9:15 AM - 9:30 AM
[AAS03-02] Monitoring the Madden-Julian Oscillation with upper-level geopotential height gradient ∇xz'
Keywords:Madden-Julian Oscillation, diagnostic parameter, geopotential height, zonal anomalous height gradient, MJO index
This research explores an alternative MJO diagnostic parameter option, the 150-hPa zonal anomalous height gradient (∇xz'), which may overcome the limitations of OLR. Statistical analyses of MJO events during extended winter (NDJFM) from 1979 to 2013 suggest that the 150-hPa ∇xz' is highly correlated with OLR and shows a strong signal of MJO in the wavenumber-frequency spectrum. The 150-hPa ∇xz' is also shown to be able to extract MJO signals from the version 2 of NCEP Climate Forecast System (CFSv2) output while OLR fails in a case study during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign in 2011. It is believed that 150-hPa ∇xz' is a good alternative option of OLR for studying MJOs before the satellite era and in model evaluations.