A Map of Dominant Cloud‐Controlling Factors for Cloud Fraction and Total Liquid Water Path can Identify Marine Low‐Level Cloud Types

Daily means of Moderate resolution Imaging Spectroradiometer cloud fraction and multi‐sensor advanced climatology total liquid water path (TLWP) products are collected for open ocean regions spanning a 5‐year period. These two cloud properties are analyzed with respect to cloud‐controlling factors, or environmental metrics enabling estimation of changes in clouds given changes in their environment. The cloud data are filtered to only retain days with low‐level clouds, subsidence and surface sensible heat fluxes out of the ocean. Spearman's rank correlation coefficients are calculated in 1° × 1° oceanic boxes for a variety of environmental metrics and the metric with the largest coefficient is mapped. The map of the dominant cloud‐ controlling factors (DCCF) for TLWP is presented for the first time with surface wind, column water vapor and a lower‐troposphere stability metric dominating most of the global oceans. When pairing the environmental metrics that dominate for cloud fraction with those that dominate for TLWP, known cloud type regimes emerge on the map including stratocumulus, stratocumulus‐to‐cumulus transition, and trade wind cumulus regimes. In the extratropics, a shortlist of eight metric pairs characterize most oceanic locations. Some pairs are coincident with storm tracks, while others highlight where western boundary currents dominantly influence clouds. Closer to the 30th parallels, metric pairs tend to match those characteristic of subtropical controlling factors on clouds. Overall, the DCCF map can be used to isolate regions with distinct characteristics that are likely important for understanding and representing low‐level cloud feedbacks. Plain Language Summary Clouds are notoriously difficult to model. However, their coverage and opacity are strongly impacted by the environment in which they form. Therefore, by finding the environmental variables that best relate to cloud properties, one can estimate how they change in a changing climate. Using satellite observations of cloud cover and liquid water content, and a series of environmental variables obtained from a reanalysis or satellite product, the environmental factors that correlate the most with cloud fraction and TLWP are identified to create a map of the DCCF for low‐level clouds (i.e., those with a top below 500 hPa). By pairing the factors for both cloud properties, a new map is obtained that helps delineate the various cloud types that populate the global oceans. The pairs are found to characterize homogeneous regions with types comparable with those identified in previous studies.