INDICATOR DEFINITION Monthly means of three-hourly pressures, reduced to mean sea level, for Australian Antarctic stations Casey, Davis, Mawson, Macquarie Island and Heard Island.
TYPE OF INDICATOR There are three types of indicators used in this report: 1.Describes the CONDITION of important elements of a system; 2.Show the extent of the major PRESSURES exerted on a system; 3.Determine ... RESPONSES to either condition or changes in the condition of a system.
This indicator is one of: CONDITION
RATIONALE FOR INDICATOR SELECTION Measurement of the pressure over Antarctica and the Southern Ocean is considered important for monitoring behaviour of pressure systems on a local and global scale, which will help to interpret global climate change.
DESIGN AND STRATEGY FOR INDICATOR MONITORING PROGRAM Spatial Scale: Australian Antarctic stations: Casey (lat 66 degrees 16' 54.5" S, long 110 degrees 31' 39.4" E), Davis (lat 68 degrees 34' 35.8" S, long 77 degrees 58' 02.6" E), Mawson (lat 67 degrees 36' 09.7" S, long 62 degrees 52' 25.7" E), Macquarie Island (lat 54 degrees 37' 59.9" S, long 158 degrees 52' 59.9" E), Atlas Cove, Heard Island (lat 53 degrees 1' 8" S, long 73 degrees 23' 30" E) and Spit Bay, Heard Island (lat 53 degrees 6' 30" S, 73 degrees 43' 21" E).
Measurement technique: Barometry.
RESEARCH ISSUES There is need to develop a high-quality data set from the available data, correcting erroneous data and estimating missing data. Adjustment may be necessary for changes in site location or exposure, and for changes in instrumentation or observing practices.
Some of these changes are documented in the station history files held by the Regional Observations Section. These history files are currently held as paper records, although more recent information is held electronically and there is an effort to digitise the older records.
Before the data can be used for the detection of change, a concerted effort will need to be made to identify deficiencies in the data, and then make compensations where possible. This is made more difficult by the lack of suitable comparison sites.
LINKS TO OTHER INDICATORS SOE Indicators 1 - Monthly mean air temperatures for Australian Antarctic Stations SOE Indicators 2 - Monthly highest temperatures for Australian Antarctic Stations SOE Indicators 3 - Monthly lowest temperatures for Australian Antarctic Stations SOE Indicators 4 - Monthly mean lower-stratospheric temperature above Australian Antarctic Stations SOE Indicators 5 - Monthly mean mid-tropospheric temperature above Australian Antarctic Stations SOE Indicators 38 - Mean sea level SOE Indicators 62 - Water levels of Deep Lake, Vestfold Hills
Note - Station codes in the data are as follows: 300000 - Davis 300001 - Mawson 300004 - Macquarie Island 300005 - Atlas Cove, Heard Island 300017 - Casey 300028 - Spit Bay, Heard Island
The fields in this dataset are: Mean MSL Pressure Year Month Station Station Code Field Value Enough Observations Number Observations
Mean monthly atmospheric pressure is calculated from all the available 3-hourly observations made during a given month. Each three-hourly air pressure observation is 'reduced' to the equivalent value at mean sea level, using an algorithm embedded in the AWS. If less than 200 observations are present for that month, the monthly value is flagged and removed from the State of Environment dataset. ... The monthly atmospheric pressure anomaly is calculated as the difference between the mean atmospheric pressure for a given month and the long-term mean atmospheric pressure for that calendar month between 1971 and 2000, so that:
Anomaly (for given month) = Value (for given month) - Long-term Mean (for relevant calendar month)
Although the Bureau of Meteorology uses the period from 1961 to 1990 as the standard period for calculation of long-term means, it was decided that for Antarctic stations, the 1971-2000 dataset was in most cases more complete, and would therefore provide a more accurate long-term mean.
These records require analysis for variability and trends. However, there are likely to be significant errors in the data, and these need to be addressed first (see Research Issues).
With regard to Heard Island, unfortunately, the two AWS are not 'normal' ones (they are actually ocean drifting buoys that have been strapped down). They do provide temperature and pressure, but not wind or daily maximum and minimum temps. Also, they do not report to a fixed, regular schedule, instead sending when they are within the satellite footprint. The system set up for the other sites assumes the regular 3-hourly schedule. The irregularity of the Heard data could cause curious biases, which have not been explored. Also, the criteria used to flag that there are 'enough' data (greater than 200 obs in the month) may not really work with these more frequent, and irregular, reporting schedules.
Heard Island (Atlas Cove) WMO number: 95997 Elevation: 3 m Barometer elevation: 3.5 m
Heard Island (The Spit) WMO number: 94997 Elevation: 12 m Barometer elevation: 12.5 m
Data arising from this project are available from the state of the environment indicator at the provided URL.