Abstract
This study examined the impacts of model horizontal resolution on vertical structures of convection in the tropics by performing sensitivity experiments with the NCAR CESM1. It was found that contributions to the total precipitation between top-heavy and bottom-heavy convection are different among various resolutions. A coarser resolution tends to produce a greater contribution from top-heavy convection and, as a result, stronger precipitation in the western Pacific ITCZ; while there is less contribution from bottom-heavy convection and weaker precipitation in the eastern Pacific ITCZ. In the western Pacific ITCZ, where the convection is dominated by a top-heavy structure, the stronger precipitation in coarser resolution experiments is due to changes in temperature and moisture profiles associated with a warmer environment (i.e., thermodynamical effect). In the eastern Pacific ITCZ, where the convection is dictated by a bottom-heavy structure, the stronger precipitation in finer resolution experiments comes from changes in convection structure (i.e., dynamic effect) which favors a greater contribution of bottom-heavy convection as the model resolution goes higher. The moisture budget analysis further suggested that the very different behavior in precipitation tendencies in response to model resolution changes between the western and eastern Pacific ITCZs are determined mainly by changes in convective structure rather than changes in convective strength. This study pointed out the importance of model spatial resolution in reproducing a reasonable contribution to the total precipitation between top-heavy and bottom-heavy structure of convection in the tropical Pacific ITCZs.
Highlights
The core of tropical dynamics involves strong interaction between cumulus convection and large-scale perturbations
The atmospheric model used in this study is the Community Atmospheric Model version 5 (CAM5) (Neale et al 2010), which is the atmospheric component of the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM), with a finite-volume dynamical core (Lin 2004) and an integration time step of 1800 s (30 min)
A greater contribution from bottom-heavy convection and less contribution from top-heavy convection are found in the finer resolution experiments (Fig. 2). (2) From the regional point of view, coarser resolution experiments exhibit stronger precipitation in the western Pacific warm pool, but weaker precipitation in the eastern Pacific ITCZ
Summary
The core of tropical dynamics involves strong interaction between cumulus convection and large-scale perturbations. Most of the climate models used in CMIP5 have increased spatial resolution compared to those used in CMIP3, some still keep relatively low resolution, e.g., CMSS-CESM (3 .75◦ × 3.75◦ ), HadCM3 ( 3.75◦ × 2.5◦ ), FGOALS-g2 and MIROC-ESM ( 2.8125◦ × 2.8125◦ ), GFDL-CM2.1 ( 2.5◦ × 2◦ ) and GISSE2-H ( 2◦ × 2.5◦ ) It is worth knowing how the model’s spatial resolution impacts the vertical structure of convection in the Tropics because the efficiency of moist static energy export by cumulus convection depends largely on the structure of convection (Back and Bretherton 2006; Bui et al 2016).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
