Observations of eastward propagation of atmospheric intraseasonal oscillations from the Pacific to the Atlantic

Significant 40–60 day intraseasonal variability in surface winds, sea level, and thermocline depth were observed in the tropical Atlantic during the Atlantic Niño year of 2002. Satellite-derived QuikSCAT winds and NOAA Outgoing Longwave Radiation (OLR) measurements for the period of 2000–2006, together with reanalysis of winds from a longer record, are analyzed to understand the sources of this 40–60-day wind variability and the global propagation of the Madden-Julian Oscillation (MJO) surface signatures. The results demonstrate that the MJO propagated eastward from the Indo-Pacific Ocean to the Atlantic during winter and spring of 2002, causing 40–60 day wind variations in the equatorial Atlantic. The Isthmus of Panama appears to be a dominant pathway for these surface wind anomalies to propagate into the Atlantic, where they can produce important climate impacts. This result is consistent with previous work that has demonstrated a strong MJO influence on the North American Monsoon (NAM) region, and complements other work demonstrating the propagation of intraseasonal wind anomalies and accompanying sea level pressure signals associated with dry equatorial Kelvin waves that reach the Caribbean through the Panama gap. The MJO is also shown to have a large influence on the subtropical Atlantic Ocean. Seasonality of the MJO impact on Atlantic surface winds is investigated using data from an extended record, and the most direct influence is found to be during boreal winter and spring, with a delayed influence during summer and fall.