Thursday, November 23rd, 2017

* Waning- the decreasing of the moon's visible illuminated surface, from full moon to new moon.
* Warm front - the leading edge of a mass of relatively warm air
* Warm front-A front that forms when moving warm air collides with a stationary or slower moving cold air mass. The moving warm air rises over the denser cold air as the two masses collide, cools adiabatically, and the cooling generates clouds and precipitation.
* Wash-An intermittent stream channel found in a desert.
* Water cycle- The transfer of water between numerous temporary storage reservoirs. These include the ocean, rivers and streams, glacial ice, beer cans, dogs and cats, groundwater, and the atmosphere.
* Water gap - a pass in a mountain ridge through which a stream flows.
* Water Table- The surface between where the pore space in rock is filled with water and where the pore space in rock is filled with air.
* Water table-The upper surface of a body of groundwater at the top of the zone of saturation and below the zone of aeration.
* Water Vapor- The substance water (H2O) in its vapor, or gaseous, phase. Water vapor, a strong greenhouse gas, varies, vertically and horizontally, in concentration in the atmosphere from 0 to 4 percent. Highest concentrations are found in the troposphere.
* Watershed- the entire area drained by a stream and its tributaries.
* Waterspout - a funnel-shaped rotating cloud, or tornado, extending from the base of a cloud down to the surface of an ocean or lake.
* Wave height-The vertical distance from the crest to the trough of a wave.
* Wave period-The time interval between two crests (or two troughs) as a wave passes a stationary observer.
* Wave-cut cliff-A cliff created when a rocky coast is eroded by waves.
* Wave-cut platform-A flat or gently-sloping platform created by erosion of a rocky shoreline.
* Wavelength - the distance between two successive wave crests.
* Wavelength-The distance between successive wave crests (or troughs).
* Waxing- the increasing of the moon's visible illuminated surface, from new moon to full moon.
* Weather Satellite- An instrument platform in earth orbit which views the atmosphere with a variety of sensors including visible and infrared cameras. A weather satellite may produce data used to form any of a number of satellite images or raw data used in research and forecasting.
* Weather- The state of the atmosphere and its short term variations as defined by various weather elements, most notably, temperature, wind, humidity, cloudiness, visibility and precipitation, and storminess.
* Weathering - "Making little ones out of big ones." Weathering includes the processes which mechanically and chemically break down the mountains into little pieces, so they can be eroded and transported to the beach
* Weathering-The decomposition and disintegration of rocks and minerals at the Earth's surface by mechanical and chemical processes.
* Weather-The state of the atmosphere on a particular day as characterized by temperature, wind, cloudiness, humidity, and precipitation, (see "climate").
* Weight -The gravitational force exerted on a body.
* Welded tuff-A hard, tough glass-rich pyroclastic rock formed by cooling of an ash flow that was hot enough to deform plastically and partly melt after it stopped moving; it often appears layered or streaky.
* Well- A hole dug into the ground in the attempt to intersect water or other subsurface fluids.
* Well-A hole dug or drilled into the Earth, generally for the production of water, petroleum, natural gas, brine, sulfur, or for exploration.
* Wet adiabatic lapse rate-The rate of cooling that occurs when moist air rises and condensation occurs, without gain or loss of heat.
* Wet-bulb depression - Dependent on the temperature and the humidity of the air, it is the difference between the dry bulb and the wet bulb readings.
* Wet-bulb thermometer - A thermometer used to measure the lowest temperature in the ambient atmosphere in its natural state by evaporating water from a wet muslin-covered bulb of a thermometer. The wet bulb temperature is used to compute dew point and relative humidity. One of the two thermometers that make up a psychrometer.
* Wetlands-Areas known variously as swamps, bogs, marshes, sloughs, mud flats, flood plains, and many other names, wetlands are the boundary between land and water. Some are water soaked or flooded throughout the entire year; others are dry for much of the year and wet only during times of high water. Some are wet only during exceptionally wet years and may be dry for several years at a time.
* White dwarf -A whitish star of high surface temperature and low intrinsic brightness with a mass approximately equal to that of a Sun but with a density many times larger.
* White dwarf-A stage in the life of a star when fusion has halted and the star glows solely from the residual heat produced during past eras. White dwarfs are very small stars.
* Wind- Air in motion relative to the surface of the earth. Because the vertical (up/down) component of wind is generally small compared to the horizontal component, wind generally refers to the horizontal wind. When the vertical component is discussed, vertical wind is commonly used.
* Wind Direction- The direction from which the wind blows. For example, a wind blowing from south to north is a southerly wind.
* Wind shear-A condition in which air currents rise and fall simultaneously within the same cloud.
* Wind-chill Factor- The accelerated heat loss from exposed skin due to increased wind speed. A nonphysical value which combines the effect of air temperature and the wind speed to illustrate how the air "feels." Wind chill is calculated by combining air temperature and wind speed and reported as a wind-chill temperature in degrees Celsius (degrees Fahrenheit) or as a cooling rate in Watts per square meter.
* Wind-Horizontal air flow caused by the pressure differences resulting from unequal heating of the Earth's atmosphere. Winds near the Earth's surface always flow from a region of high pressure toward a low-pressure region.
* Windward- The side facing into the wind.
* Winter- see Solstice
* Winter Storm- A large-scale disturbance, often hundreds of kilometers across, associated with a low-pressure system, or cyclone, that develops along a front during the cooler part of the year. Winter storms can produce strong winds, heavy precipitation (rain, freezing rain, ice pellets or snow) and cold temperatures.
* Withdrawal-Any process that uses water, and then returns it to the Earth locally.

* X-ray -Electromagnetic radiation of very short wavelength and very high energy; x-rays have shorter wavelengths than ultraviolet light but longer wavelengths than gamma rays.

* Yellow Snow- 1) Snow which has a yellow or golden color due to the presence of pine or cypress pollen in or on it. 2) Snow patches with a yellow color that has been contaminated by urine (usually from dogs).
* Yellow stars- These are warm stars, such as the Sun. Their temperature is about 10,000°F.
* Young -When used to describe a planetary surface, "young" means that the visible features are of relatively recent origin, i.e. That older features have been destroyed by erosion or lava flows. Young surfaces exhibit few impact craters and are typically varied and complex; in contrast, an "old" surface is one that has changed relatively little over geologic time. The surfaces of Earth and Io are young; the surfaces of Mercury and Callisto are old.

* Zenith-The point on the celestial sphere directly above your head.
* Zone of ablation (or wastage)- The area below the snowline where snow melt exceeds snowfall, and material is lost from a glacier.
* Zone of accumulation- The area above the snowline where snowfall exceeds snow melt, and material is added to a glacier.
* Zone of aeration-A subsurface zone above the water table that may be moist but is not saturated; it lies above the zone of saturation. (syn: unsaturated zone)
* Zone of saturation-A subsurface zone below the water table in which the soil and bedrock are completely saturated with water.
* Zone of wastage-The lower portion of a glacier where more snow melts in summer than accumulates in winter so there is a net loss of glacial ice. (syn: ablation area)