What record?

The Bureau of Meteorology (BOM) is at it again.

“On Monday the average maximum daily temperature record for Australia was broken at 40.33°C. The previous record, 40.17°C on 21 December 1972, was held for 40 years. The daily average maximum temperature yesterday (8 January 2013) is a close third at 40.11°C.”

This statement was contained in a press release on Wednesday 9 January 2013, quoting Assistant Director of Climate Information Services, Neil Plummer, and repeated with breathless enthusiasm by the media.

The average maximum daily temperature is a new term, one we haven’t seen before, to my knowledge.  However, if BOM can calculate an average annual or monthly temperature, then they probably can calculate an average daily temperature.

This announcement is crying out for a reality check.

Maxima are recorded at 9.00 a.m. on the day following, so Monday’s maxima would not be recorded until Tuesday morning, 8 January.  It normally takes a couple of months for data to be “quality assured”, checked for obvious mistakes, and then analysed for climate statements.  Yet Monday’s data, recorded on Tuesday, were accepted as correct and analysed one day later, and Tuesday’s data, recorded on Wednesday morning were processed and analysed in much less than 12 hours, and released to a gullible media and public.  Why the haste?

Australia’s climate analyses until last year were based on the High Quality (HQ) Network of weather stations, which had enormous problems and has now been superseded by the Australian Climate Observation Reference Network- Surface Air Temperatures (ACORN-SAT, or Acorn) which comprises daily data from 112 sites supposed to be the best available for length of record and quality siting.  One can only assume that these Acorn sites were the ones used to calculate the record average maximum daily temperature.  It didn’t take long to check daily maxima on Climate Data Online for 7 January from these sites.

Of the 112 sites, 3 have ceased recording and 1 had no data for the 7th January.

The remaining 108 sites had an average daily maximum temperature of:

35.91 degrees Celsius.

That’s 4.42 degrees short of 40.33, and 4.26 short of the record.

Pretty warm, but no cigar.

The median was 35.2C.  34 of 108 sites had maxima of 40.3 or more.  74 had less.

Perhaps they used a weighted average?  Here’s the temperature map for Monday 7 January.map 70113

See the dark brown area representing 45C and above?  Six (6) Acorn thermometers are in that area, recording 45C or more.

Perhaps BOM used stations other than Acorn?  If so, transparency demands they are revealed.  A map of their locations would help as they would have to be over represented in hotter parts of the country (in the dark red, grey, and brown areas on the map above).

Further, BOM needs to explain why they were used and not the official Acorn sites.  If analysis of Australia wide temperature is to be based on these sites, BOM needs to explain why they went to the trouble and expense of creating Acorn, if they are not going to use it.

Neil Plummer, you have some explaining to do.  Half truths, exaggerations, and misrepresentations are not acceptable.

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13 Responses to “What record?”

  1. Bugsy Says:

    Hiya, did you just average all the stations outputs? Or did you employ a weighted algorithm that takes into account the surface area for each isotherm region? If you take a look at the position map of the ACORN network (http://www.geos.ed.ac.uk/research/earthtemp/themes/1_in_situ_satellite/Trewin_Earthtemp_Edinburgh_2012_Poster.pdf) then you will see that the stations are HEAVILY weighted towards the southeast coastal region of Australia, so that region will certainly bias a simple averaging of all the stations maxima. I’m guessing the BOM already have a representative surface area (i.e. weighted) algorithm in place for averaging the countries temperatures, as this would be the only valid way of doing it for the whole country.

  2. kenskingdom Says:

    Unfortunately a weighted average depends on the integrity of the data from a very small number of stations, as there are very few in central Australia. BOM in fact did use 700 to 800 stations, but we dont know which they were, but we can be sure that the great majority were in SE Australia, and proportionately even less in remote areas. We don’t know, and we don’t know the quality either. Why not use Acorn, with whatever algorithm?

  3. Ian Says:

    Is there any way one can access the number of stations used to establish this record? I believe the BOM said they averaged over 700 stations so they couldn’t have used ACORN.
    The temperatures in Qld, NSW, Vic and SA were higher on 10th Jan, 1939 judging on the stations opened at that time with daily temps given.
    I did notice that the temps for Bourke in Jan, 1939 have all been adjusted downwards in the ACORN record, some by 0.9C.

    By the way, have you ever seen a coldest day temp average?

    • kenskingdom Says:

      I know some people who have identified what they believe are most of the stations, about 720.
      1939 indeed had very high temperatures. Acorn has adjusted quite a lot of historic extremes (lowered max and raised min usually). I have never heard of an Australian daily average anything before, least of all coldest (although state or territory daily averages are given e.g. climate summary for 2012). The unusual run of lower than normal minima in 2012 was far more important than a short heatwave.

  4. chaamjamal Says:

    the media is not gullible as much as it is a sucker for sensationalism. they need viewers and readers so they can sell advertisements. this is the media business model.

  5. Ian Says:

    Thanks Ken.
    You would think that unless the BOM compared temps with those that were open in any given year then the so-called Australian record day would be a worthless exercise.

    By the way, is there any valid reason as to why the BOM have adjusted these temps? They seem to be just random adjustments, anywhere from 0.1C to 0.9C in regard to Bourke’s Jan, 1939 temps.
    I know they adjusted Mildura’s 50.8C in 1906 down to about 48 degrees based on the temp at Deniliquin (almost 400kms away).

    • kenskingdom Says:

      For their explanation for why and how they made adjustments, you will need to read the Technical Papers at the Acorn site.

      • Ian Says:

        Read the technical report briefly but can’t understand why such a variety of changes for the same station in the same month. Always down except for the lower temps.
        Jan raw ACORN
        1st 38.9 38.4
        2nd 40 39.1
        3rd 42.2 41.9
        4th 38.1 37.9
        5th 38.9 38.4
        6th 41.7 41.5
        7th 41.7 41.5
        8th 43.4 43
        9th 46.1 45.7
        10th 48.3 47.9
        11th 47.2 46.8
        12th 46.2 45.8
        13th 45.7 45.3
        14th 46.1 45.7
        15th 47.2 46.8
        16th 46.7 46.3
        17th 40 39.1
        18th 40.1 39.1
        19th 40 39.1
        20th 41.9 41.7
        21st 42.5 42.1
        22nd44.2 43.8
        23rd 36.7 36.5
        24th 40.3 39.2
        25th 36.6 36.5
        26th 29.4 29.5
        27th 29.3 29.4
        28th 28.8 28.9
        29th 30.6 30.5
        30th 35.6 35.4
        31st 38.6 38.3
        Highest daily 48.3 47.9
        Lowest daily 28.8 28.9
        Monthly mean 40.4 40.03548387

        • kenskingdom Says:

          You’re not alone in not understanding it! Each day is apparently compared with 40 nearest stations one at a time.

          • Ian Says:

            Just one last comment, Ken, before I bore the socks off you. Checked the raw temps and ACORN temps for Cobar (the closest w/s to Bourke). The first ten days are mostly increased whereas Bourke temps are all reduced.
            raw ACORN Diff (between raw and ACORN)
            38.9 38 -0.9
            41.2 41.3 0.1
            41.2 41.3 0.1
            37.8 37.4 -0.4
            37.2 36.8 -0.4
            41.7 41.9 0.2
            41.7 41.9 0.2
            44.4 44.7 0.3
            46.1 46.4 0.3
            46.7 47 0.3
            Bourke’s temp for the first ten has been reduced by 0.4C and Cobar’s increased by 0.2C.
            Bourke is hotter than Cobar using the raw temp but Cobar is hotter using ACORN.
            This also holds true for the whole month.
            Sigh!

          • Ken Stewart Says:

            Ian, you are brave. You’ve only got another 39 sites to go to see if you can find why Bourke was adjusted so much! But I doubt if you will ever find out. Acorn is a crock and I’ve pretty much given up on it.
            Ken

  6. marchgeo Says:

    Hi Ken,
    Do you know if records from Tebbutts Observatory near Winsdor (1860s-1940s+) are on line? Among the records is a reprt of a reading of 122 Fahrenheit in jan 1939
    see…http://trove.nla.gov.au/ndp/del/article/85811924

    Tebbutt’s meticulous work does not appear to have picked up by the BOM.

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