Har

Har or HAR may refer to:

Frost

Frost is the coating or deposit of ice that may form in humid air in cold conditions, usually overnight. In temperate climates it most commonly appears as fragile white crystals or frozen dew drops near the ground, but in cold climates it occurs in a greater variety of forms. Frost is composed of delicate branched patterns of ice crystals formed as the result of fractal process development.

Frost is known to damage crops or reduce future crop yields, therefore farmers in those regions where frost is a problem often invest substantial means to prevent its formation.

Introduction

Frost forms when the temperature of a solid surface in the open cools to below the freezing point of water and for the most clearly crystalline forms of frost in particular, below the frost point in still air. In most temperate countries such temperatures usually are the result of heat loss by radiation at night, so those types of frost sometimes are called radiation frost.

Types of frost include crystalline hoar frost from deposition of water vapor from air of low humidity, white frost in humid conditions, window frost on glass surfaces, advection frost from cold wind over cold surfaces, black frost without visible ice at low temperatures and very low humidity, and rime under supercooled wet conditions.