Responses of Shallow Cumulus Convection to Large - scale 1 Temperature and Moisture Perturbations : a comparison of 2 large - eddy simulations and a convective parameterization based

7 Responses of shallow cumuli to large-scale temperature/moisture perturbations are examined 8 through diagnostics of large-eddy-simulations (LES) of the undisturbed Barbados Oceano9 graphic and Meteorological Experiment (BOMEX) case and a stochastic parcel model. The 10 perturbations are added instantaneously and allowed to evolve freely afterwards. The par11 cel model reproduces most of the changes in the LES-simulated cloudy updraft statistics in 12 response to the perturbations. Analyses of parcel histories show that a positive temperature 13 perturbation forms a buoyancy barrier, which preferentially eliminates parcels that start with 14 lower equivalent potential temperature or have experienced heavy entrainment. Besides the 15 amount of entrainment, the height at which parcels entrain is also important in determining 16 their fate. Parcels entraining at higher altitudes are more likely to overcome the buoyancy 17 barrier than those entraining at lower altitudes. Stochastic entrainment is key for the parcel 18 model to reproduce the LES results. Responses to environmental moisture perturbations 19 are quite small compared to those to temperature perturbations, because changing envi20 ronmental moisture is ineffective in modifying buoyancy in the BOMEX shallow cumulus 21 case. 22 The second part of the paper further explores the feasibility of a stochastic-parcel-based 23 cumulus parameterization. Air parcels are released from the surface layer and tempera24 ture/moisture fluxes effected by the parcels are used to calculate heating/moistening ten25 dencies due to both cumulus convection and boundary layer turbulence. Initial results show 26 that this conceptually simple parameterization produces realistic convective tendencies and 27 also reproduces the LES-simulated mean and variance of cloudy updraft properties, as well 28 as the response of convection to temperature/moisture perturbations. 29