Geographical Variability of Processes Associated with the MJO

Diagnostics obtained as an extension of empirical orthogonal function (EOF) analysis are shown to address many disadvantages of using EOF-based indices to assess the state of the Madden-Julian Oscillation (MJO). The diagnostics allow for the geographical variability of anomalous conditions associated with the MJO to be easily assessed throughout its lifecycle. The Realtime Multivariate MJO (RMM) index and the Filtered MJO OLR (FMO) index are used in combination with the diagnostics to evaluate the geographical variability of the moisture and moist static energy budgets of the MJO.

Moisture anomalies associated with the MJO are amplified by the net effects of anomalous vertical moisture advection and cloud processes during both enhanced and suppressed convective phases. This is a robust feature of the MJO that is present from the Indian Ocean to the west Pacific Ocean, and is shown to have a geographical distribution that corresponds closely with that of precipitation anomalies. Incomplete cancelation between anomalous horizontal advection and anomalous surface latent heat flux results in the eastward propagation of moisture anomalies. In the deep tropics (5°N-5°S) of the eastern hemisphere, anomalous horizontal advection is primarily the result of the anomalous winds acting on the mean state moisture gradient. Over the broader tropics (15°N-15°S) the anomalous horizontal advection appears to result primarily from the modulation of synoptic scale eddy activity by the MJO.

Hindcasts of the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011(CINDY) Dynamics of the MJO (DYNAMO) field campaign are performed using the Ocean-Land-Atmosphere Model (OLAM). Results from OLAM, featuring a refined mesh in the DYNAMO region, will be presented in the context of the findings of the moisture and MSE budgets.