Convection Modeling of Pure-steam Atmospheres
Convection Modeling of Pure-steam Atmospheres
复制标题
纯蒸汽气氛的对流模拟
DOI：
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发表时间：
2021
影响因子：
7.9
通讯作者：
R. Pierrehumbert
中科院分区：
文献类型：
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作者：
Xianyu Tan;M. Lefèvre;R. Pierrehumbert
可冷凝物种对塑造地球气候至关重要。广泛的行星气候系统涉及了解非稀释可冷凝物质及其对气候动力学的影响。在大尺度动力学效应和一维对流参数化方面已经取得了进展，但在非稀释条件下的三维湿对流仍然没有得到解决，尽管它可以对温度/湿度剖面和云结构产生深远的影响。在这项工作中，我们使用三维、高分辨率的对流数值模拟来解决纯蒸汽大气中的这个问题。我们发现大气由两个特征区组成，一个以重力波为主的上层凝聚区和一个以对流翻转单体为特征的下层非凝聚区。冷凝区域的速度比较低的非冷凝区域的速度要小得多，并且水平温度变化很小。热光球中的凝结在很大程度上是由辐射冷却驱动的，并且在统计上趋于均匀。由于重力波和对流穿透的触发，一些凝结也发生在更深的地方，靠近凝结区域的边界，并表现出随机的斑块。这种定性结构对不同的模型参数不敏感，但定量细节可能不同。我们的结果证实了理论上的预期，即接近纯蒸汽极限的大气在冷凝区域没有有组织的深层对流羽流。Ding和Pierrehumbert讨论的广义对流参数化方案适用于处理纯蒸汽极限附近大气的基本结构，但不能捕捉三维对流分辨模型中出现的重力波及其混合。
Condensable species are crucial to shaping planetary climate. A wide range of planetary climate systems involve understanding nondilute condensable substances and their influence on climate dynamics. There has been progress on large-scale dynamical effects and on 1D convection parameterization, but resolved 3D moist convection remains unexplored in nondilute conditions, though it can have a profound impact on temperature/humidity profiles and cloud structure. In this work, we tackle this problem for pure-steam atmospheres using three-dimensional, high-resolution numerical simulations of convection in postrunaway atmospheres. We show that the atmosphere is composed of two characteristic regions, an upper condensing region dominated by gravity waves and a lower noncondensing region characterized by convective overturning cells. Velocities in the condensing region are much smaller than those in the lower, noncondensing region, and the horizontal temperature variation is small. Condensation in the thermal photosphere is largely driven by radiative cooling and tends to be statistically homogeneous. Some condensation also happens deeper, near the boundary of the condensing region, due to triggering by gravity waves and convective penetrations and exhibits random patchiness. This qualitative structure is insensitive to varying model parameters, but quantitative details may differ. Our results confirm theoretical expectations that atmospheres close to the pure-steam limit do not have organized deep convective plumes in the condensing region. The generalized convective parameterization scheme discussed in Ding & Pierrehumbert is appropriate for handling the basic structure of atmospheres near the pure-steam limit but cannot capture gravity waves and their mixing which appear in 3D convection-resolving models.