Haze Review

Review of Regional Haze Situation for May 2020

1.1 The inter-monsoon conditions that prevailed over the ASEAN region in May 2020 transitioned to Southwest Monsoon conditions in late-May 2020. The presence of the monsoon rain band further north of the Equator brought an increase in shower activities over the Mekong sub-region in the latter half of the month. In the southern ASEAN region, scattered showers fell over most parts of the region. During the review period, the prevailing winds over the ASEAN region were light and variable in direction but gradually shifted to blow from the southeast or southwest with the start of the Southwest Monsoon season.

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

1.2 In early May 2020, most of the hotspot activities were detected in Lao PDR, Myanmar and Viet Nam. An increase in shower activities over the northern ASEAN region during the month contributed to a gradual reduction of hotspot activities in the Mekong sub-region. In the southern ASEAN region, the hotspot activities continued to remain subdued due to wet weather over many parts of the region.

Figure 2: Hotspot count for the northern ASEAN region for May 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 May 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 May 2020, clusters of hotspots were detected mostly in the northern part of Lao PDR. These hotspots persisted for about one week. Isolated hotspots were also detected in Cambodia and Viet Nam on many days. In the southern ASEAN region, short-lived isolated hotspots were detected on some days.

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

1.4 In May 2020, hotspot activities were more intense in the northern parts of Myanmar and Lao PDR. Some of these hotspot activities contributed to the occurrence of smoke haze in the sub-region.

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

1.5 The increase in shower activities brought a further improvement to the haze situation in the Mekong sub-region in the first half of May 2020. During periods of drier weather in early May 2020, moderate smoke haze was observed mainly in the northern parts of Lao PDR. Localised smoke plumes were also observed to emanate from some of the hotspots in the Mekong sub-region on some days. In the southern ASEAN region, while there were localised hotspot activities, no significant smoke haze was observed.

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 May 2020.