The BomWatch blog has published Day/Night temperature spread fails to confirm IPCC prediction examining max min and DTR temperature data from the BoM purpose built weather station Giles 13017 in far eastern WA near the WA-SA-NT border junction. The main points of the BomWatch article is that Giles is a pristine site and that DTR has not closed as the IPCC expects. In 2014 I blogged on the loony-toon BoM adjustments to Giles for ACORN 1. So I have a 2013 Giles Basic Climatological Station Metadata pdf – a sort of station diary – on my HDD. A check of the Giles pdf shows that a gravel road that ran through the instruments area near the screen was bitumen sealed in the 12 months between the Sep 2011 and Sep 2012 site maps. Ken Stewart blogged on the Giles site in 2019 The Wacky World of Weather Stations: No. 171- Giles (WA) and Ken shows Google Earth images that indicate the screen was ~20m from the sealed road. So the sealed road would introduce some quota of UHI into the data. Ken also pointed out that a 2019 site photo from JoNova shows the whole area of the screen fenced rectangle covered by gravel with no grass – Ken rates the site “non-compliant”. The 2013 Giles Basic Climatological Station Metadata pdf shows on page 23 Station Equipment History that on 1st June 1992 under Air Temperature that – “INSTALL Temperature Probe – Dry Bulb (Type Rosemount)”.
So prior to 1st June 1992 temperatures would have been recorded by liquid in glass thermometers probably in older/larger type Stevenson screen. The post 1992 probe would produce readings over very short periods of seconds which would lead to higher temperatures being recorded than would have been recorded by a liquid in glass thermometer.
You can also see the road is even closer than 20m and the installation dates from the current site info.
www.bom.gov.au/clim_data/cdio/metadata/pdf/siteinfo/IDCJMD0040.013017.SiteInfo.pdf
Jo Nova did a post on Giles after going there in 2019. Which as any good research should, also mentions the date that road went in.
joannenova.com.au/2019/10/giles-weather-station-sited-next-to-the-only-bitumen-for-500-km/
Her first photo shows the cable going up into the screen via the gaps in the bottom that allow heat off the hot steel pole to rise up through it past the thermometer probe and out the 1 inch holes in the ceiling into the open roof cavity. I mention this cable because the place where the other end of that cable goes can be seen in the her second photo. It is the electronics cabinet at the base of the anemometer pole.
There would be two red wires and two white wires or similar running cabinet to probe. One red/white pair to provide a stable constant small current to the probe and the other red/white pair to return the Voltage at the same connection point at the platinum resistance within the probe back to the electronics to be read every second. The voltage being read and then logged as the corresponding temperature from the ISO standard tables for PT100. The platinum resistance is the most classic form of analogue device. The “digital” conversion at the other end of that cable in the electronics under the anemometer, is where a reading is taken at 1 second intervals. The one second reading interval time is not that important but is divided down from a crystal reference clock so will not change no matter what type of probe is connected.
The two timings that really do matter and should never be confused with that sampling rate are the thermal time constant of the probe and the averaging time of the samples after collection by the electronics. Against WMO recommendations the BoM do not average post conversion samples. They instead have tried many different thermal time constants to attempt to match what a glass thermometer’s thermal time constant is. Their scant documentation of this mentions adjusting the thickness of metal sleaving.
As for DTR anyone can download the daily sunspot count and see that most observational records show a strong DTR to sunspot anti correlation if both sets of data are running averaged for around eleven years.
So any any genuine look at DTR should show either a closing or opening at an 11 year rate that would also be proportional to the particular sunspot cycle.
Lance Pidgeon.
Dr Marohasy has just blogged at WattsUpWithThat
Australia’s Broken Temperature Record (Part 1) 26Jan2022 on similar subjects.