Representing subgrid convective initiation in the Community Earth System Model

In an effort to address this issue, a model-consistent subgrid convective trigger is demonstrated in the Community Earth System Model (CESM). Subgrid convective initiation is achieved by first calculating a convective threshold within the Community Atmosphere Model (version 5.3).

The convective threshold is then passed to each subgrid land cover type within the Community Land Model (version 4.0) and convection is considered to be active if the convective threshold is exceeded and the convective available potential energy (CAPE) exceeds 70 J kg(-1) (the default trigger). In total, three simulations are performed: (1) a Control (CTL) with the default CAPE trigger, (2) a simulation with the default CAPE trigger as well as the subgrid trigger (HCF trigger) applied over land and ocean, and (3) a simulation the same as the HCF trigger but only applied over land (HCF land).