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时间:2010-05-28 00:54来源:蓝天飞行翻译 作者:admin
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from an automated system. Some AWOS locations
will be augmented by certified observers who will
provide weather and obstruction to vision information
in the remarks of the report when the reported
visibility is less than 7 miles. These sites, along with
the hours of augmentation, are to be published in the
A/FD. Augmentation is identified in the observation
as “OBSERVER WEATHER.” The AWOS wind
speed, direction and gusts, temperature, dew point,
and altimeter setting are exactly the same as for
manual observations. The AWOS will also report
density altitude when it exceeds the field elevation by
more than 1,000 feet. The reported visibility is
derived from a sensor near the touchdown of the
primary instrument runway. The visibility sensor
output is converted to a visibility value using a
10−minute harmonic average. The reported sky
condition/ceiling is derived from the ceilometer
located next to the visibility sensor. The AWOS
algorithm integrates the last 30 minutes of ceilometer
data to derive cloud layers and heights. This output
may also differ from the observer sky condition in
that the AWOS is totally dependent upon the cloud
advection over the sensor site.
3. These real-time systems are operationally
classified into four basic levels:
(a) AWOS−A only reports altimeter setting;
NOTE−
Any other information is advisory only.
(b) AWOS−l usually reports altimeter setting,
wind data, temperature, dew point, and density
altitude;
(c) AWOS−2 provides the information provided
by AWOS−l plus visibility; and
(d) AWOS−3 provides the information provided
by AWOS−2 plus cloud/ceiling data.
4. The information is transmitted over a discrete
VHF radio frequency or the voice portion of a local
NAVAID. AWOS transmissions on a discrete VHF
radio frequency are engineered to be receivable to a
maximum of 25 NM from the AWOS site and a
maximum altitude of 10,000 feet AGL. At many
locations, AWOS signals may be received on the
surface of the airport, but local conditions may limit
the maximum AWOS reception distance and/or
altitude. The system transmits a 20 to 30 second
weather message updated each minute. Pilots should
monitor the designated frequency for the automated
weather broadcast. A description of the broadcast is
contained in subparagraph c. There is no two-way
communication capability. Most AWOS sites also
have a dial-up capability so that the minute-by-minute
weather messages can be accessed via telephone.
5. AWOS information (system level, frequency,
phone number, etc.) concerning specific locations is
published, as the systems become operational, in the
A/FD, and where applicable, on published Instrument
Approach Procedures. Selected individual
systems may be incorporated into nationwide data
collection and dissemination networks in the future.
c. AWOS Broadcasts. Computer-generated
voice is used in AWOS to automate the broadcast of
the minute-by-minute weather observations. In
addition, some systems are configured to permit the
addition of an operator-generated voice message;
e.g., weather remarks following the automated
parameters. The phraseology used generally follows
that used for other weather broadcasts. Following are
explanations and examples of the exceptions.
AIM 2/17/05
7−1−22 Meteorology
1. Location and Time. The location/name and
the phrase “AUTOMATED WEATHER OBSERVATION,”
followed by the time are announced.
(a) If the airport’s specific location is
included in the airport’s name, the airport’s name is
announced.
EXAMPLE−
“Bremerton National Airport automated weather
observation, one four five six zulu;”
“Ravenswood Jackson County Airport automated weather
observation, one four five six zulu.”
(b) If the airport’s specific location is not
included in the airport’s name, the location is
announced followed by the airport’s name.
EXAMPLE−
“Sault Ste. Marie, Chippewa County International Airport
automated weather observation;”
“Sandusky, Cowley Field automated weather
observation.”
(c) The word “TEST” is added following
“OBSERVATION” when the system is not in
commissioned status.
EXAMPLE−
“Bremerton National Airport automated weather
observation test, one four five six zulu.”
(d) The phrase “TEMPORARILY INOPERATIVE”
is added when the system is inoperative.
 
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