chervin

Transboundary smoke haze from land and forest fires during the traditional dry period between June and October has been a recurrent feature in the southern ASEAN region in the past few decades. These annual fires are caused mainly by land clearing and “slash and burn” agricultural practices in Indonesia, particularly Sumatra and Kalimantan. In the northern ASEAN region, agricultural burning activities are common during the traditional dry season between December and March can also cause large scale smoke haze at times. The smoke haze situation is usually exacerbated when it coincides with the El Niño, a climatic phenomenon that often leads to prolonged and drier weather conditions in the region.  
Apart from satellite imageries, various haze related information, air quality indicators and dispersion model forecasts are used as monitoring and assessment tools in regional fire and smoke haze surveillance

 Mild haze began to affect Singapore on 13 June,^[107] before air quality worsened and remained in theUnhealthy range for a few days.^[108] Pollutant Standards Index (PSI) first hit levels unseen in 16 years when a PSI of 155 was recorded at 10 p.m. on 17 June 2013. The highest in the 16 years of the haze was finally broken.^[54] At 10 p.m. on 19 June 2013, the 3-hour PSI reading of 321 breached theHazardous zone for the first time in the nation's history, surpassing its previous record of 226 (Very unhealthy) during the 1997 haze.^[109] However, the 10 p.m. reading was released 57 minutes late at 10:57 p.m. and the reading soon decreased to 282 at 11 p.m., and 218 at 12 a.m., both of which are in the Very unhealthy range. At 1 p.m. on 20 June 2013, the 3-hour PSI reading reached record levels once again with a reading of 371 in the Hazardous range a jump from 299 an hour ago, which was only one point shy of the "Hazardous" level. The PM2.5 concentration also reached 300 for the first time in the nation's history.^[110]