Answer to Question 1
ANSWER: The typical cloud-to-ground lightning flash is called negative cloud-to-ground-lightning, because the stroke carries negative charges from the cloud to the ground. About 90 percent of all cloud-to-ground lightning is negative. However, when the base of the cloud is positively charged and the ground negatively charged, a positive cloud-to-ground lightning flash may result. Positive lightning, most common with severe thunderstorms, has the potential to cause more damage because it generates a much higher current level and its flash lasts for a longer duration than negative lightning.
Answer to Question 2
ANSWER: In the United States thunderstorms occur most frequently in the southeastern United States along the Gulf Coast, with a maximum in Florida. The region with the fewest thunderstorms is the Pacific coastal and interior valleys. The reason for this distribution is that the combination of warmth and moisture make equatorial landmasses especially conducive to thunderstorm formation. Here, thunderstorms occur on about one out of every three days. Thunderstorms are also prevalent over water along the intertropical convergence zone, where the low-level convergence of air helps to initiate uplift. Thunderstorms are much less prevalent in dry climates, such as the polar regions and the desert areas dominated by subtropical highs.
Gram-positive and Gram-negative bacteria.
The human birth process as an example of positive feedback.
Uranus's southern hemisphere in approximate natural colour (left) and in shorter wavelengths (r
Clouds: Cloud Coverage and Observation
Negative and positive feedback loops
Mechanisms of positive control of transcription