When super typhoon Sepat came close to the Fujian coastline on the night of 18 August 2007 (coded as 0709 in Chinese convention), an associated tornado-like severe storm developed at 2307–2320 Beijing Standard Time i...When super typhoon Sepat came close to the Fujian coastline on the night of 18 August 2007 (coded as 0709 in Chinese convention), an associated tornado-like severe storm developed at 2307–2320 Beijing Standard Time in Longgang, Cangnan County, Wenzhou Prefecture, Zhejiang Province approximately 300 km away in the forward direction of the typhoon. The storm caused heavy losses in lives and property. Studying the background of the formation of the storm, this paper identifies some of its typical characteristics after analyzing its retrieval of Doppler radar data, vertical wind shear and so on. Synoptic conditions, such as unstable weather processes and TBB, are also studied.展开更多
The purposes of the paper are threefold: 1) to show the fundamental possibility of physical simulation of non-stationary wall-free concentrated air vortices (called here as tornado-like vortices) under laboratory cond...The purposes of the paper are threefold: 1) to show the fundamental possibility of physical simulation of non-stationary wall-free concentrated air vortices (called here as tornado-like vortices) under laboratory conditions without using of the mechanical rotation, 2) to find the heating rates of underlying surface and air temporal and spatial temperature shear which lead to the stable genesis of wall-free vortices, and 3) to investigate the some parameters of the process of generation of vortices and their characteristics. The wall-free vortices were generated over underlying surface of aluminum sheet due to its controlled heating from below as a result of development of unstable stratifycation of air.展开更多
In this paper,the effects of surface roughness on tornado-like vortices are studied in the laboratory for simulating tornado vortex at the Disaster Prevention Research Institute,Kyoto University,Japan. In the experime...In this paper,the effects of surface roughness on tornado-like vortices are studied in the laboratory for simulating tornado vortex at the Disaster Prevention Research Institute,Kyoto University,Japan. In the experiments,the distribution of the horizontal wind speed and direction at five different heights were measured with a hot-wire anemometer and a mini-vane.The characteristics of wind speed and direc- tion distribution for the tornado vortex on the various rough surfaces were first revealed with the simulative method in laboratory.By changing the swirl ratio(S=tanθ/2a)of simulation device,it is found that,the size of tornado-like vortex core will become almost identical,as the swirl ratio S exceeds a certain value (S>1.5). The experimental results can be used not only to explain the observed facts in the atmosphere but also to provide the experimental bases for some theoretical studies.展开更多
During the Mw9 Tohoku-Oki earthquake, gradual increases in both ionosphere total electron content (TEC) and geomagnetic declination signals were observed, starting from ~40 minutes before the mainshock, followed by im...During the Mw9 Tohoku-Oki earthquake, gradual increases in both ionosphere total electron content (TEC) and geomagnetic declination signals were observed, starting from ~40 minutes before the mainshock, followed by impulsive enhancements ~10 minutes after the mainshock. There have been many studies on pre-seismic TEC enhancements, including their characteristics, debates regarding whether TEC anomalies are real signals or artefacts, and the explainable models, and many studies have reported that the impulsive TEC enhancement was caused by a tsunami-induced neutral atmospheric gravity wave. Since TEC and geomagnetic declination anomalies were synchronized so that their origin should be attributed to the same seismic activities, any models must explain both anomalous phenomena, but not the case considered herein. Compared with the corresponding TEC anomalies, we re-examined the characteristics of geomagnetic variation just before and after the mainshock, focusing on the generation process of the impulsive enhancement immediately after the mainshock. We showed that the observed anomaly could be explained if there are quasi-static electric currents of 20 - 30 kA generated near the epicentre area. The possible mechanism of the current generation is discussed in terms of the ionization process in the atmosphere near the sea surface.展开更多
基金Natural Science Foundation of China (40875025,40875030)
文摘When super typhoon Sepat came close to the Fujian coastline on the night of 18 August 2007 (coded as 0709 in Chinese convention), an associated tornado-like severe storm developed at 2307–2320 Beijing Standard Time in Longgang, Cangnan County, Wenzhou Prefecture, Zhejiang Province approximately 300 km away in the forward direction of the typhoon. The storm caused heavy losses in lives and property. Studying the background of the formation of the storm, this paper identifies some of its typical characteristics after analyzing its retrieval of Doppler radar data, vertical wind shear and so on. Synoptic conditions, such as unstable weather processes and TBB, are also studied.
文摘The purposes of the paper are threefold: 1) to show the fundamental possibility of physical simulation of non-stationary wall-free concentrated air vortices (called here as tornado-like vortices) under laboratory conditions without using of the mechanical rotation, 2) to find the heating rates of underlying surface and air temporal and spatial temperature shear which lead to the stable genesis of wall-free vortices, and 3) to investigate the some parameters of the process of generation of vortices and their characteristics. The wall-free vortices were generated over underlying surface of aluminum sheet due to its controlled heating from below as a result of development of unstable stratifycation of air.
文摘In this paper,the effects of surface roughness on tornado-like vortices are studied in the laboratory for simulating tornado vortex at the Disaster Prevention Research Institute,Kyoto University,Japan. In the experiments,the distribution of the horizontal wind speed and direction at five different heights were measured with a hot-wire anemometer and a mini-vane.The characteristics of wind speed and direc- tion distribution for the tornado vortex on the various rough surfaces were first revealed with the simulative method in laboratory.By changing the swirl ratio(S=tanθ/2a)of simulation device,it is found that,the size of tornado-like vortex core will become almost identical,as the swirl ratio S exceeds a certain value (S>1.5). The experimental results can be used not only to explain the observed facts in the atmosphere but also to provide the experimental bases for some theoretical studies.
文摘During the Mw9 Tohoku-Oki earthquake, gradual increases in both ionosphere total electron content (TEC) and geomagnetic declination signals were observed, starting from ~40 minutes before the mainshock, followed by impulsive enhancements ~10 minutes after the mainshock. There have been many studies on pre-seismic TEC enhancements, including their characteristics, debates regarding whether TEC anomalies are real signals or artefacts, and the explainable models, and many studies have reported that the impulsive TEC enhancement was caused by a tsunami-induced neutral atmospheric gravity wave. Since TEC and geomagnetic declination anomalies were synchronized so that their origin should be attributed to the same seismic activities, any models must explain both anomalous phenomena, but not the case considered herein. Compared with the corresponding TEC anomalies, we re-examined the characteristics of geomagnetic variation just before and after the mainshock, focusing on the generation process of the impulsive enhancement immediately after the mainshock. We showed that the observed anomaly could be explained if there are quasi-static electric currents of 20 - 30 kA generated near the epicentre area. The possible mechanism of the current generation is discussed in terms of the ionization process in the atmosphere near the sea surface.
