QBO/Solar Modulation of the Madden-Julian Oscillation: A Composite Analysis

Malori Redman1,2, Lon Hood2, and Thomas Galarneau1

1Department of Hydrology and Atmospheric Sciences, 2Lunar and Planetary Laboratory

The University of Arizona, Tucson, AZ

The Madden-Julian Oscillation (MJO) is the primary driver of intraseasonal weather and climate variability in the tropics, and has been linked to weather variability in the midlatitudes. Recent studies have shown that the stratospheric quasi-biennial oscillation (QBO) modulates the amplitude of the MJO in Northern Hemisphere winter, where larger amplitudes occur during the easterly phase of the QBO (QBOE) compared to the westerly phase (QBOW). Evidence has also been presented that indicates changes in vertical motion in the lower stratosphere are linked to the 11-year solar cycle, where increased (decreased) ascent and reduced (increased) static stability occurs during solar minima (maxima). The largest MJO amplitudes and occurrence rates, and weakest static stabilities in the lower stratosphere occur during the QBOE phase at solar minimum conditions, while the opposite is true during QBOW at solar maximum conditions. The aim of this presentation is to compare MJO events during the above conditions using atmospheric dynamic diagnostics. Preliminary results suggest that the MJO influence on midlatitue flow may be modulated by the QBO and solar cycle. It is suggested that these results are potentially useful for weather and climate applications regarding the effects of stratospheric processes on tropical deep convection and seasonal-to-subseasonal variability.