Category Archives: Haze Review

Review of Regional Haze Situation for June 2021

1.1 The ASEAN region transitioned to Southwest Monsoon conditions in June 2021, with prevailing winds over regions south of the equator blowing from the southeast while prevailing winds over regions north of the equator blew mainly from the southwest.

1.2 During this period, the monsoon rain band stayed in close proximity to the equator and shower activities were observed over most of the ASEAN region. However, drier conditions persisted in the Lesser Sunda Islands and eastern Java (Figure 1).

1.3 The hotspot counts over most of the ASEAN region for June 2021 were comparable to those in previous years. More hotspots were detected in Cambodia and the Philippines compared to previous years while lesser hotspots were detected in Sumatra and Peninsular Malaysia compared to previous years. (Figures 2 and 3)

1.4 In June 2021, isolated hotspots were detected in most parts of the southern ASEAN region, contributed by brief periods of drier weather. Isolated to scattered hotspots were also detected in the eastern and central parts of the Mekong sub-region but were alleviated by an increase in shower activities. On the whole, hotspot activities remained relatively subdued in the ASEAN region with no significant smoke haze observed from satellite imagery (Figures 4 and 5).

Review of Regional Haze Situation for May 2021

1.1 Inter-monsoon conditions prevailed over most of the ASEAN region in May 2021. While most of the region experienced light and variable winds, the prevailing winds over Java, the Lesser Sunda Islands, the Philippines, and Sulawesi blew from the east or southeast.

1.2 During this period, shower activities were observed over most of the ASEAN region. However, drier conditions persisted in the Lesser Sunda Islands and eastern Java (Figure 1).

1.3 For the May review period, the hotspot counts over the ASEAN region for 2021 were slightly lower or comparable to those in previous years (Figures 2 and 3).

1.4 Although hotspot activities were detected in most parts of the ASEAN region, no significant smoke haze was observed in May 2021. Isolated hotspots were detected in most of the southern ASEAN region, contributed by the development of drier conditions there. In the northern ASEAN region, although some hotspot clusters were detected, an increase in shower activities throughout the month led to a gradual improvement of the hotspot situation. ASMC declared the end of the northern ASEAN dry season on 21 May 2021 with the downgrading of Alert Level 1 to Alert Level 0 (Figures 4 and 5).

Review of Regional Haze Situation for April 2021

1.1 In April 2021, Northeast Monsoon conditions transitioned to Inter-monsoon conditions as the prevailing winds over most of the ASEAN region became light and variable in direction, except over the Philippines where the prevailing winds blew from the north or northeast.

1.2 During this period, there was an increase in shower activities over most of the northern ASEAN region as the monsoon rainband shifted northwards to be located near the Equator. However, the northern and northwestern parts of the Mekong sub-region experienced drier conditions compared to the other parts of the sub-region. In the southern ASEAN region, wet conditions generally prevailed (Figure 1).

1.3 The hotspot counts over the ASEAN region for April 2021 were either comparable or lower than the previous years in the same review period except for Kalimantan where hotspot counts were higher than previous years (Figures 2 and 3).

1.4 Hotspot activities were detected in most parts of the northern ASEAN region in April 2021. The hotspot clusters over Myanmar and the northern parts of Lao PDR were more persistent and widespread due to drier conditions over these areas (Figures 4 and 5).

1.5 Moderate to dense smoke haze was observed to emanate from hotspot clusters detected in the northern and southern parts of Lao PDR, and most parts of Myanmar (Figure 6). Smoke haze from the eastern parts of Myanmar and northern parts of Lao PDR was also observed to have been blown into the northern parts of Lao PDR and Viet Nam respectively by the prevailing winds on some days. In view of increased shower activities towards the end of April 2021 helping to improve the hotspot and haze situation over the Mekong sub-region, the Alert Level was downgraded from Alert Level 2 to Alert Level 1 on 30 April 2021.

1.6 In the southern ASEAN region, brief periods of drier conditions led to the development of isolated hotspots mostly in Peninsular Malaysia, Borneo Island, Sumatra and Sulawesi (Figures 4 and 5). No smoke plumes were observed to have emanated from these hotspots (Figure 6).

Review of Regional Haze Situation for March 2021

1.1 In March 2021, Northeast Monsoon conditions gradually weakened over the ASEAN region and the prevailing winds started to turn light and variable on several days. In the northern ASEAN region, the prevailing winds blew mainly from the northeast or southeast, although light and variable winds prevailed over the western parts of the Mekong sub-region. Extended dry conditions persisted over the sub-region in this month as its traditional dry season became established.

1.2 For the southern ASEAN region, the prevailing winds blew mainly from the northeast or east. Northern and central Sumatra as well as parts of Peninsular Malaysia experienced drier conditions in early March 2021 under the influence of the dry phase of the Northeast Monsoon. Elsewhere over the ASEAN region, isolated to scattered showers were observed.

1.3 For March 2021, slightly higher hotspot counts were detected in Cambodia compared to previous years for the same period. In other parts of the ASEAN region, the hotspot counts for March this year were lower or comparable to previous years (Figures 2 and 3).

1.4 Widespread to scattered hotspot activities were detected in most parts of the Mekong sub-region in March 2021, especially in Myanmar, northern Thailand, northern Cambodia and Lao PDR where persistent clusters of hotspots were detected on many days (Figures 4 and 5), contributed by continued dry conditions throughout the month.

1.5 Moderate to dense haze was observed emanating from clusters of hotspots on most days in the Mekong sub-region, particularly over Myanmar and northern parts of Thailand, Lao PDR and Cambodia (Figure 6).

1.6 In the southern ASEAN region, there were brief periods of drier weather in the first half of March 2021 over northern and central Sumatra, Peninsular Malaysia and West Kalimantan. This led to the development of isolated hotspots with localised smoke plumes on several days in the drier areas. As shower activities returned in late March 2021, the hotspot activities and smoke haze situation became more subdued.

Review of Regional Haze Situation for February 2021

1.1 Northeast Monsoon conditions continued to prevail over the ASEAN region in February 2021. In the northern ASEAN region, the prevailing winds blew mainly from the east or the northeast although the strength of the winds was weaker over the Mekong sub-region. For parts of the southern ASEAN region north of the Equator, the winds blew mainly from the north, while south of the Equator, they blow from the northwest or west.

1.2 Dry conditions persisted over the Mekong sub-region in February 2021. Additionally, Sumatra, Peninsular Malaysia, and the northern and western parts of Borneo Island experienced periods of drier weather. Isolated to scattered showers fell elsewhere over the ASEAN region.

1.3 In Myanmar and Kalimantan, the hotspot counts were slightly higher for the month of February this year as compared to prior years for the same review period. In other parts of the ASEAN region, the hotspot counts this year were comparable to previous years (Figures 2 and 3).

1.4 In the northern ASEAN region, hotspot activities were detected in most parts of the Mekong sub-region. Persistent clusters of hotspots were also detected in Cambodia, southern Lao PDR, and northern Myanmar (Figures 4 and 5).

1.5 Throughout the month, intermittent cloudy conditions were observed over various parts of the Mekong sub-region which were associated with isolated to scattered showers. In areas that received rainfall, the hotspot and smoke haze situation was temporarily subdued. However, by the end of the month, dry and fair conditions had returned to the sub-region. This led to an escalation of the fire and smoke haze situation, particularly over northern Myanmar, northwestern Thailand, and northern Cambodia where moderate to dense smoke haze was observed (Figure 6).

1.6 In the southern ASEAN region, periods of drier weather over northern Sumatra, Peninsular Malaysia and the western parts of Borneo Island led to a progressive escalation of hotspot activities in these areas during the month. Localised smoke plumes were observed to emanate from some of these hotspots on several days. By the end of the month, moderate to dense smoke haze were observed to emanate from persistent hotspot clusters in West Kalimantan and Central Kalimantan.

Figure 6: Number of days with moderate to dense smoke haze observed in February 2021 over an area based on satellite imagery, ground observations and air quality reports.