BoM forecast for Perth 31st May 2013 – “frost possible” -yet Perth central weather stations have not recorded a 0° minimum in May in over a century

An interesting call because Perth Regional Office weather station 9034 never recorded a minimum of 0°C for any month in all the years 1897-1992, see my table below. Chris Gillham has an account of the history of the various locations for Perth weather instruments.
BoM forecast late afternoon 30 May 2013 –

From 1993 and current Perth weather is recorded at “Perth Metro” which is at Mount Lawley near Edith Cowan University. As my table shows Perth Metro like Perth Regional Office has never recorded a frost in May and probably will not this morning. It looks obvious to me from my table that the ever growing Perth urban heat island has suppressed frost over a century while stations more peripheral to Perth commonly record frosts in the cooler months.


However the newly created (ACORN-SAT) dataset, a flagship data product of the Bureau of Meteorology has created 40 frost days in Perth history, where NONE existed before.
ACORN adds 40 days of 0°C or colder including 3 days in May 1964. 29th,30th and 31st. 29th = -1.4(3.0 neg adjusted), 30th = -0.1(4.1 neg adjusted) & 31st = -0.7(3.9 neg adjusted),
Year-Mon-Day- Ajusted ACORN minimum temperature
1916 7 16 0
1920 7 1 0
1955 6 27 0
1990 7 1 0
1992 8 29 0
1916 7 6 -0.1
1917 7 28 -0.1
1931 6 11 -0.1
1950 7 1 -0.1
1964 5 30 -0.1
1998 7 27 -0.2
2010 7 4 -0.2
1973 6 25 -0.3
1986 8 12 -0.3
1969 7 11 -0.4
1979 7 24 -0.4
1979 7 25 -0.4
1920 7 30 -0.5
1943 7 24 -0.5
1964 6 1 -0.5
1966 6 25 -0.5
1990 6 27 -0.5
2006 6 18 -0.5
2010 7 5 -0.5
1914 6 29 -0.6
1990 6 28 -0.6
1964 5 31 -0.7
2012 7 25 -0.7
1937 6 11 -0.8
2006 7 22 -0.8
2010 7 3 -1
1916 7 7 -1.1
1968 6 21 -1.1
1946 6 27 -1.2
1920 6 30 -1.3
2006 6 17 -1.3
1955 6 22 -1.4
1964 5 29 -1.4
1990 6 30 -1.5
1914 5 11 -1.8

2 comments to BoM forecast for Perth 31st May 2013 – “frost possible” -yet Perth central weather stations have not recorded a 0° minimum in May in over a century

  • D Cotton

    Whatever the forecasts, they have nothing to do with carbon dioxide.

    If you believe that planetary surface temperatures are all to do with radiative forcing rather than non-radiative heat transfers, then you are implicitly agreeing with IPCC authors (and Dr Roy Spencer) that a column of air in the troposphere would have been isothermal but for the assumed greenhouse effect. You are believing this because you are believing the 19th century simplification of the Second Law of Thermodynamics which said heat only transfers from hot to cold – a “law” which is indeed true for all radiation, but only strictly true in a horizontal plane for non-radiative heat transfer by conduction.
    The Second Law of Thermodynamics in its modern form explains a process in which thermodynamic equilibrium “spontaneously evolves” and that thermodynamic equilibrium will be the state of greatest accessible entropy.
    Now, thermodynamic equilibrium is not just about temperature, which is determined by the mean kinetic energy of molecules, and nothing else. Pressure, for example, does not control temperature. Thermodynamic equilibrium is a state in which total accessible energy (including potential energy) is homogeneous, because if it were not homogeneous, then work could be done and so entropy could still increase.
    When such a state of thermodynamic equilibrium evolves in a vertical plane in any solid, liquid or gas, molecules at the top of a column will have more gravitational potential energy (PE), and so they must have less kinetic energy (KE), and so a lower temperature, than molecules at the bottom of the column. This state evolves spontaneously as molecules interchange PE and KE in free flight between collisions, and then share the adjusted KE during the next collision.
    This postulate was put forward by the brilliant physicist Loschmidt in the 19th century, but has been swept under the carpet by those advocating that radiative forcing is necessary to explain the observed surface temperatures. Radiative forcing could never explain the mean temperature of the Venus surface, or that at the base of the troposphere of Uranus – or that at the surface of Earth.
    The gravitationally induced temperature gradient in every planetary troposphere is fully sufficient to explain all planetary surface temperatures. All the weak attempts to disprove it, such as a thought experiment with a wire outside a cylinder of gas, are flawed, simply because they neglect the temperature gradient in the wire itself, or other similar oversights.
    The gravity effect is a reality and the dispute is not an acceptable disagreement.
    The issue is easy to resolve with a straight forward, correct understanding of the implications of the spontaneous process described in statements of the Second Law of Thermodynamics.
    Hence radiative forcing is not what causes the warming, and so carbon dioxide has nothing to do with what is just natural climate change.

  • George Bailley

    A lack of knowledge is a dangerous thing. Minimum temperatures are recorded about 1.5m above ground – but near surface temperatures are generally colder. March, April and May have all seen below zero surface temperatures at Perth Airport.

    On the 31st Jandakot recorded 0.5C and Pearce 0.6C at 1.5m. It seems highly likely that some areas in the Perth Metro area saw surface frost.

    An excellent forecast.

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