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A recent study based on observations has shown that after precipitation over tropical oceans rather shallow temperature structures occur in the lower troposphere and that their magnitude depends on climatological low- to midtropospheric humidity. As any process that produces temperature perturbations in the lower troposphere can be of great significance for the formation of atmospheric deep convection, the vertical temperature structure associated with evaporation of stratiform precipitation and its sensitivity to low- to midtropospheric humidity are studied by conducting three-dimensional, high-resolution, idealized simulations with the Advanced Research version of the Weather Research and Forecasting (WRF) Model. In the simulations, rainwater with mixing ratio and number concentration characteristic of stratiform precipitation associated with mesoscale convective systems is added in a large round area at roughly 560 hPa. Evaporative cooling and subsidence warming below result in a cold anomaly at roughly 560–750 hPa and, especially, a warm anomaly at roughly 750–900 hPa. The cold-over-warm anomalies are stronger with smaller low- to midtropospheric relative humidity in the initial conditions, with the maximum magnitude of the warm anomaly ranging between 0.7 and 1.2 K. The temperature anomalies propagate to the environment and still remain present after precipitation stops. The results show that evaporation of stratiform precipitation alone can lead to temperature structures, which are on the same order of magnitude as the observed ones, that potentially inhibit subsequent convection by increasing convective inhibition. Therefore, the representation of microphysical processes affecting the location, amount, and vertical and horizontal distribution of stratiform precipitation and its evaporation in numerical models requires special attention. A recent study based on observations has shown that after precipitation over tropical oceans rather shallow temperature structures occur in the lower troposphere and that their magnitude depends on climatological low- to midtropospheric humidity. As any process that produces temperature perturbations in the lower troposphere can be of great significance for the formation of atmospheric deep convection, the vertical temperature structure associated with evaporation of stratiform precipitation and its sensitivity to low- to midtropospheric humidity are studied by conducting three-dimensional, high-resolution, idealized simulations with the Advanced Research version of the Weather Research and Forecasting (WRF) Model. In the simulations, rainwater with mixing ratio and number concentration characteristic of stratiform precipitation associated with mesoscale convective systems is added in a large round area at roughly 560 hPa. Evaporative cooling and subsidence warming below result in a cold anomaly at roughly 560–750 hPa and, especially, a warm anomaly at roughly 750–900 hPa. The cold-over-warm anomalies are stronger with smaller low- to midtropospheric relative humidity in the initial conditions, with the maximum magnitude of the warm anomaly ranging between 0.7 and 1.2 K. The temperature anomalies propagate to the environment and still remain present after precipitation stops. The results show that evaporation of stratiform precipitation alone can lead to temperature structures, which are on the same order of magnitude as the observed ones, that potentially inhibit subsequent convection by increasing convective inhibition. Therefore, the representation of microphysical processes affecting the location, amount, and vertical and horizontal distribution of stratiform precipitation and its evaporation in numerical models requires special attention.

A cloud-resolving model is used to study the effects of a vertical temperature dipole on convective cloud development. Such dipole anomalies, with a warm-above-cool structure in the troposphere, are known to be forced by mesoscale convective systems (MCSs) in the Tropics. The experiments involve letting convection develop in perturbed initial soundings with open lateral boundary conditions. Convection is driven solely by surface fluxes. In the control run, a field of deep convection ensues. With a strong dipole anomaly that is warm in the upper troposphere, no clouds ascend beyond the middle troposphere. In this case, cumulus congestus clouds strongly moisten the midtroposphere with relative humidity increases by up to 24% by the end of the 6-h simulation. With a half-strength anomaly, a mixed population results: mainly middle-topped congestus clouds, but with some intermittent deep cells. The partitioning between cloud types is somewhat sensitive to model resolution, with a change from 1- to 0.5-km grid spacing resulting in relatively more congestus clouds and fewer deep cells.

The effect of peripheral convection on the formation and intensification of tropical cyclones has been studied earlier with diagnostic models and with prognostic models that do not resolve convection. In this paper, a prognostic, axisymmetric model with explicit convection is used to study the effect of peripheral convection on tropical cyclone formation from a weak mesoscale vortex. Peripheral convection becomes stronger in the model if downdrafts extinguish deep convection in the core of the mesoscale vortex. The subsequent concentration of convection in the core of the vortex and the onset of rapid intensification of the vortex occur simultaneously. In model experiments, relative humidity in the midtroposphere reaches a value of 90% within 100 km from the center of the vortex before the onset of rapid intensification occurs. Decreasing the sea surface fluxes of sensible and latent heat artificially in the outer region of the vortex decreases the amount of outer convection in the model. This re...