May 22 - July 31
Madden-Julian Oscillation (MJO) Teleconnections and their Impact on Precipitation in South America
Jacob Hamil, Tatiana Esteva-Ingram, Naoko Sakaeda
What is already known:
- The MJO impacts the extratropics through the generation of Rossby Wave Trains.
- There is a greater understanding of how MJO teleconnections impact the Northern Hemisphere than in the Southern Hemisphere.
- The MJO is the leading source of predictability on sub-seasonal timescales, so any improvement in our understanding of MJO teleconnections will improve forecasting at this timescale.
What this study adds:
- The MJO has robust impacts on precipitation in South America but the impacts exhibit strong seasonality.
- During the Southern Hemisphere winter (June-July-August), an MJO-initiated Rossby Wave Train exists and likely provides synoptic forcing for precipitation in Central South America.
- During the Southern Hemisphere summer (December-January-February), MJO impacts precipitation in Northern South America in a manner different from the Rossby Wave Train which remains unknown.
Abstract:
The Madden-Julian Oscillation (MJO) is a tropical planetary scale area of active and suppressed convection in the Indian and Pacific Oceans that impacts extratropical weather through teleconnections. Understanding MJO teleconnections is important because they are an important source of predictability on subseasonal timescales (30 to 90 days). There is a broad understanding of how MJO teleconnections impact the Northern Hemisphere, but there is less understanding of how they impact the Southern Hemisphere. This study will attempt to fill this gap by exploring the seasonality of MJO-induced precipitation in the Southern Hemisphere and seeing if any teleconnections lead to increased or decreased precipitation anomalies. The data sources that will be utilized include MJO tracking indexes, IMERG daily rainfall data, and ERA5 200 hPa height data. All three of these data sources will be used to create precipitation anomaly and 200 hPa height anomaly graphics for each phase of the MJO. We found that the MJO generates a Rossby wave train in the Southern Hemisphere during JJA and generates the height patterns over South America that are related to positive rainfall anomalies during MJO phases 1 and 2. However, we also found that height patterns from the Rossby wave train do not seem to explain MJO-associated rainfall anomalies during phase 8 of DJF. This information could be beneficial to forecasters in South America as it could give more lead time to prepare for extreme precipitation or drought episodes.