Based on the model of regular condensation it was found that at low concentrations of CN (LC mode) at a height of about 10 m from the condensation level narrow spectra of cloud drop are formed. Their dispersion quickl...Based on the model of regular condensation it was found that at low concentrations of CN (LC mode) at a height of about 10 m from the condensation level narrow spectra of cloud drop are formed. Their dispersion quickly decreases with increasing height. For high concentrations (HC mode) broad spectra are formed immediately due to the absence of separation into growing drops and CN covered with water. The process of spectra evolution is conducted at a constant height results, in all the cases, in the appearance of asymptotic spectra with a relative width rb ≥ 0.215. To approximate these calculated asymptotic spectra, the modified gamma-distribution with the fixed parameter α = 3 and a variable parameter γ are most suitable. For the intermediate spectra applicable are the simpler mirror-transformed known distributions. The comparison of the above distributions with the experimental spectra of a fog artificially formed in the Big Aerosol Chamber (BAC) of RPA “Typhoon” and the spectra of the morning fog and super cooled stratiform clouds demonstrated their good agreement. The phenomenon of multimodal spectra formation at a sharp rise of stratiform clouds with the velocity more than 0.1 - 0.3 m/s was theoretically shown and experimentally confirmed. The effect of CN high concentrations, evolution processes and sharp fluctuations of vertical velocities on the formation of cloud spectra observed in nature is discussed.展开更多
Downburst is a very dangerous weather phenomenon for aeroplane taking off or landing. In order to understand the initial formation and evolution of downburst and to study the effects of at- mospheric environment condi...Downburst is a very dangerous weather phenomenon for aeroplane taking off or landing. In order to understand the initial formation and evolution of downburst and to study the effects of at- mospheric environment condition and the microstructure of cloud-precipitation particles on the downburst development processes, we have designed and carried out a modeling scheme by making use of our own non-hydrostatic compressible mesoscale-γ model including necessary cloud-precipi- tation processes. The initial conditions of temperature, humidity and wind are from an observation case in which the downburst occurred. The results of computations demonstrate the evolution of downburst and show the variation of various environmental and microphysical parameters. Some of the mechanisms about the downburst occurrence have been obtained. Computation results may help airport forecasters to determine the occurrence of downburst better.展开更多
文摘Based on the model of regular condensation it was found that at low concentrations of CN (LC mode) at a height of about 10 m from the condensation level narrow spectra of cloud drop are formed. Their dispersion quickly decreases with increasing height. For high concentrations (HC mode) broad spectra are formed immediately due to the absence of separation into growing drops and CN covered with water. The process of spectra evolution is conducted at a constant height results, in all the cases, in the appearance of asymptotic spectra with a relative width rb ≥ 0.215. To approximate these calculated asymptotic spectra, the modified gamma-distribution with the fixed parameter α = 3 and a variable parameter γ are most suitable. For the intermediate spectra applicable are the simpler mirror-transformed known distributions. The comparison of the above distributions with the experimental spectra of a fog artificially formed in the Big Aerosol Chamber (BAC) of RPA “Typhoon” and the spectra of the morning fog and super cooled stratiform clouds demonstrated their good agreement. The phenomenon of multimodal spectra formation at a sharp rise of stratiform clouds with the velocity more than 0.1 - 0.3 m/s was theoretically shown and experimentally confirmed. The effect of CN high concentrations, evolution processes and sharp fluctuations of vertical velocities on the formation of cloud spectra observed in nature is discussed.
基金The project is supported by the National Natural Science Foundation of China
文摘Downburst is a very dangerous weather phenomenon for aeroplane taking off or landing. In order to understand the initial formation and evolution of downburst and to study the effects of at- mospheric environment condition and the microstructure of cloud-precipitation particles on the downburst development processes, we have designed and carried out a modeling scheme by making use of our own non-hydrostatic compressible mesoscale-γ model including necessary cloud-precipi- tation processes. The initial conditions of temperature, humidity and wind are from an observation case in which the downburst occurred. The results of computations demonstrate the evolution of downburst and show the variation of various environmental and microphysical parameters. Some of the mechanisms about the downburst occurrence have been obtained. Computation results may help airport forecasters to determine the occurrence of downburst better.
