Tuesday, 11 February 2003: 5:15 PM
Moisture Variations Associated with the Initiation of Madden-Julian Oscillation
The role of moisture variations in the initiation of Madden and Julian Oscillation (MJO) variability is examined. Composite Singular Value Decomposition (CSVD) analyses at various time lags are carried out to discern the complex space-time relationships between convection, low level specific humidity and divergence, and surface evaporation. The utilized data are 850hPa moisture and winds and surface evaporation from the NCEP-NCAR Reanalysis and Outgoing Longwave Radiation (OLR) from NOAA satellite observations for the period 1981-2000. These data are filtered at each point using a 150 point Lanczos filter capturing well the 20-100 day periodicities. The two dominant CSVDs describe an eastward propagating quasi-zonal wave number one system in all of the analyzed variables. The dominate moisture and latent heat flux variations lead those of OLR by approximately 10 days. The positive moisture anomalies develop near and to the east of the ensuing convective perturbations; positive latent heat flux variations generally occur far to the east. Moisture variations develop at least 15 days preceding a convective event and have stronger correlations with OLR than those of simultaneous low level divergence. Modifications are made to current theories describing the initiation of MJO events.