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.