Review of Regional Haze Situation for August 2023 |

Review of Regional Haze Situation for August 2023

1.1 In August 2023, the southwest monsoon conditions continued as the prevailing winds blew from the southwest or west over the northern ASEAN region and blew from the southeast or southwest over the southern ASEAN region (Figure 1). The southwesterly winds over the northern parts of the Philippines were strong at times under the influence of Super Typhoon Saola towards the end of the month.

1.2 As the monsoon rainband moved further north of the Equator, it was dry on most days of the month over Java, the Lesser Sunda Islands, Sulawesi and the southern parts of Sumatra and Kalimantan. Showers were observed over the rest of the ASEAN region on most days. In particular, Super Typhoon Saola brought intense and widespread rainfall over the northern parts of the Philippines (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for August 2023. (Source: JAXA GsMaP and GFS, respectively)

1.3 Compared to July 2023, there was a significant increase in the number of hotspots over the southern ASEAN region in August 2023 with the highest increase in hotspot activity observed over Kalimantan. Year-on-year comparison (Figure 2) also shows higher hotspot counts in Kalimantan compared to the past 3 years and were comparable to the hotspot count in 2019. In the rest of the ASEAN region, the overall hotspot counts were lower or comparable to previous years.

Figure 2: Hotspot counts for the southern ASEAN region for August (2019-2023) based on NOAA-20 satellite surveillance.

Figure 3: Hotspot counts for the northern ASEAN region for August (2019-2023) based on NOAA-20 satellite surveillance.

1.4 Under the prolonged dry conditions, clusters of hotspots were detected in Kalimantan (Figure 4) with more intense and persistent hotspots located mostly in South and West Kalimantan (Figure 4 and 5). Isolated hotspots were also detected mainly in Java, the Lesser Sunda Islands, Sulawesi and the southern and central parts of Sumatra (Figure 4). Moderate smoke haze was observed on some days in Kalimantan as well as in the southern and central parts of Sumatra (Figure 9). The smoke haze situation over South and West Kalimantan escalated towards the end of the month with dense smoke haze observed on some days (Figure 6 and 8). The smoke haze over West Kalimantan was also observed to drift northwards into western Sarawak on a few occasions (Figure 6 and 7). In the northern ASEAN region, the hotspot activity remained low under the prevailing wet weather with isolated hotspots mostly detected in Viet Nam (Figure 4).

Figure 4: Distribution of hotspots detected in August 2023 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in August 2023 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense haze observed in August 2023 based on NOAA-20 satellite surveillance.

Figure 7: Slight to moderate smoke haze was observed in West Kalimantan drifting northwards towards western Sarawak on 31 August 2023. (Source: Himawari-9 satellite)

Figure 8: Moderate to dense smoke haze were observed over South Kalimantan on 31 August 2023. (Source: Himawari-9 satellite)

Figure 9: Moderate smoke plumes were observed to emanate from hotspots detected in the southern parts of Sumatra on 31 August 2023. (Source: Himawari-9 satellite)