The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） f...The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） flashes and Cloud-to-Ground （CG） flashes, and the ADTD （ADvanced TOA and Direction system; TOA denotes time of arrival） network of China for CG lightning. Fourteen isolated hail-bearing thunderstorms in this region were examined in this study, using the data of SAFIR and ADTD. The peak of lightning frequency, for both total lightning and CG lightning, was often observed in advance of the occurrence of hailstones on the ground, with a trend of a rapid increase of lightning frequency before the hail was reported. The average lead times of the two types of lightning jump before hail events were obtained （total lightning： 32.2 min; CG： 25.4 min） through the 2a lightning jump algorithm. Additionally, in hailstorms with a high ratio of positive CG flashes, the diameter of hail was larger and the duration of hail was longer; when negative CG flashes dominated, the diameter of hail was relatively small. The comparison of the characteristics of total lightning and CG flashes in hailstorms in this study is expected to serve as a supplementary tool for hail forecasting.展开更多
Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the ...Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the cloud-to-ground（CG） lightning data of a CG lightning location system,and the echo data of a Doppler radar.Both hailstorms exhibited two lightning frequency peaks：the first was before the hailfall and the second was after the hailfall,with the second peak greater than the first.The dominant polarity of the CG lightning was positive in the stage around the first frequency peak,but changed to negative in the stage around the second frequency peak.The evolution of radar echoes and the height distribution of lightning radiation sources are explored,revealing that both hailstorms had stronger convection and the main positive charge occurred at mid levels during the stage around the first frequency peak.However,whilst the Beijing hailstorm experienced the enhancement of convection,with the main positive charge at upper levels around the second frequency peak,the Tianjin hailstorm generated its second frequency peak during the period when the convection kept weakening and the main positive charge dropped to mid-lower levels.Through evaluation of the radar parameters,we investigate the mechanisms responsible for the second stage of active lightning discharge.Furthermore,the lightning activity exhibited a close relationship with radar echo parameters and hailfall.Lightning jump signals were found before the hailfall and were associated with the change ratio of the 40-dBZ echo volume above the-15℃ level,which demonstrates the application value of lightning data in severe weather warning.展开更多
基金Supported by the National Natural Science Foundation of China (41030960 and 41105122)Project for Integration and Application of Meteorological Key Technology by the China Meteorological Administration (CAMGJ2012M78)National Science and Technology Support Program of China (2008BAC36B04)
文摘The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks： SAFIR （Systeme d＇Alerte Fondre par Interferometrie Radioelecctrique） for total lightning, including IntraCloud （IC） flashes and Cloud-to-Ground （CG） flashes, and the ADTD （ADvanced TOA and Direction system; TOA denotes time of arrival） network of China for CG lightning. Fourteen isolated hail-bearing thunderstorms in this region were examined in this study, using the data of SAFIR and ADTD. The peak of lightning frequency, for both total lightning and CG lightning, was often observed in advance of the occurrence of hailstones on the ground, with a trend of a rapid increase of lightning frequency before the hail was reported. The average lead times of the two types of lightning jump before hail events were obtained （total lightning： 32.2 min; CG： 25.4 min） through the 2a lightning jump algorithm. Additionally, in hailstorms with a high ratio of positive CG flashes, the diameter of hail was larger and the duration of hail was longer; when negative CG flashes dominated, the diameter of hail was relatively small. The comparison of the characteristics of total lightning and CG flashes in hailstorms in this study is expected to serve as a supplementary tool for hail forecasting.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2014CB441402)Basic Research Project of the Chinese Academy of Meteorological Sciences(2014R017 and 2013Z006)+1 种基金Key Laboratory Open Project of Disasters Research(2014LASW-B08)Natural Science Research for Jiangsu Provincial Higher Education Colleges(14KJA170005)
文摘Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the cloud-to-ground（CG） lightning data of a CG lightning location system,and the echo data of a Doppler radar.Both hailstorms exhibited two lightning frequency peaks：the first was before the hailfall and the second was after the hailfall,with the second peak greater than the first.The dominant polarity of the CG lightning was positive in the stage around the first frequency peak,but changed to negative in the stage around the second frequency peak.The evolution of radar echoes and the height distribution of lightning radiation sources are explored,revealing that both hailstorms had stronger convection and the main positive charge occurred at mid levels during the stage around the first frequency peak.However,whilst the Beijing hailstorm experienced the enhancement of convection,with the main positive charge at upper levels around the second frequency peak,the Tianjin hailstorm generated its second frequency peak during the period when the convection kept weakening and the main positive charge dropped to mid-lower levels.Through evaluation of the radar parameters,we investigate the mechanisms responsible for the second stage of active lightning discharge.Furthermore,the lightning activity exhibited a close relationship with radar echo parameters and hailfall.Lightning jump signals were found before the hailfall and were associated with the change ratio of the 40-dBZ echo volume above the-15℃ level,which demonstrates the application value of lightning data in severe weather warning.
