Abstract In this study, we examine the seasonal variability and long–term trends in aerosol distribution over peninsular Southeast Asia (SEA: 90°–105°E, 15°–28°N) based on MERRA–2 reanalysis datasets for a period of 30 years (1985–2015). Special emphasis has been given on the loading and distribution of carbonaceous aerosols, in response to changes in vegetation cover and biomass burning over SEA. MERRA–2 reanalysis reveals a distinct seasonality in columnar AOD distribution, that peaks (0.3–0.45) in the pre-monsoon (March–May) season, with a maximum contribution from carbonaceous aerosols (~60%). The ratio of organic carbon (OC) to black carbon (BC) column mass density indicates a dominant contribution from biomass burning along with biogenic emissions (OC/BC > 10), while the OC (BC) aerosols during pre-monsoon vertically vary between ~6 and 12 μgm−3 (~0.6–1.6 μgm−3) in the lower troposphere (surface to 700 hPa) during pre-monsoon. Interestingly, linear regression in monthly variability of the enhanced vegetation index (EVI) over SEA shows a slightly increasing tendency during the recent decade (2004–2015), while the number of fire counts decreased during the same time period. In addition, a slightly positive trend in OC–AOD is likely associated with the increase in vegetation cover that contributes to the rising trend of biogenic OC emissions, while the reduction in biomass burning is linked with the declining trend of BC–AOD. The pre-monsoon average shortwave flux at the top of the atmosphere (TOA) obtained from MERRA–2 over SEA varies from −12 to −6 Wm−2 and presents a decreasing tendency during the last 30 years due to a decrease in absorbing BC fraction. The temperature anomalies are well related to changes in BC–AOD, and OC–AOD at 850 hPa level, revealing important atmospheric heating.

中文翻译：

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东南亚碳质气溶胶的长期变化通过再分析：与植被覆盖和生物量燃烧变化的关联

摘要 在这项研究中，我们基于 MERRA-2 再分析数据集，研究了东南亚半岛（SEA：90°–105°E，15°–28°N）气溶胶分布的季节性变化和长期趋势。 30 年（1985-2015 年）。特别强调了碳质气溶胶的加载和分布，以响应 SEA 上植被覆盖和生物量燃烧的变化。MERRA-2 再分析揭示了柱状 AOD 分布的明显季节性，在季风前（3 月至 5 月）季节达到峰值（0.3-0.45），其中碳质气溶胶的贡献最大（~60%）。有机碳 (OC) 与黑碳 (BC) 柱质量密度的比率表明生物质燃烧和生物排放的主要贡献 (OC/BC > 10)，而在季风前的对流层低层（地表至 700 hPa）中，季风前的 OC (BC) 气溶胶在垂直方向上在 ~6 到 12 μgm-3 (~0.6-1.6 μgm-3) 之间变化。有趣的是，在最近十年（2004-2015 年），SEA 增强型植被指数 (EVI) 每月变化的线性回归显示出略有增加的趋势，而同期火灾数量减少。此外，OC-AOD 的略微正趋势可能与植被覆盖的增加有关，这有助于生物源 OC 排放的上升趋势，而生物量燃烧的减少与 BC-AOD 的下降趋势有关。从 MERRA-2 在 SEA 上获得的大气顶部季风前平均短波通量 (TOA) 从 -12 到 -6 Wm-2 变化，并且在过去 30 年中由于吸收 BC 的减少而呈现下降趋势分数。温度异常与 BC-AOD 和 850 hPa 水平的 OC-AOD 的变化密切相关，揭示了重要的大气加热。