Numerical simulation of meso-β-scale convective cloud systems associated with a PRE-STORM MCC case has been carried out using a 2-D version of the CSU Regional Atmospheric Modeling System (RAMS) nonhydrostatic model ...Numerical simulation of meso-β-scale convective cloud systems associated with a PRE-STORM MCC case has been carried out using a 2-D version of the CSU Regional Atmospheric Modeling System (RAMS) nonhydrostatic model with parameterized microphysics. It is found that the predicted meso-r-scale convective phenomena arc basically unsteady under the situation of strong shear at low-levels, while the meso-β-scale convective system is maintained up to 3 hours or more. The meso -β- scale cloud system exhibits characteristics of a multi-celled convective storm in which the meso-r-scale convective cells have lifetime of about 30 min. Pressure perturbation depicts a meso-low after a half hour in the low levels. As the cloud system evolves, the meso-low intensifies and extends to the upshear side and covers the entire domain in the mid-lower levels with the peak values of 5-8 hPa. Temperature perturbation depicts a warm region in the middle levels through the entire simulation period. The meso-r-scale warm cores with peak values of 4-8 ℃ are associated with strong convective cells. The cloud top evaporation causes a stronger cold layer around the cloud top levels.Simulation of microphysics exhibits that graupel is primarily concentrated in the strong convective cells forming the main source of convective rainfall after one hour of simulation time. Aggregates are mainly located in the stratiform region and decaying convective cells which produce the stratiform rainfall. Riming of the ice crystals is the predominant precipitation formation mechanism in the convection region, whereas aggregation of ice crystals is the predominant one in the stratiform region, which is consistent with observations. Sensitivity experiments of ice-phase mierophysical processes show that the microphysical structures of the convective cloud system can be simulated better with the diagnosed aggregation collection efficiencies.展开更多
Cloud microphysical data observed with PMS probes have been combined with radar and other in-situ data collected by a NOAA P-3 aircraft that flew through the stratiform and transition regions of a mesoscale convective...Cloud microphysical data observed with PMS probes have been combined with radar and other in-situ data collected by a NOAA P-3 aircraft that flew through the stratiform and transition regions of a mesoscale convective complex(MCC).The combined data have been analyzed with respect to the mescscale structure of the storm systems.The characteristics of ice particles in the transition and stratiform regions were quite differeat.The ice particle concentrations in the transition region were about 4 to 6 times that found in the stratiform region,and the size of ice particles in the stratiform region was about twice that in the transition region.The relatively lower radar reflectivity in the transition region is a result of smaller particle sizes.The main precipitation particle growth mechanisms are riming and aggregation in the transition region ard the aggregation process predominates in the stratiform region referred from the microphysical structures.The ag- gregation starts in the upper,colder levls but becomes more efficient as the particles approach the melting layer.展开更多
A case of mesoscale convective complex(MCC)which evolved into a vortex is documented in this paper.As the MCC entered into the dissipating phase,a well-defined spirally banded structure became visible in the satellite...A case of mesoscale convective complex(MCC)which evolved into a vortex is documented in this paper.As the MCC entered into the dissipating phase,a well-defined spirally banded structure became visible in the satellite image. The blackbody temperature(TBB)of the residual cold-cloud-shield indicates the vortex existed in the layer from 400 to 250 hPa.According to the upper air analysis,the upper level vortex was an anticyclone.The MCC-generated vortex was visualized in the satellite images because it was located in the subtropical high where the wind field was very weak.展开更多
文摘Numerical simulation of meso-β-scale convective cloud systems associated with a PRE-STORM MCC case has been carried out using a 2-D version of the CSU Regional Atmospheric Modeling System (RAMS) nonhydrostatic model with parameterized microphysics. It is found that the predicted meso-r-scale convective phenomena arc basically unsteady under the situation of strong shear at low-levels, while the meso-β-scale convective system is maintained up to 3 hours or more. The meso -β- scale cloud system exhibits characteristics of a multi-celled convective storm in which the meso-r-scale convective cells have lifetime of about 30 min. Pressure perturbation depicts a meso-low after a half hour in the low levels. As the cloud system evolves, the meso-low intensifies and extends to the upshear side and covers the entire domain in the mid-lower levels with the peak values of 5-8 hPa. Temperature perturbation depicts a warm region in the middle levels through the entire simulation period. The meso-r-scale warm cores with peak values of 4-8 ℃ are associated with strong convective cells. The cloud top evaporation causes a stronger cold layer around the cloud top levels.Simulation of microphysics exhibits that graupel is primarily concentrated in the strong convective cells forming the main source of convective rainfall after one hour of simulation time. Aggregates are mainly located in the stratiform region and decaying convective cells which produce the stratiform rainfall. Riming of the ice crystals is the predominant precipitation formation mechanism in the convection region, whereas aggregation of ice crystals is the predominant one in the stratiform region, which is consistent with observations. Sensitivity experiments of ice-phase mierophysical processes show that the microphysical structures of the convective cloud system can be simulated better with the diagnosed aggregation collection efficiencies.
文摘Cloud microphysical data observed with PMS probes have been combined with radar and other in-situ data collected by a NOAA P-3 aircraft that flew through the stratiform and transition regions of a mesoscale convective complex(MCC).The combined data have been analyzed with respect to the mescscale structure of the storm systems.The characteristics of ice particles in the transition and stratiform regions were quite differeat.The ice particle concentrations in the transition region were about 4 to 6 times that found in the stratiform region,and the size of ice particles in the stratiform region was about twice that in the transition region.The relatively lower radar reflectivity in the transition region is a result of smaller particle sizes.The main precipitation particle growth mechanisms are riming and aggregation in the transition region ard the aggregation process predominates in the stratiform region referred from the microphysical structures.The ag- gregation starts in the upper,colder levls but becomes more efficient as the particles approach the melting layer.
基金This study was supported by the National Natural Science Foundation of China,No.49335062.
文摘A case of mesoscale convective complex(MCC)which evolved into a vortex is documented in this paper.As the MCC entered into the dissipating phase,a well-defined spirally banded structure became visible in the satellite image. The blackbody temperature(TBB)of the residual cold-cloud-shield indicates the vortex existed in the layer from 400 to 250 hPa.According to the upper air analysis,the upper level vortex was an anticyclone.The MCC-generated vortex was visualized in the satellite images because it was located in the subtropical high where the wind field was very weak.
