Stratospheric filamentation into the upper tropical troposphere

We investigate the process of Rossby wave breaking on the subtropical tropo pause and the resulting filamentary structures of stratospheric air transpo rted into the upper tropical troposphere. We make extensive use of the Meas urements of Ozone by Airbus In-Service Aircraft (MOZAIC) flight database, b oth for identifying individual wave-breaking events and for analyzing the s mall-scale features of the filamentation process. Two models are used to pr ovide a dynamically consistent description of the evolution of a particular wave-breaking event, one a limited area, high-resolution general circulati on model, MesoNH, the other an isentropic contour advection model. The abil ity of both of these to represent the small-scale evolution of the filament is examined by explicit comparison with the MOZAIC ozone data; at larger s cales, comparison is made with analyses from the European Centre for Medium -Range Weather Forecasts. Two other wave-breaking events are presented brie fly, on the one hand, verifying that the filamentary structure is ubiquitou s, on the other hand, illustrating additional, distinct features of the evo lution. A simple analysis of all the MOZAIC flights over the southern tropi cal Atlantic provides an indication of the frequency of wave-breaking event s over this region. Together with the small-scale development suggested by the model studies and present in the MOZAIC data we infer a potentially sig nificant contribution to the global stratosphere-troposphere exhange from t he wave-breaking processes.