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-Troposphere Experiment: Radiation, Aerosols, and Ozone (STERAO-A) July 10, 1996, storm by the Office National d'Etudes et de Recherches Aérospatiales (ONERA) lightning VHF interferometer and the National Lightning Detection Network (NLDN) system. Both cloud-to-ground and total lightning activity were observed and studied for the entire 5-hour life of the storm. The July 10 storm was a multicellular complex, which became unicellular during the last hour. It primarily exhibited high intracloud activity with only 1.5% cloud-to-ground flashes. The maximum value of the total flash rate was 58 flashes per minute. Cloud-to-ground (CG) flashes occurred after some intracloud flashes with a delay ranging from 3 to 26 min for the different cells of the storm. Our study revealed that measured flash duration ranged from 23 μs to 1.8 s. Flash duration, averaged over 5-min periods, increased during the storm 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 km mean sea level (msl). The short-duration flashes were recorded in cells where 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 technique to distinguish negative CG flashes from other flashes by identifying the VHF signature of the negative downward stepped leader-return stroke process in the flash VHF signal.