Assessment of the MJO Activity in the Navy Operational Global Atmospheric Prediction System (NOGAPS)

The Madden-Julian Oscillation is the dominant mode of intraseasonal variability in the tropics and a primary source of predictability on the subseasonal time scale. As the first step to examine the subseasonal/seasonal prediction skill of the Navy's NOGAPS model, the characteristics and variability of the MJO in the NOGAPS analysis data are compared with those derived from the NCEP-DOE Reanalysis 2 (NNR2) as well as satellite observations, following the MJO metrics developed by the U.S. Climate Variability and Predictability (CLIVAR) MJO working group. Although the wave-number frequency diagram of 200-hPa zonal wind shows that the NOGAPS analysis has slightly weaker MJO signals than the NNR2, the wind field composites derived from the NOGAPS analysis are in good agreement with those from the NNR2. The differences in relative humidity composites between the two datasets are relatively larger compared to the dynamic fields, in particular when active convection is located over the Maritime Continent and over the western hemisphere. To further examine the model deficiency, Q1 and Q2 are derived from the NOGAPS analysis and are evaluated against the satellite retrievals.