Evaluating the Characteristics of Persistent Anomalies in a Warmer, Moister World

As a dynamical driver behind several classes of high-impact weather such as droughts, extreme temperatures, and extratropical transition events, persistent anomalies (PAs) are influential features of the mid-latitude atmosphere. While not dynamically synonymous with atmospheric blocks, PAs are often associated with blocking patterns and exert an equally important influence on mid-latitude flow. Like many features of the Earth's large-scale circulation, PAs are shaped by interactions with the broader climate system, of which latent heat release and environmental baroclinicity are two of the most influential. Therefore, it is important to understand how changes to this system affect PA characteristics such as frequency, duration, and strength. While much work has been done to close the gap on our understanding of PA-environment interaction in a changing climate, previous studies of climate change and blocking do not yield a consensus, a consequence of the myriad of potential influences in the system.

Therefore, we approach this issue from a process-level perspective, attempting to link changes in PA activity to specific environmental characteristics. This question requires a careful consideration of the environment surrounding developing persistent anomalies, addressed in this work through idealized sensitivity tests. Using the Weather Research and Forecasting model in an idealized mode, we examine the sensitivity of PA formation and maintenance to its background environment, with a focus on the increasing role of latent heat release in a warmer world. The resulting analysis is a scenario-independent examination of PA climatologies in multiple idealized environments, with sensitivity evaluated through changes to PA frequency, strength, and duration. Such analysis sheds light on how processes such as increased latent heat release from transient eddy-PA interactions can link back upscale to these large-scale atmospheric drivers.