Simulations of tropical atmospheric circulation response to surface warming vary substantially across models, causing large uncertainties in projections of regional precipitation change. Understanding the physical processes that drive the model spread in tropical circulation changes is critically needed. Here we employ the basic mass balance and energetic constraints on tropical circulation to identify the dominant factors that determine multidecadal circulation strength and area changes in climate models. We show that the models produce a robust weakening of descent rate under warming regardless of surface warming patterns; however, ascent rate change exhibits inter-model spread twice as large as descent rate because of diverse model responses in the radiative effects of clouds, water vapor, and aerosols. As ascent area change is dictated by the disparate descent and ascent rate changes due to the mass budget and the inter-model spread in descent rate change is small, the model spread in ascent area change is dominated by that of ascent rate change, resulting in a strong anti-correlation of –0.85 between the fractional changes of ascent strength and area across 77 climate model simulations. This anti-correlation leads to a corresponding inverse relationship between the rates of precipitation intensifying and narrowing of the inter-tropical convergence zone (ITCZ), suggesting tropical ascent area change can be potentially used to constrain the ITCZ precipitation change. Longwave cloud radiative effect at the top-of-atmosphere (TOA) in the convective region is identified to be a major source of uncertainties for tropical ascent rate change and thus for regional precipitation change.

不同模式对热带大气环流响应的模拟变化很大，导致区域降水变化预测中存在很大的不确定性。迫切需要了解驱动模型在热带环流变化中传播的物理过程。在这里，我们利用基本的质量平衡和热带环流的能量约束来确定决定气候模式中多年代环流强度和面积变化的主导因素。我们表明，无论表面变暖模式如何，模型在变暖下均会导致下降速率的减弱。然而，由于云，水蒸气和气溶胶的辐射效应中的各种模型响应，上升速率的变化显示出模型间的扩展是下降速率的两倍。由于上升区域的变化是由不同的下降决定的，而上升率的变化是由于大量预算而造成的，而模型间下降率的变化很小，因此上升区域变化的模型差主要由上升率的变化决定，因此在77个气候模型模拟中，上升强度和面积的分数变化之间有–0.85的强反相关性。这种反相关性导致降水增加速率与热带辐合带（ITCZ）变窄之间的相应反比关系，这表明热带上升面积的变化可以潜在地用来限制ITCZ的降水变化。