Temperature gradient is the difference in snow temperature across a given vertical range in the snowpack. In practice, it is usually expressed in degrees celsius per 10 centimetres.
As a general rule, a temperature gradient less than 1 C per 10 cm contributes to strengthening bonds between snow grains. This process is called rounding.
A temperature gradient greater than 1 C per 10 cm weakens bonds between snow grains. This is called faceting.