The consistency of MJO teleconnection patterns: An explanation using linear Rossby wave theory
Journal
Journal of Climate
Journal Volume
32
Journal Issue
2
Pages
531-548
Date Issued
2019
Author(s)
Abstract
The Madden-Julian oscillation (MJO) excites strong variations in extratropical atmospheric circulations that have important implications for subseasonal-to-seasonal (S2S) prediction. A previous study showed that particular MJO phases are characterized by a consistent modulation of geopotential heights in the North Pacific and adjacent regions across different MJO events, and demonstrated that this consistency is beneficial for extended numerical weather forecasts (i.e., lead times of two weeks to one month). In this study, we examine the physical mechanisms that lead some MJO phases to have more consistent teleconnections than others using a linear baroclinic model. The results show that MJO phases 2, 3, 6, and 7 consistently generate Pacific-North American (PNA)-like patterns on S2S time scales while other phases do not. A Rossby wave source analysis is applied and shows that a dipole-like pattern of Rossby wave source on each side of the subtropical jet can increase the pattern consistency of teleconnections due to the constructive interference of similar teleconnection signals. On the other hand, symmetric patterns of Rossby wave source can dramatically reduce the pattern consistency due to destructive interference. A dipole-like Rossby wave source pattern is present most frequently when tropical heating is found in the Indian Ocean or the Pacific warm pool, and a symmetric Rossby wave source is present most frequently when tropical heating is located over the Maritime Continent. Thus, the MJO phase-dependent pattern consistency of teleconnections is a special case of this mechanism. © 2018 American Meteorological Society.
Subjects
Intraseasonal variability; Pacific-North American pattern/oscillation; Planetary waves; Tropical variability
SDGs
Other Subjects
Climatology; Ocean currents; Tropics; Weather forecasting; Constructive interference; Destructive interference; Intraseasonal variability; Madden-Julian oscillation; North American; Numerical weather forecasts; Planetary Waves; Tropical variability; Mechanical waves; atmospheric circulation; Madden-Julian oscillation; planetary wave; Rossby wave; seasonal variation; teleconnection; theoretical study; weather forecasting; Indian Ocean; Pacific Ocean; Pacific Ocean (North)
Type
journal article