MJO Prediction and Teleconnections

1. MJO Prediction and Teleconnections Science Objectives. • The relationship between the MJO and High Impact Weather in the tropics and the potential for predictive skill for these events • Tropical-extratropical teleconnections associated with the MJO and the potential for extratropical skill associated with the MJO • How well do S2S models represent (A/B) • Does (A/B) lead to enhanced predictive skill for (HIW/Extra-tropics)?

2. MJO and HIW • Evaluate how well operational S2S models capture the observed relationship between the MJO and high-impact weather events • Identify whether the relationship between the MJO and high-impact weather events lead to enhanced predictive skill for these events for particular phases of the MJO or whilst there is strong MJO activity • Investigate whether errors in the representation of the relationship between high-impact weather and the MJO be attributed to: e.g. • errors in the model basic state; • errors in the modulation of the large-scale environmental conditions associated with the MJO; and/or • errors in the response of physical parametrizations to the MJO modulation of the environment. • Evaluate how well S2S models capture tropical moisture exports, potential vorticity streamers, and their interactions, associated with extreme rainfall events in the tropics and subtropics.

3. Percent of heavy precipitation events (> 90%ile) in each phase of MJO during MAM compared to total number of days in that phase. The percentages of grid points within the (land) domain with fewer than 6% or more than 14% heavy events (the chosen local significance levels) are shown in the top-left and top-right, respectively, of each map. Wind vectors (m s−1) show 850-hPa wind anomalies (phase indicated minus inactive). Dots in the bottom-left corner of each map indicate field significance (see text for explanation) for increased (blue) and decreased (red) frequency of heavy events. From Sossa et al. (J. Clim, 2017)

4. MJO and Teleconnections • Investigate how teleconnection depend on the horizontal, vertical and temporal structure of the diabatic heating anomalies associated with the MJO? • Investigate how variations in the slowly varying background state effect the Rossby wave source and the subsequent Rossby wave propagation from the source region • Investigate how the tropical circulation, most especially the MJO, responds to forcing from the extra-tropical circulation (e.g. NAO). • Evaluate the representation of MJO teleconnections in S2S models and investigate how errors in teleconnections can be attributed to errors in the diabatic heating anomalies and/or errors in the basic state

5. NAO- NAO+ AR SB NAO- NAO+ AR SB NAO- NAO+ AR SB 0 1 2 3 4 5 6 7 8 MJO Phase All Years La Niña El Niño Change in frequency of North Atlantic Regimes for days following MJO Phase in El Niño, La Niña and all Years. e.g. NAO+ teleconnection following MJO phase 2-3-4 is greatly enhanced in El Niño years and reduced in La Niña years From Lee at al. (in prep)

6. YTMIT • Special issue of the Atmosphere-Ocean journalhighlightingscience of the YTMIT project • Review of submissions completed • YTMIT-MJO Task force collaboration • Wang et al. 2019: MJO Teleconnections over PNA region in climate models. Part I: Performance- and process-based skill metrics, J. Climate (to be submitted) • Teleconnections – YOPP • Hai Lin: Subseasonal Forecast Skill over the Northern Polar Region in Three Operational S2S Systems

7. Polar (60-90N) T2m skill dependence on MJO phase Courtesy of Hai Lin