Sensitivity of Kelvin waves and Madden-Julian oscillation to convective downdrafts in the NCAR-CAM3

Using NCAR-Community Atmosphere Model version 3 (CAM3), the sensitivity of Kelvin waves (KWs) and Madden-Julian Oscillation (MJO) simulation to convective downdrafts is examined. For this, numerical simulations are carried out by changing the downdraft intensity. Increase in the intensity of convective downdrafts in the model leads to greater re-evaporation of precipitation, which enhances the moisture in the lower troposphere, with a corresponding increase in the convective available potential energy ( CAPE). Stronger downdrafts, and hence enhanced CAPE, are found to be more favorable for low frequency variability and less favorable for the higher frequencies, leading to stronger MJO and weaker KWs. Copyright (C) 2011 Royal Meteorological Society