WHITE GOLD (MOUNTAIN SNOWPACKS)

Snowpack Accumulates
As the westerly winds move across the Pacific Ocean, water heated by the sun evaporates and adds moisture and heat energy to the air above. As the moist air rises it cools to form clouds when the vapor condenses. The latent heat given off to the surrounding atmosphere by the condensation of cloud formation provides the energy to form storms that move unto the continent's west coast. Winter rains sprinkle the San Francisco foothills and lowlands at Sacramento. When encountering the Sierra Nevada or Cascade mountain barrier the winter storms are forced upward. As the air rises, it is cooled by expansion until the rain turns to snow blanketing the mountains.

The mountains receive much more precipitation in a year than do the vallies and more than half of the precipitation is in the form of snow at the higher elevations.
Snow accumulations often can reach depths of 20 or more feet. The water stored in these snowpacks is phenomenal. The packs usually reach their maximum depth around April 1 when the melting season begins in earnest. How does this snowpack melt?

A great amount of energy (latent heat) must be added to the snow to carry out the melting process. The energy comes from sunlight, above freezing air masses, condensation of moisture upon the snow surface (frost) and some conduction from the soil below. The process, generally, runs from the surface downward. The temperatures in the entire snow pack must become isothermal at 0 degrees C. before melting can occur. The process changing the nature of the snowpack so that it can melt is often called "ripening".
Above freezing air and above freezing soil warms the pack by conduction. The snow cools the air as the air warms the snow.

Frost forming on the snow surface releases latent heat. Condensation releases the latent heat of evaporation and the latent heat of fusion combined. To say the least, a great quanitity of energy equalling almost 620 calories per cubic centimeter of condensate which is capable of melting about 620 grams of ice. Most of the sunlight is reflected back to space but some is absorbed by the snow. Eventually, enough energy is added to the pack surface to change some of the surface snow to vapor (sublimation) or liquid. The liquid quantities are at freezing temperatures and small in volume. Whatever liquid forms on the surface percolates downward into the snow and refreezes. As the liquid refreezes, the latent heat gained at the surface is released. This goes on again and again until the entire snowpack reaches 0 degrees C. At that point the pack is considered ripe (isothermal at 0 degres C.). Once ripe, any additional heat added goes into melting. The high latent heat of fusion makes melting a slow process even in a fully ripened snowpack.
The melting pack recharges the soil with moisture and begins to feed the mountain streams with water. Downhill the reservoirs have been emptied so that they have capacity to avoid flooding and to store this new water for use during the growing season.

Glossary:

Hydrogen Bond:
A chemical bond that holds two molecules together. It is the bond between an one of the electrons of hydrogen of one molecule and the oxygen atom of the adjacent molecule. In a water molecule, it is very strong and hard to break This is due to the asymmetrical arrangement of the water molecule. The angle between the hydrogen and the oxygen atoms form an angle of about 105 degrees instead of an expected 180 degrees. Thus, each water molecule is like a small magnet whose opposite sides are attracted to the adjacent water molecules.

Calorie:
A measure of heat energy. The amount of heat (energy) needed to raise the temperature of one gram of pure water one degree Celsius under standard conditions of temperature and at sea level pressure. One calorie of heat would raise the temperature of granite about 5 degrees C.
hase:
The form of a material as to whether it is in solid form, liquid, or gas. The water phases are ice, liquid, or vapor. Water is the rare substance that can exist as all three phases under normal environmental conditions. A glass of water with ice cubes will sweat as the atmospheric moisture condenses on the outside of the glass.

Latent heat:
The amount of energy taken up or given off when a substance changes phase. The energy goes to changing the phase of the substance (the arrangement of the molecules) with no change in temperature.

Latent heat of fusion/melting. Heat removed from a liquid during freezing (or added when ice melts) that produces a phase change but not a change in temperature. About eighty calories per gram of pure water at 0 degrees C. and sea level pressure.

Latent heat of vaporization/condensation. Heat added to a liquid during evaporation (or released during condensation) that produces a phase change without any change in temperature. About 539.4 calories per gram of pure water at 20 degrees C. and sea level pressure.

Heat Capacity (specific heat)
Specific heat is the amount of energy needed to raise the temperature of one cubic centimeter of a substance one degree C. The specific heat of water is 1. The specific heat of sand is about 0.2 calories. Hence, beach sand can get very hot on a sunny day while the water stays cool.

Isothermal.A term used to indicate uniform temperature throughout a mass of material.