FROST

Frost can cause serious losses to agricultural crops and a number of climatic studies have been made in Australia related to specific crops cultivated in local areas. Under calm conditions the overnight temperatures at ground level are often as much as 6Co lower than those measured in the instrument screen which has a base height of 1.1 metres and differences of 10Co have been recorded.

Only a small number of stations measure minima at ground level, the lowest recordings being -15.1 degrees C at Canberra and -11.0 degrees C at Stanthorpe (Q). Lower readings may be recorded in Alpine areas.

FROST FREQUENCY

Frost frequency depends on location and topography and even on minor variations in the contour of the land. The frost map of Australia is shown below:

FROST PERIOD - MEAN ANNUAL LENGTH DAYS PER ANNUM. A FROST DAY HAS A MINIMUM TEMPERATURE OF <= 2Co





Frost data shows:

The length of the frost period for the year is taken as the number of days between the first and last recording of an air temperature of 2 degrees C or less. The median duration of the frost period in days per annum is shown in the diagram above.

The frequency table below includes the average annual frequency of minima of 2.2Co or less for a wide selection of stations, particularly those prone to frosts:

THE AVERAGE ANNUAL NUMBER OF FROSTY NIGHTS

STATION 

ALTITUDE (M)AVERAGE NUMBER FROSTY NIGHTS
<=2.2 degrees C <= 0 degrees C
AVERAGE NUMBER HEAVY FROSTS
Adelaide Airport 1956-85  6.0
6.2
0.9
Alice Springs 1942-85 
545.0
32.7
11.9
Ballan 1957-68
442.0
62.3
20.5

Birdsville 1957-83

43.0
4.7
0.4

Brisbane Airport 1950-85

6.0
0.2
0.0

Canberra Airport 1940-85

571.0
101.1
63.6

Ceduna Airport 1943-85

24.0
18.4
4.2

Charleville Airport 1943-85

306.0 32.3
12.9
Essendon Airport 1940-70
86.0
14.2
2.6
Hobart 1943-85
55.2
17.1
1.7
Kalgoorlie Airport 1943-84
360.0
20.4
4.6
Kiandra 1957-68
1395.4 228.3
176.7
Mt Gambier Airport 1943-85 63.0
26.0
6.9
Perth Airport
1945-86
20.0
2.8
0.1
Walgett 1957-84
131.0
23.3
5.7


The above table shows:



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