Review of Regional Haze Situation for January 2023
1.1 Northeast Monsoon conditions continued to be observed over the ASEAN region in January 2023, with the prevailing low-level winds blowing predominantly from the northeast or east over areas north of the Equator and mainly from the west or northwest for areas south of the Equator (Figure 1). The strengthening of high-pressure systems over the northern Asian continent also brought a surge of strong northeasterly winds or monsoon surge over the South China Sea during the last week of January 2023.
1.2 In January 2023, dry weather prevailed over much of the Mekong sub-region under the influence of the Northeast Monsoon. As a result of the persistent dry conditions, an escalation in hotspot activity and development of smoke haze was observed in many parts of the sub-region from the second half of the month. On 27 January 2023, Alert Level 2 was activated for the Mekong sub-region as hotspot counts were persistently high and there was an increasing risk of transboundary haze. Elsewhere, rainy weather prevailed over the southern ASEAN region and the Philippines on most days of the month. In particular, monsoon surges contributed to increased rainfall over southern Peninsular Malaysia, Singapore, western Borneo, central Sumatra, and southern Philippines (Figure 1).
1.3 For January 2023, hotspot counts in the Mekong sub-region were slightly elevated compared to the same review period in 2022 (Figure 2). In particular, the highest hotspot activity was detected in Cambodia, and the hotspot count for Lao PDR and Viet Nam was slightly higher than the past 5 years. For the southern ASEAN region, hotspot activity remained generally subdued and the hotspot counts were lower or comparable to those in previous years (Figure 3).
1.4 During the review period, hotspot activity was widespread over the Mekong sub-region. On many days, clusters of hotspots were detected in northern and eastern Cambodia, as well as central Myanmar. Persistent hotspots were also detected in northern Viet Nam, as well as the northern and northeastern regions of Thailand. Over the southern ASEAN region, few hotspots were detected but most of them were short-lived (Figure 4).
1.5 The overall fire intensity in the Mekong sub-region had increased in January 2023, particularly over the fire-prone areas in central Myanmar, and northern and eastern Cambodia (Figure 5). As a result, persistent and moderate smoke haze was observed in the vicinity of the hotspot clusters in Myanmar and Cambodia (Figure 6, 7, and 8). Localised smoke plumes and occasional hazy conditions were also observed in northern Thailand, northern Viet Nam, and parts of Lao PDR.
