Turbulence and Cloudiness in Cumulus Topped Marine Boundary Layers.
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| Title: | Turbulence and Cloudiness in Cumulus Topped Marine Boundary Layers. |
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| Authors: | Ghate, Virendra P.1 (AUTHOR) vghate@anl.gov, Turner, David D.2 (AUTHOR), Mechem, David B.3 (AUTHOR), Gero, Jonathan4 (AUTHOR), Larson, Vincent E.5,6 (AUTHOR), Kleiss, Jessica7 (AUTHOR) |
| Source: | Journal of Applied Meteorology & Climatology. May2026, Vol. 65 Issue 5, p1-17. 17p. |
| Subjects: | Cloudiness, Cumulus clouds, Atmospheric radiation measurement, Turbulence, Atmospheric boundary layer, Doppler lidar, Radar |
| Abstract: | Turbulence and cloudiness in cumulus-topped marine boundary layers are studied using data from the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) site. The analysis includes eight periods of non-precipitating shallow cumulus clouds, spanning 141 hours and encompassing 603 individual clouds. On average, the cumuli had bases at 558 m, were 99 m thick, had a chord length of 500 m, and exhibited an hourly base-layer cloudiness of 12%. Changes in cloud fraction were primarily driven by variations in cloud number, not chord length. High-resolution Doppler lidar and cloud radar observations were used to estimate updraft and downdraft mass fluxes in the cumulus base layer under both clear and cloudy regions. Cloudy updrafts contributed only ~23% of the total updraft mass flux at cloud base, indicating that most upward mass flux originated from clear-air eddies. Updraft strength, rather than updraft fraction, was found to predominantly control both clear and cloudy updraft mass fluxes. Cloud base cloudiness strongly correlated with cloudy updraft mass flux but showed negligible correlation with clear-air updraft mass flux. Clear-air downdraft mass flux exhibited a strong relationship with the ratio of surface buoyancy to inversion strength. Mesoscale analysis revealed that moist patches had greater cloudiness, updraft mass flux, and vertical velocity variance compared to dry patches. Additionally, mesoscale base layer cloud fraction was highly and significantly correlated with cloudy updraft mass flux in both dry and moist environments. Results presented herein have implications for cumulus parameterization development along with climatological and model evaluation studies conducted at the ENA site. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Turbulence and cloudiness in cumulus-topped marine boundary layers are studied using data from the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) site. The analysis includes eight periods of non-precipitating shallow cumulus clouds, spanning 141 hours and encompassing 603 individual clouds. On average, the cumuli had bases at 558 m, were 99 m thick, had a chord length of 500 m, and exhibited an hourly base-layer cloudiness of 12%. Changes in cloud fraction were primarily driven by variations in cloud number, not chord length. High-resolution Doppler lidar and cloud radar observations were used to estimate updraft and downdraft mass fluxes in the cumulus base layer under both clear and cloudy regions. Cloudy updrafts contributed only ~23% of the total updraft mass flux at cloud base, indicating that most upward mass flux originated from clear-air eddies. Updraft strength, rather than updraft fraction, was found to predominantly control both clear and cloudy updraft mass fluxes. Cloud base cloudiness strongly correlated with cloudy updraft mass flux but showed negligible correlation with clear-air updraft mass flux. Clear-air downdraft mass flux exhibited a strong relationship with the ratio of surface buoyancy to inversion strength. Mesoscale analysis revealed that moist patches had greater cloudiness, updraft mass flux, and vertical velocity variance compared to dry patches. Additionally, mesoscale base layer cloud fraction was highly and significantly correlated with cloudy updraft mass flux in both dry and moist environments. Results presented herein have implications for cumulus parameterization development along with climatological and model evaluation studies conducted at the ENA site. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 15588424 |
| DOI: | 10.1175/JAMC-D-25-0132.1 |
