Madden‐Julian Oscillation in a climate model with a well‐resolved stratosphere

Abstract

[1] This work evaluates how well a coupled ocean-atmospheric climate model with a well-resolved stratosphere captures the observed Madden-Julian Oscillation (MJO) signal in the upper troposphere and lower stratosphere. The model is the Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC) coupled modeling system (CMCC-CMS) with 95 atmospheric levels. CMCC-CMS produces MJO composites of precipitation that are very similar to those of the observations and the ERA-40 reanalysis product. Furthermore, model precipitation is found to propagate eastward near the observed speed. There is also strong agreement in the tropics and subtropics in the temperature and flows at 100 and 200 hPa upon comparing the composites based on the full 340 years of model output and those for the past 20 years of the model output with those of the ERA-40 reanalysis. At the 100 hPa level the temperature anomalies in the model output and reanalysis propagate eastward at about 7 m s -1 at the equator, 25°N and 65°N. Longitude and height cross sections at 25°N suggest vertically propagating Rossby waves up to near the 10 hPa level in both the model and observations. Latitude and height cross sections of temperature and zonal and meridional winds indicate strong vertical propagation in the tropics in both the model and reanalysis. Overall, the CMCC-CMS model shows MJO characteristics in the tropical and subtropical troposphere and lower stratosphere that are in very good agreement with observed analyses.

Simulation of the Central Indian Ocean Mode in CESM: Implications for the Indian Summer Monsoon System

“…Some detailed MJO features in simulations require further improvement; for example, the MJO period tends to be a little longer and the eastward‐westward power ratio of the intraseasonal spectral peaks is smaller in CESM simulations (not shown; Li et al, ; Waliser et al, ). In addition, WACCM lies slightly outside the spread of LEN values, which implies the role of QBO in modulating the MJO properties (Son et al, ; Weare et al, ). The detailed discussion on the relationship between the stratosphere and the MJO is beyond the scope of this study.…”

MJO‐Related Tropical Convection Anomalies Lead to More Accurate Stratospheric Vortex Variability in Subseasonal Forecast Models

“…It is well known that tropical diabatic heating associated with the Madden‐Julian Oscillation (MJO), the dominant mode of intraseasonal variability in the tropics (Madden & Julian, ), excites subtropical planetary waves via barotropic vorticity perturbations which then propagate poleward (Ferranti et al, ; Gill, ; Lukens et al, ; Seo & Son, ; Weare et al, ). These wave perturbations are known to influence northern hemispheric weather patterns in the troposphere (Cassou, ; Johnson & Feldstein, ; L'Heureux & Higgins, ; Lin et al, ; Riddle et al, ; Yoo et al, ).…”

Impact of the MJO on the boreal winter extratropical circulation

“…It is well known that tropical diabatic heating associated with the MJO, the dominant mode of intraseasonal variability in the tropics [Madden and Julian, 1994], excites subtropical planetary waves via barotropic vorticity perturbations which then propagate poleward [Gill, 1980;Ferranti et al, 1990;Weare et al, 2012;Seo and Son, 2012]. These wave perturbations are known to influence northern hemispheric weather patterns in the troposphere [Cassou, 2008;L'Heureux and Higgins, 2008;Lin et al, 2009;Johnson and Feldstein, 2010;Yoo et al, 2012;Riddle et al, 2013].…”