Review of Regional Haze Situation for March 2021 |

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.

Figure 1: Average Daily Rainfall and Mean Wind for March 2021. (Source: JAXA GsMaP and GFS respectively)

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).

Figure 2: Hotspot counts for the northern ASEAN region for the month of March (2017 – 2021). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2017 – 2018 are based on the Suomi-NPP satellite.]

Figure 3: Hotspot counts for the southern ASEAN region for the month of March (2017 – 2021). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2017 – 2018 are based on the Suomi-NPP satellite.]

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.

Figure 4: Distribution of hotspots detected in March 2021 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in March 2021 based on NOAA-20 satellite surveillance.

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