Publication Date:
2017-04-04
Description:
The status of the numerical reproduction of the
Madden–Julian Oscillation (MJO) by current global
models was assessed through diagnoses of four pairs of
coupled and uncoupled simulations. Slow eastward
propagation of the MJO, especially in low-level zonal
wind, is realistic in all these simulations. However, the
simulated MJO suffers from several common problems.
The MJO signal in precipitation is generally too weak
and often eroded by an unrealistic split of an equatorial
maximum of precipitation into a double ITCZ structure
over the western Pacific. The MJO signal in low-level
zonal wind, on the other hand, is sometimes too strong
over the eastern Pacific but too weak over the Indian
Ocean. The observed phase relationship between precipitation
and low-level zonal wind associated with the
MJO in the western Pacific and their coherence in general
are not reproduced by the models. The seasonal
migration in latitude of MJO activity is missing in most
simulations. Air–sea coupling generally strengthens the
simulated eastward propagating signal, but its effects on
the phase relationship and coherence between precipitation
and low-level zonal wind, and on their geographic
distributions, seasonal cycles, and interannual variability
are inconsistent among the simulations. Such inconsistency
cautions generalization of results from MJO simulations
using a single model. In comparison to
observations, biases in the simulated MJO appear to be
related to biases in the background state of mean precipitation,
low-level zonal wind, and boundary-layer
moisture convergence. This study concludes that, while
the realistic simulations of the eastward propagation of
the MJO are encouraging, reproducing other fundamental
features of the MJO by current global models
remains an unmet challenge.
Description:
Published
Description:
573-592
Description:
JCR Journal
Description:
reserved
Keywords:
oscillation
;
01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
