An Operational Approach to Predicting the Global Circlulation Impacts of Simultaneous Interaction between the MJO and Equatorial Rossby Waves

The Madden-Julian Oscillation (MJO) is the leading mode of intraseasonal rainfall variability in the tropics. The MJO has been proven to play a role in intraseasonal temperature and precipitation variability in both the tropics and extratropics. Indices of the MJO thus provide insight about the likelihood of changes in the extratropical circulation. Recent research indicates that further insight can be obtained by considering the simultaneous states of convectively coupled equatorial waves along with the MJO. For example, composite 500-hPa geopotential height anomalies based on MJO indices exhibit significantly higher amplitudes when the simultaneous effects of phasing with equatorial Rossby waves (ERWs) are also considered. Operationally, understanding the interaction between these tropical modes and their roles in modulating the extratropical circulation yields benefits in improving the skill of long range forecasting.

A 30 year analysis of the simultaneous signals in the MJO and ERWs and the associated signals in 200-hPa streamfunction anomalies, 500-hPa geopotential height anomalies and 1000-hPa temperature anomalies is performed using the Climate Forecast System (CFS ) version two reanalysis dataset. A real time ERW index is used to define a phase space for tracking ERWs while Wheeler and Hendon's RMM index is utilized to identify the MJO. Statistical analysis is utilized to identify a systematic approach to grouping ERW signals based on statistically similar extratropical responses. Composite maps, histograms, and tables are then generated to diagnose how interactions between the MJO and ERW affect the risk for heat or cold over the continental United States.

This presentation will identify the constructive and destructive relationships between the MJO, ERW and heat and cold risk across the Midwest-East (US) region as defined by EarthRisk Technologies. Results from the operational implementation of the aforementioned MJO and ERW interactions will also be presented.