Rocket tapes a new page into the station log and writes CLOUD LOG across the top in capital letters.
"Three looks a day," Raven says. "Morning, midday and late afternoon. Same spot, same direction, every time."
Rocket squints upward and then quickly looks away. "Too bright over there."
Nova moves to hover between Rocket and the brightest part of the sky. "Never look toward the Sun," she says. "The clouds you need are everywhere else."
Raven holds up a card with ten cloud names on it, sorted into high, middle and low. "What do you notice about the names?"
"They are all built from the four roots," Rocket says. "Cirro, cumulo, strato, nimbo. This is going to be easy."
Nova hums. "Easy to name," she says. "Harder to tell apart. That is what the log is for."
You will observe the sky three times today from the same spot and record cloud cover, cloud type and height level.
Use the ten basic cloud types below. They come from the National Weather Service, which follows the international cloud atlas.
Height levels are for the temperate region, the band between the tropics and the polar circles.
| Level | Height in the temperate region | Cloud types |
|---|---|---|
| High | 16,500 to 45,000 feet | Cirrus, cirrocumulus, cirrostratus |
| Middle | 6,500 to 23,000 feet | Altocumulus, altostratus, nimbostratus |
| Low | Surface to 6,500 feet | Cumulus, stratocumulus, stratus, cumulonimbus |
High clouds are thin and white and made of ice crystals. Middle clouds are mostly water droplets. Low clouds are water droplets.
The prefix alto marks a middle level cloud. Cumulonimbus starts low but can tower into the high level.
Here is how the National Weather Service describes each type in plain words.
| Cloud | Level | What to look for |
|---|---|---|
| Cirrus | High | Delicate white filaments or narrow bands, hair-like or silky |
| Cirrocumulus | High | A thin white patchy sheet of tiny grains or ripples |
| Cirrostratus | High | A transparent whitish veil; a halo often rings the Sun or Moon |
| Altocumulus | Middle | White or gray patches, rounded masses or rolls |
| Altostratus | Middle | Gray or bluish sheet; the Sun shows faintly, as through frosted glass |
| Nimbostratus | Middle | Dark gray layer thick enough to hide the Sun, with steady rain or snow |
| Cumulus | Low | Detached dense puffs with flat bases and cauliflower tops |
| Stratocumulus | Low | Gray or whitish patches or rolls with a honeycomb look |
| Stratus | Low | A uniform gray layer; may give drizzle |
| Cumulonimbus | Low to high | A heavy towering cloud, often with a flat anvil top; the thunderstorm cloud |
| Time | Cloud cover | Cloud type | Level | Notes |
|---|---|---|---|---|
| Morning | ||||
| Midday | ||||
| Late afternoon |
| What the lab shows | True or false? |
|---|---|
| High clouds are made of ice crystals. | ? |
| Low clouds have bases within about 6,500 feet of the ground. | ? |
| Nimbostratus is a thin white cloud. | ? |
| You should look toward the Sun to see clouds better. | ? |
Great observing. Tomorrow you will read the National Weather Service cloud chart and learn what each cloud predicts.