The Response to MJO-like Forcing in a Nonlinear Shallow-Water Model

Friday, 19 December 2014
Ming Bao, Nanjing University, School of Atmospheric Sciences, Nanjing, China and Dennis L Hartmann, University of Washington Seattle Campus, Seattle, WA, United States; University of Washington, Department of Atmospheric Sciences, Seattle, WA, United States
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.