference in potential temperature between the sea surface and 800 hPa, a parameter used to locate cold air outbreak conditions. However, the cloud vertical extent and liquid water path are found to be better correlated with sea-air temperature contrast, a parameter related to turbulent surface fluxes. The strength of the relationships between the cloud characteristics and these metrics does not differ for PCF and non-PCF periods. However, the strength of the metrics differs between PCF and non-PCF periods and can explain cloud property differences. The results suggest both the properties of the boundary layer and the presence of an upper-level cyclone associated with the cold front determine PCF cloud properties.