January and February are often associate with haze episodes in northern SE Asia due to seasonal dry weather which is used by small farmers and large companies to clear land by burning. The year 2023, was different. Large-scale burning is carried out to prepare land for planting of commercial crops such as corn and tapioca. In Myanmar and Laos there has been an increase in areas under plantations and contract farming for big agricultural processing companies, which means that there has been pressure to clear by burning. Burning is the easiest and most economical method to clear land, and the situation has been exacerbated by a long and intense dry and hot spell which started in October 2022. As a consequence, Luang Prabang in Laos, Yangon in Myanmar and Hanoi in Vietnam ranked amongst the cities with the world’s worst air quality in April 2023. In addition, the region was under the influence of a heat wave resulting in record high air temperatures of e.g. 42.7 degC in Luang Prabang.
Photographs from a flight to Luang Prabang in April 2023, show a distinct demarcation between the clear air aloft and the thick haze layer below the airplane (22 April). Visibility drops dramatically as the plane descend into the haze (15 April). The dense smoke in the atmosphere amplifies normal red sunsets due to increased absorption of blue and enhanced scattering of red wavelength of visible light on the large haze particles. The extent of the haze is clearly visible on the regional haze map for 20 April, which shows a large number of hot spots (fires on the ground) over northern Thailand, Laos and Vietnam and the associated dense haze within the dark purple boundary.
Update: My commentary on the causes of the burning and haze and why the second half of the year could also see significant haze due to a developing strong El Niño, are available as part of the CNA Insight programme "Why Does The Haze In Thailand And Laos Keep Getting Worse?”, which was broadcast on 8 Aug 2023: https://www.youtube.com/watch?v=hhyZPQPayQg
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