Improved Madden–Julian Oscillations with Improved Physics: The Impact of Modi¿ed Convection Parameterizations

TY - JOUR

T1 - Improved Madden–Julian Oscillations with Improved Physics

T2 - The Impact of Modi¿ed Convection Parameterizations

AU - Zhou, L.

AU - Neale, R.B.

AU - Murtugudde, R.

AU - Jochum, Markus

PY - 2012/2

Y1 - 2012/2

N2 - Two modifications are made to the deep convection parameterization in the NCAR Community Climate System Model, version 3 (CCSM3): a dilute plume approximation and an implementation of the convective momentumtransport (CMT). These changes lead to significant improvement in the simulated Madden-Julian oscillations (MJOs). With the dilute plume approximation, temperature and convective heating perturbations become more positively correlated. Consequently, more available potential energy is generated and the intraseasonal variability (ISV) becomes stronger. The organization of ISV is also improved, which is manifest in coherent structures between different MJO phases and an improved simulation of the eastward propagation of MJOs with a reasonable eastward speed. The improved propagation can be attributed to a better simulation of the low-level zonal winds due to the inclusion of CMT. The authors posit that the large-scale zonal winds are akin to a selective conveyor belt that facilitates the organization of ISVs into highly coherent structures, which are important features of observed MJOs. The conclusions are supported by two supplementary experiments, which include the dilute plume approximation and CMT separately.

AB - Two modifications are made to the deep convection parameterization in the NCAR Community Climate System Model, version 3 (CCSM3): a dilute plume approximation and an implementation of the convective momentumtransport (CMT). These changes lead to significant improvement in the simulated Madden-Julian oscillations (MJOs). With the dilute plume approximation, temperature and convective heating perturbations become more positively correlated. Consequently, more available potential energy is generated and the intraseasonal variability (ISV) becomes stronger. The organization of ISV is also improved, which is manifest in coherent structures between different MJO phases and an improved simulation of the eastward propagation of MJOs with a reasonable eastward speed. The improved propagation can be attributed to a better simulation of the low-level zonal winds due to the inclusion of CMT. The authors posit that the large-scale zonal winds are akin to a selective conveyor belt that facilitates the organization of ISVs into highly coherent structures, which are important features of observed MJOs. The conclusions are supported by two supplementary experiments, which include the dilute plume approximation and CMT separately.

M3 - Journal article

SN - 0894-8755

VL - 25

SP - 1116

EP - 1136

JO - Journal of Climate

JF - Journal of Climate

ER -