Review of Regional Haze Situation for April 2022 |

Review of Regional Haze Situation for April 2022

1.1 The Northeast Monsoon gradually transitioned to inter-monsoon conditions in April 2022 as the monsoon rainband moved northwards over the equator. The prevailing winds over most parts of the ASEAN region were light and variable in direction on most days, except for the Philippines where winds blew mostly from the northeast or east (Figure 1).

1.2 Most parts of the Mekong sub-region experienced prolonged dry weather in April 2022, except for southern Cambodia and northern Myanmar where showers were observed on some days. Rainy weather conditions were observed elsewhere in the ASEAN region on most days during this period, although drier conditions prevailed over northern Philippines and the Lesser Sunda Islands. Heavy rainfall was observed in parts of central and southern Philippines, contributed by the passage of Tropical Storm Megi in the second week of April 2022 (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for April 2022. (Source: JAXA GsMaP and GFS, respectively)

1.3 For April 2022, the total number of hotspots were lower or comparable to previous years for the same period (Figures 2 and 3), except for Lao PDR where significantly higher numbers of hotspots were detected in April 2022 compared to previous years. Slightly more hotspots were detected in Sumatra compared to previous years.

Figure 2: Hotspot counts for the northern ASEAN region for the month of April (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

Figure 3: Hotspot counts for the southern ASEAN region for the month of April (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

1.4 Under the prevailing dry weather in April 2022, scattered to widespread hotspots were detected in most parts of the Mekong sub-region on many days. In particular, persistent clusters of high intensity hotspots, were detected in northern and central Lao PDR, as well as western and northeastern Myanmar during the month (Figures 4 and 5). Widespread moderate to dense smoke haze was observed to emanate from these hotspots on several days in early to mid- April, with transboundary haze observed to drift from Lao PDR into Thailand, Viet Nam and Cambodia on several days (Figures 6 and 7). As a result, Alert Level 3 was issued on 11 April 2022. As shower activities returned later in the month, the overall hotspot and smoke haze situation improved and a downgrade to Alert Level 2 was issued on 29 April 2022.

1.5 The hotspot and smoke haze situation in the southern ASEAN region remained comparatively subdued as rainy conditions prevailed. Isolated hotspots were detected and localised smoke plumes were observed to emanate from some of these hotspots in West Kalimantan and the western coastal areas of central Sumatra on some days (Figure 8).

Figure 4: Distribution of hotspots detected in April 2022 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in April 2022 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in April 2022 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate to dense smoke haze was observed over western and central
Myanmar, as well as over Lao PDR drifting into Thailand, Viet Nam and Cambodia (right).

Figure 8: Localised smoke plumes were observed to emanate from isolated hotspots in West Kalimantan (left) and the western coast of Central Sumatra (right) on some days.