The influence of the MJO diversity on midlatitude teleconnection patterns
Abstract
The Madden-Julian Oscillation (MJO) is the most pronounced tropical instraseasonal mode of variability and has been shown to modulate extratropical weather on subseasonal to seasonal timescales through exciting Rossby wave packets. Previous research has demonstrated that the extratropical teleconnection pattern can vary according to other climate modes by modifying MJO dynamic structures. This study focuses on investigating the direct influences of MJO intensity and speed on baroclinic wave packets over the North Pacific storm track and atmospheric river activity over the Pacific Northwest. An MJO tracking method is applied to estimate MJO characteristics, and composite teleconnection patterns are analyzed in terms of MJO diversity. Stronger MJO events result in stronger periodic patterns of atmospheric river activity over the Pacific Northwest due to robust Pacific-North America (PNA)-like structure triggered by intense MJO heating. The response of atmospheric river activity is found to be shifted earlier as the MJO propagation speed increases.
For the majority of MJO events, a positive geopotential height anomaly over the Central Pacific moves toward the east as the tropical convective heating propagates eastward following MJO phase 3. In contrast, the positive anomaly tends to remain over the Central Pacific for slow-propagating events, which is consistent with the extratropical response to found in previous idealized modeling studies with steady tropical heating. The positive height anomaly eventually shifts toward the north, resulting in opposite-signed atmospheric river activity over the Pacific Northwest. The results demonstrate the direct roles of MJO dynamic structures on midlatitude weather and provide the basis for potentially increasing forecast skill of atmospheric river events along the West Coast of North America.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA209...04T
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3362 Stratosphere/troposphere interactions;
- ATMOSPHERIC PROCESSES;
- 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSES