资源环境科技发展态势分析平台

A fundamental aspect of vertical velocities in the atmosphere is their asymmetric nature, with stronger upward than downward motions. Here we study this asymmetry from a synoptic-scale perspective, by employing a storm-tracking algorithm in observations and climate change simulations. We show that midlatitude cyclones and anticyclones are both skewed toward stronger upward motions, and that this asymmetry intensifies in a warmer climate. Downward motions are generally influenced by changes in the dry static stability, which increases in a warmer climate, and therefore weaken. However, upward motions are influenced by a reduced static stability, which takes into account the influence of latent heating on saturated ascent. The latter decreases locally in regions of upward motions, especially for strong cyclones, leading to an intensification of the upward velocity. The projected increase in the upward velocity of strong storms has potential implications for extreme midlatitude precipitation events.

Plain Language Summary The asymmetry of atmospheric vertical velocities toward stronger upward flows has important consequences for weather and climate, for example, through its direct relation to precipitation and its extremes. A large part of this asymmetry is related to moisture. Upward motions typically involve warm and moist air, which condenses and forms precipitation, and this enhances the upward motion even further. Conversely, downward motions often involve colder and drier air, and very little moisture is involved. Understanding how this asymmetry responds to climate change is of high importance, especially given that atmospheric moisture content is expected to increase under global warming. In this study, we investigate the asymmetry of vertical motions by analyzing cyclones and anticyclones in observational data and climate change simulations. We show that the asymmetry intensifies in a warmer climate, as downward motions weaken and upward motions slightly intensify. Moreover, we find that the upward motion associated with strong cyclones increases more dramatically. Since precipitation is influenced by both the atmospheric moisture content and the strength of the upward velocity, the projected increases in both of these may yield more extreme precipitation events in a warmer climate.