Changes in stratiform heating structure due to surface warming weaken and accelerate convectively coupled Kelvin waves

Mu-Ting Chien , Daehyun Kim

Although stratiform heating plays a crucial role in tropical convective systems, we do not fully understand (1) how stratiform heating would change in response to surface warming and (2) how those changes would affect convectively-coupled equatorial waves. This study analyzes the changes in stratiform heating structure and convectively-coupled Kelvin waves (KWs) associated with surface warming using a set of aquaplanet simulations. Results show that the melting level rises with warming, causing ice particles falling from the stratiform clouds to melt at lower pressure levels. The upward shift of melting-induced cooling results in a decrease in temperature and vertical motion variability associated with stratiform clouds in the lower free-troposphere and upper boundary layer. These changes lower the degree to which stratiform (i.e., the second baroclinic mode) and deep convective clouds (i.e., the first baroclinic mode) are coupled within KWs, causing KWs to weaken and accelerate with warming.