On the relationship between mesoscale cellular convection and meteorological forcing: Comparing the Southern Ocean against the North Pacific

• Main Authors: Lang, Francisco, Siems, Steven T., Huang, Yi, Ackermann, Luis
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Pacific; Southern Ocean
• Online Access: https://doi.org/10.5194/egusphere-2023-518; https://noa.gwlb.de/receive/cop_mods_00065838; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00064348/egusphere-2023-518.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-518/egusphere-2023-518.pdf

Marine atmospheric boundary layer (MABL) clouds cover vast areas over the ocean and have important radiative effects on the Earth’s climate system. These radiative effects are known to be sensitive to the local organization, or structure, of the mesoscale cellular convection (MCC). A convolution neural network model is used to identify the two ideal classes of MCC clouds, namely open and closed, over the Southern Ocean (SO) and Northwest Pacific (NP) from high-frequency geostationary Himawari-8 satellite observations. The results of the climatology show that MCC clouds are roughly distributed over the midlatitude storm tracks for both hemispheres, with peaks poleward of the 40° latitude. Open MCC clouds are more prevalent than closed MCC in both regions. An examination of meteorological forcing associated with open and closed MCC clouds is conducted to illustrate the influence of large-scale meteorological conditions. We establish the importance of the Kuroshio western boundary current in the spatial coverage of open and closed MCC across the NP, presumably through the supply of strong heat and moisture fluxes during marine cold air outbreaks events. For both regions, closed MCC cloud are more frequent at higher static stability than on air-sea temperature difference, opposite to the open MCC cloud behavior. The diurnal cycle reveals a pronounced daily cycle in the frequency of occurrence of closed MCC over the SO, while the NP closed MCC daily cycle is less noticeable.