A new tool, the spatio-temporal wavelet transform, can isolate wavelengths and frequencies in weather disturbances and provide information about their energy content at a given time and location. The technique has been applied to study the multi-scale

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New Tool Throws Light on Major Tropical Weather
Disturbance
Kazuyoshi Kikuchi and Bin Wang
Kelvin Wave
MJO
A new tool, the spatio-temporal wavelet
transform, can isolate wavelengths and
frequencies in weather disturbances and provide
information about their energy content at a given
time and location. The technique has been applied
to study the multi-scale structure of the
Madden-Julian Oscillation (MJO). Both the MJO
and moist Kelvin wave propagate eastward but
incorporate bursts of westward propagating
inertia-gravity waves (WIGs). The transform
method has allowed IPRC researchers to
discriminate between the properties of the WIGs
associated with the MJO and moist Kelvin waves.
The findings may provide an essential clue to
understanding the multi-scale physical processes
respon-sible for the very slow eastward
propagation of the MJO and the moist Kelvin wave.
longitude
zonal wavenumber
frequency
date
date
Top Hovmoller diagram of equatorial OLR (W/m2 )
filtered to isolate high-frequency components
associated with the eastward-propagating MJO and
moist Kelvin wave. Red arrows highlight prominent
westward-propagating inertia-gravity waves
(WIGs). Middle and bottom Local wavelet spectra
showing the signature of WIGs.