humidity

HUMIDITY

Australia is a dry continent in terms of the water vapour content of the air and this element may be compared with the evaporation to which it is related. Moisture content is most commonly expressed as Relative Humidity (RH). Relative Humidity isopleths for January and July at 9am and 3pm are shown in the table below:

AVERAGE RELATIVE HUMIDITY (%)

STATION	JANUARY		JULY
	9AM	3 PM	9AM	3 PM
Alice Springs	34	20	59	30
Armidale	63	44	77	52
Broome	71	65	47	34
Carnarvon	58	59	69	52
Ceduna	53	42	80	55
Charleville	47	28	66	35
Cloncurry	52	32	45	26
Esperance	58	56	77	58
Halls Creek	51	34	31	22
Kalgoorlie	45	24	74	47
Katanning	57	30	88	6
Kiandra	61	50	90	78
Marble Bar	44	25	39	25
Mildura	50	26	86	54
Mundiwindi	31	19	49	28
Thursday Island	84	78	80	67
Townsville	72	66	67	51

Source: Climatic Atlas of Australia, 1988

The above table shows:

Over the interior of the continent there is a marked dryness during most of the year, notably towards the northern coast in the dry season of May-October.

The coastal fringes are comparatively moist although, this is less evident along the northwest coast of WA where continental effects are marked.

In northern Australia, the highest values occur during the summer wet season of December-February and the lowest during the winter dry season of June-August.

In most of southern Australia, the highest values are experienced in the winter rainy season of July-August and the lowest in summer, December-February.

Relative humidity (RH) is dependent on temperature and if the water content of the air remains constant, it decreases with increasing temperature. For example, Perth for January has a mean 9am RH of 60% but for 3 pm when the mean temperature is higher, the mean RH is 11%.