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- Author or Editor: James Correia Jr. x
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Abstract
Dropsonde observations from the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) are used to document the spatiotemporal variability of temperature, moisture, and wind within mesoscale convective systems (MCSs). Onion-type sounding structures are found throughout the stratiform region of MCSs, but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each subregion of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. It was found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet-bulb potential temperature profiles seem to indicate that air within the lowest several kilometers comes from a variety of source regions. It was also found that lapse-rate transitions across the 0°C level were more common than isothermal, melting layers. The authors discuss the implications these findings have and how they can be used to validate future high-resolution numerical simulations of MCSs.
Abstract
Dropsonde observations from the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) are used to document the spatiotemporal variability of temperature, moisture, and wind within mesoscale convective systems (MCSs). Onion-type sounding structures are found throughout the stratiform region of MCSs, but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each subregion of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. It was found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet-bulb potential temperature profiles seem to indicate that air within the lowest several kilometers comes from a variety of source regions. It was also found that lapse-rate transitions across the 0°C level were more common than isothermal, melting layers. The authors discuss the implications these findings have and how they can be used to validate future high-resolution numerical simulations of MCSs.
Abstract
The development and propagation of mesoscale convective systems (MCSs) was examined within the Weather Research and Forecasting (WRF) model using the Kain–Fritsch (KF) cumulus parameterization scheme and a modified version of this scheme. Mechanisms that led to propagation in the parameterized MCS are evaluated and compared between the versions of the KF scheme. Sensitivity to the convective time step is identified and explored for its role in scheme behavior. The sensitivity of parameterized convection propagation to microphysical feedback and to the shape and magnitude of the convective heating profile is also explored.
Each version of the KF scheme has a favored calling frequency that alters the scheme’s initiation frequency despite using the same convective trigger function. The authors propose that this behavior results in part from interaction with computational damping in WRF. A propagating convective system develops in simulations with both versions, but the typical flow structures are distorted (elevated ascending rear inflow as opposed to a descending rear inflow jet as is typically observed). The shape and magnitude of the heating profile is found to alter the propagation speed appreciably, even more so than the microphysical feedback. Microphysical feedback has a secondary role in producing realistic flow features via the resolvable-scale model microphysics. Deficiencies associated with the schemes are discussed and improvements are proposed.
Abstract
The development and propagation of mesoscale convective systems (MCSs) was examined within the Weather Research and Forecasting (WRF) model using the Kain–Fritsch (KF) cumulus parameterization scheme and a modified version of this scheme. Mechanisms that led to propagation in the parameterized MCS are evaluated and compared between the versions of the KF scheme. Sensitivity to the convective time step is identified and explored for its role in scheme behavior. The sensitivity of parameterized convection propagation to microphysical feedback and to the shape and magnitude of the convective heating profile is also explored.
Each version of the KF scheme has a favored calling frequency that alters the scheme’s initiation frequency despite using the same convective trigger function. The authors propose that this behavior results in part from interaction with computational damping in WRF. A propagating convective system develops in simulations with both versions, but the typical flow structures are distorted (elevated ascending rear inflow as opposed to a descending rear inflow jet as is typically observed). The shape and magnitude of the heating profile is found to alter the propagation speed appreciably, even more so than the microphysical feedback. Microphysical feedback has a secondary role in producing realistic flow features via the resolvable-scale model microphysics. Deficiencies associated with the schemes are discussed and improvements are proposed.
