Intraseasonal moist static energy budget in reanalysis data

Abstract

[1] The vertically integrated moist static energy (MSE) budget and moisture budgets of the Madden-Julian oscillation (MJO) are studied using 16 years of National Centers for Environmental Prediction Reanalysis II data and European Centre for Medium Range Weather Forecasts interim reanalysis data. Longitudinal distributions of vertically integrated MSE and latent heat (Lq) anomalies as well as their advective tendency terms are studied as a function of MJO phase. They are shown to have similar patterns and magnitudes, indicating that variations in MSE are mainly governed by moisture on intraseasonal time scales. MSE anomalies are approximately in phase with precipitation. Reanalysis MSE budget results are compared with the general circulation model results of Maloney (2009) (hereinafter M09). Many aspects of the reanalysis MSE budget resemble those of M09, with strong contributions from horizontal advection in increasing (decreasing) column MSE before (after) peak MJO convection. Other terms in the vertically integrated MSE budget, including vertical advection, are relatively larger in the reanalysis compared to M09 model results. Vertical advection contributes as much or more than horizontal advection to MSE buildup in advance of MJO convection in the reanalysis data sets. A large budget residual also exists which appears to suggest a missing moistening source in advance of MJO convection that provides a caveat to the results derived here. A positive covariance between radiative and surface fluxes and precipitation anomalies indicates that these flux terms slow the discharge of column MSE during an MJO event and may help to destabilize the MJO. As in the work of M09, variability in synoptic eddy activity as a function of the MJO phase dominates the meridional advection term. Suppression of synoptic eddies appears to contribute to anomalous moistening of the atmospheric column in advance of MJO convection.