Preparing the geological maps, slope, land use, high altitudes, groundwater level, decline, isohyet
, and isothermal status.
In semi-arid, subtropical southern Queensland, chloride concentration in rainfall was a function of distance from the coast (Biggs 2006); extrapolation -200 km south-west to the 500-mm rainfall isohyet
in north-western NSW yielded a value of ~1.
The early winter's first approach of the so-called 540 isohyet
, where it is zero degrees Celcius on the surface, lies only a hundred kilometres south of Cape Town by Tuesday, and the effect of the cold will be felt across the entire Namibia.
This value should exclude Ngaoundere from the African meningitis belt, for which the southern limit of annual rainfall was classically considered to be the 1,100-mm isohyet
In the early twentieth century, Thomas Griffith Taylor, a prominent early geographer, in a major work on Australian rainfall and the climatic factors limiting agriculture and settlement, had perceptively described the line as an 'ecological isopleth' (8), and the historian Archibald Grenfell Price had seen in it a 'vegetation line' (9), but the explanation that had become widely accepted and entrenched in the first half of the twentieth century was that the line approximated an isohyet
of average annual rainfall.
The relationship of these 4 AEZs to the 500 mm rainfall isohyet
and the area delineated by the definition of the HRZ, as R > E/3 for >9 months, is illustrated in Fig.
These regions, as defined approximately by above and below the 1600 mm annual rainfall isohyet
, were formed into two zones.