edu.ucar.opensky::articles:21393 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-25T16:07:40.110072 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7pr7znp Why do modeled and observed surface wind stress climatologies differ in the trade wind regions? 2018-01-01T00:00:00Z publication https://n2t.org/ark:/85065/d7pr7znp https://doi.org/10.1175/JCLI-D-17-0255.1 Simpson, Isla R. author Bacmeister, Julio author Sandu, I. author Rodwell, M. J. author UCAR/NCAR - Library publisher Global climate models (GCMs) exhibit stronger mean easterly zonal surface wind stress and near-surface winds in the Northern Hemisphere (NH) trade winds than observationally constrained reanalyses or other observational products. A comparison, between models and reanalyses, of the processes that contribute to the zonal-mean, vertically integrated balance of momentum reveals that this wind stress discrepancy cannot be explained by either the resolved dynamics or parameterized tendencies that are common to each. Rather, a substantial residual exists in the time-mean momentum balance of the reanalyses, pointing toward a role for the analysis increments. Indeed, they are found to systematically weaken the NH near-surface easterlies in winter, thereby reducing the diagnosed surface wind stress. Similar effects are found in the Southern Hemisphere, and further analysis of the spatial structure and seasonality of these increments demonstrates that they act to weaken the near-surface flow over much of the low-latitude oceans in both summer and winter. This suggests an erroneous/missing process in GCMs that constitutes a missing drag on the low-level zonal flow over oceans. This indicates either a misrepresentation of the drag between the surface and the atmosphere or a missing internal atmospheric process that amounts to an additional drag on the low-level zonal flow. If the former is true, then observation-based surface stress products, which rely on similar drag formulations to GCMs, may be underestimating the strength of the easterly surface wind stress. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2018 American Meteorological Society (AMS). None eng geoscientificInformation