melted precipitation is measured to determine liquid
equivalent. The overflow cylinder may also be used to
take a core sample of accumulated frozen precipitation.
When the sample is melted, it is measured in the
graduated cylinder to obtain liquid equivalent.
The primary maintenance action for the ML-217
rain gauge is keeping the gauge clean. Water and, if
necessary, mild detergent may be used to clean the
plastic parts. The steel support tripod will need periodic
rust removal and repainting.
Q34. How much precipitation can the graduated
cylinder of the 1-inch rain gauge hold?
Q35. Which rain gauge is used primarily for the
measurement of frozen precipitation?
LEARNING OBJECTIVES: Define trans-
missometer. Describe the operation and
maintenance of the major components of the
AN/GMQ-32 system. Explain the required
AN/GMQ-32 recorder chart notations.
Describe the operation and maintenance of the
OA-7900/GMQ-10 converter/indicator group.
A transmissometer is an instrument that measures
how well light travels through a substance. In
meteorology, a transmissometer is a device used to
measure the transmissivity of light through air to
determine visibility. In addition to the visual-range
sensor on the ASOS, there is one system used by Naval
and Marine Corps shore activities-the AN/GMQ-32
transmissometer system (formerly called the
The AN/GMQ-32 transmissometer provides a
visual and graphic record of the transmissivity of light
between the projector and the detector. This charted
value, with some standard adjustments, may be
converted to sector visibility or to runway visual range.
Sector visibility is how far an unlighted object can be
seen during the day, while runway visual range (RVR)
is how far the runway lights can be seen by a pilot.
Without any change in weather conditions, the runway
visual range may be increased by simply turning up the
intensity of the runway lighting.
The AN/GMQ-32 transmissometer system (fig.
2-34) consists of one or more sets of ML-461/GMQ-10
transmissometer projectors and R-547/GMQ-10
receivers, located on the airfield; their associated
electrical equipment and cables; and either the ID-
353B/GMQ-10 or the ID-820/GMQ-10 trans-
missometer indicator/recorder unit. A separate
equipment system, used with most AN/GMQ-32
Figure 2-34.AN/GMQ-32 transmissometer equipment installation.