[1] Although dry/moist potential vorticity (( · ∇θe)/ρ) is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of two-dimensional (2-D) simulations. A new vorticity vector ( × ∇θe)/ρ (convective vorticity vector (CVV)) is introduced in this study to analyze 2-D cloud-resolving simulation data associated with 2-D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2-D x-z frame. Analysis of zonally averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004JD004807

A convective vorticity vector associated with tropical convection: A two‐dimensional cloud‐resolving modeling study

[1] Moist ( × ∇qv/ρ, MVV) and dynamic ( × /ρ, DVV) vorticity vectors are introduced to study 2-D tropical convection with 2-D cloud-resolving simulation data. The cloud model is forced by vertical velocity, zonal wind, horizontal advection, and sea surface temperature data obtained from TOGA COARE and is integrated for a selected 10-day period. The MVV and DVV have zonal and vertical components in the 2-D x-z frame. Analysis of zonally averaged and mass-integrated quantities shows that the vertical (zonal) component of the MVV and the sum of the cloud hydrometeor mixing ratios are in phase with a correlation coefficient of 0.78 (0.32), and the vertical (zonal) component of the DVV and the sum of the mixing ratios are in (out of) phase with a correlation coefficient of 0.52 (−0.62), indicating that the vertical component of the MVV and both zonal and vertical component of the DVV are closely associated with tropical convection. The tendency equations for the MVV and DVV are derived, and the zonally averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the MVV is mainly determined by the interaction between the vorticity and the zonal gradient of condensational/depositional heating. The tendency of the zonal component of the DVV is controlled by the interaction between the vorticity, buoyancy, and vertical pressure gradient, whereas the tendency of the vertical component is determined by the interaction between the vorticity and zonal pressure gradient.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004JD005675

A modeling study of moist and dynamic vorticity vectors associated with two‐dimensional tropical convection

The effects of ice microphysics on rainfall and thermodynamic processes in the tropical deep convective regime are examined based on hourly zonal-mean data from a pair of two-dimensional cloud-resolving simulations: one simulation with ice clouds and the other without ice clouds. The model is integrated for 21 days with the imposed large-scale vertical velocity, zonal wind, and horizontal advections obtained from the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. The experiment without ice clouds produces a larger amount of cloud water and a smaller surface rain rate than the experiment with ice clouds because of the exclusion of vapor deposition processes in the experiment without ice clouds. The experiment without ice clouds produces cold and moist states simply because it generates a smaller cloud heating rate and consumes a smaller amount of vapor than does the experiment with ice clouds.

Impacts of ice microphysics on rainfall and thermodynamic processes in the tropical deep convective regime : A 2D cloud-resolving modeling study

Cloud microphysical processes associated with the diurnal variations of tropical convection are investigated based on hourly data from a 2D coupled ocean-cloud resolving atmosphere simulation. The model is forced by the large-scale vertical velocity and zonal wind derived from TOGA COARE for a 50-day period. The diurnal composites are carried out in weak diurnal SST variations (case W) and strong diurnal SST signals (case S). The ice water path is larger than the liquid water path in case W than it is in case S. The difference is enhanced in the morning in case W and in the early afternoon in case S when the surface rain rates reach their peaks. Further comparison of cloud microphysics budgets, associated with rainfall peaks, between cases S and W shows that solar heating in case S warms air to reduce the contribution of vapor deposition to cloud growth, which decreases ice water path compared to those in case W. While the collection of cloud water by rain is a major contributor to the surface precipitation in both cases, the melting of precipitation ice (sum of snow and graupel) contributes less to the rainfall in case S than in case W.

Cloud microphysical processes associated with the diurnal variations of tropical convection: A 2D cloud resolving modeling study

Effects of diurnal variations on tropical heat and water vapor equilibrium states are investigated based on hourly data from two-dimensional cloud-resolving simulations. The model is integrated for 40 days and the simulations reach equilibrium states in all experiments. The simulation with a time-invariant solar zenith angle produces a colder and drier equilibrium state than does the simulation with a diurnally varied solar zenith angle. The simulation with a diurnally varied sea surface temperature generates a colder equilibrium state than does the simulation with a time-invariant sea surface temperature. Mass-weighted mean temperature and precipitable water budgets are analyzed to explain the thermodynamic differences. The simulation with the time-invariant solar zenith angle produces less solar heating, more condensation, and consumes more moisture than the simulation with the diurnally varied solar zenith angle. The simulation with the diurnally varied sea surface temperature produces a colde...

Effects of diurnal variations on tropical equilibrium states : A two-dimensional cloud-resolving modeling study

Understanding cloud processes and the associated interactions with their environment is crucial for better predictions of tropical climate. The cloud-resolving model is demonstrated to be a powerful tool for process studies. In this paper, cloud modeling in the tropical deep convective regime is reviewed based on the author's research work. The review focuses on model setup, cloud-radiation interaction processes, convective-radiative processes associated with the diurnal variation of tropical oceanic convection, dominant cloud microphysical processes producing precipitation, precipitation efficiency, physical processes responsible for the phase relation between surface rain rate and convective available potential energy, and the effects of precipitation on the tropical upper ocean.

Xiaofan Li

Papers

Cloud modeling in the tropical deep convective regime