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The dynamical, radiative, and chemical processes involved in stratosphere-troposphere (ST) interactions are essential for understanding climate variability and change. Studies utilizing observational data and high-resolution models have been demonstrating that stratospheric processes affect various tropospheric phenomena.
Increasing attempts have recently been made to understand ST interaction processes, improve subseasonal-to-seasonal predictions of ST coupled variations, and develop statistics-/informatics-based studies. Other notable studies include those that treat the stratosphere and mesosphere integrally as the "middle atmosphere" and that deal with the "whole atmosphere" extending from the surface (land and ocean) to the upper atmosphere (the thermosphere and ionosphere). Due to the above background, SPARC (Stratosphere-troposphere Processes And their Role in Climate) changed its name to APARC (Atmospheric Processes and their Role in Climate) in 2024.
In this session, we welcome studies focusing on various ST processes as well as those extending the target upward to the mesosphere and upper atmosphere and/or downward to the surface. Inheriting the significance of the SPARC sessions held at past JpGU meetings, this session aims to enhance the development of this field in close coordination  with the atmospheric chemistry session.