Large-Scale Circulation Regimes and Tropical Cyclone Characteristics Over the Western Pacific Ocean
Abstract
The basic structure of the variability Of the large-scale circulations over the tropical western North Pacific is investigated with respect to its influence on tropical cyclone characteristics. A vector empirical orthogonal function analysis and a fuzzy cluster algorithm are used to define six recurrent 700 mb circulation patterns that represent large-scale variabilities associated with the monsoon trough and subtropical ridge. Three circulation patterns are associated with an active monsoon trough, and two patterns represent an inactive monsoon trough. One pattern depicts small deviations from the long-term climatology. The 700 mb circulation patterns are shown to be physically consistent with outgoing longwave radiation anomalies and the 200 mb stream function and velocity potential anomalies. A seventh set of circulation patterns is defined to contain transition periods between the active, inactive and small anomaly patterns. Transitions between recurrent circulation patterns may be within the active or the inactive patterns, or be transitions across the active/inactive boundary that are associated with major circulation changes. These significant transitions occur over a very limited set of paths, which are shown to be associated with interactions among tropical and midlatitude circulation systems. The recurrent circulation patterns and their transitions are shown to explain much of the observed intraseasonal variability in the occurrence and track types (recurving versus straight-moving) of tropical cyclones over the western North Pacific. Tropical cyclones, Circulation regimes, Low-frequency variability, Tropical cyclone motion, Monsoons, Cluster analysis.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1993
- Accession Number
- ADA273004
Entities
People
- Patrick A. Harr
Organizations
- Naval Postgraduate School