Probing into responses of moist convection to large-scale temperature perturbations using a Lagrangian Particle Dispersion Model

How moist convection responds to small large-scale temperature and moisture perturbations has a strong influence on the behavior of moist convecting atmospheres; convectively coupled waves being one example. While such responses, sometimes called linear response functions, have been constructed using a cloud-resolving model (CRM), the processes by which convection produces such responses, and how such processes vary with the state of that moist atmosphere, require further clarification. In particular, it was found recently that convective responses to perturbations strongly depend on the degree of convective organization. For unorganized convection, effects of temperature and moisture anomalies in the free troposphere on convection are broadly consistent with a parcel view of moist convection: a warm anomaly forms a buoyancy barrier that eliminates some of the convective updraft parcels, leading to cooling at and above the perturbed layer, while a moist anomaly reduces the degree of entrainment drying experienced by the parcels and allow them to reach higher, leading to warming at and above the perturbed layer. On the other hand, when convection is highly organized, the general behavior is more consistent with a layer mode of convective overturning, where a warm anomaly in the lower troposphere (above the cloud base) leads to warming of the entire free troposphere and cooling of the sub-cloud layer, while a warm anomaly in the middle and upper troposphere has the opposite effect. In this study, we embed a Lagrangian Particle Dispersion model in the CRM to explore the processes underlying these different convective responses, such as the relative importance of buoyancy and mechanical lifting of air parcels in organized and unorganized convection.