Understanding the Asian summer monsoon onset in terms of catastrophe theory

Monsoon has been puzzling that the monsoon occurrence is sudden with the rapid onset observed while the evolution of the differentiating heating is gradual with time of year. Here, focusing on the Asian summer monsoon, we use catastrophe theory to show how gradual changes in the atmospheric heating source with time will cause an abrupt variation of the relevant South Asian High (SAH) to atmospheric circulations and thus lead to the monsoon onset. This argumentation illustrates that the Asian summer monsoon is essentially caused by temporal changes in the differentiating heating owing to surface inhomogeneites such as land-sea contrasts, and the monsoon onset results, in nature, from the nonlinearity of the complex atmospheric system itself. Employing the cusp catastrophe (one of the elementary catastrophes) model, it is found that a sudden change like the rapid monsoon onset is an inevitable outcome when the control parameters such as the differentiating heating exceed a threshold though the parameters evolves gradually.