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warm front

the forward edge of an advancing warm air mass that is displacing cooler air in its path.

warm low

at a given level in the atmosphere, any low that is generally characterized by warmer air near its center than around its periphery; the opposite of a cold low.

water sky

the dark appearance of the underside of a cloud layer when it is over a surface of open water; it is darker than land sky, and much darker than ice blink or snow blink.

water vapor

water substance in vapor (gaseous) form; one of the most important of all constituents of the atmosphere.

waterbody encircling a palsa

a water-filled depression surrounding a palsa.

watermelon snow

snow with red algae growing on it.

wave ogives

ogives that show some vertical relief on a glacier; usually the dark bands are in the hollows and the light bands are in the ridges; form at the base of steep, narrow ice falls.


the state of the atmosphere, mainly with respect to its effects upon life and human activities; distinguished from climate by focusing on short-term (minutes to about 15 days) variations of the atmosphere state.

weathered ice

glacier ice that has been exposed to sun or warm wind so that the boundaries between ice crystals are partly disintegrated.


the processes of ablation and accumulation which gradually eliminate irregularities in an ice surface.

wedge ice

ice occurring in an ice wedge.

well-bonded permafrost

ice-bearing permafrost in which all the soil particles are held together by ice.


the dominant west-to-east motion of the atmosphere, centered over the middle latitudes (35 to 65 degrees latitude) of both hemispheres.


a condition in which daylight is diffused by multiple reflections between a snow surface and an overcast sky; contrasts vanish, and the observer is unable to distinguish the horizon or any snow surface feature.

World Meteorological Organization

created by the World Meteorological Convention and recognized as a special agency of the United Nations in 1951; the WMO consists of more than 185 member countries; and facilitates international cooperation in all aspects of meteorology.

World Meteorological Organization Program

any scientific project (field experiment, inter-comparison, etc.) internationally performed under the aegis of the World Meteorological Organization.

World Weather Watch

the world-wide, coordinated system of meteorological facilities and services provided by World Meteorological Organization members for the purpose of ensuring that all members obtain the meteorological information required both for operational work and for research; the essential elements of the WWW are: the global observing system, the global data-processing system, and the global telecommunication system.