Lightning

• is a large discharge, or spark in the atmosphere
• two types of discharges:
  • in cloud
  • cloud to ground (less frequent) -->>
• the lightning stroke heats the air instantaneously to 30,000°C
• this heating generates a shock wave that propagates away form the flash- heard as thunder
• we see the lightning flash instantaneously, but thunder is often heard shortly thereafter as sound travels at about 330 m/s. Hence, thunder travels about 1 km in 3 seconds (1 mile per 5 seconds)
• Global lightning distribution
• Sometimes you can see the lightning flash, but can't hear the thunder...., why???

photo by C. Bouchard (04)