Chiang Mai suffers from adverse haze associated with heavy biomass burning (BB) during almost every dry season (February to April). As an important source of light-absorbing carbonaceous aerosols (black carbon and brown carbon), BB can have strong radiative effects on local and regional climate. However, studies on characterizing the impacts of BB aerosols on climate in Chiang Mai are quite limited. In this study, we use a global chemical transport model (GEOS-Chem) coupled with the rapid radiative transfer model for GCMs (RRTMG) to estimate the radiative forcing (RF) of BB aerosols in Chiang Mai. Brown carbon (BrC) is included as an absorber and treated as an individual tracer in the model. To our best knowledge, this is the first study to estimate the BrC RF in Chiang Mai. As evaluated, our simulations that were assigned with medium- and high-absorbing k_BrC (BrC imaginary refractive index) well reproduces the absorption coefficient of ambient BrC in Chiang Mai. Based on our estimations, 33–40% of total carbonaceous aerosol absorption at 440 nm is attributed to BrC and 60–67% to BC during dry season. As estimated, BrC contributes 14 ± 3% to the instantaneous RF of total carbonaceous aerosol (IRF_CAs) at the top of atmosphere (TOA) and 16 ± 3% to IRF_CAs at surface. Moreover, including BrC in model strengthens (reduces) the surface (TOA) cooling effect of total organic carbon by 9 ± 5% (9 ± 3%), indicating the warming effect of BrC in the atmosphere in Chiang Mai.

几乎在每个旱季（2 月至 4 月），清迈都会遭受与大量生物质燃烧 (BB) 相关的不利雾霾。BB作为吸光碳质气溶胶（黑碳和棕碳）的重要来源，可以对局地和区域气候产生强烈的辐射效应。然而，关于表征 BB 气溶胶对清迈气候影响的研究非常有限。在这项研究中，我们使用全球化学传输模型 (GEOS-Chem) 结合 GCM 的快速辐射传输模型 (RRTMG) 来估计清迈 BB 气溶胶的辐射强迫 (RF)。棕色碳 (BrC) 作为吸收剂包括在内，并作为模型中的单个示踪剂处理。据我们所知，这是第一项估算清迈 BrC RF 的研究。经评估，k _BrC（BrC 虚折射率）很好地再现了清迈环境 BrC 的吸收系数。根据我们的估计，在旱季，440 nm 处碳质气溶胶吸收总量的 33-40% 归因于 BrC，60-67% 归因于 BC。据估计，BRC有助于14±3％至总碳气溶胶的瞬时RF（IRF_的CA在气氛（TOA）和16±3％的顶到IRF）_的CA在表面上。此外，模型中包含 BrC 使总有机碳的表面 (TOA) 冷却效果增强（降低）9 ± 5% (9 ± 3%)，表明 BrC 在清迈大气中的变暖效应。