Dry Tropics Biodiversity Group Inc.

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Evaluation of climate data for Nth Qld./Brisbane
24 Nov 1997, recalculated by D. Silke, from data supplied by the Commonwealth Bureau of Meteorology.

Data is presented: rain | temp | humidity | altitude temperature effect |
Note: the figure in brackets after the name of the town is the years of record for that town. E.g. "Brisbane (48)" indicates that the data depicted for Brisbane was taken over 48 years. E.g. "Ingham (1)" in the evaporation chart, means that only one year's data was available (so forget that line on the chart, it is useless)

Rainfall summary at major centres:
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Most rain falls in the wet, the dry is very dry.

"Bowen/Ayr/Townsville" have very similar rainfall say = "x1"

Charters Towers has less rain….. = "x0.6"

Ingham and Cairns have the same rainfall characteristic = "x1.8" (Mackay's is the same except appreciably less in the first 4 months of the year)

Innisfail has what seems to me to be a ridiculous rainfall….. = "x2.7!!!"


Evaporation summary:

Appears to be a function of relative humidity, wind and sunshine hours/day length. Note well that the evaporation in Townsville exceeds the mean rainfall for almost 9 months of the year!!! So the growing season for plants here in natural conditions is often only about 3 months

e.g. "Ingham (1): the "(1)"= years of data, vis data for Ingham is useless.


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Temperature summary at major centres:

Summer temperatures are all about the same, Bowen thru to Cairns

Mackay’s Summer temperatures are 1-2 deg C less.

(Brisbane’s Summer temperatures are 2-3 deg C lower)

Cairns temperature varies least throughout the year

Brisbane temperatures vary most throughout the year

i.e. Brisbane’s Winter temperature is 7 deg less than Cairns, and varies proportionally with latitude in between.

Elevation reduces temperatures by 6.5 deg C per 1000m.(see more below, ref. Perry)

As go inland get greater daily variation, e.g. Charters Towers (elev. 300 m) has 2 deg C lower minimums (corresponds with drop due to height) and 1 deg C higher maximums (corrected for height is +3 deg C)… all c/f Townsville.

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Humidity summary at major centres:

Except for Innisfail (clearly consistently higher) and Charters Towers (clearly consistently lower), Nth Qld coastal township's humidity are closest together Oct-Feb, spread apart for the other months, are highest in Feb (e.g. Townsville 70%) and lowest (e.g. Townsville 55%) in September. The relative ranking of recording sites is very consistent throughout the year.

Note that as moisture leaves (rain), and as temperatures warm, inland humidity rapidly lowers with distance beyond the Range. e.g. Charter’s Towers.

On average variation is:

Innisfail has average rel. humidity at 75%
Mackay/Bowen/Ingham/Cairns have average rel. humid. 70%
(rel. humidity in Mackay, Bowen & Ingham exceeds that of Cairns almost all the time)
Ayr has average rel. humidity 65%
Townsville has average rel. humidity 60%
Charter’s Towers has average rel. humidity 50%
Brisbane has the same rel. humidity as Townsville except appreciably less in Summer

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Altitude effect upon temperature:

Altitude has the largest effect on climate, a far greater effect than does latitude.

Theory (more data is required to check all this in practice.)

Temperature drops approximately 6.5 deg C with 1000 m rise in altitude (e.g. Paluma township... in Mt. Spec National park just north of Townsville), or in proportion linearly with altitude (ref Perry, chemical engineering handbook). Temperature drop in summer apparently is less, perhaps because of thermodynamic effects when cloud/rain forms???

To achieve something like the same drop in temperature on the coast as at Paluma it is necessary to go south to Brisbane (2-3 deg less in summer, 7 deg less in winter all c/f Townsville.

With the counter opposed temperature/humidity/latitude effects, the elevated climatic conditions around Townsville are really quite unique (as are our lowland conditions, though perhaps less striking).

24 Nov 1997, recalculated by D. Silke, from data supplied by the Commonwealth Bureau of Meteorology.
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