NovaLynx Corporation
Weather Monitoring Instruments and Systems
Rain Gauges and Snow Gauges
 2500 Rain Gauge |
 2501 Rain Gauge |
 Alter-Type Wind Screen |
 Forestry Gauge |
 Std Gauge |
 Plastic Gauge |
NovaLynx manufactures a complete line of instruments for measurement of rainfall, including tipping bucket rain gauges, National Weather Service type standard rain and snow gauges, and forestry gauges. We also offer several methods of retrieving and viewing gathered measurements, and accessories such as calibrators and mounting hardware.
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NWS OBSERVING HANDBOOK NO. 2
SECTION 2: PRECIPITATION
2.1 INTRODUCTION
There are two types of precipitation: liquid and solid. Liquid precipitation includes rain and drizzle. Since precipitation, by definition, falls to the ground, dew (which forms where it is found) is not precipitation. Solid precipitation includes snow, hail, ice pellets, etc. Precipitation is measured in terms of its depth:
a) Liquid (including the water equivalent of solid precipitation which has melted) to the nearest hundredth of an inch, and
b) Solid to the nearest tenth inch.
2.1.1 PRECIPITATION GAGES
In its simplest form, a precipitation gage is an open-mouthed can with straight sides, installed with the open end upward and sides vertical. Precipitation gages are also called rain gages. Improved gages record the amount of precipitation falling per unit time on a chart (usually a punch tape or rotating drum). See section 2.2 below.
2.1.2 EXPOSURE OF GAGES
The exposure of a rain gage is very important for obtaining accurate measurements. Gages should not be located close to isolated obstructions such as trees and buildings, which may deflect precipitation due to erratic turbulence. Gages should not be located in wide-open spaces or on elevated sites, such as tops of buildings, because of wind and the resulting turbulence problems. The best location is where the gage is uniformly protected in all directions, such as in an opening in a grove of trees. The height of the protection should not exceed twice its distance from the gage. As a general rule, the windier the gage location is, the greater the precipitation error will be.
Wind shields (exhibit 2.1) may be used to minimize the loss of precipitation. This loss is much greater during snowfall than rainfall, so shields are seldom installed at cooperative stations unless at least 20 percent of the annual precipitation falls in the form of snow.
In areas where heavy snowfall occurs; e.g., mountainous areas in the western U.S., gages are mounted on towers at a height considerably above the maximum level to which snow accumulates, at or somewhat below the level of tree tops. See exhibit 2.2.
Good exposures are not always permanent. Man-made alterations to the area and the growth of vegetation may change an excellent exposure to an unsatisfactory one in a very short time, necessitating the moving of precipitation gages to sites having better exposures.
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