In an attempt to allow the effects of rainfall to be incorporated into the regression-tree DSM, covariates were tested that would better explain the target OC percentage variability due to rainfall, but without the isohyet
effects, and with better variation with terrain.
The biggest change in the regime of humidity was given in those towns that had a regimen hydric dry subhumid to semi-arid, that were located to the west of the isohyet
of 800 mm, corresponding to the oldest period.
For the delineation of the dry-farming limit, Nutzel mentions the 300/350 mm isohyet
, while most researchers in the Near East actually define the 250 mm isohyet
as the theoretical dry-land farming limit.
Furthermore, there is almost no dry farming in the Karoo (which leads to much greater infiltration of water), as it has been banned below the 16 in (400 mm) isohyet
, except on soils more than 4 ft (1.2 m) deep.
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 ~1.2mg/L (-0.5 t/[km.sup.2].year).
The 600mm annual isohyet
fringes our northern borders, comparisons may be odious.
The Sahara, the world's largest desert, covers an area of approximately 8.6 million [km.sup.2], including the area below the 4 in (100 mm) mean annual rainfall isohyet
. It stretches 3,418 mi (5,500 km) from east to west along the 20th parallel from Port Sudan (Sudan) on the Red Sea at 37[degrees]E to Nouadhibou (Mauritania) on the Atlantic coastline at 17[degrees]W.
The increase in mean annual rainfall in Moav and Edom, situated south of the west-east section of the 300 mm isohyet
in Israel, is related to the orographic influence of the high elevation of this area.
By world standards, the 500mm isohyet
divides crop from pastoral agricultural potential.
Much of the scrub of northern Africa and the wastes and scrubs of the Iberian Peninsula above the 8 in (200 mm) annual rainfall isohyet
are secondary in nature, derived from forests of Aleppo pine (Pinus halepensis), junipers (Juniperus phoenicea, J.
The ecological region known as the Sahel lies south of the Sahara, between the 4 in (100 mm) and the 24 in (600 mm) annual rainfall isohyet
. It occupies a strip 373 mi (600 km) wide (from north to south) and 3,107 mi (5,000 km) long (from west to east) and thus occupies roughly 3 million [km.sup.2].
Jun-Sep 2017 precipitation (mm) for West Africa: (a) total accumulation; 100-mm isohets (red dashed line), 600-mm isohyets
(red solid line), (b) Departure from 1981-2010 climatology.
The average annual rainfall is defined by the continental equatorial regime, with annual isohyets
around 700 to 1,200 mm.
The six rainiest day's isohyets
in the flooding window, November-December 2011.
Mean rainfall isohyets
have shifted by more than 185 km southwards (Jauro, 2007).