The response to MJO-like forcing in a nonlinear shallow-water model

Abstract

This study examines the response to Madden-Julian Oscillation (MJO)-like heat forcing in a nonlinear shallow-water model, including monopolar heating source traveling eastward with an around the world period of 48 days and dipolar heating with zonal wave period of 48 days, with zonal wave number 2 confined in longitude to the MJO active regions. A jet localized in the Pacific is compared to a zonally uniform boreal basic flow. The results show that the Rossby wave response downstream exhibits intensified quasi-stationary anomalies in the Pacific jet exit region when the MJO-like heat forcing passes the Maritime Continent, in accord with the observational analysis by Adames and Wallace (2014). The dynamical mechanism suggested in this study can be used to interpret the intraseasonal MJO-Pacific North American pattern coherence and other extratropical intraseasonal events. Key Points Response to MJO-like forcing is simulated in a nonlinear shallow-water model Strong quasi-stationary Rossby wave response in the Pacific jet exit region Extraction of kinetic energy from the mean flow in the jet exit region is vital ©2014. American Geophysical Union. All Rights Reserved.