UntitledSource: Journal of Climate:;2017:;volume( 030 ):;issue: 019::page 7933Author:Wang, Bin;Lee, Sun-Seon
DOI: 10.1175/JCLI-D-16-0873.1Publisher: American Meteorological Society
Abstract: AbstractEastward propagation is an essential characteristic of the Madden?Julian oscillation (MJO). Yet, simulation of MJO propagation in general circulation models (GCMs) remains a major challenge and understanding the causes of propagation remains controversial. The present study explores why the GCMs have diverse performances in MJO simulation by diagnosis of 24 GCM simulations. An intrinsic linkage is found between MJO propagation and the zonal structural asymmetry with respect to the MJO convective center. The observed and realistically simulated MJO eastward propagations are characterized by stronger Kelvin easterly waves than Rossby westerly waves in the lower troposphere, which is opposite to the Gill pattern where Rossby westerly waves are 2 times stronger than Kelvin easterly waves. The GCMs simulating stronger Rossby westerly waves tend to show a stationary MJO. MJO propagation performances are robustly correlated with the quality of simulated zonal asymmetries in the 850-hPa equatorial zonal winds, 700-hPa diabatic heating, 1000?700-hPa equivalent potential temperature, and convective instability. The models simulating realistic MJO propagation are exemplified by an eastward propagation of boundary layer moisture convergence (BLMC) that leads precipitation propagation by about 5 days. The BLMC stimulates MJO eastward propagation by preconditioning and predestabilizing the atmosphere, and by generating lower-tropospheric heating and available potential energy to the east of precipitation center. The MJO structural asymmetry is generated by the three-way interaction among convective heating, moisture, and equatorial wave and boundary layer dynamics. In GCMs, differing convective heating representation could produce different MJO structural asymmetry, and thus different propagations. Diagnosis of structural asymmetry may help revealing the models? deficiency in representing the complex three-way interaction processes, which involves various parameterized processes.
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| contributor author | Wang, Bin;Lee, Sun-Seon | |
| date accessioned | 2018-01-03T11:01:27Z | |
| date available | 2018-01-03T11:01:27Z | |
| date copyright | 7/13/2017 12:00:00 AM | |
| date issued | 2017 | |
| identifier other | jcli-d-16-0873.1.pdf | |
| identifier uri | http://138.201.223.254:8080/yetl1/handle/yetl/4246183 | |
| description abstract | AbstractEastward propagation is an essential characteristic of the Madden?Julian oscillation (MJO). Yet, simulation of MJO propagation in general circulation models (GCMs) remains a major challenge and understanding the causes of propagation remains controversial. The present study explores why the GCMs have diverse performances in MJO simulation by diagnosis of 24 GCM simulations. An intrinsic linkage is found between MJO propagation and the zonal structural asymmetry with respect to the MJO convective center. The observed and realistically simulated MJO eastward propagations are characterized by stronger Kelvin easterly waves than Rossby westerly waves in the lower troposphere, which is opposite to the Gill pattern where Rossby westerly waves are 2 times stronger than Kelvin easterly waves. The GCMs simulating stronger Rossby westerly waves tend to show a stationary MJO. MJO propagation performances are robustly correlated with the quality of simulated zonal asymmetries in the 850-hPa equatorial zonal winds, 700-hPa diabatic heating, 1000?700-hPa equivalent potential temperature, and convective instability. The models simulating realistic MJO propagation are exemplified by an eastward propagation of boundary layer moisture convergence (BLMC) that leads precipitation propagation by about 5 days. The BLMC stimulates MJO eastward propagation by preconditioning and predestabilizing the atmosphere, and by generating lower-tropospheric heating and available potential energy to the east of precipitation center. The MJO structural asymmetry is generated by the three-way interaction among convective heating, moisture, and equatorial wave and boundary layer dynamics. In GCMs, differing convective heating representation could produce different MJO structural asymmetry, and thus different propagations. Diagnosis of structural asymmetry may help revealing the models? deficiency in representing the complex three-way interaction processes, which involves various parameterized processes. | |
| publisher | American Meteorological Society | |
| type | Journal Paper | |
| journal volume | 30 | |
| journal issue | 19 | |
| journal title | Journal of Climate | |
| identifier doi | 10.1175/JCLI-D-16-0873.1 | |
| journal fristpage | 7933 | |
| journal lastpage | 7952 | |
| tree | Journal of Climate:;2017:;volume( 030 ):;issue: 019 | |
| contenttype | Fulltext |