%0 Journal Article %1 Grise2016Understanding %A Grise, Kevin M. %A Medeiros, Brian %D 2016 %I American Meteorological Society %J J. Climate %K theory climate jet clouds %R 10.1175/jcli-d-16-0295.1 %T Understanding the varied influence of mid-latitude jet position on clouds and cloud-radiative effects in observations and global climate models %U http://dx.doi.org/10.1175/jcli-d-16-0295.1 %X AbstractThis study examines the dynamical mechanisms responsible for changes in mid-latitude clouds and cloud-radiative effects (CRE) that occur in conjunction with meridional shifts in the jet streams over the North Atlantic, North Pacific, and Southern Oceans. When the mid-latitude jet shifts poleward, extratropical cyclones and their associated upward vertical velocity anomalies closely follow. As a result, a poleward jet shift contributes to a poleward shift in high-topped storm track clouds and their associated longwave CRE. However, when the jet shifts poleward, downward vertical velocity anomalies increase equatorward of the jet, contributing to an enhancement of the boundary layer inversion strength (EIS) and an increase in low cloud amount there. Because shortwave CRE depends on the reflection of solar radiation by clouds in all layers, the shortwave cooling effects of mid-latitude clouds increase with both upward vertical velocity anomalies and positive EIS anomalies. Over mid-latitude oceans where a poleward jet shift contributes to positive EIS anomalies but downward vertical velocity anomalies, the two effects cancel, and net observed changes in shortwave CRE are small.Global climate models generally capture the observed anomalies associated with mid-latitude jet shifts. However, there is large inter-model spread in the shortwave CRE anomalies, with a subset of models showing a large shortwave cloud-radiative warming over mid-latitude oceans with a poleward jet shift. In these models, mid-latitude shortwave CRE is sensitive to vertical velocity perturbations, but the observed sensitivity to EIS perturbations is underestimated. Consequently, these models might incorrectly estimate future mid-latitude cloud feedbacks in regions where appreciable changes in both vertical velocity and EIS are projected.

@article{Grise2016Understanding, abstract = {AbstractThis study examines the dynamical mechanisms responsible for changes in mid-latitude clouds and cloud-radiative effects (CRE) that occur in conjunction with meridional shifts in the jet streams over the North Atlantic, North Pacific, and Southern Oceans. When the mid-latitude jet shifts poleward, extratropical cyclones and their associated upward vertical velocity anomalies closely follow. As a result, a poleward jet shift contributes to a poleward shift in high-topped storm track clouds and their associated longwave CRE. However, when the jet shifts poleward, downward vertical velocity anomalies increase equatorward of the jet, contributing to an enhancement of the boundary layer inversion strength (EIS) and an increase in low cloud amount there. Because shortwave CRE depends on the reflection of solar radiation by clouds in all layers, the shortwave cooling effects of mid-latitude clouds increase with both upward vertical velocity anomalies and positive EIS anomalies. Over mid-latitude oceans where a poleward jet shift contributes to positive EIS anomalies but downward vertical velocity anomalies, the two effects cancel, and net observed changes in shortwave CRE are small.Global climate models generally capture the observed anomalies associated with mid-latitude jet shifts. However, there is large inter-model spread in the shortwave CRE anomalies, with a subset of models showing a large shortwave cloud-radiative warming over mid-latitude oceans with a poleward jet shift. In these models, mid-latitude shortwave CRE is sensitive to vertical velocity perturbations, but the observed sensitivity to EIS perturbations is underestimated. Consequently, these models might incorrectly estimate future mid-latitude cloud feedbacks in regions where appreciable changes in both vertical velocity and EIS are projected.}, added-at = {2018-06-18T21:23:34.000+0200}, author = {Grise, Kevin M. and Medeiros, Brian}, biburl = {https://www.bibsonomy.org/bibtex/2759ea7dd2f49e0e3e82efccc8f7609a5/pbett}, citeulike-article-id = {14139038}, citeulike-linkout-0 = {http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0295.1}, citeulike-linkout-1 = {http://dx.doi.org/10.1175/jcli-d-16-0295.1}, day = 16, doi = {10.1175/jcli-d-16-0295.1}, interhash = {e03d89248963c25e420e2321039011e4}, intrahash = {759ea7dd2f49e0e3e82efccc8f7609a5}, journal = {J. Climate}, keywords = {theory climate jet clouds}, month = sep, posted-at = {2016-09-17 08:36:24}, priority = {2}, publisher = {American Meteorological Society}, timestamp = {2018-06-22T18:36:38.000+0200}, title = {Understanding the varied influence of mid-latitude jet position on clouds and cloud-radiative effects in observations and global climate models}, url = {http://dx.doi.org/10.1175/jcli-d-16-0295.1}, year = 2016 }