O-Net 2021

(items 55-60)

Snow, like every thing else, including apple trees, emits and absorbs
radiation. While ultraviolet and visible radiation are strongly reflected (not absorbed) by snow, it is however a strong absorber of infrared radiation. The
battle between the absorption and emission of radiation determines whether
5 there is net warming or cooling of the snow - or neither.
So why would snow under a tree melt faster? At night, snow in the
open absorbs in frared radiation from the ground and the sky which can
be below -30°C when it is clear.
Snow under neath a tree absorbs radiation emitted by the ground and
10 by the tree which is likely to be significantly warmer than the sky
This difference is sufficient to explain why snow under neath a tree
might melt faster than snow of the same depth that is outin the open and
also explains why frost often does notform around trees.
It is also possible that shelter provided by the tree when the snow was
15 falling led to a thinner layer of snow there than in the rest of theimmediate
vicinity.

The passage says that frost often does not form around trees because_.

1. the temperature underneath trees is warmer
2. there is too little infrared radiation to make ice cover the area
3. trees are not big enough to protect frost from melting
4. snow will melt slower when it covers the area around trees
5. the area in the open around a tree is not cold enough

Answer: 1. the temperature underneath trees is warmer