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Perth Metro BoM station 09225 looks to be reading too warm from mid-2011 – could much publicised summer hot days be exaggerated ?

Perth summers (Dec-Jan-Feb) as measured at Perth Metro in Mount Lawley looked too warm for 2012 and 2013 when compared with Perth Airport 09021. The differences for summer mean max between the Airport and the old Regional office (1898-1992) going back to 1945 and Perth Metro 1994-2013 show that 2012 and 2013 fall clearly outside a long established band.

I noticed there were instrument changes at Perth Metro in July 2011 – not sure if they were the instruments that read the daily max. I checked Perth Airport summers against Pearce RAAF 1994-2013 and all differences fell in a band – which also suggests that Perth Metro is faulty.
Anybody reading our media just now will find plenty of articles from the BoM spruiking the “hottest summer ever” for Australia.
Here the BoM were claiming the hottest summer ever in Perth before summer had ended.

Looking forward to hearing what others think of the Perth data.

5 comments to Perth Metro BoM station 09225 looks to be reading too warm from mid-2011 – could much publicised summer hot days be exaggerated ?

  • Philip Bradley

    Yesterday in Perth, under sunny skies, the high was just under 34C, 500 km to the east, Kalgoorlie, normally a few degrees warmer than us in the summer, reached a high of just 15C, because of cloud all day.

    Cloud albedo determines temperatures in warm to hot climates.

    Re: the graph

    Perth’s official station moved in 1992 from Plain Street opposite a large irrigated park to Mt Lawley. Hence the jump in (night time) temperatures.

  • Philip Bradley

    I had a look at Gosnells, about 10 kms south of Mount Lawley and the airport. Only data for 2012, but Jan/Feb bang on the 30 year average.

    Looks like you are correct about instrument problems.

    www.bom.gov.au/jsp/ncc/cdio/cvg/av

  • WSH

    Thanks Philip for checking Gosnells.
    Here is Airport minus Metro for the monthly max – shows a pattern of greater warm season differences for years; then after July 2011 – Metro jumps warmer to be much closer to Airport numbers. Thanks to those who have emailed too.

  • WSH

    Chris Gillham has a page on this subject too. He takes his analysis further than I have.

    Is Perth’s record heat a thermometer error?

  • Well done in spotting this inexplicable shift in Perth Metro maximum temperatures, Warwick, and thanks also for the reference link.

    I can accept occasional variations (up to 7C … hmmmm) between Perth Metro and Perth Airport because of freakish local weather conditions on a given day, but an immediate, large and permanent shift can only mean it’s artificial rather than natural.

    My analysis suggests that for maxima there’s been an average .6C shift up at Metro to a near zero difference with the airport since mid 2011 when there was a site equipment change, and there’s been a string of monthly, seasonal and annual records established at Perth (Metro) since then.

    Have a look at www.waclimate.net/perth-difference.html and you’ll find several very strange changes to min/max averages and site temperature differences since 1994.

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