Haze Review

Review of Regional Haze Situation for March 2020

1.1 While Northeast Monsoon conditions continued to prevail over the ASEAN region in March 2020, the prevailing winds over the Mekong sub-region during the month were mostly blowing from southeast or southwest. Despite an increase in isolated showers over the eastern parts of the Mekong sub-region, the weather over the sub-region remained largely dry during this period. In contrast, scattered showers fell over the southern ASEAN region, particularly over areas south of the equator.

Figure 1: Average Daily Rainfall for Mar 2020. (Source: JAXA GsMaP)

1.2 Scattered hotspots were detected in the Mekong sub-region, while hotspot activities remained subdued in the southern ASEAN region. In terms of the hotspot count, Lao PDR recorded one of the highest number of hotspots in March 2020 in comparison with previous years. Elsewhere in the region, there was no significant trend observed during the review period.

Figure 2: Hotspot count for the northern ASEAN region for Mar 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

Figure 3: Hotspot count for the southern ASEAN region for Mar 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

1.3 In March 2020, persistent hotspots were detected in many parts of the Mekong sub-region, particularly in Myanmar, northern and southern Lao PDR, parts of northern and central Thailand, northern Cambodia, as well as a few areas in southern Viet Nam. In the southern ASEAN region, hotspots were detected on occasions and these were mostly short-lived.

Figure 4: Distribution of hotspots detected based on NOAA-20 satellite surveillance for Mar 2020.

1.4 Over the aforementioned areas in the Mekong sub-region with persistent hotspots, the intensity of fires was also high relative to the other parts of the ASEAN region.

Figure 5: Maximum fire intensity based on NOAA-20 satellite surveillance in Mar 2020.

1.5 March 2020 saw a further deterioration in the haze situation over the Mekong sub-region, where many areas were enveloped in widespread smoke haze. In particular, dense haze was observed over eastern Myanmar, parts of northern and central Thailand, as well as the northern parts of Lao PDR and Viet Nam, where there were occurrences of transboundary smoke haze. On some days, transboundary smoke haze also affected southern Lao PDR, southern Viet Nam and northern Cambodia. The air quality levels in northern Thailand remained in the Unhealthy to Very Unhealthy range on most days in March 2020. Smoke haze in the Mekong sub-region also contributed to reduced visibility readings across several parts of the sub-region. In the southern ASEAN region, no significant smoke haze was observed except for localized smoke plumes from the short-lived hotspots in central Sumatra.

Figure 6: Number of days with moderate to dense smoke haze observed over an area based on satellite imageries, ground observations and air quality reports in Mar 2020.