EARTHSC 2GG3 Lecture Notes - Cumulus Congestus Cloud, Cumulonimbus Cloud, Lightning

• School: McMaster University
• Department: Earth Sciences
• Course: EARTHSC 2GG3
• Professor: Sergei Basik

Document Summary

1,800 thunderstorms occur at any moment around the world (16 million a year) The worldwide map shows average density of annual lightning flashes per square kilometer. Most common latitudes are those near the equator. Form as unstable, warm and moist air rapidly rises into colder air and condenses releasing heat and causing updraft. Water droplets freeze in anvil-shaped cumulonimbus clouds. Cold air pushing under warm air along cold front is a common triggering mechanism. Thunderstorms can: travel for more than 1,000km. Strong winds knock down trees, power lines and buildings. Cause numerous wildfires, hail, tornadoes, flash floods. Most likely time for hail, heavy rain, frequent lightning, strong winds, tornadoes. Occasionally has black or dark green appearance. Lasts about 10-20 minutes (some storms last much longer) Results from strong separation of charge that builds up between top and bottom of cumulonimbus cloud.