A normal-mode analysis of rapid teleconnections in a numerical weather prediction model. Part II. Tropical and extratropical aspects

Journal Article · Tue Dec 01 04:00:00 UTC 1992 · Monthly Weather Review; (United States)

DOI:https://doi.org/10.1175/1520-0493(1992)120<2914:ANMAOR>2.0.CO;2· OSTI ID:6617449

Gelaro, R ^[1]

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1. Naval Research Lab., Monterey, CA (United States)

A unique analysis is applied to the annual modes of the US Navy's global operational numerical weather prediction model to investigate time using responses in the tropics and extratropics to tropical Pacific sea surface temperature anomalies. With this new analysis, the modes are partitioned according to their latitudinal variances. This allows the response energy to be separated into tropical and extratropical contributions. The partitioned responses are derived by grouping those modes whose fractional variance within a prescribed latitudinal band [epsilon][mu] exceeds some threshold value. Since the parameters [epsilon][mu] and [beta] may be chosen arbitrarily, this technique greatly increases the flexibility of the annual-mode diagnostic approach. The partitioned responses reveal distinct differences between the evolution and vertical scales of the dominant modes in the tropics and extratropics. In the tropics, the structure is dominated by the external mode and a medium-depth internal mode. The internal mode is determined by the profile of the large-scale divergence and subsequent rotational wind (Walker circulation) response driven by enhanced convection. In the extratropics, the dominant structure is equivalent barotropic. The external rotational modes grow rapidly within the extratropics in a manner that suggests that meridional propagation alone does not fully explain the growth of the extratropical response. 12 refs., 10 figs., 1 tab.

• OSTI ID: 6617449
• Journal Information: Monthly Weather Review; (United States), Journal Name: Monthly Weather Review; (United States) Vol. 120:12; ISSN MWREAB; ISSN 0027-0644
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ATMOSPHERIC CIRCULATION
COMPUTERIZED SIMULATION
CONVECTION
ENERGY TRANSFER
FORECASTING
HEAT TRANSFER
MASS TRANSFER
NORMAL-MODE ANALYSIS
SIMULATION
TROPICAL REGIONS
WEATHER