The Dynamics of Teleconnections Induced by Short Term Tropical Forcing.

Recent observational and modeling studies have suggested that transient tropical perturbations may induce significant intraseasonal teleconnections between the tropics and midlatitudes. We have investigated the mechanisms for such teleconnections using a nonlinear global shallow water model with a r...

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Bibliographic Details
Main Author: Malsick, Mark D.
Other Authors: NAVAL POSTGRADUATE SCHOOL MONTEREY CA
Format: Text
Language:English
Published: 1995
Subjects:
Meteorology
Computer Programming and Software
*COMPUTERIZED SIMULATION
*WEATHER FORECASTING
*PERTURBATIONS
*TROPICAL CYCLONES
MATHEMATICAL MODELS
ANOMALIES
TRANSIENTS
GROWTH(GENERAL)
COHERENCE
VORTICES
REGIONS
SHALLOW WATER
RESPONSE
PATTERNS
TROPICAL REGIONS
NORTH ATLANTIC OCEAN
EXITS
WAVES
NORTH PACIFIC OCEAN
INDUCTION SYSTEMS
GRADIENTS
NORTH AMERICA
OCEAN BASINS
BENGAL BAY
ROSSBY WAVES
*TELECONNECTIONS
WESTERN NORTH PACIFIC OCEAN
Pacific
North Atlantic
Online Access:http://www.dtic.mil/docs/citations/ADA305941
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA305941
Description
Summary:Recent observational and modeling studies have suggested that transient tropical perturbations may induce significant intraseasonal teleconnections between the tropics and midlatitudes. We have investigated the mechanisms for such teleconnections using a nonlinear global shallow water model with a realistically wavy basic state. The model perturbations were designed to simulate tropical cyclones with prescribed growth, decay, and propagation. The model responses to the tropical perturbations showed distinct midlatitude wavetrain responses to the perturbation. The typical response became large within a few days and retained as a coherent pattern for two to three weeks after the demise of the tropical perturbation. The response was particularly strong if the perturbation propagated close to an extratropical jet. This propagation allowed Rossby wave induction as divergent outflow from the perturbation crossed the jet's region of high ambient vorticity gradient. This initial wave response was then guided by the jet and amplified in barotropically unstable regions on the jet flanks. This produced a persistent response downstream of the jet exit (e.g., over the northeast Pacific and North America). The response showed a marked variation with the season and with the tropical ocean basin in which the perturbation occurred, apparently because of temporal and spatial changes in the basic state conditions. The responses closely resemble observed anomaly patterns associated with transient tropical perturbations, and are dynamically consistent with the responses to more persistent tropical perturbations (e.g., ENSO events).

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