In the field of fluid dynamics and atmospheric science, McIntyre, together with Peter H. Haynes, established the Impermeability Theorem[9][10] for potential vorticity (PV), which states that there can be no net transport of PV across isentropic surfaces, and that PV can neither be created nor destroyed within a volume bounded by isentropic surfaces. In light of the aforementioned result, PV substance, which corresponds to PV multiplied by the mass density in isentropic coordinates, integrated over a volume of an isentropic layer, is either diluted or concentrated by diabatic mass flux through the isentropic layer bounds.
Books
In 2021, he published a book, titled "Science, Music, and Mathematics: The Deepest Connections" [11] which draws on his experience as a musician as well as a scientist. A wide variety of topics is covered including, for instance, how the skilful use of language can be informed by the way music works, and what science can and cannot tell us about the climate problem and its uncertainties. A second edition of the book will be published in August 2023.
