Page:Hunt - The climate and weather of Australia - 1913.djvu/93

1909. Figures 68 and 69. The tendency to this distribution was very pronounced during the seven winter months of 1899, and in particular during the months of July and August, when the inland rains were very scanty.

In the following table the years are arranged in two sections—(a) and (b)—representing the two most distinct drought types, and the barometric departures from the normal for the whole year at the various capital cities are also given to show how far these support the classification. As will be seen, they do this fairly well:—

Departure from Normal Annual Air Pressure.

Year.	Hobart.	Melbourne.	Sydney.	Brisbane.	Adelaide.
Type (a).
1888	+.029	+.060	+.053	+.039	+.051
1895	..	-.004	+.010	-.001	+.009
1907	-.035	-.017	+.007	-.013	-.015
Type (b).
1902	+.058	+.029	+.032	+.020	+.033
1896	+.021	+.016	+.017	+.009	+.018
1897	+.032	+.007	+.015	+.007	+.015
1899	+.041	+.020	+.020	+.010	+.023
1911	+.022	-.009	-.008	-.012	-.001

The weather charts, Figures 60-62, illustrate the 1888 type, and Figures 63-65 show some typical of 1902 pressure distribution.

Variation of the Winter Rainfall over Northern Victoria with Mean Pressure and Pressure Ranges (1887—1911).

A detailed study of the relation between the inland rains over Victoria, the mean air pressure at Melbourne and the extreme pressure ranges as shown during the passage of storm systems over Victoria during each month, gave the following results for the seven months, April—October inclusive. "Agreement" in the case of mean pressure requires departures from normal opposite in sign to those from rainfall, and in the case of pressure ranges the same sign with those for rainfall:—

—		April.	May.	June.	July.	August.	September.	October.
Mean Pressure $\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Agreement	12	16	15	16	17	13	12
	Disagreement	10	9	7	9	8	11	11
Pressure Ranges $\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Agreement	12	19	11	18	17	12	11
	Disagreement	13	6	14	7	8	13	14

This shows a certain tendency for the rainfall to vary inversely with the mean monthly pressure, but it is not a very pronounced one for the first and last two months of the series, and seems to be more especially a winter relationship.