# BLOWING SNOW

Snow raised from the ground and carried by the wind to such a height that both vertical and horizontal visibility are considerably reduced. The expression DRIFTING SNOW is used when only the horizontal visibility is reduced.

## Related Terms

The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.

### GYROSCOPIC DRIFT

The horizontal rotation of the spin axis of a gyroscope about the vertical axis

### HORIZONTAL EARTH RATE

The rate at which the spin axis of a gyroscope must be tilted about the horizontal axi

### HAZE

Fine dust or salt particles in the air, too small to be individually apparent but in sufficient number to reduce horizontal visibility and give the atmosphere a characteristic hazy appearance which casts a bluish or yellowish veil over the landscape, subduing its colors. This is sometimes called a dry haze to distinguish it from damp haze, small water droplets or very hygroscopic particles in the air, smaller and more scattered than light fog.

### HORIZONTAL PARALLAX

The geocentric parallax when a body is on the horizon. The expression is usually used only in connection with the moon, for which the tabulated horizontal parallax is given for an observer on the equator. The parallax at any altitude is called PARALLAX IN ALTITUDE.

### HORIZONTALLY POLARIZED WAVE

A plane polarized electromagnetic wave in which the electric field vector is in a horizontal plane.

### HORIZONTAL

Parallel to the plane of the horizon; perpendicular to the direction of gravity

### HORIZONTAL GEODETIC DATUM

The basis for computations of horizontal control surveys in which the curvature of the earth is considered It consists of the astronomical and geodetic latitude and the astronom- ical and geodetic longitude of an initial point (origin); an azimuth of a line from this point; the parameters (radius and flattening) of the reference ellipsoid; and the geoidal separation at the origin. A change in any of these quantities affects every point on the datum. For this reason, while positions within a system are directly and accurately relatable, those points from different datums must be transformed to a common datum for consistency. The horizontal geodetic datum may extend over a continent or be limited to a small area.

### ICE SHELF

A floating ice sheet attached to the coast and of considerable thickness, showing 20 to 50 meters or more above sea level. Usually of great horizontal extent and with a level or gently undulating surface, the ice shelf is augmented by annual snow accumulation and often also by the seaward extension of land glaciers. Limited areas of the ice shelf may be aground. The seaward edge is called

### ANCHOR WINCH

A horizontal capstan in the bow used for weighing anchor.

### Related questions

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