The prevalence of precipitation from polar supercooled clouds

Journal Article · Wed Mar 17 00:00:00 EDT 2021 · Atmospheric Chemistry and Physics (Online)

DOI:https://doi.org/10.5194/acp-21-3949-2021· OSTI ID:1771237

Silber, Israel ; Fridlind, Ann M. ; Verlinde, Johannes ; Ackerman, Andrew S. ; Cesana, Grégory V. ; Knopf, Daniel A.

Supercooled clouds substantially impact polar surface energy budgets, but large-scale models often underestimate their occurrence, which motivates accurately establishing metrics of basic processes. An analysis of long-term measurements at $$Utqia\dot{g}vik$$, Alaska, and McMurdo Station, Antarctica, combines lidar-validated use of soundings to identify supercooled cloud layers and colocated ground-based profiling radar measurements to quantify cloud base precipitation. We find that more than 85 % (75 %) of sampled supercooled layers are precipitating over the Arctic (Antarctic) site, with more than 75 % (50 %) precipitating continuously to the surface. Such high frequencies can be reconciled with substantially lesser spaceborne estimates by considering differences in radar hydrometeor detection sensitivity. While ice precipitation into supercooled clouds from aloft is common, we also find that the great majority of supercooled cloud layers without ice falling into them are themselves continuously generating precipitation. Such sustained primary ice formation is consistent with continuous activation of immersion-mode ice-nucleating particles (INPs), suggesting that supercooled cloud formation is a principal gateway to ice formation at temperatures greater than ~-38 °C over polar regions. The prevalence of weak precipitation fluxes is also consistent with supercooled cloud longevity and with well-observed and widely simulated case studies. An analysis of colocated microwave radiometer retrievals suggests that weak precipitation fluxes can be nonetheless consequential to moisture budgets for supercooled clouds owing to small liquid water paths. The results here also demonstrate that the observed abundance of mixed-phase clouds can vary substantially with instrument sensitivity and methodology. Finally, we suggest that these ground-based precipitation rate statistics offer valuable guidance for improving the representation of polar cloud processes in large-scale models.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center; NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Aeronautics and Space Administration (NASA)
• Contributing Organization: PNNL, BNL, ANL, ORNL
• Grant/Contract Number: SC0017981; SC0018046; SC0020006; SC0021034; NNX17AJ12G
• OSTI ID: 1771237
• Alternate ID(s): OSTI ID: 1771330; OSTI ID: 1779343
• Journal Information: Atmospheric Chemistry and Physics (Online), Journal Name: Atmospheric Chemistry and Physics (Online) Vol. 21 Journal Issue: 5; ISSN 1680-7324
• Publisher: Copernicus GmbH
• Country of Publication: Germany
• Language: English

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