Stratospheric Modulation of the MJO through Cirrus Cloud Feedbacks

Abstract Recent observations have indicated significant modulation of the Madden Julian Oscillation (MJO) by phase stratospheric Quasi-Biennial (QBO) during boreal winter. Composites MJO show that upper tropospheric ice cloud fraction and water vapor anomalies are generally collocated, an eastward tilt with height in exists. Through radiative transfer calculations, it is shown clouds a stronger forcing than do anomalies, highlighting importance incorporating tropospheric/lower processes into simple models MJO. The coupled troposphere-stratosphere linear model previously developed authors extended including mean wind stratosphere prognostic equation for cirrus clouds, which forced dynamically allowed to modulate cooling, similar effect previous formulations. Under these modifications, still produces slow, propagating mode resembles sign zonal control both upward wave propagation vertical structure mode. varying interactive radiation, MJO-like has weaker growth rates under westerlies easterlies, consistent observed MJO-QBO relationship. These results directly attributable enhanced barotropic QBO easterlies. It also differential advection leads Implications limitations theory discussed.