Diagnosis and Sensitivity of the 200 hPa Circulation in NCAR Community Climate Models

The purpose of this report is to determine the nature of systematic errors in several different seasonal cycle versions of the National Center for Atmospheric Research (NCAR) Community Climate Models (CCMs) and to assess the dynamical impact of such errors on climate perturbation studies. Our diagnosis focuses on the seasonal mean December- January-February (DJF) 200 hPa circulation and evaluates the sensitivity of that flow to anomalous tropical forcing. Other features of the CCM climatologies for January and July, including the mass fields and hydrologic cycle, are evaluated in Hurrell et al. (1993). A linear barotropic stationary wave model is used to examine the sensitivity of observed and CCM climatological flows to idealized tropical forcing. The forcing consists of a mass source/sink dipole over the equatorial Pacific that mimics the horizontal structure of anomalous rainfall during El Niño. The climatological flows on which the forcing is imposed differ among the various CCMs, and these in turn differ from observations. Differences between the responses to tropical forcing imposed on each base state relative to observations then indicate the dynamical significance of the CCM climate errors. The northern wintertime teleconnections during El Niño are particularly strong with the Northern Hemisphere (NH) flow, and our assessment of the significance of the CCM climate biases focuses on how such errors impact the NH stationary wave response. Of course, the full CCM behavior during El Niño is considerably more complicated than just the steady barotropic response to tropical forcing. As such, the approach taken herein should be viewed as only one component of a more thorough model evaluation that ultimately requires diagnosis of CCM integrations with interannual sea surface temperature (SST) anomalies. Relationships between climate errors in CCM divergent and rotational flow components are examined in the context of the linear model. These experiments are designed to determine the link between various features of the CCM 200 hPa circulation biases, and to provide guidance for, model development. Our principal results common to all the CCM versions studied herein are: * The zonally averaged zonal wind at 200 hPa has a westerly bias in the tropics. The error is not zonally uniform but is strong locally with a 20 m s-1 maximum over the equatorial central Pacific. This is associated with an erroneous westward shift of the CCMs' subtropical Pacific stationary wave troughs in both hemispheres.

To Access Resource:

Questions? Email Resource Support Contact:

  • opensky@ucar.edu
    UCAR/NCAR - Library


Resource Type publication
Temporal Range Begin N/A
Temporal Range End N/A
Temporal Resolution N/A
Bounding Box North Lat N/A
Bounding Box South Lat N/A
Bounding Box West Long N/A
Bounding Box East Long N/A
Spatial Representation N/A
Spatial Resolution N/A
Related Links N/A
Additional Information N/A
Resource Format PDF
Standardized Resource Format PDF
Asset Size N/A
Legal Constraints

Copyright Author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Access Constraints None
Software Implementation Language N/A

Resource Support Name N/A
Resource Support Email opensky@ucar.edu
Resource Support Organization UCAR/NCAR - Library
Distributor N/A
Metadata Contact Name N/A
Metadata Contact Email opensky@ucar.edu
Metadata Contact Organization UCAR/NCAR - Library

Author Hoerling, Martin
DeHaan, Laurel
Hurrell, James
Publisher UCAR/NCAR - Library
Publication Date 1993-01-01T00:00:00
Digital Object Identifier (DOI) Not Assigned
Alternate Identifier N/A
Resource Version N/A
Topic Category geoscientificInformation
Progress N/A
Metadata Date 2023-08-18T18:04:59.095330
Metadata Record Identifier edu.ucar.opensky::technotes:160
Metadata Language eng; USA
Suggested Citation Hoerling, Martin, DeHaan, Laurel, Hurrell, James. (1993). Diagnosis and Sensitivity of the 200 hPa Circulation in NCAR Community Climate Models. UCAR/NCAR - Library. http://n2t.net/ark:/85065/d7rj4hvd. Accessed 25 May 2024.

Harvest Source