What causes lightning and thunder in clouds?

Question

What causes lightning and thunder in clouds?

Answer 1

The precursor of any lightning strike is the polarization of positive and negative charges within a storm cloud. The tops of the storm clouds are known to acquire an excess of positive charge and the bottom of the storm clouds acquire an excess of negative charge. Two mechanisms seem important to the polarization process. One mechanism involves a separation of charge by a process which bears resemblance to frictional charging. Clouds are known to contain countless millions of suspended water droplets and ice particles moving and whirling about in turbulent fashion. Additional water from the ground evaporates, rises upward and forms clusters of droplets as it approaches a cloud. This upwardly rising moisture collides with water droplets within the clouds. In the collisions, electrons are ripped off the rising droplets, causing a separation of negative electrons from a positively charged water droplet or a cluster of droplets.

The second mechanism which contributes to the polarization of a storm cloud involves a freezing process. Rising moisture encounters cooler temperatures at higher altitudes. These cooler temperatures cause the cluster of water droplets to undergo freezing. The frozen particles tend to cluster more tightly together and form the central regions of the cluster of droplets. The frozen portion of the cluster of rising moisture becomes negatively charged and the outer droplets acquire a positive charge. Air currents within the clouds can rip the outer portions off the clusters and carry them upward toward the top of the clouds. The frozen portion of the droplets with their negative charge tend to gravitate towards the bottom of the storm clouds. Thus, the clouds become further polarized.

These two mechanisms are believed to be the primary causes of the polarization of storm clouds. In the end, a storm cloud becomes polarized with positive charges carried to the upper portions of the clouds and negative portions gravitating towards the bottom of the clouds.

Lightning causes thunder because a strike of lightning is incredibly hot. A typical bolt of lightning can immediately heat the air to between 15,000 to 60,000 degrees Fahrenheit.

A lightning strike can heat the air in a fraction of a second. When air is heated that quickly, it expands violently and then contracts, like an explosion that happens in the blink of an eye. It's that explosion of air that creates sound waves, which we hear and call thunder.  

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Answer 2

"In a thunderstorm, the air currents cause electrostatic charge differences between the clouds and the ground or between different clouds. When this charge difference is great enough, there will be a discharge of electricity that is called lightning. That discharge is extremely hot and the super heating of the air causes it to expand so rapidly that it produces a shock wave called thunder."

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