Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Observed Sensitivity of Low Cloud Radiative Effects to Meteorological Perturbations over the Global Oceans

TitleObserved Sensitivity of Low Cloud Radiative Effects to Meteorological Perturbations over the Global Oceans
Publication TypeJournal Article
Year of Publication2020
AuthorsScott, Ryan C., Myers Timothy A., Norris Joel R., Zelinka Mark D., Klein Stephen A., Sun Moguo, and Doelling David R.
JournalJournal of Climate
Abstract / Summary

Understanding how marine low clouds and their radiative effects respond to changing meteorological conditions is crucial to constrain low cloud feedbacks to greenhouse warming and internal climate variability. In this study, we use observations to quantify the low-cloud radiative response to meteorological perturbations over the global oceans to shed light on physical processes governing low-cloud and planetary radiation budget variability in different climate regimes. We assess the independent effect of perturbations in sea surface temperature, estimated inversion strength, horizontal surface temperature advection, 700-hPa relative humidity, 700-hPa vertical velocity, and near-surface wind speed. Stronger inversions and stronger cold advection greatly enhance low-level cloudiness and planetary albedo in eastern ocean stratocumulus and mid-latitude regimes. Warming of the sea surface drives pronounced reductions of eastern ocean stratocumulus cloud amount and optical depth, and hence reflectivity, but has a weaker and more variable impact on low clouds in the tropics and middle latitudes. By reducing entrainment drying, higher free tropospheric relative humidity enhances low-level cloudiness. At low latitudes, where cold advection destabilizes the boundary layer, stronger winds enhance low-level cloudiness; by contrast, wind speed variations have weak influence at mid-latitudes where warm advection frequently stabilizes the marine boundary layer, thus inhibiting vertical mixing. These observational constraints provide a framework for understanding and evaluating marine low cloud feedbacks and their simulation by models.

URLhttps://staging.journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-19-1028.1/348639/Observed-Sensitivity-of-Low-Cloud-Radiative
DOI10.1175/JCLI-D-19-1028.1
Journal: Journal of Climate
Year of Publication: 2020
Publication Date: 07/2020

Understanding how marine low clouds and their radiative effects respond to changing meteorological conditions is crucial to constrain low cloud feedbacks to greenhouse warming and internal climate variability. In this study, we use observations to quantify the low-cloud radiative response to meteorological perturbations over the global oceans to shed light on physical processes governing low-cloud and planetary radiation budget variability in different climate regimes. We assess the independent effect of perturbations in sea surface temperature, estimated inversion strength, horizontal surface temperature advection, 700-hPa relative humidity, 700-hPa vertical velocity, and near-surface wind speed. Stronger inversions and stronger cold advection greatly enhance low-level cloudiness and planetary albedo in eastern ocean stratocumulus and mid-latitude regimes. Warming of the sea surface drives pronounced reductions of eastern ocean stratocumulus cloud amount and optical depth, and hence reflectivity, but has a weaker and more variable impact on low clouds in the tropics and middle latitudes. By reducing entrainment drying, higher free tropospheric relative humidity enhances low-level cloudiness. At low latitudes, where cold advection destabilizes the boundary layer, stronger winds enhance low-level cloudiness; by contrast, wind speed variations have weak influence at mid-latitudes where warm advection frequently stabilizes the marine boundary layer, thus inhibiting vertical mixing. These observational constraints provide a framework for understanding and evaluating marine low cloud feedbacks and their simulation by models.

DOI: 10.1175/JCLI-D-19-1028.1
Citation:
Scott, RC, TA Myers, JR Norris, MD Zelinka, SA Klein, M Sun, and DR Doelling.  2020.  "Observed Sensitivity of Low Cloud Radiative Effects to Meteorological Perturbations over the Global Oceans."  Journal of Climate.  https://doi.org/10.1175/JCLI-D-19-1028.1.