Convection Scheme More Important Than Model Resolution

1
Convection Scheme More Important Than Model
Resolution in Simulating the Madden-Julian
Oscillation Ping Liu,1 Yoshiyuki Kajikawa,1 Bin
Wang,1 Akio Kitoh,2 Tetsuzo Yasunari,3 Tim Li,1
et al. 1 IPRC, 2 Meteorological Research
Institute, 3 Nagoya University
Observations
Observations
Model
Model
Power spectra in 850 hPa zonal wind during boreal
winter
Lag regression of OLR onto 90oE, 0oN during
boreal winter.
High vertical and horizontal resolutions in a
climate model do not guarantee realistic
simulation of the Madden-Julian Oscillation
(MJO). Using the well-known Arakawa-Schubert
convection scheme, the MRI-TL959L60 AGCM
simulates mean tropical zonal winds and
precipitation that correspond reasonably well to
observations. This AGCM, however, produces only a
weak MJO in the 850 hPa zonal winds (bottom left
panel) with an almost standing structure (bottom
right panel) as opposed to the observed eastward
propagation. Further analysis of the model output
revealed that the weak and standing MJO is
attributable to convection biases in the model,
the anomalously high specific humidity either
lags or accompanies convection, whereas in
observations, the high specific humidity precedes
convection.