(1) combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes (2) reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches.
mound or layer of moraine in the ablation zone of a glacier; the rock has been plucked from the mountainside by the moving glacier and is melting out on the ice surface.
the difference, taken without regard to sign, between the values of two variables
absolute error
the difference between the measured or inferred value of a quantity and its actual value.
absolute humidity
(1) the ratio of the mass of water vapor to the volume occupied by a mixture of water vapor and dry air (2) mass of water contained in a unit volume of moist air.
growth of a cloud or precipitation particle by the collision and union of a frozen particle (ice crystal or snowflake) with a super-cooled liquid droplet which freezes on impact.
all processes by which snow or ice are added to a glacier, this is typically the accumulation of snow, which is slowly transformed into ice; other accumulation processes can include avalanches, wind-deposited snow, and the freezing of rain within the snow pack.
the extent to which the readings of an instrument approach the true value of the calculated or measured quantities, supposing that all possible corrections are applied.
rain or snow containing acidic substances, resulting from the atmospheric pollution mainly with sulfur and nitrogen; acid precipitation has a lower pH than unpolluted rain.
when a mountain glacier's terminus extends farther downvalley than before; glacial advance occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.
an extensive body of the atmosphere in which physical properties, particularly temperature and humidity, exhibit only small and continuous differences in the horizontal plane; it may extend over an area of several million square kilometers and over a height of several kilometers.
the ambient temperature indicated by a thermometer exposed to the air but sheltered from direct solar radiation, or placed in an instrument shelter 1.5 to two meters above ground; also called surface temperature.