Lightning activity for the July 10, 1996, storm during the Stratosphere-Troposphere Experiment: Radiation, Aerosol, and Ozone-A (STERAO-A) experiment

We have analyzed the lightning activity recorded during the Stratosphere-Tr oposphere Experiment: Radiation, Aerosols, and Ozone (STERAO-A) July 10, 19 96, storm by the Office National d'Etudes et de Recherches Aerospatiales (O NERA) lightning VHF interferometer and the National Lightning Detection Net work (NLDN) system Both cloud-to-ground and total lightning activity were o bserved and studied for the entire 5-hour life of the storm, The July 10 st orm was a multicellular complex, which became unicellular during the last h our. It primarily exhibited high intracloud activity with only 1.5% cloud-t o-ground flashes. The maximum value of the total flash rate was 58 flashes per minute. Cloud-to-ground (CG) flashes occurred after some intracloud fla shes with a delay ranging from 3 to 26 min for the different cells of the s torm. Our study revealed that measured flash duration ranged from 23 mus to 1.8 s. Flash duration, averaged over 5-min periods, increased during the s torm life. Short-duration flashes (<1 ms) did not occur until 30 min after the initial flash in the storm when the 50 dBZ vertical profile reached 8 k m mean sea level (msl). The short-duration flashes were recorded in cells w here high reflectivity reached high altitude. Detailed analysis showed that the ONERA and NLDN reports were temporally and spatially consistent in the measurement of the cloud-to-ground flashes. Finally, we developed a new te chnique to distinguish negative CG flashes from other flashes by identifyin g the VHF signature of the negative downward stepped leader-return stroke p rocess in the flash VHF signal.