Category Archives: Haze Review

Review of Regional Haze Situation for May 2022

1.1 Inter-monsoon conditions started to give way to Southwest Monsoon conditions through May 2022 as the monsoon rainband continued to move northwards over the northern ASEAN region. The prevailing winds over the ASEAN region blew generally from the southeast or southwest, except for regions close to the Equator where winds were light and variable in direction (Figure 1).

1.2 Rainy weather was observed over most of the ASEAN region in May 2022 although drier conditions prevailed over the Lesser Sunda Islands and the northernmost parts of the Mekong sub-region. Heavy rainfall was observed in parts of southern Philippines, as well as the southern parts of both Myanmar and Thailand (Figure 1).

1.3 For May 2022, the total number of hotspots were lower or comparable to previous years for the same period (Figures 2 and 3), except in Sumatra and Kalimantan where a slightly higher number of hotspots were detected in May 2022 compared to previous years.

1.4 Isolated to scattered hotspots (Figures 4 and 5) and moderate smoke haze (Figure 6) were observed in the first week of May 2022 over northern parts of the Mekong sub-region. However, the onset of wetter conditions over the northern ASEAN region in subsequent weeks helped to suppress hotspot and smoke haze activities here. As wet conditions became established, the Alert Level over the Mekong sub-region was downgraded to Alert Level 1 on 10 May 2022, and the End of Dry Season (Alert Level 0) was declared on 19 May 2022.

1.5 The hotspot and smoke haze situation in the southern ASEAN region remained subdued as rainy conditions continued to prevail. Isolated hotspots were detected (Figures 4 and 5) and localised smoke plumes were observed to emanate from some of these hotspots in Borneo and the central Sumatra on some days.

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).

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.

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).

Review of Regional Haze Situation for March 2022

1.1 In March 2022, Northeast Monsoon conditions prevailed over the ASEAN region. While the prevailing winds over the areas north of the Equator blew mostly from the northeast or east, the winds over the Mekong sub-region were light and variable in direction. The prevailing winds over the areas south of the Equator blew mostly from the west or northwest. As the Northeast Monsoon conditions gradually weakened in the second half of the month, the prevailing winds over most of the ASEAN region were light and variable in direction on several days during the review period (Figure 1).

1.2 The dry conditions over the Mekong sub-region continued in March 2022, even though isolated showers were observed over the sub-region on some days. In the rest of the ASEAN region, generally wet conditions were observed but brief periods of drier weather were experienced in Sumatra and West Kalimantan (Figure 1).

1.3 For March 2022, the total number of hotspots were lower or comparable compared to previous years for the same period (Figure 2 & 3).

1.4 Scattered to widespread hotspots were detected during the continued dry weather conditions over the Mekong sub-region. Clusters of hotspots were more intense and persistent in Myanmar, Lao PDR and northeastern Cambodia, with smoke haze observed to emanate from these hotspots on several days. In particular, smoke haze was observed to be denser over parts of Myanmar and northern Lao PDR.

1.5 Elsewhere in the ASEAN region, isolated to scattered hotspots were observed mostly in the Philippines, central Sumatra, West Kalimantan and Sulawesi. Localised smoke plumes were observed to emanate from the hotspots detected in West Kalimantan and the western coastal areas of central Sumatra on some days in the second half of the month.

Review of Regional Haze Situation for February 2022

1.1 The ASEAN region continued to be influenced by Northeast Monsoon conditions in February 2022. Over areas north of the equator, the prevailing winds blew mainly from the northeast even though the winds were relatively weaker and more variable in direction over the Mekong sub-region. For areas south of the equator, the prevailing winds blew mostly from the west or northwest (Figure 1).

1.2 Dry conditions persisted over the Mekong sub-region throughout the review period of February 2022, except for isolated shower activities in the southern parts of the sub-region on some days. Elsewhere in the ASEAN region, rainy weather was observed in many areas. However, parts of Sumatra, Borneo, and the Philippines experienced brief periods of drier weather.

1.3 Prolonged dry conditions over the Mekong sub-region led to an increase in overall hotspot activity in February 2022. While isolated to scattered hotspots were detected in most parts of the sub-region on several days, the hotspot counts were generally lower this year compared to previous years (Figure 2). In the southern ASEAN region, hotspot activity was generally subdued, with only isolated hotspots detected in Sumatra and Kalimantan. The hotspot counts were also lower compared to previous years (Figure 3).

1.4 In view of the increase in hotspots and escalating smoke haze situation in the Mekong sub-region, ASMC activated Alert Level 2 for the sub-region on 11 February 2022. From the middle of the month, persistent hotspots and a few localised smoke plumes were detected in many parts of the Mekong sub-region, particularly over Myanmar, northern Cambodia, and southern Lao PDR (Figures 4 and 5). By the end of the month, moderate to dense smoke haze was observed to emanate from persistent hotspot clusters in Myanmar, northern Thailand, northern Cambodia, and southern Lao PDR (Figures 6 and 7).

Review of Regional Haze Situation for January 2022

1.1 Northeast Monsoon conditions persisted over the ASEAN region in January 2022. This month, the prevailing low-level winds over regions north of the Equator blew mostly from the northeast or east while the prevailing low-level winds over regions south of the Equator blew mainly from the west or northwest. Under the influence of the Northeast Monsoon, persistent dry conditions were observed over the Mekong sub-region. Relatively dry weather was also observed over parts of Peninsular Malaysia, Singapore, the Philippines and Sumatra in January 2022. Wetter conditions were observed over regions south of the Equator during the review period in line with the monsoon rainband’s position south of the Equator.

1.2 In January 2022, hotspot activities started to increase in the Mekong sub-region as dry conditions prevailed, while wet conditions helped subdue hotspot activities in the southern ASEAN region. The hotspot counts for the Mekong sub-region in January 2022 were mostly lower compared to previous years, while the hotspot counts over the southern ASEAN region were generally similar to previous years (Figures 2 and 3).

1.3 The Mekong sub-region remained at Alert Level 1 for the month as the risk of transboundary haze remained low. However, there was an increase in hotspot activities with localized smoke plumes in persistently dry areas of the sub-region. In particular, clusters of scattered hotspots with visible smoke plumes were detected in northeastern Cambodia on several days. Elsewhere in the ASEAN region, hotspot activities remained mostly subdued (Figures 4 and 5).

Review of Regional Haze Situation for December 2021

1.1 By December 2021, Northeast Monsoon conditions had become fully established over the ASEAN region. The prevailing low-level winds over regions north of the equator blew mostly from the north or northeast while the winds over regions south of the equator blew mainly from the west or northwest. Alert Level 1 for the Mekong sub-region was issued on 7 December 2021, indicating the start of the dry season. Persistent dry conditions were observed over the sub-region in December 2021. Higher rainfall was observed over the rest of the ASEAN region, particularly over Peninsular Malaysia and the southern Philippines, which were affected by heavy rainfall in December 2021 (Figure 1). In particular, Super Typhoon Rai made landfall over the southern Philippines on December 16, 2021 and caused severe damage, flooding and loss of lives. Floods also affected several Malaysian states including Pahang, Melaka, Negri Sembilan and Johor in the second half of December, resulting in significant damage and casualties.

1.2 For the December 2021 review period, overall hotspot activities started to increase in the Mekong sub-region following the onset of dry conditions, while wet conditions continued to subdue hotspot activities in the southern ASEAN region. The hotspot counts for the Mekong sub-region in December 2021 were mostly lower compared to previous years, while the hotspot counts over the southern ASEAN region were generally comparable to those in previous years (Figures 2 and 3).

1.3 During the review period, isolated to scattered hotspots were detected throughout the Mekong sub-region and isolated smoke plumes were sometimes observed to emanate from the detected hotspots. Although isolated hotspots were detected in Sumatra, parts of Peninsular Malaysia and Kalimantan, the hotspot activities were generally subdued over the southern ASEAN region (Figures 4 and 5).

Review of Regional Haze Situation for November 2021

1.1 In November 2021, the inter-monsoon conditions gradually made way for the Northeast Monsoon over the ASEAN region. The prevailing low-level winds over the northern ASEAN region blew mostly from the northeast or east while the winds over most parts of the southern ASEAN region were light and variable in direction. Wet weather conditions were observed over most parts of the ASEAN region, except for the northern parts of the Philippines as well as the northern, western and central parts of the Mekong sub-region where conditions were persistently drier. Overall, the observed rainfall amount was higher over the coastal areas of central Viet Nam, the southern parts of Thailand and the coastal areas of northern Peninsular Malaysia (Figure 1). Due to the heavy rainfall, floods affected several southern Thailand and central Viet Nam provinces in November 2021.

1.2 For the November review period, overall hotspot activities were mostly subdued due to the wet conditions over the ASEAN region. The hotspot counts over the region for 2021 were mostly lower or comparable to those in previous years (Figures 2 and 3).

1.3 During the review period, isolated to scattered hotspots were detected mainly in the Mekong sub-region and central Sumatra. While these hotspots were mostly short-lived, hotspots were relatively more persistent in the southern parts of Myanmar, northern Viet Nam and central Thailand. On most days, no smoke plumes were discernable.

Review of Regional Haze Situation for October 2021

1.1 Southwest Monsoon conditions transitioned to the inter-monsoon in mid-October 2021 as the winds over most parts of the ASEAN region turned light and variable (Figure 1). In the first half of October 2021, Tropical Storm Lionrock and Typhoon Kompasu contributed to increased rainfall over the northern parts of the Philippines and central parts of Viet Nam. In particular, Typhoon Kompasu caused significant damage and casualties in the Philippines due to landslides and flash floods. The southern ASEAN region experienced continued shower activities during the review period and Alert Level 0 was issued for the region on 18 October 2021, signaling the end of its traditional dry season. Average daily rainfall was relatively higher in western Kalimantan and northern Sumatra, while persistent dry conditions were observed over eastern Java and the Lesser Sunda Islands.

1.2 In October 2021, overall hotspot activity in the ASEAN region was subdued, contributed by wet weather conditions. While most of the hotspots in the southern ASEAN region were detected in Kalimantan, the number of hotspots for the southern ASEAN region were lower or comparable to previous years’ counts (Figure 2), except for Sabah and Sarawak where it was slightly higher. For the northern ASEAN region, most of the hotspots were detected in Viet Nam. The number of hotspots detected in the northern ASEAN region were also lower or comparable to previous years (Figure 3).

1.3 For the October 2021 review period, isolated to scattered hotspots were detected mainly in central Viet Nam, Borneo, and Sumatra (Figure 4 and 5). On a few days, short-lived localized smoke haze was observed to emanate from clusters of hotspots in central Kalimantan. There was no transboundary smoke haze observed over the ASEAN region during the review period.

Review of Regional Haze Situation for September 2021

1.1 In September 2021, Southwest Monsoon conditions persisted over the ASEAN region as the prevailing winds blew mainly from the southeast or southwest (Figure 1). In particular, there were three tropical cyclones that affected the northern ASEAN region during the review period. In the first half of September 2021, Typhoon Chanthu and Tropical Storm Conson contributed to the increased rainfall over northern parts of the Philippines. In the last week of the review period, Tropical Storm Dianmu made landfall over Viet Nam, and widespread showers with gusty winds caused floods and landslides in Viet Nam, Lao PDR and Thailand. For the southern ASEAN region, rainy weather was observed over many areas despite this period of the year being its traditional dry season. Average daily rainfall was highest in Sabah, western Kalimantan, and central Sumatra, while relatively drier conditions were observed over the Java Sea region.

1.2 For the September 2021 review period, hotspot activity in the ASEAN region was generally subdued due to wet weather. Most hotspots in the southern ASEAN region were detected in Kalimantan. Overall, the number of hotspots for the southern ASEAN region were lower or comparable to previous years’ counts (Figure 2). For the northern ASEAN region, a majority of the hotspots were detected in Viet Nam. The hotspot counts in Viet Nam, Lao PDR and Myanmar were slightly elevated compared to the same review period in previous years, while the hotspot counts elsewhere in the northern ASEAN region were lower compared to the same review period in previous years (Figure 3).

1.3 In September 2021, isolated to scattered hotspots were detected mainly in Viet Nam, Borneo, and southern Sumatra (Figure 4 and 5). On a few days in the month, localized smoke haze was observed to emanate from persistent hotspot clusters in western Kalimantan. Slight smoke plumes were occasionally detected from some of the isolated hotspots in eastern Kalimantan and southern Sumatra. Otherwise, no significant transboundary smoke haze was observed over the ASEAN region during the review period.

Review of Regional Haze Situation for August 2021

1.1 With the low-level winds blowing from the southeast or southwest on most days, Southwest Monsoon conditions continued to prevail over the ASEAN region in August 2021 (Figure 1). The first week of August was relatively dry for most parts of the southern ASEAN region, with the monsoon rain band located north of the Equator. In subsequent weeks, the movement of the monsoon rain band closer to the Equator brought wet weather to much of the ASEAN region except its southernmost regions (Java, the Lesser Sunda Islands and southern Sumatra).

1.2 For the August 2021 review period, the hotspot counts over the southern ASEAN region were much lower than those detected in previous years (Figure 2). The hotspot counts over the northern ASEAN region were similar to those detected in previous years, with the exception of Thailand and Viet Nam which recorded higher hotspot counts (Figure 3).

1.3 Isolated to scattered hotspots continued to be detected in most parts of the southern ASEAN region in August 2021 (Figures 4 and 5). There was increased hotspot activity in areas where drier conditions were experienced, such as over the southern ASEAN region in the first week of August, and throughout the month in Java and the Lesser Sunda Islands. At times this month, localised smoke plumes were observed emanating from clusters of hotspots in Sumatra and Kalimantan. This was particularly so for West Kalimantan, where a persistent cluster of hotspots was observed on most days this month (Figure 5).

1.4 Isolated hotspots were detected mainly in the southeastern parts of the northern ASEAN region in August 2021. Towards the middle of the month, localised smoke plumes were observed in parts of central Viet Nam; no smoke plumes were observed elsewhere in the northern ASEAN region (Figures 4 and 5).