Role of the Madden‐Julian Oscillation in the Transport of Smoke From Sumatra to the Malay Peninsula During Severe Non‐El Niño Haze Events

In June 2013, the Malay Peninsula experienced severe smoke pollution, with daily surface particulate matter (PM) concentrations in Singapore greater than 350 μg/m3, over 2 times the air quality standard for daily mean PM10 set by the U.S. Environmental Protection Agency. Unlike most haze episodes in the Malay Peninsula in recent decades (e.g., the September 2015 event), the June 2013 haze occurred in the absence of an El Niño, during negative Indian Ocean Dipole conditions, with smoke carried eastward to the Peninsula from fires in the Riau province of central Sumatra. We show that June 2013 was not an exceptional event; inspection of visibility data during 2005–2015 reveals two other severe haze events in the Malay Peninsula (August 2005 and October 2010) occurring under similar conditions. Common to all three events was a combination of anomalously strong westerly winds over Riau province concurrent with late phases of the Real‐Time Multivariate Madden‐Julian Oscillation Index, during negative phases of the Indian Ocean Dipole. Our work suggests that identifying the meteorological mechanism driving these westerly wind anomalies could help stakeholders prepare for future non‐El Niño haze events in Singapore and the Malay Peninsula. Key Points Three recent, severe haze events in the Malay Peninsula cannot be explained by El Nino‐positive Indian Ocean Dipole conditions All three events are associated with anomalous westerly wind speeds occurring over Riau as the Madden‐Julian Oscillation moves across Indonesia Late phases of the MJO are associated with the transport of extreme smoke pollution from Riau province to the Malay Peninsula