Rutherglen weather station
Homogeneity adjustments for Rutherglen
The Bureau has been asked about temperature adjustments at Rutherglen, and their relation to a potential change in the location of the Rutherglen weather station.
The analysis of data for Rutherglen has been carried out in the same, consistent and objective manner as the analysis for all other ACORN-SAT sites, using our standard and published methods.
The need for the adjustment made to Rutherglen data for the period prior to 1966 was determined from an objective statistical test that showed an artificial jump in the data during this period.
While it is not necessary to have supporting documentation to justify correcting a statistically determined artificial jump in the data, it is of interest that the change at Rutherglen is very likely associated with a change in the location of the weather station.
The Bureau's site catalogue for ACORN-SAT sites does not list a site move for Rutherglen, since there is no firm documentation for this change. The site catalogue provides a brief overview of weather stations, including the main points that can be found in historical documentation.
There is, however, evidence beyond the statistical test indicating that the site at Rutherglen has moved at least once. The Bureau has located 12 documents, covering a period from 1939 and 1978 that provide various pieces of information suggesting a site move.
Evidence for a site move prior to 1975
The Rutherglen observation site is located at the Victorian Department of Environment and Primary Industries research centre, to the southeast of the town of Rutherglen. The current observation site is located about 700 metres south of the main research centre buildings (Figure 1), on flat ground and just to the east of a dirt road (Figures 2a, 2b), at an elevation of 175 metres above sea level. Station photos from February 1975 (Figure 3) show the site in, or very close to, its current location.
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Figure 1. A map of the Rutherglen research centre, showing the current location of the observation site, the likely location of the site in 1958 and earlier years, and other key features of the property.
Figure 2a. A site diagram
Figure 2b. Station photograph looking north, 12 December 2012.
Figure 3. Station photograph at Rutherglen, looking north-northeast, February 1975
No document has been located which states explicitly that the observation site moved. However, there are a number of documents from 1958 or earlier which make references to the site which are not consistent with it being in its current location, indicating that the site moved on one or more occasions at some point between 1958 and 1975. There are also additional documents which indicate a strong likelihood of a move or other changes.
Inconsistencies between pre-1958 site and current site
A number of documents present information about the pre-1958 site which is inconsistent with the current location. The major relevant items are:
- A 1939 station inspection report (Figure 4) which refers to the site as 'Station flat but country falls slightly to north'. This does not match the current site, which is on flat ground for several hundred metres around, with a slope rising steeply approximately 500 metres to the north.
- A 1953 document (Figure 5) which refers to a hill of over 700 feet (213 metres) approximately 300 yards (270 metres) to the south of the site. No hill exists for several kilometres south of the current site. The possibility that the '300 yards to south' is a reference to the station buildings, not the observing site, can be ruled out as the hill on the Rutherglen property—whose height closely matches this description—is to the west, not the south, of the buildings. (The coordinates listed are not useful in accurately determining the site location as they are given only to the nearest minute, and would therefore only specify the location to about the nearest kilometre).
- A site sketch from a November 1958 inspection report (Figure 6). This shows a woolshed 18 feet high approximately 150 feet (45 metres) west of the screen, and shows no indication of any road to the west of the screen, neither of which match the current site. (The possibility cannot, however, be ruled out from the available information that the woolshed might have been removed after 1958, or the road might have been built between 1958 and 1975).
- A reference in the November 1958 inspection report (Figure 7b) to the site being '1/4 mile from office' (400 metres). This differs considerably from the present site which is 700 metres from the office.
None of these documents give a definitive location for the pre-1958 site. However, the site shown on Figure 1 as 'likely pre-1958 site' matches these descriptions in a number of ways, including the slope of the ground, its location with respect to the hill and a currently existing woolshed, and the absence of a nearby road. It is also about 500 metres from the station buildings and thus matches the '1/4 mile' reference more closely than the current site does.
Figure 4. Station inspection report from 1939.
Figure 5. Note from 12 June 1953 making reference to site location relative to nearby hills.
Figure 6. Site sketch from 1958 inspection report.
Figure 7a. Left page of November 1958 site inspection report, containing reference to site being ¼ mile from office (right).
Figure 7b. Right page of November 1958 site inspection report, containing reference to site being ¼ mile from office.
Other documents consistent with one or more site moves
A number of other documents are consistent with one or more site moves having taken place. These include:
- Internal Bureau correspondence (Figure 8) which is a reply to a request for advice from Rutherglen on appropriate station layout. (Note that this letter is dated 26 January 1965, but the fact that it refers to a letter from November 1965, and its position in the file, suggests that this date is incorrect and the correct date is likely to be 26 January 1966). This is indicative that a site move and/or a reconfiguration of the instrument enclosure is likely to have taken place shortly after this date.
- An inspection report dated 27 November 1974 (Figure 9). This refers to the site having new coordinates, which is likely to indicate a site move took place shortly before this date (although the possibility exists that it could be a resurvey). The report also states that the site was to be upgraded with additional instruments, something which would potentially require a new site and/or expanded instrument enclosure.
Note that the 1966 and 1974 dates match the two breakpoints in minimum temperature identified at Rutherglen through a statistical comparison of its data with other site data in the region.
Figure 8. Correspondence from 1965–66 relating to the layout of the Rutherglen site.
Figure 9. Site inspection report from 27 November 1974, stating that the site has new coordinates, and that an upgrade of the station is pending.
Conclusions
- The observation site at Rutherglen that existed in 1958 and earlier years was not in the same location as that which has been operating from 1975 to the present. This conclusion is based on documentation of aspects of the site's topographic setting which cannot be consistent with the current site, features of the 1958 site (woolshed, absence of road) which do not match the site as it existed in 1975, and a reference to the distance of the 1958 site from the main research station buildings which indicates either a different site to the 1975 site or a substantial distance estimation error by the 1958 inspector.
- While no firm evidence exists as to the exact location of the site in 1958 and earlier years, an approximate location has been identified which is consistent with all documented features of the pre-1958 site. This location is more elevated, and has less flat country in its vicinity, than the post-1975 site and would therefore be expected to have warmer minimum temperatures, which is consistent with the observed data.
- As a logical consequence of (1), the site moved at least once between November 1958 and February 1975. Based on the documentation described above, it is likely that the site moved twice, with the moves taking place in the months following January 1966, and in the months preceding November 1974. (It is possible that the 1966 'move' could instead have been a reconfiguration of the instrument enclosure in situ ). No documentation has been located between 1966 and 1974 which gives any direct or indirect indication of the site's location or configuration during the 1966–1974 period.
