The diurnal cycle of boundary layer structures during MJO propagation in the Maritime Continent from DOE-ARM observations

The Madden-Julian oscillation (MJO) is the dominant intraseasonal (20-100 day) variability in the tropics. Our understanding of the MJO and its propagation across the Maritime Continent (MC) has been improved greatly over the last few decades. However, MJO-associated boundary layer structures and their variability at the sub-daily scale has received little attention. We use surface meteorological observations, radiosonde and microwave radiometer products during 2000-2014 from three Department of Energy – Atmospheric Radiation Measurement (DOE-ARM) sites (Darwin, Manus, and Nauru) to study the diurnal evolution of these structures. In particular, we focus on the diurnal evolution of temperature, humidity, moist static energy, winds, and boundary layer depth during MJO propagation for different seasons. A composite-based approach that is time-synced to the passage of the MJO centroid over Manus is applied to events over the 2000-2014 period. Preliminary results indicate that the evolution in boundary layer moist static energy is controlled by temperature during the suppressed and discharge phases , and by humidity during the recharge and active phases. A seven-day oscillation in the MSE, present during the suppressed phase, extends from the surface to the mid-to-upper troposphere. The implications of these results in the context of MJO organization will be discussed.