Lin's Tips for Cloud Observers
º Low cumulus cloud cells (the individual puffs of cloud) are about the size of your fist or larger, when you hold up your hand at arms' length.
º When cumulus clouds are just forming or evaporating, they can look considerably different from those that are fully-formed. Do not be fooled! Sometimes you can tell that the clouds are forming or evaporating if there is strong wind and both new and fully-formed clouds are moving along in the same layer. Other times you may have to look for other clues.
º Mid-level cumulus cloud cells (altocumulus) are about the size of your thumbnail when you hold your hand at arm's length. (Note that in the picture the clouds look larger then my thumb. This is because the photo was taken from behind me, considerably more than an arm's length from my thumb.
º If it rained recently or is about to rain, you are most likely dealing with a low level stratus cloud. While it is possible for rain to fall from mid-level clouds, it is quite rare.
º If it is raining during your observation, you have nimbostratus (or cumulonimbus - but the difference should be obvious! The latter is a thunderstorm). The terms nimbo/nimbus are from a Latin word for rain.
º If a stratus cloud is so thick you can't even figure out where the sun is, most likely it is a low level stratus. The visual opacity of such a cloud is opaque.
º If you can see the sun but it looks diffused (like looking through a glass bottle), most likely you have altostratus. The visual opacity would be translucent.
º High-level cirrostratus will generally be thin enough that the sun is still quite distinct. If the cirrostratus is not between you and the sun, you may be able to distinguish cirrostratus as being so thin that parts of the cloud appear bluish (that is, you are seeing through to blue sky). The visual opacity is transparent.
Questions or comments about these tips? Send the cloud team a note.
Page Curator: Tina Rogerson
NASA Official: Jessica Taylor
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