Aeronautical Information Manual (AIM), page 473

Index   472 -- Page 473 -- 474

12/10/15                                                                                                                                                                                                           AIM

  e. TBL 7-1-3 contains a comparison of weather                                                   inserts the correct or missing value for the automated
observing programs and the elements reported.                                                     ASOS/AWSS elements. This service is provided by
                                                                                                  air traffic controllers under the Limited Aviation
   f. Service Standards. During 1995, a govern-                                                   Weather Reporting Station (LAWRS) process, FSS
ment/industry team worked to comprehensively                                                      and NWS observers, and, at selected sites,
reassess the requirements for surface observations at                                             Non-Federal Observation Program observers.
the nation's airports. That work resulted in agreement
on a set of service standards, and the FAA and NWS                                                Two categories of airports require detail beyond
ASOS sites to which the standards would apply. The                                                Service Level C in order to enhance air traffic control
term "Service Standards" refers to the level of detail                                            efficiency and increase system capacity. Services at
in weather observation. The service standards consist                                             these airports are typically provided by contract
of four different levels of service (A, B, C, and D) as                                           weather observers, NWS observers, and, at some
described below. Specific observational elements                                                  locations, FSS observers.
included in each service level are listed in                                                           3. Service Level B is a service in which weather
TBL 7-1-4.                                                                                        observations consist of all elements provided under
      1. Service Level D defines the minimum                                                      Service Level C, plus augmentation of additional data
acceptable level of service. It is a completely                                                   beyond the capability of the ASOS/AWSS. This
automated service in which the ASOS/AWSS                                                          category of airports includes smaller hubs or special
observation will constitute the entire observation,                                               airports in other ways that have worse than average
i.e., no additional weather information is added by a                                             bad weather operations for thunderstorms and/or
human observer. This service is referred to as a stand                                            freezing/frozen precipitation, and/or that are remote
alone D site.                                                                                     airports.
                                                                                                      4. Service Level A, the highest and most
    2. Service Level C is a service in which the
                                                                                                  demanding category, includes all the data reported in
human observer, usually an air traffic controller,
                                                                                                  Service Standard B, plus additional requirements as
augments or adds information to the automated
                                                                                                  specified. Service Level A covers major aviation
observation. Service Level C also includes backup of
                                                                                                  hubs and/or high volume traffic airports with average
ASOS/AWSS elements in the event of an ASOS/
                                                                                                  or worse weather.
AWSS malfunction or an unrepresentative
ASOS/AWSS report. In backup, the human observer
                                                                                 TBL 7-1-3
                                                                   Weather Observing Programs
                                                                                                                                                                   Runway Surface


                                                                                                                                                                                    Freezing Rain





                                         Dew Point






    AWSS           X       X                 X            X             X             X                 X                                             X                                        X                   X
    ASOS           X       X                 X            X             X             X                 X                                             X                                        X                   X
  AWOS-A                                                  X
 AWOS-A/V                  X                              X
   AWOS-1          X                         X            X             X
   AWOS-2          X       X                 X            X             X
   AWOS-3          X       X                 X            X             X             X
  AWOS-3P          X       X                 X            X             X             X                 X
  AWOS-3T          X       X                 X            X             X             X                                  X
 AWOS-3P/T         X       X                 X            X             X             X                 X                X
   AWOS-4          X       X                 X            X             X             X                 X                X              X             X                 X                      X
    Manual         X       X                 X            X                           X                 X                                                                                                          X
 REFERENCE- FAA Order 7900.5B, Surface Weather Observing, for element reporting.

Meteorology                                                                                                                                                                                                      7-1-29

Page 473 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   472 -- Page 473 -- 474