Category Archives: Haze Review for Year 2023

Review of Regional Haze Situation for December 2023

1.1 In December 2023, the prevailing winds over areas north of the Equator in the ASEAN region blew mostly from the northeast or east while the prevailing winds over areas south of the Equator were predominantly light and variable in direction (Figure 1). This signalled the establishment of Northeast Monsoon conditions over the ASEAN region. At times during the month, the northeasterly winds strengthened over parts of the Mekong sub-region and the South China Sea as well as over Peninsular Malaysia and Singapore, and brought periods of widespread rainfall associated with the monsoon surge.

1.2 Dry conditions were observed over the Mekong sub-region except for the coastal areas in the southern parts of Viet Nam where some showers occurred (Figure 1). The Alert Level 1 for the onset of the dry season for the northern ASEAN region was issued on the 14 December 2023. Rainfall was recorded over the rest of the ASEAN region except for the northern and the central parts of the Philippines where conditions were dry. Rainfall was noticeably higher over the eastern coastal areas of Peninsular Malaysia, southern parts of Thailand and the northern parts of Sabah, East Malaysia partly due to the occurrence of the monsoon surge (Figure 1). During the monsoon surge that occurred towards the end of the month, floods and landslides were reported which resulted in fatalities, displacement of people from homes and infrastructure damages in Peninsular Malaysia and the southern parts of Thailand. Higher rainfall amounts were also observed over Mindanao region, Philippines (Figure 1) partly due to the influence of Tropical Storm Jelawat which passed through the island between 17 and 19 December 2023, causing floods in the region.

1.3 The overall hotspot counts for the southern ASEAN region were mostly higher in December 2023 compared to previous years, particularly in Kalimantan and Sumatra as well as Sabah and Sarawak (Figure 2). In the northern ASEAN region, the hotspot counts were comparable to previous years (Figure 3).

1.4 Isolated to scattered hotspots were detected in the Mekong sub-region (Figure 4). While most of the hotspots were short-lived, some were persistent and intense. Clusters of hotspots were observed in the southern parts of Myanmar as well as the southwestern and eastern parts of Cambodia (Figure 4 and 5). A few persistent hotspots were also detected in parts of Thailand (Figure 4). A localised moderate smoke plume was observed to emanate from the hotspots detected in the southwestern parts of Cambodia on a few days (Figure 6 and 7)

Review of Regional Haze Situation for November 2023

1.1 The inter-monsoon conditions prevailed over the ASEAN region in November 2023. The prevailing low-level winds over the northern ASEAN region blew from the northeast to east while the winds over most parts of the southern ASEAN region were generally light and variable in direction (Figure 1).

1.2 Most of the ASEAN region experienced wet weather during November 2023, except for the northeastern and central parts of the Mekong sub-region where the conditions were relatively drier. Over the northern ASEAN region, rainfall amount was higher over the coastal areas of Viet Nam, Philippines and the southern parts of the Mekong sub-region. Widespread rainfall fell over much of the southern ASEAN region with the heaviest rainfall observed over the northern and eastern parts of Peninsular Malaysia (Figure 1). The ASMC Alert Level 0 was issued on the 14 November 2023, signalling the end of the dry season for the region.

1.3 For the southern ASEAN region, the overall hotspot activity in November 2023 was generally higher than previous years, except for November 2019 (Figure 2). Over the Mekong sub-region, the overall hotspot counts in November 2023 were mostly comparable to previous years. (Figure 3).

1.4 Throughout the review period, few to isolated hotspots were detected in the ASEAN region. While most of these hotspots were short-lived, hotspots were relatively more persistent in the central parts of Thailand and the southern parts of Myanmar and Sumatra (Figure 4). The overall fire intensity in the ASEAN region was generally low, except for the southern parts of Sumatra where relatively higher fire intensity was observed (Figure 5). Moderate smoke haze was mainly observed in the southern parts of Sumatra during the beginning of the month (Figures 6 and 7).

Review of Regional Haze Situation for October 2023

1.1 The Southwest Monsoon gradually transitioned into inter-monsoon conditions from the end of October 2023. As the monsoon rainband moved towards the Equator, the prevailing winds weakened and turned light and variable over the equatorial regions (Figure 1). During the first week of October, Typhoon Koinu (Figure 9) brought about heavy rainfall and strong winds over parts of the northern Philippines.

1.2 Dry weather persisted over much of the southern ASEAN region for the first half of October, with moderate to dense haze observed mainly over southern and central Sumatra, as well as southern and central Kalimantan (Figure 6). Towards the end of October, there was an increase in showers over parts of southern Kalimantan and southern Sumatra, which helped to improve the hotpot and haze situation (Figure 1). On 24 October 2023, the ASMC Alert Level for the southern ASEAN region was downgraded to Alert Level 1 as the risk of transboundary haze subsided. Over the northern ASEAN region, wet weather prevailed, and the overall haze situation was subdued in the region (Figure 1).

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

1.3 Over the southern ASEAN region, the hotspot counts in October 2023 were mostly higher compared to previous years, especially over Sumatra and Kalimantan where there was a significant rise in hotspot activity with the highest count recorded in five years (Figure 2). Over the Mekong sub-region, the overall hotspot count in October 2023 was mostly comparable to or lower than in previous years (Figure 3).

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

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

1.4 In October, hotspot activities were persistent in parts of central and southern Sumatra, southern and central Kalimantan, as well as parts of the Lesser Sunda Islands and Sulawesi (Figure 4). The fire intensity was highest for parts of southern Sumatra and Kalimantan (Figure 5). Moderate to dense smoke haze was observed in central and southern Sumatra, as well as southern and eastern Kalimantan on many days this month (Figures 6, 7 and 8). Lighter smoke haze drifted under prevailing winds to affect parts of Peninsular Malaysia and Singapore in early October 2023.

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

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

Figure 6: Number of days with moderate to dense smoke haze observed in October 2023 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate to dense smoke haze was observed in southern and eastern Kalimantan on 3 October 2023. (Source: Himawari-9 satellite surveillance)

Figure 8: Moderate to dense smoke haze was observed in parts of central and southern Sumatra on 16 October 2023. (Source: Himawari-9 satellite surveillance)

Figure 9: Typhoon Koinu over the western Pacific Ocean on 4 October 2023. (Source: MODIS satellite surveillance)

Review of Regional Haze Situation for September 2023

1.1 Southwest monsoon conditions persisted over the ASEAN region in September 2023. The prevailing low-level winds blew mainly from the southeast over areas south of the Equator and turned to blow from the southwest or west over areas north of the Equator (Figure 1). There were two notable tropical cyclones during the review period, namely Typhoon Saola and Typhoon Haikui, which developed one after another from late August to early September 2023 (Figure 2). Heavy rains and strong winds brought by the storms had affected many areas in northern parts of the ASEAN region, particularly the Philippines, where significant events of floods and landslides were reported.

1.2 The southern ASEAN region remained under its traditional dry season throughout September 2023. Dry conditions prevailed over many parts of the region while there were isolated shower activities over parts of northern Sumatra, Malaysia, and northeastern Kalimantan (Figure 1). Over the fire-prone areas in Sumatra and Kalimantan, hotspot activity gradually escalated from middle of the month and the overall hotspot count for the month of September 2023 was the highest since 2019 (Figure 3). Most of the hotspots with high fire intensity were detected in southern Sumatra and southern Kalimantan while isolated hotspots were also detected in central Sumatra and western Kalimantan on some days (Figure 4 and 5). During the first three weeks of September 2023, slight to moderate smoke plumes were observed mainly in the Indonesian provinces of South Sumatra, South Kalimantan, Central Kalimantan, and West Kalimantan. On some days, transboundary smoke haze was observed to drift northwards from West Kalimantan into western Sarawak (Figure 8). Towards the last week of the month, the smoke haze emanating from persistent hotspot clusters in southern Sumatra and southern Kalimantan became denser and more widespread and was observed to drift towards the northwest and north (Figure 6, 7, and 8). On 29 Sep 2023, ASMC activated Alert Level 2 for Sumatra, indicating a risk of transboundary haze for the region.

1.3 The weather was generally wet over the northern ASEAN region in September 2023 as its traditional wet season prevailed. Hotspot activity was subdued by widespread rains and the overall hotspot count in September 2023 was comparable to the count in previous years (Figure 9). While there were isolated hotspots detected in parts of central Thailand and Viet Nam, these hotspots were mostly short-lived and with low fire intensity (Figure 4 and 5). No significant smoke haze was observed over the region during the review period (Figure 6).

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

Figure 2: Typhoon Saola and Typhoon Haikui which affected many parts of the northern ASEAN region during late August and early September 2023. (Source: Himawari-9 satellite surveillance)

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

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

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

Figure 6: Number of days with moderate to dense smoke haze observed in September 2023 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Haze situation over Sumatra in September 2023. (Source: Himawari-9 satellite surveillance)

Figure 8: Haze situation over Kalimantan in September 2023. (Source: Himawari-9 satellite surveillance)

Figure 9: Hotspot counts for the northern ASEAN region for September (2019-2023) based on NOAA-20 satellite surveillance.

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)

Review of Regional Haze Situation for July 2023

1.1 Southwest Monsoon conditions persisted in July 2023, with the monsoon rainband located predominantly over the northern ASEAN region. The prevailing winds over areas north of the equator blew mainly from the southeast or southwest, while the prevailing winds over areas south of the equator blew mostly from the east or southeast (Figure 1). Typhoon Talim (Figure 9) and Super Typhoon Doksuri (Figure 10) brought about periods of strong winds over the northern half of the equator.

1.2 Over the southern ASEAN region, brief periods of dry weather conditions were observed for most of July 2023. Towards the end of the month, dry conditions persisted over Kalimantan with clusters of scattered hotspots and slight to moderate smoke haze observed over the western and southeastern parts of Kalimantan. On some days, smoke haze emanating from clusters of hotspots in West Kalimantan was observed to drift northwards into western Sarawak. On 28 July 2023, Alert Level 2 was activated for Kalimantan as hotspot counts were persistently high and there was an increasing risk of transboundary haze. Over the northern ASEAN region, wet weather was observed on most days during the month, subduing the overall haze situation in the region. High rainfall amounts were recorded over the northern parts of the Philippines due to Typhoon Talim which made landfall over the Philippines on July 13, 2023 and Super Typhoon Doksuri which passed the northern tip of the Philippines between July 25 and July 27, 2023.

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

1.3 Over the southern ASEAN region, there was a rise in overall hotspot activity due to periods of drier conditions, with the hotspot counts in the region higher or comparable to previous years (Figure 2). Notably, Kalimantan experienced the most significant rise in hotspot activity, with the highest count recorded in five years. Over the Mekong sub-region, the overall hotspot count in 2023 was mostly comparable to or lower than in previous years (Figure 3).

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

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

1.4 Towards the end of July 2023, hotspot activities were persistent in West and South Kalimantan, as well as parts of the Lesser Sunda Islands (Figure 4). The overall fire intensity for the ASEAN region was low, except for over parts of western Kalimantan where moderate fire intensity was detected (Figure 5). Slight to moderate smoke haze was observed over the western and southeastern parts of Kalimantan (Figures 6, 7 and 8).

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

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

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

Figure 7: Slight to moderate smoke haze was observed in West Kalimantan drifting northwards towards Sarawak on 27 July 2023. (Source: Himawari-9 satellite surveillance)

Figure 8: Moderate smoke plumes were observed to emit from the hotspots detected in South Kalimantan on 29 July 2023. (Source: NOAA-20 satellite surveillance)

Figure 9: Typhoon Talim over the western Pacific Ocean (Source: MODIS satellite surveillance)

Figure 10: Super Typhoon Doksuri over the western Pacific Ocean (Source: NOAA-20 satellite surveillance)

Review of Regional Haze Situation for June 2023

1.1 Southwest Monsoon conditions were fully established in June 2023, with the passage of the monsoon rainband north of the Equator. The prevailing winds over areas north of the equator blew mainly from the southeast or southwest, while the prevailing winds blew mostly from the east or southeast (Figure 1).

1.2 Brief periods of dry weather conditions were observed over parts of southern Sumatra, southern Kalimantan, Java, and the Lesser Sunda Islands. Elsewhere in the ASEAN region, shower activities were observed on most days during the month (Figure 1).

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

1.3 There was an increase in overall hotspot activity in June 2023 over the southern ASEAN region due to brief periods of dry conditions, with the hotspot counts in the region higher or comparable to previous years (Figure 2). In particular, the highest hotspot activity was detected in Sumatra, and the hotspot counts for both Sumatra and Kalimantan were the highest in 5 years. Over the Mekong sub-region, the overall hotspot count was mostly lower than in previous years (Figure 3).

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

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

1.4 Hotspot activities were more persistent in parts of western and central Sumatra, as well as West Kalimantan during the review period of June 2023. Localised smoke plumes were also observed to emanate from a few hotspots in Sumatra and Kalimantan on some days (Figures 6 and 7). However, the overall fire intensity has generally remained low.

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

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

Figure 6: Localised smoke plumes moving in the north-northwest direction were observed in central Sumatra on 20 June 2023. (Source: Himawari-9 satellite surveillance)

Figure 7: A localised smoke plume moving in the northeast direction was observed to emanate from a hotspot in western Kalimantan on 26 June 2023. (Source: NOAA-20 satellite surveillance)

Review of Regional Haze Situation for May 2023

1.1 Inter-monsoon conditions prevailed over the ASEAN region in May 2023 and the wind conditions were light and variable in direction on most days (Figure 1). Two tropical cyclones affected parts of the region in May 2023, namely Tropical Cyclone Mocha over Bay of Bengal (Figure 2) and Super Typhoon Mawar over the western Pacific Ocean (Figure 3). The storms brought brief periods of widespread rainfall and strong winds over Myanmar and the Philippines, respectively. According to the Joint Typhoon Warning Centre (JTWC), Super Typhoon Mawar was the strongest Northern Hemisphere tropical cyclone ever recorded in the month of May. By the end of May 2023, the inter-monsoon period had gradually transitioned into the Southwest Monsoon for most parts of the ASEAN region.

1.2 Over the northern ASEAN region, dry conditions continued over much of the Mekong sub-region in early May 2023. Elevated hotspot activity persisted in many parts of the sub-region, particularly in Lao PDR and Myanmar (Figure 4). On many days, isolated to scattered hotspots were detected in northern and western parts of the sub-region, where moderate to dense smoke haze, occasionally transboundary, was observed (Figure 6 – 9). Following the return of showers from the second week of May 2023, hotspot activity over the Mekong sub-region had steadily decreased. The ASMC Alert Level for the sub-region was downgraded to Alert Level 1 on 9 May 2023, and subsequently the end of dry season for the sub-region was declared on 24 May 2023.

1.3 For the southern ASEAN region, the weather was rainy and cloudy for most of May 2023. However, periods of drier conditions began to set in over some parts of the region from last week of the month, as monsoon rain band shifted further north from the Equator. Few to isolated hotspots, some with localised smoke plumes, were observed in the fire-prone areas of Sumatra, Kalimantan, and Peninsular Malaysia. A slight increase in hotspot activity was also detected, following the gradual onset of Southwest Monsoon conditions (Figure 5). On 29 May 2023, ASMC activated Alert Level 1 for the southern ASEAN region, signaling the start of the traditional dry season.

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

Figure 2: Tropical Cyclone Mocha over the Bay of Bengal and made landfall over Myanmar on 15 May 2023. (Source: Himawari-9 satellite surveillance)

Figure 3: Super Typhoon Mawar over the western Pacific Ocean brought widespread rainfall and strong winds over the Philippines during the last week of May 2023. (Source: Himawari-9 satellite surveillance)

Figure 4: Hotspot counts for the northern ASEAN region for May (2019-2023) based on NOAA-20 satellite surveillance. Hotspot counts were generally comparable to the counts in previous years, with majority of the hotspots detected in Lao PDR and Myanmar.

Figure 5: Hotspot counts for the southern ASEAN region for May (2019-2023) based on NOAA-20 satellite surveillance. Hotspot counts were slightly higher than the counts in previous years due to the gradual onset of the traditional dry season towards the end of May 2023.

Figure 6: Distribution of hotspots detected in May 2023 based on NOAA-20 satellite surveillance. Scattered hotspots were persistent over northern parts of Thailand and Lao PDR, as well as in parts of Myanmar and Viet Nam. Elsewhere in the ASEAN region, there were isolated and short-lived hotspots over the fire-prone areas in southern Sumatra and western Kalimantan.

Figure 7: Maximum fire intensity in May 2023 based on NOAA-20 satellite surveillance. The overall fire intensity was moderate over much of the Mekong sub-region, but particularly high over northern Lao PDR where clusters of hotspots persisted.

Figure 8: Number of days with moderate to dense smoke haze observed in May 2023 based on satellite imagery, ground observations, and air quality reports. Hazy conditions persisted mainly over western and northern parts of the Mekong sub-region.

Figure 9: Moderate smoke haze was observed in eastern Myanmar, northern Thailand and northern Lao PDR on 6 May 2023. Blown by the prevailing winds, transboundary smoke haze was observed to drift eastwards across northern Thailand, northern Lao PDR, and parts of Viet Nam. (Source: NOAA-20 satellite surveillance)

Review of Regional Haze Situation for April 2023

1.1 The Northeast Monsoon conditions gradually gave way to the inter-monsoon as the monsoon rainband shifted northwards towards the Equator in April 2023. The prevailing winds over the Mekong sub-region blew mostly from the southeast or southwest. For the rest of ASEAN region, the prevailing winds were light and variable in direction except over the Philippines where the prevailing winds blew from the northeast or east (Figure 1).

1.2 The prevailing dry conditions over the Mekong sub-region persisted for most of April 2023, although some showers returned over parts of the sub-region towards the end of the month. While wet weather was generally observed over the rest of the ASEAN region, it was dry over the Philippines. Parts of Peninsular Malaysia and Borneo also experienced brief period of drier conditions during the period (Figure 1).

1.3 Under the influence of the prolonged dry conditions, the hotspots counts in the Mekong sub-region during the review period were mostly higher compared to the previous years. In particular, the hotspot counts for Lao PDR and Myanmar in April 2023 were the highest in 5 years (Figure 2). In the southern ASEAN region, the hotspot counts were generally lower than or comparable to the previous years except for Kalimantan where hotspot counts were slightly higher than the previous years (Figure 3).

1.4 The elevated hotspot and smoke haze activity persisted over the Mekong sub-region for most of April 2023. Scattered to widespread hotspots were detected over may parts of the sub-region. In particular, clusters of hotspots were persistent and more intense (Figure 5) over parts of Myanmar as well as the northern parts of Thailand and the northern and central parts of Lao PDR. The return of the showers helped to alleviate the hotspot situation towards the end of the month. Elsewhere in the ASEAN region, isolated hotpots were detected in the Philippines, Peninsular Malaysia, Sumatra and Borneo but most of them were short-lived (Figure 4).

1.5 Widespread moderate to dense transboundary smoke haze was observed to blanket the eastern parts of Myanmar as well as the northern parts of Thailand, Lao PDR and Viet Nam on many days of the month. Moderate to dense smoke haze was also observed on many days over the northern, western and central parts of Myanmar (Figure 6 & 7). Moderate smoke haze was observed over the central parts of Thailand on some days of the month (Figure 6 & 8). In view of the improving hotspot and smoke haze situation with the return of shower activities towards the end of the month, the Alert Level for the Mekong sub-region was downgraded from Alert Level 3 to Alert Level 2 on 24 April 2023. For the southern ASEAN region, localized smoke plumes were observed to emit from isolated hotspots along the east coast of Peninsular Malaysia and Sumatra on some days during brief drier periods.

Review of Regional Haze Situation for March 2023

1.1 In March 2023, the ASEAN region continued to experience Northeast Monsoon conditions. Over areas north of the equator, the prevailing winds blew mainly from the northeast although light and variable winds prevailed over most parts of the Mekong sub-region. The prevailing winds over areas south of the Equator blew mostly from the west or northwest. As the Northeast monsoon conditions gradually weakened in the last week of the month, the prevailing winds over most of the ASEAN region started to turn light and variable on several days. (Figure 1).

1.2 The dry conditions over the Mekong sub-region and northern Philippines persisted throughout the review period of March 2023, except for isolated shower activities in some parts of the sub-region on a few days. Elsewhere in the ASEAN region, generally wet conditions were observed in many areas. (Figure 1).

1.3 For March 2023, the hotspot counts in the Mekong sub-region were higher or comparable to previous years under extended dry conditions, leading to an increase in overall hotspot activity (Figure 2). In particular, the highest hotspot activity was detected in Lao PDR, and the hotspot counts for Lao PDR were the highest in 5 years. For the southern ASEAN region, hotspot activity remained generally subdued and the hotspot counts were generally lower than in previous years (Figure 3).

1.4 Scattered to widespread hotspots were detected in the Mekong sub-region during the continued dry weather conditions. Clusters of hotspots were more intense and persistent in eastern and central Myanmar, Lao PDR, northern Thailand, and northeastern Cambodia. Isolated hotspots were also detected in northern Viet Nam. Over the southern ASEAN region, few hotspot activities were detected but most of them was short-lived (Figure 4).

1.5 The overall fire intensity in the Mekong sub-region had increased in March 2023, particularly over the fire-prone areas in Lao PDR, eastern and central Myanmar. (Figure 5). Widespread transboundary moderate to dense smoke haze was observed in the vicinity of the hotspot clusters in eastern Myanmar, northern and central Thailand, Lao PDR and northern Cambodia (Figure 6, 7 and 8) on many days. With the deteriorating hotspots and haze situation, Alert Level 3 was issued for the Mekong sub-region on 2 Mar 2023. Localised smoke plumes and occasional hazy conditions were also observed in northern Viet Nam on some days.