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

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) with95 atmospheric levels. CMCC-CMS produces MJO composites of precipitation that arevery 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 and200 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 the100 hPa level the temperature anomalies in the model output and reanalysis propagate eastward at about 7 m s–1at 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.