Chapter 9 Flashcards
1
Q
What are thermals
A
Bubbles or columns of rising air
2
Q
What cloud type typically starts from thermals
A
Cumulus clouds - That is why they are vertically developing
3
Q
Characteristics of Thermals
A
- Diameter of a few hundred to a few thousand feet
- lifetime of a few minutes
- vertical speeds from a few hundred - ~2,000 fpm
- more common during day (due to heat), but can happen at night
4
Q
What surfaces are best at creating thermals?
A
Dry land and paved surfaces.
5
Q
Would you expect strong thermals over water?
A
No because Water has high heat capacity - water absorbs more heat and doesn’t dissipate it upwards
6
Q
Example of a small rotating thermal
A
Dust devils
7
Q
Dust Devils
A
- need light winds and hot surfaces
- lifetime of a few mins
- upper limits of 100 - 300 feet, but can go much higher
- ~20 mph - have seen up to 50 mph
