From the BOM site, the following is relevant in this argument:
The Bureau's Regional Instrument Centre publishes reports on a variety of sensors and can provide copies of these reports or advice on the suitability of sensors. A number of the Centre's Instrument Test Reports are listed in Appendix 2.
ALGORITHMS
The algorithms used to derive meteorological variables should be meaningful, documented, and comparable between networks.
For example, the maximum temperature derived from one second readings can be quite different to a maximum temperature derived from hourly readings, wind gusts based on one second readings will be significantly greater than gusts based on three second readings, and scalar averaging of wind direction generally produces meaningless results.
Documenting the algorithms used, and all changes to those algorithms, is necessary for future users of the data.
It should be noted that many AWS manufacturers are unaware of the subtleties involved with the algorithms and with the meaning of the meteorological variables derived.
Bureau Specification A2669 details the algorithms used in the Bureau's AWSs. These algorithms are compatible with those recommended by the WMO, and as used by other National Meteorological Services.
The Bureau's AWS Co-ordinator, the Instrument Engineering Section and the Regional Instrument Centre are available to provide advice on processing algorithms.
MAINTENANCE
AWS should be chosen for their ease of maintenance.
Maintenance should be able to be performed on an AWS without affecting the climatological record. For example, the temperature and humidity sensors should be able to be disabled before the instrument shelter is washed.
Many of the cheaper AWS cannot be adjusted in the field and need to be returned to the manufacturer for periodic calibration. In addition, many of these AWS lack robustness and require frequent maintenance visits to replace electronics and/or sensors.
It is important to consider the lifetime costs of an AWS rather than simply the initial cost. Generally, the lower the initial cost, the higher the ongoing cost to maintain acceptable data. In the end, this may result in either a higher total cost or long periods with no useful data.
The Bureau's Engineering Maintenance Section (and the Regional Engineering Services Sections in each State) can provide advice regarding the inspection and maintenance of AWS.
Looks like there is quite a sound protocol surrounding the AWS, but like all these things that rely on automation, the algorithms drive the reports that the pilot hears when he/she "logs on" or "phones in" are the heart and soul of the system. GIGO [Garbage in garbage out!!]
More reading at: Bureau of Meteorology - Automatic Weather Stations
and the reason for existence:
The Bureau of Meteorology operates under the authority of the Meteorology Act 1955 and the Water Act 2007 which provide the legal basis for its activities, while its operation is continually assessed in accordance with the national need for climatic records, water information, scientific understanding of Australian weather and climate and effective service provision to the Australian community. The Bureau of Meteorology must also fulfill Australia's international obligations under the Convention of the World Meteorological Organization (WMO) and related international meteorological treaties and agreements.