Lightning

Question 1

Main types of lightning

Answer 1

1. Cloud to ground
2. Cloud to air
3. Intracloud
4. Spider lightning

Question 2

What are the steps of lightning formation?

Answer 2

1. Charge Seperation
2. Stepped Leader
3. Ground Spark
4. Return Stroke

Question 3

Charge Seperation

Answer 3

-separation of positive and negative charges into different regions of the cloud
-typically positive charges accumulate at the top of the cloud, and the negative at the lower part of the cloud (this is likely produced by interaction between ice crystals and hail)
-because negative charge at base of cloud, there is a positive charge that accumulates at the surface

Question 4

Stepped Leader

Answer 4

-the rapid and staggered advance of a shaft of negatively charged air
-advances at about 50 m at a time, in between pauses of about 50 microseconds electrons pile up at the top
-usually not visible

Question 5

Ground Spark

Answer 5

as the leader approaches the ground, a spark is created

Question 6

Return Stroke

Answer 6

-When the leader and the spark connect, a stroke travels upwards
-positive charge at the surface moving up towards the negative charge of the cloud
-Currents heat the air to about 30,000K
-Dart leader follows, producing other strokes

Question 7

What types of clouds must lighting occur in?

Answer 7

Lighting only occurs in clouds above freezing level, so must be precipitating

Question 8

What is the first lighting stroke of a storm likely to be?

Answer 8

It is likely to be positive. Wind shear can cause positive charged top of cloud to more ahead of the storm. This creates a negative charge at the surface and may result in a lighting strike.