Cirrus Implexus | Alto-Strato-Cumulus |
Types of Upper Clouds. | |
Cumulus | Stratus |
Types of Lower Clouds. | |
Cumulo-Nimbus | Nimbus |
Types of Rain Clouds. | |
"Well," said the Forecaster, "suppose you put one of those in here as an example of cirro-stratus. There couldn't be a halo without it. All the upper clouds are made of ice crystals and it is the refraction of the sunlight through these ice crystals that forms most halos. By the way, boys, don't confuse a halo with a corona. They're quite easy to tell apart, because a halo, unless it is one of the unusual white ones, always has red as the inside color and a corona always has the red on the outside."
"How can I tell them apart on a photograph plate, sir?" asked Ralph. "That doesn't show any colors."
"By their distance from the sun," the meteorologist replied. "Halos are seldom seen except at distances of about twenty-two degrees and forty-six degrees from the sun. There are lots of others, but they are rare. You'll soon learn to catch those distances by eye. Coronas are usually much smaller.
"I think one of the most striking forms of cirro-stratus is the polar 'band,' which stretches from one side of the sky to the other, like a wide white road."
"Ah knows that one, Mistah Levin," put in Dan'l. "Noah, he done stretch that road for the animals to get out of the Ark."
The Forecaster glanced at the aged darky.
"You certainly did manage to pick up a lot of queer superstitions in that article of yours, Dan'l. I've heard that cloud called a Noah's Ark cloud, but I never knew why."
"Yas, suh; oh, yas, suh," Dan'l repeated earnestly, "Noah, he done make that cloud, jest like the rainbow was made to convince Noah that there weren't goin' to be no more floods."
"A high cirro-stratus which looks as if some cream had been poured on the blue sky and hadn't mixed properly yet," the Forecaster continued, "is cirro-nebula. It's very hard to photograph, and even when you do get it on a plate, it doesn't look like much.