时间：2011-04-18 00:50来源：蓝天飞行翻译 作者：航空 点击：次
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b.Automated Weather Observing System (AWOS). 1. Automated weather reporting systems are increasingly being installed at airports. These systems consist of various sensors, a processor, a computer-generated voice subsystem, and a transmit-ter to broadcast local, minute-by-minute weather data directly to the pilot. NOTE. When the barometric pressure exceeds 31.00 inches Hg., see paragraph 7.2.2, Procedures, for the altimeter setting procedures. 2. The AWOS observations will include the prefix “AUTO” to indicate that the data are derived from an automated system. Some AWOS locations will be augmented by certified observers who will provide weather and obstruction to vision informa-tion 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 set-ting, wind data, temperature, dew point, and density altitude; (c)AWOS.2 provides the information pro-vided by AWOS.l plus visibility; and (d)AWOS.3 provides the information pro-vided 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 Meteorology 7.1.25 have a dial-up capability so that the minute-by-min-ute 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 Instru-ment 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. 1. Location and Time. The location/name and the phrase “AUTOMATED WEATHER OBSERVA-TION,” 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 observa-tion, 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 observa-tion test, one four five six zulu.” (d) The phrase “TEMPORARILY INOP-ERATIVE” is added when the system is inoperative. EXAMPLE. “Bremerton National Airport automated weather observ-ing system temporarily inoperative.” 2. Visibility. (a)The lowest reportable visibility value in AWOS is “less than 1/4.” It is announced as “VISIBILITY LESS THAN ONE QUARTER.” (b)A sensor for determining visibility is not included in some AWOS. In these systems, visibility is not announced. “VISIBILITY MISSING” is announced only if the system is configured with a visibility sensor and visibility information is not available. 3.Weather. In the future, some AWOSs are to be configured to determine the occurrence of precipitation. However, the type and intensity may not always be determined. In these systems, the word “PRECIPITATION” will be announced if precipita-tion is occurring, but the type and intensity are not determined. |
