Bureau of Meteorology database bug

It's worth being aware of database adjustments made by the BOM.

In December 2009 the BoM warmed the RAW mean minimum and maximum temperatures by about half a degree from the temperatures that had previously been recorded on the BOM website database for August 2009.

Below are 32 Western Australia locations with their original data in the top light blue and red row as posted by the BOM from September 1 to November 17, and the new adjusted data in the darker blue and red row below:

August 2009:

Minimum and maximum as recorded from September 1 to November 17 2009 on BOM web database

Minimum and maximum as recorded since November 17 2009 following correction to BOM database bug

Albany

9.0	16.2
9.4	16.6

Balladonia

5.0	20.7
5.5	21.1

Bridgetown

5.7	15.7
6.2	16.1

Broome

14.6	29.2
15.1	29.7

Bunbury

8.2	16.7
8.7	17.2

Busselton

8.7	17.0
9.2	17.4

Cape Leeuwin

11.8	16.2
12.2	16.6

Cape Naturaliste

10.5	16.7
11.0	17.1

Carnarvon

11.4	23.2
11.8	23.6

Derby

15.0	32.7
15.6	33.2

Donnybrook

6.7	17.2
7.2	17.6

Esperance

8.3	17.7
8.8	18.1

Eucla

7.9	21.5
8.4	21.9

Eyre

4.3	21.6
4.5	22.0

Geraldton

9.5	20.0
10.0	20.5

Halls Creek

16.1	32.6
16.6	33.0

Kalgoorlie

6.8	20.3
7.2	20.7

Katanning

6.1	14.7
6.5	15.1

Kellerberrin

5.3	18.6
5.6	18.9

Laverton

7.5	22.4
7.9	22.9

Marble Bar

13.8	31.1
14.3	31.5

Merredin

6.1	17.7
6.5	18.1

Mt Barker

6.8	15.6
7.0	15.8

Northam

6.2	18.4
6.6	18.7

Onslow

13.8	27.7
14.3	28.1

Perth

8.8	18.5
9.3	18.9

Rottnest Island

12.4	17.3
12.9	17.7

Southern Cross

4.6	18.1
5.0	18.6

Wandering

5.3	16.1
5.6	16.6

Wiluna

7.5	24.8
7.7	25.2

Wyndham

18.3	34.0
18.8	34.4

York

5.6	17.9
5.9	18.3

The BOM was questioned as to what had happened and on December 7 2009 sent this reply …

"Thanks for pointing this problem out to us. Yes, there was a bug in the Daily Weather Observations (DWO) on the web, when the updated version replaced the old one around mid November. The program rounded temperatures to the nearest degree, resulting in mean maximum/minimum temperature being higher. The bug has been fixed since and the means for August 2009 on the web are corrected."

The temperatures for all WA locations in the BOM web database remain at the higher adjusted temperatures for August 2009 and there was no change from the adjustment made on November 17 prior to my correspondence.

The reply was confusing so another question was sent to the BOM, as below and with the response on December 9 ...

"Thanks for the reply but I'm still a bit puzzled. Below are August 2009 min and max data for 32 WA sites I keep an eye on, the top temps being those recorded on the BoM website from Sep 1 to Nov 17, and the bottom temps the updated version since Nov 17. The rounded temperature bug seems to have only affected August as there has been no adjustment to any other month including September. I've just checked the BoM site and there's no change to the August data. Can you please let me know which of the temps below are correct?"

Reply: "The bottom ones are correct. The bug only affected averages for August 2009."

It is worth noting the frequency of adjustments on the BOM database as presented on the web.

For example, in July 2010 the existing temperatures presented on the BoM website were compared with how the temperatures were originally posted at a variety of West Australian weather station dating back to June 2009. It was found the most consistent adjustment by the BoM was for temperatures in January 2010 wherein most but not all locations saw a small reduction in their mean maximum:

As originally posted on BoM website database

As recorded on August 10 2010

Albany adjustments for January 2010

16.4	23.1
16.4	23.0

Balladonia adjustments for January 2010

16.1	34.4
16.1	34.1

Balladonia adjustments for September 2009

4.3	21.7
4.4	21.7

Bridgetown adjustments for January 2010

12.1	30.5
12.1	30.4

Broome adjustments for January 2010

26.6	33.1
26.6	33.0

Bunbury adjustments for January 2010

15.5	31.7
15.5	31.6

Busselton adjustments for January 2010

14.7	30.6
14.7	30.5

Busselton adjustments for April 2009

11.4	23.3
11.3	23.3

Cape Leeuwin adjustments for January 2010

17.3	23.2
17.3	23.1

Cape Naturaliste adjustments for January 2010

15.2	27.7
15.2	27.6

Carnarvon adjustments for January 2010

22.5	30.8
22.5	30.9

Derby adjustments for November 2009

25.0	39.4
25.0	39.5

Derby adjustments for February 2010

26.5	36.5
26.4	36.5

Donnybrook adjustments for January 2010

15.9	33.1
15.9	33.0

Esperance adjustments for January 2010

16.1	27.8
16.1	27.6

Esperance Airport adjustments for January 2010

15.0	29.4
15.0	29.2

Eucla adjustments for January 2010

18.2	30.3
18.2	30.1

Eyre adjustments for January 2010

14.3	30.9
14.3	30.7

Geraldton adjustments for January 2010

18.3	33.0
18.3	32.9

Kalgoorlie adjustments for January 2010

19.8	36.8
19.8	36.6

Katanning adjustments for January 2010

13.1	31.2
13.1	31.1

Kellerberrin adjustments for October 2009

8.3	26.8
8.9	27.2

Kellerberrin adjustments for December 2009

14.7	34.4
14.5	34.4

Kellerberrin adjustments for January 2010

16.5	38.0
16.3	37.8

Kellerberrin adjustments for February 2010

17.5	35.8
17.6	36.0

Kellerberrin adjustments for April 2009

10.6	27.9
10.6	27.8

Marble Bar adjustments for January 2010

26.8	41.9
26.8	42.0

Merredin adjustments for February 2010

18.5	37.6
18.5	37.4

Mt Barker adjustments for September 2009

7.0	14.8
6.3	14.9

Mt Barker adjustments for January 2010

11.8	27.9
11.8	28.3

Northam adjustments for January 2010

17.7	37.4
17.7	37.3

Onslow adjustments for January 2010

24.0	36.3
24.0	36.6

Perth Metro adjustments for January 2010

18.9	33.5
18.9	33.4

Rottnest Island adjustments for November 2009

16.0	23.6
16.0	23.7

Rottnest Island adjustments for January 2010

19.5	27.3
19.5	27.2

Southern Cross adjustments for January 2010

18.3	37.4
18.2	37.3

Southern Cross adjustments for February 2010

18.7	36.1
18.6	36.0

Wandering adjustments for January 2010

14.3	34.7
14.3	34.6

Wandering adjustments for March 2010

13.4	30.1
13.4	29.9

Wiluna adjustments for October 2009

14.7	33.6
14.9	33.8

Wiluna adjustments for December 2009

23.1	38.3
23.1	38.1

Wiluna adjustments for January 2010

25.2	41.1
24.8	41.2

York adjustments for January 2010

16.5	36.7
16.5	36.6

The upward adjustments almost perfectly counter the downward adjustments. However, the consistency of adjustments made to January 2010 observations suggests a database bug correction was again responsible for the "incorrect" original recording.

Monthly mean temperature anomalies for Western Australia have been faithfully collated since July 2008, using High Quality dataset anomalies until March 2012 and ACORN anomalies since the new network was introduced in that month.

The table below shows the changes that have occurred since July 2008 due to the introduction of ACORN 2.2.

acorn anomaly changes

The chart below illustrates data from the table above.

acorn anomalies chart

The presence of software bugs for extended periods, as well as sporadic adjustments without a seeming pattern, raise questions about the reliability of data from the BOM website for research purposes.

Top of page

This website produced by Scribeworks 2008-2023