Australia’s Wacky Weather Station Comparison 1: Keith (SA)

After surveying 666 weather stations across Australia and finding nearly half (49.25%) are not compliant with Bureau of Meteorology siting specifications, in this series of posts I compare daily temperature data from pairs of compliant and non-compliant stations.

The difficulty is to find pairs of sites in close physical proximity and similar surroundings.  Large numbers of non-compliant stations especially in WA and SA have no compliant neighbours. 

Another difficulty is that it is impossible to control variables other than siting.  Screen maintenance, enclosure maintenance, probe or thermometer accuracy, are some of the variables that may adversely affect comparisons.  Never-the-less, we shall try.

I have restricted analysis to the last 10 years (2010 – 2019).

Keith and Munkora

These stations are in the far south-east of South Australia, not far from the Victorian border:

Fig. 1:  Keith map location per Google Maps

 They form the closest pair of stations I have found, just 2.66 kilometres apart, as this map shows.

Fig.2:  Keith and Munkora (Keith West)

Keith 25507 is in the middle of town between the highway and the rail line between Adelaide and Melbourne.

Fig. 3:  Keith (Google satellite image 2019)

Munkora 25557 is in an open rural setting, but is really “marginal” rather than compliant, as the grass in the enclosure is up to 0.5m high, and the surrounding paddock has at times been a cultivation, as the 2017 site plan shows:

Fig. 4:  Munkora site plan 2017

Still, it’s better than Keith.

Fig. 5:  Munkora  (Google satellite image 2020)

There is only 2 metres difference in altidude.  However, an important difference is that Keith is a manual station with liquid-in-glass thermometers, while Munkora is an Automatic Weather Station (installed 2001) with an electronic temperature probe transmitting data every minute.

If we plot all daily maxima from 2010 to 2019 for Munkora against Keith, we see that temperatures match quite closely:

Fig. 6:  Tmax at Munkora as a function of Tmax at Keith

A time series of the 31 day centred mean of the daily difference between them shows more detail:

Fig. 7:  31 day mean daily difference Keith minus Munkora Tmax

Values above zero mean Keith is warmer than Munkora; below zero, Keith is cooler.  Note that Keith is warmer in cooler months but Munkora is warmer in summer and autumn.  Note also strange things happen in the summers of 2010-2011, 2014-2015, and 2015-2016.

This is a plot of mean differences by month:

Fig. 8: 31 day mean daily difference Keith minus Munkora Tmax by month

Keith is warmer in cool months (May to September).  However, the warmer maxima at Munkora in warmer months may be due to the rapid response of the AWS probe to sudden temperature changes which an LIG maximum thermometer will not detect.  The BOM denies this happens.

Minimum temperatures don’t match as closely…

Fig. 9:  Tmin at Munkora as a function of Tmin at Keith

But minima at Keith are consistently warmer (averaging about 1.5 degrees C) than 2.7km out of town, and the differences are much greater:

Fig. 10:  31 day mean daily difference Keith minus Munkora Tmin

Keith is warmer in all seasons, especially spring and summer.

Fig. 11: 31 day mean daily difference Keith minus Munkora Tmin by month

A note on accuracy:

The centred 31 day running correlation is useful for detecting inconsistencies.

Fig. 12:  Centred  31 day running correlation between Keith and Munkora maxima

Fig. 13:  Centred  31 day running correlation between Keith and Munkora minima

Although there are a couple of obvious inconsistencies in maxima, the correlation in minima has been getting worse over the years and was much worse in 2019.

Fig. 14:  Daily difference in minima

There are examples of up to 10 degrees difference on some days, possibly due to observation or recording error- for example, by recording temperature on the wrong day.

In recent years, Keith 25507, a manual station that does not comply with site specifications, has warmer winter maxima but cooler summer maxima than the AWS at Munkora 25557 just 2.66km out of town, and has warmer minima all year round. 

Keith, with a population of just over 1,000, appears to have an Urban Heat Island (UHI) effect, due to its poor siting.

In this example, siting non-compliance has a large effect on temperature.

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One Response to “Australia’s Wacky Weather Station Comparison 1: Keith (SA)”

  1. Bill In Oz Says:

    Well ken, this is interesting. But sort of predictable given what we know about the two sites and the gear the BOM has operating at each.
    1: UHI exists even in a small town like Keith.. And this is especially apparent with Winter minimums temperatures.
    And of course BOM uses this as evidence of Winter warming ! How scientific is that ? NOT scientific at all.But good propaganda !

    2: The electronic probe temperature gear registers even brief seconds of a given “hottest” temperature compared to the old style mercury thermometers which respond much more slowly but which were standrad equipment from the 1880’s to the late 1990’s in the BOM’s network.

    So once again we have here an excellent BOM propaganda opportunity to scare us with warmer Summer temperatures = GOREBULL WARMING !

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