The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. Under what conditions do thunderstorms develop? What provides the energy that drives clouds to the top of the troposphere? How do meteorologists explain lightning? (E)

Thunderstorms develop under three main conditions: unstable air, sufficient moisture in the lower atmosphere, and a lifting mechanism such as fronts, air convergence, or heating of the ground. The energy that propels clouds to the top of the troposphere comes from the release of latent heat which occurs when moist air rises, cools, and condenses into water droplets forming clouds. This condensation process releases heat that warms the surrounding air, reducing its density and causing it to continue rising. Lightning is caused by the separation of electric charges within a storm cloud. Ice and water particles within the cloud collide, separating positive and negative charges. Positive charges gather at the top of the cloud while negative charges concentrate at the bottom. This separation forms an electric field in and around the cloud, and when the field becomes strong enough, it breaks the air's insulating properties to cause a lightning discharge which can happen within the cloud, between clouds or between the cloud and the ground.