Projecting the Madden-Julian Oscillation (MJO) modulation of atmospheric circulation onto Chilean winter precipitation

The Madden-Julian Oscillation (MJO) is the leading intraseasonal mode of tropical atmospheric variability. While a planetary scale circulation, it has been shown to modulate both synoptic and mesoscale precipitation and circulation. Winter precipitation in Chile has been connected to both synoptic- and mesoscale forcing mechanisms, including those from traveling mid-latitude cyclones, flow blocking, and local barrier jets. This study explored the links between the two, first examining the variability of Chilean precipitation using a sampling of different surface and remote-sensing datasets (surface gauges, the Tropical Rainfall Measuring Mission TRMM, and a proxy from outgoing longwave radiation) and then examining the variability of mesoscale-scale forcing and circulation. Particular attention was paid to how the MJO modulates flow blocking and the development of low-level wind maxima upstream and parallel to the Andes. These barrier jet phenomena have been shown to be important contributors to total precipitation during the winter season in central Chile.