The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the ...The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the non-hydrostatic mesoscale model MM5. This period covered the process of typhoon HERB landfall at Taiwan and Fujian Provinces. Results show that the model successfully simulated the landfall process of typhoon HERB, revealed the most important characteristics of the mesoscale dynamic and thermodynamic and cloud-rain physical structure during its landfall. The simulated typhoon track was close to the observation. The center of cyclonic circulation simulated at 0000 UTC on 1 August 1996 (24 h integration) was located in shore near Fuqing, Fujian Province at which the typhoon was reported to landfall two hours later. It shows that strong upward motion formed by low level convergence existed in the eye-wall and subsidence at the eye. The wind field shows clear asymmetrical structure near the typhoon center. The cloud and rainband was screw-typed distributed around typhoon center, and consisted of meso-β scale rain cores. During the period of typhoon HERB staying near and passing over Taiwan, the lower cloud was developed in the eye region so that the previous clear typhoon eye on the satellite pictures became fuzzy. Observation shows that the typhoon center was 'warm', but the model simulations with higher space resolution show that in the mid-troposphere the region of eye-wall with stronger upward motion and more cloud-and rain- water was warmer than the eye. During the period of typhoon passing over Taiwan and its following landfall at Fujian, the track of model typhoon deviated about 30 km northward (i. e., rightward) because of the orographic effects of Taiwan Island, but the strength of the typhoon was not affected remarkably. The amount of rainfall on Taiwan in the 36 h simulations was enhanced more than six times by the orographic lifting of Taiwan Mountain.展开更多
Diagnosis is performed of a thunderstorm rainstorm event occurring in the summer of 1996 at Nanjing and numerical simulation undertaken in the context of hydrostatic equilibrium framework of MM5 as the fifth version o...Diagnosis is performed of a thunderstorm rainstorm event occurring in the summer of 1996 at Nanjing and numerical simulation undertaken in the context of hydrostatic equilibrium framework of MM5 as the fifth version of the PSU/NCAR mesoscale model.Analyses show that the rainstorm-associated thermal condition was the accumulation of unstable potential energy and the dynamic condition was vigorous convergence updrafts.And the simulation within the hydrostatic framework indicates the significant role of latent heat release in the rainstorm occurrence:that even for a 30 km grid spacing horizontally of great importance to the successful modeling of the meso-β event was a convection parameterization scheme that led to less rainfall in our run based only on its explicit version but to the prediction in closer agreement with the observed when its implicit version was used in combination:for the thunderstorm-accompanied torrential rain.the Grell scheme was superior to the version of Kuo and the improved Arakawa-Schubert parameterization scheme(Grell 1993:Anthese and Kuo 1987:Arakawa and Scherbt 1974:Grell et al,1991).Moreover,better results came from the simulation in the context of hydrostatic framework of the MM5 compared to those from the run within the nonhydrostatic equilibrium framework,a problem that awaits further efforts.展开更多
基金Supported by the Program of "Research on the Formation MechanismPrediction Theory of Severe Synoptic Disasters in China" (G1998040907).
文摘The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the non-hydrostatic mesoscale model MM5. This period covered the process of typhoon HERB landfall at Taiwan and Fujian Provinces. Results show that the model successfully simulated the landfall process of typhoon HERB, revealed the most important characteristics of the mesoscale dynamic and thermodynamic and cloud-rain physical structure during its landfall. The simulated typhoon track was close to the observation. The center of cyclonic circulation simulated at 0000 UTC on 1 August 1996 (24 h integration) was located in shore near Fuqing, Fujian Province at which the typhoon was reported to landfall two hours later. It shows that strong upward motion formed by low level convergence existed in the eye-wall and subsidence at the eye. The wind field shows clear asymmetrical structure near the typhoon center. The cloud and rainband was screw-typed distributed around typhoon center, and consisted of meso-β scale rain cores. During the period of typhoon HERB staying near and passing over Taiwan, the lower cloud was developed in the eye region so that the previous clear typhoon eye on the satellite pictures became fuzzy. Observation shows that the typhoon center was 'warm', but the model simulations with higher space resolution show that in the mid-troposphere the region of eye-wall with stronger upward motion and more cloud-and rain- water was warmer than the eye. During the period of typhoon passing over Taiwan and its following landfall at Fujian, the track of model typhoon deviated about 30 km northward (i. e., rightward) because of the orographic effects of Taiwan Island, but the strength of the typhoon was not affected remarkably. The amount of rainfall on Taiwan in the 36 h simulations was enhanced more than six times by the orographic lifting of Taiwan Mountain.
基金National Natural Science Foundation of China under Grants 49375246.
文摘Diagnosis is performed of a thunderstorm rainstorm event occurring in the summer of 1996 at Nanjing and numerical simulation undertaken in the context of hydrostatic equilibrium framework of MM5 as the fifth version of the PSU/NCAR mesoscale model.Analyses show that the rainstorm-associated thermal condition was the accumulation of unstable potential energy and the dynamic condition was vigorous convergence updrafts.And the simulation within the hydrostatic framework indicates the significant role of latent heat release in the rainstorm occurrence:that even for a 30 km grid spacing horizontally of great importance to the successful modeling of the meso-β event was a convection parameterization scheme that led to less rainfall in our run based only on its explicit version but to the prediction in closer agreement with the observed when its implicit version was used in combination:for the thunderstorm-accompanied torrential rain.the Grell scheme was superior to the version of Kuo and the improved Arakawa-Schubert parameterization scheme(Grell 1993:Anthese and Kuo 1987:Arakawa and Scherbt 1974:Grell et al,1991).Moreover,better results came from the simulation in the context of hydrostatic framework of the MM5 compared to those from the run within the nonhydrostatic equilibrium framework,a problem that awaits further efforts.
