Absorbing aerosols, like black carbon (BC), give rise to rapid adjustments, and the associated perturbation to the atmospheric temperature structure alters the cloud distribution. The level of scientific understanding of these rapid cloud adjustments—otherwise known as semi-direct effects (SDEs)—is considered low, with models indicating a likely negative (−0.44 to +0.1 Wm⁻²) forcing. Recent studies suggest this negative SDE is primarily driven by decreases in high-level clouds and enhanced longwave cooling. Here, we investigate the SDE using multiple models driven by observationally constrained fine-mode aerosol forcing without dust and sea salt. Unlike aerosol simulations, which yield a relatively vertically uniform aerosol atmospheric heating profile with significant upper-tropospheric heating, observation-based heating peaks in the lower-troposphere and then decays to zero in the mid-troposphere. We find a significant global annual mean decrease in low- and mid-level clouds, and weaker decreases in high-level clouds, which leads to a positive SDE dominated by shortwave radiation. Thus, in contrast to most studies, we find a robust positive SDE, implying cloud adjustments act to warm the climate system. Sensitivity tests with identical average, but vertically uniform observationally constrained aerosol atmospheric heating result in a negative SDE, due to enhanced longwave cooling as a result of large reductions in high-level clouds. Our results therefore suggest that model simulations lead to a negatively biased SDE, due to an aerosol atmospheric heating profile that is too vertically uniform.

吸收性气溶胶，例如黑碳（BC），会引起迅速的调节，并且对大气温度结构的相关扰动会改变云的分布。人们对这些快速云调整的科学理解水平（也称为半直接效应（SDE））被认为很低，其模型表明可能为负（-0.44至+0.1 Wm ^-2。）强迫。最近的研究表明，这种负SDE主要是由高层云的减少和增强的长波冷却引起的。在这里，我们使用由无尘和无海盐的受观测约束的精细模式气溶胶强迫驱动的多种模型研究了SDE。与气溶胶模拟不同，气溶胶模拟产生相对垂直的气溶胶大气加热剖面，同时对流层上空加热明显，在下对流层中基于观测的加热峰达到峰值，然后在对流层中层衰减至零。我们发现，低层和中层云的全球年均平均值显着下降，而高层云的下降幅度较弱，这导致以短波辐射为主的SDE呈正值。因此，与大多数研究相反，我们发现了一个强大的正SDE，这意味着云调节可起到温暖气候系统的作用。在平均水平相同但观测值垂直一致的情况下进行气溶胶大气加热的敏感性测试导致SDE为负，这是由于高空云的大量减少导致了长波冷却的增强。因此，我们的结果表明，由于气溶胶大气加热剖面在垂直方向上过于均匀，因此模型仿真会导致SDE产生负偏差。