Angular Momentum From A Suite of Atmospheric General Circulation Models
Abstract
As part of a diagnostic subproject of the second phase of the Atmospheric Model In- tercomparison Project (AMIP-2), covering the period 1979-1995, we are evaluating how well the current generation of atmospheric general circulation models simulates relative atmospheric angular momentum (AAM) from boundary forcing alone. AAM, a measure of the atmosphereSs circulation that depends on the strength and distribu- tion of the zonal winds, is a parameter whose variations have been shown to be closely related to changes in the length of day. With up to approximately 30 models expected in the AMIP-2 project, we focus on the spread within the ensemble of models. Com- parison of the AMIP-2 models with their predecessors in the earlier AMIP-1 phase reveals improvements in the simulation of mean wind regionally, in the seasonal and in the interannual components, as compared to SobservedT values from atmospheric & cedil;reanalyses. AAM maxima during El Nino events are generally simulated by the mod- els, though there is considerable spread of values. An assessment of AAM variations from the AMIP-2 models will be presented and summarized in novel diagrams such as those in Taylor (2001), which combine amplitude and correlation statistics. Interest- ingly, the median set from the group of models appears to be the best realization. We will discuss the implication of AAM modeling in understanding the planetary angular momentum balance, including the impact on LOD fluctuations.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.2648S