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AIM
e.
5 contains a comparison of weather observing programs and the elements reported.
f. Service Standards.
During 1995, a government/industry team worked to comprehensively reassess the
requirements for surface observations at the nation’s airports. That work resulted in agreement on a set of service
standards, and the FAA and NWS ASOS sites to which the standards would apply. The term “Service Standards”
refers to the level of detail in weather observation. The service standards consist of four different levels of service
(A, B, C, and D) as described below. Specific observational elements included in each service level are listed
6.
1. Service Level D
defines the minimum acceptable level of service. It is a completely automated service
in which the ASOS/AWOS observation will constitute the entire observation, i.e., no additional weather
information is added by a human observer. This service is referred to as a stand alone D site.
2. Service Level C
is a service in which the human observer, usually an air traffic controller, augments or
adds information to the automated observation. Service Level C also includes backup of ASOS/AWOS elements
in the event of an ASOS/AWOS malfunction or an unrepresentative ASOS/AWOS report. In backup, the human
observer inserts the correct or missing value for the automated ASOS/AWOS elements. This service is provided
by air traffic controllers under the Limited Aviation Weather Reporting Station (LAWRS) process, FSS and NWS
observers, and, at selected sites, Non
−
Federal Observation Program observers.
Two categories of airports require detail beyond Service Level C in order to enhance air traffic control efficiency
and increase system capacity. Services at these airports are typically provided by contract weather observers,
NWS observers, and, at some locations, FSS observers.
3. Service Level B
is a service in which weather observations consist of all elements provided under Service
Level C, plus augmentation of additional data beyond the capability of the ASOS/AWOS. This category of
airports includes smaller hubs or special airports in other ways that have worse than average bad weather
operations for thunderstorms and/or freezing/frozen precipitation, and/or that are remote airports.
4. Service Level A
, the highest and most demanding category, includes all the data reported in Service
Standard B, plus additional requirements as specified. Service Level A covers major aviation hubs and/or high
volume traffic airports with average or worse weather.
TBL 7
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1
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5
Weather Observing Programs
Element
Reported
Type
W
ind
V
isibility
Temperatur
e
Dew Point
Altimeter
Density
Altimeter
Cloud/Ceiling
Pr
ecipitation
Identification
Thunderstorm
/
Lightning
Pr
ecipitation
Occurr
ence
Rainfall
Accumulation
Runway Surface
Condition
Fr
eezing Rain
Occurr
ence
Remarks
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 JO 7900.5, Surface Weather Observing, for element reporting.
Meteorology
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1
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