Roles of the moisture and wave feedbacks in shaping the Madden-Julian oscillation

Fei Liu; Bin Wang

doi:10.1175/JCLI-D-17-0003.1

Roles of the moisture and wave feedbacks in shaping the Madden-Julian oscillation

Fei Liu
, Bin Wang

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

Abstract

This study investigates the moisture and wave feedbacks in the Madden-Julian oscillation (MJO) dynamics by applying the general three-way interaction theoretical model. The three-way interaction model can reproduce observed large-scale characteristics of the MJO in terms of horizontal quadrupole-vortex structure, vertically tilted structure led by planetary boundary layer (PBL) convergence, slow eastward propagation with a period of 30-90 days, and planetary-scale circulation. The moisture feedback effects can be identified in this model by using diagnostic thermodynamic and momentum equations, and the wave feedback effects are investigated by using a diagnostic moisture equation. The moisture feedback is found to be responsible for producing the MJO dispersive modes when the convective adjustment process is slow. The moisture feedback mainly acts to reduce the frequency and growth rate of the short waves, while leaving the planetary waves less affected, so neglecting the moisture feedback is a good approximation for the wavenumber-1 MJO. The wave feedback is shown to slow down the eastward propagation and increase the growth rate of the planetary waves. The wave feedback becomes weak when the convective adjustment time increases, so neglecting the wave feedback is a good approximation for the MJO dynamics during a slow adjustment process. Sensitivities of these two feedbacks to other parameters are also discussed. These theoretical findings suggest that the two feedback processes, and thus the behaviors of the simulated MJO mode, should be sensitive to the parameters used in cumulus parameterizations.

Original language	English
Pages (from-to)	10275-10291
Number of pages	17
Journal	Journal of Climate
Volume	30
Issue number	24
DOIs	https://doi.org/10.1175/JCLI-D-17-0003.1
State	Published - Dec 1 2017
Externally published	Yes

Funding

Acknowledgments. This work was supported by the China National 973 Project (2015CB453200), the National Natural Science Foundation of China (41420104002), grants from the IPOVAR Project (GASI-IPOVAI-02), and the Natural Science Foundation of Jiangsu Province (BK20150907). BW acknowledges supports from the NSF (Award AGS-1540783), the NOAA DYNAMO (Award NA13OAR4310167), and the National Research Foundation (NRF) of Korea through a Global Research Laboratory (GRL) grant (MEST, 2011-0021927). This paper is Earth System Modeling Center (ESMC) Contribution 184. This work was supported by the China National 973 Project (2015CB453200), the National Natural Science Foundation of China (41420104002), grants from the IPOVAR Project (GASI-IPOVAI-02), and the Natural Science Foundation of Jiangsu Province (BK20150907). BW acknowledges supports from the NSF (Award AGS-1540783), the NOAADYNAMO(AwardNA13OAR4310167), and the National Research Foundation (NRF) of Korea through a Global Research Laboratory (GRL) grant (MEST, 2011-0021927). This paper is Earth System Modeling Center (ESMC) Contribution 184.

Keywords

Madden-Julian oscillation
Madden-Julian oscillation

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10.1175/JCLI-D-17-0003.1

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title = "Roles of the moisture and wave feedbacks in shaping the Madden-Julian oscillation",

abstract = "This study investigates the moisture and wave feedbacks in the Madden-Julian oscillation (MJO) dynamics by applying the general three-way interaction theoretical model. The three-way interaction model can reproduce observed large-scale characteristics of the MJO in terms of horizontal quadrupole-vortex structure, vertically tilted structure led by planetary boundary layer (PBL) convergence, slow eastward propagation with a period of 30-90 days, and planetary-scale circulation. The moisture feedback effects can be identified in this model by using diagnostic thermodynamic and momentum equations, and the wave feedback effects are investigated by using a diagnostic moisture equation. The moisture feedback is found to be responsible for producing the MJO dispersive modes when the convective adjustment process is slow. The moisture feedback mainly acts to reduce the frequency and growth rate of the short waves, while leaving the planetary waves less affected, so neglecting the moisture feedback is a good approximation for the wavenumber-1 MJO. The wave feedback is shown to slow down the eastward propagation and increase the growth rate of the planetary waves. The wave feedback becomes weak when the convective adjustment time increases, so neglecting the wave feedback is a good approximation for the MJO dynamics during a slow adjustment process. Sensitivities of these two feedbacks to other parameters are also discussed. These theoretical findings suggest that the two feedback processes, and thus the behaviors of the simulated MJO mode, should be sensitive to the parameters used in cumulus parameterizations.",

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author = "Fei Liu and Bin Wang",

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N2 - This study investigates the moisture and wave feedbacks in the Madden-Julian oscillation (MJO) dynamics by applying the general three-way interaction theoretical model. The three-way interaction model can reproduce observed large-scale characteristics of the MJO in terms of horizontal quadrupole-vortex structure, vertically tilted structure led by planetary boundary layer (PBL) convergence, slow eastward propagation with a period of 30-90 days, and planetary-scale circulation. The moisture feedback effects can be identified in this model by using diagnostic thermodynamic and momentum equations, and the wave feedback effects are investigated by using a diagnostic moisture equation. The moisture feedback is found to be responsible for producing the MJO dispersive modes when the convective adjustment process is slow. The moisture feedback mainly acts to reduce the frequency and growth rate of the short waves, while leaving the planetary waves less affected, so neglecting the moisture feedback is a good approximation for the wavenumber-1 MJO. The wave feedback is shown to slow down the eastward propagation and increase the growth rate of the planetary waves. The wave feedback becomes weak when the convective adjustment time increases, so neglecting the wave feedback is a good approximation for the MJO dynamics during a slow adjustment process. Sensitivities of these two feedbacks to other parameters are also discussed. These theoretical findings suggest that the two feedback processes, and thus the behaviors of the simulated MJO mode, should be sensitive to the parameters used in cumulus parameterizations.

AB - This study investigates the moisture and wave feedbacks in the Madden-Julian oscillation (MJO) dynamics by applying the general three-way interaction theoretical model. The three-way interaction model can reproduce observed large-scale characteristics of the MJO in terms of horizontal quadrupole-vortex structure, vertically tilted structure led by planetary boundary layer (PBL) convergence, slow eastward propagation with a period of 30-90 days, and planetary-scale circulation. The moisture feedback effects can be identified in this model by using diagnostic thermodynamic and momentum equations, and the wave feedback effects are investigated by using a diagnostic moisture equation. The moisture feedback is found to be responsible for producing the MJO dispersive modes when the convective adjustment process is slow. The moisture feedback mainly acts to reduce the frequency and growth rate of the short waves, while leaving the planetary waves less affected, so neglecting the moisture feedback is a good approximation for the wavenumber-1 MJO. The wave feedback is shown to slow down the eastward propagation and increase the growth rate of the planetary waves. The wave feedback becomes weak when the convective adjustment time increases, so neglecting the wave feedback is a good approximation for the MJO dynamics during a slow adjustment process. Sensitivities of these two feedbacks to other parameters are also discussed. These theoretical findings suggest that the two feedback processes, and thus the behaviors of the simulated MJO mode, should be sensitive to the parameters used in cumulus parameterizations.

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Roles of the moisture and wave feedbacks in shaping the Madden-Julian oscillation

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