Abstract. Through analyzing observations and simulations from the Weather Research and Forecasting model coupled with Chemistry, we investigated instant and delayed responses of large-scale atmospheric circulations and precipitation to biomass burning (BB) aerosols over the Indochina Peninsula (ICP) in the peak emission of March. The results show that the BB aerosols inhibit precipitation over the ICP in March, and promote precipitation from early-April to mid-April. Specifically, the March BB aerosols over the ICP can induce mid-to-lower tropospheric heating and planetary boundary layer cooling, to enhance local atmospheric stability; meanwhile, the perturbation heating can trigger an anomalous low in the lower troposphere to moisten the mid troposphere. However, the convection suppression due to the stabilized atmosphere dominates over the favorable water-vapor condition induced by large-scale circulation responses, leading to an overall reduced precipitation over the ICP in March. For the delayed effect, the anomalous low can provide more water vapor as the monsoon advances in early-April, although it becomes much weaker without BB aerosols’ strong heating. On the other hand, the convective instability above 850 hPa is enhanced by more water vapor, resulting in enhanced precipitation over the ICP, northern South China Sea, and southern China. Thereafter, the condensational latent heating gradually takes over from the BB aerosol radiative heating, acting as the main driver for maintaining the anomalous circulation and thus the delayed effect in mid-April.

中文翻译：

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三月生物质燃烧气溶胶在印度支那半岛的即时和延迟效应

摘要。通过分析天气研究和预报模型结合化学的观测和模拟，我们研究了 3 月排放峰值中中南半岛 (ICP) 上空的大规模大气环流和降水对生物质燃烧 (BB) 气溶胶的即时和延迟响应。 . 结果表明，BB气溶胶抑制了3月ICP上空的降水，并促进了4月上旬至4月中旬的降水。具体来说，ICP上空的March BB气溶胶可以引起对流层中下层加热和行星边界层冷却，以增强局部大气稳定性；同时，摄动加热可以触发对流层低层的异常低压，从而润湿对流层中层。然而，大气稳定导致的对流抑制主导了大规模环流响应引起的有利水汽条件，导致 3 月 ICP 上空的降水量总体减少。对于延迟效应，随着 4 月初季风的推进，异常低压可以提供更多的水汽，尽管在没有 BB 气溶胶强烈加热的情况下它会变得更弱。另一方面，850 hPa以上的对流不稳定性因更多的水汽而增强，导致ICP、南海北部和华南地区降水增加。此后，凝结潜热逐渐取代BB气溶胶辐射加热，成为维持异常环流的主要驱动力，从而延迟了4月中旬的影响。