# Forming a permanent ice cap by continuous hail precipitation

Permanent ice caps are formed when the rate at which water falling under the form of snow is higher than the rate at which the water is removed from a certain region either by evaporation or outflow, so that the cap of ice last more than one year.

Would it be possible, on a Earth-like planet, to have an ice cap forming as consequence of abundant and continuous hail precipitations?

• Is this what you are asking for? weather.gov/media/ama/hail_glaciers.pdf – Mołot Mar 5 at 9:38
• @Mołot, what I get from the ppt is that it lasted a few days at most. I would have not called it a glacier. – L.Dutch Mar 5 at 9:58
• The National Weather Service of the USA clearly would, as you can see. If you are using "hail glacier" as something else than already established meaning of it, please describe clearly what is the thing you want, and consider not using the name associated with things you do not want. – Mołot Mar 5 at 10:02
• @Mołot, doesn't the first period of my question explain what I take as glacier? – L.Dutch Mar 5 at 10:11

Just take a look at how hail forms. Strong updrafts (think thunderstorm) which lift water droplets above the "freezing-line", causing them form the hail and come crashing down.

So you'd need three things for your idea to be feasible:

• constant thunderstorms or very strong updrafts
• air temperatures at ground level below freezing
• air temperatures above freezing at about 1 to 3 km height

Thunderstorms or updrafts would be possible at the windward sides of large mountain ranges, so no hassle there.

Air temperatures at ground level below freezing in order for the hail to not to thaw. Surely possible.

Warm air at some height - also no problem.

The problem is, that you can combine only two out of this three prerequisites. Freezing updrafts or warm updrafts, sure. Warm air above cold air, that's called an inversion, no problem. But inversions only form, when the air does move only slightly or not at all. So you either have your hail, or the conditions for your hail to not to thaw, but not both.

Short expansion on the inversions: You might have cold air below warm air any time a low pressure system rolls in - but in order to have such a situation over the very long time it takes to form a glacier, you'd need an inversion. A very persisten inversion. For like 200 years.

• You beat me to answer, but yours is better than mine. I completely forgot the need for an inversion! – DarthDonut Mar 5 at 10:35