If a true north reference line was used at a shore
station, no further computations are necessary. Aboard
ship, however, you will need to obtain the ship’s course
and speed during the time of the observation, and
compute true wind speed and direction.
Maintenance
The only recommended routine maintenance for
the AN/PMQ-3 is a semiannual oiling of the wind-
speed transmitter unit. Partial disassembly is required;
consult the handbook for instructions. You should also
wipe the instrument down with a towel dampened in
freshwater to remove any salt deposits. Mild detergent
may be used to remove dirt and grime.
Q26.
Q27.
Q28.
Q29.
Q30.
Q31.
Q32.
Q33.
REVIEW QUESTIONS
Other than automated observing systems, name
three types of anemometers still used by the
Navy?
When should the analog recorder chart of the
AN/UMQ-5 be changed?
When should a time check be made on the analog
recorder of the AN/UMQ-5?
What type of wind measurement is made by the
Type B3 wind indicator?
At sea, what method should you use to verify true
wind speed and direction?
How does the true wind speed compare to the
apparent wind speed when the apparent wind
direction is forward of the beam?
What procedure should you follow when using
the AN/PMQ-3 at sea?
When should the low-speed, range-selecting
switch be activated on the AN/PMQ-3?
RAIN GAUGES
LEARNING OBJECTIVES Describe the
operation and maintenance of standard rain
gauges ML-588 and ML-217.
In addition to automated observing systems, the
Navy has two other standard rain gauges: the ML-
588/UMQ-14 tipping-bucket rain gauge, discussed
earlier as part of the AN/GMQ-29 system, and the ML-
217 4-inch plastic rain gauge.
The ML-217 rain gauge (fig. 2-33) has a 4-inch
funnel opening that collects and dumps precipitation
into a small, graduated cylinder. The cylinder collects
up to 1 inch of liquid, and measures the liquid to the
nearest 1/100 of an inch. A 4-inch-diameter plastic
outer casing is used to collect any overflow from the
graduated cylinder. The steel support tripod that holds
the rain gauge should be securely mounted on a firm,
level surface.
OPERATION
The rain gauge is used to measure liquid
precipitation or liquid equivalent of frozen
precipitation. The amount of liquid precipitation in the
graduated cylinder is read directly from the scale. A
cylinder full to the brim is exactly 1 inch. After
emptying, the graduated cylinder is used to measure
water from the overflow cylinder.
Although it is a backup for liquid precipitation
measurements, the ML-217 is the primary measuring
instrument for frozen precipitation not handled by the
ML-588 rain gauge or ASOS/SMOOS. When solid
precipitation is expected, the collector funnel and the
graduated cylinder should be removed from the 4-inch
overflow cylinder to allow the frozen precipitation to
accumulate directly into the overflow cylinder. The
Figure 2-33.—ML-217 4-inch plastic rain gauge.
2-24
