In a biome, what term refers to the natural supply of water in the form of rain?

The correct answer is precipitation.

Explanation:

The term that is used to illustrate the falling of water from the sky because of the condensation of water found in the clouds is precipitation. Precipitation is the natural supply of water that comes in the form of hail, rain, sleet or drizzle.  

It is considered as one of the prime sources of the supply of water in the biome. The other kinds of water supply are surface water and ground water.  

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.