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Title: Wind Turning in the Planetary Boundary Layer in CMIP6 Models
Abstract A set of CMIP6 models is evaluated for the turning of the wind over the planetary boundary layer (PBL) and the corresponding cross-isobaric mass flux. The bulk Richardson number method is used to calculate the height of the PBL to allow for comparisons with a climatology of observed wind-turning angles documented by Lindvall and Svensson based on more than 800 stations in the Integrated Global Radiosonde Archive. Wind-turning angles are found to be underestimated in all models, with the GFDL CM4 model having the closest distribution to the observations. Large, negative cross-isobaric mass fluxes (flow toward higher pressure) are found over high-terrain areas and the North Atlantic storm-track region in all models and the ERA-Interim reanalysis. Bulk Richardson number–derived PBLs are particularly shallow in the Norwegian Earth System Model, medium atmosphere-medium ocean resolution (NorESM2-MM), likely caused by a change in the turbulence and cloud scheme as compared to the CESM2 model that uses the same atmospheric model, leading to small wind-turning angles and cross-isobaric mass fluxes. Using the 850-hPa level as the upper boundary broadens the wind-turning angle distribution and increases the amount of cross-isobaric mass flux for all models. This makes the models closer to the observations, although substantial differences are still present. The assumption of a constant geostrophic wind throughout the PBL possibly affects the calculated mass fluxes.  more » « less
Award ID(s):
1916689
PAR ID:
10438377
Author(s) / Creator(s):
 ;  
Publisher / Repository:
American Meteorological Society
Date Published:
Journal Name:
Journal of Climate
Volume:
36
Issue:
17
ISSN:
0894-8755
Page Range / eLocation ID:
p. 5729-5742
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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