Michael Percy writes

I was talking about land with less than 10 inches of rain avg, in your
setting that would start well south of Catherine.

What I am trying to point out to you is that the rainfall per se is not
the only, nor often, the most important aspect of aridity.

IT depends on the transpiration rates and the periods where growth stops
due to lack of moisture.

In the UK, for example, were I blessed with 10" rainfall evenly spread
through the year to roughly match transpiration I would be growing
massive crops with nary a worry in the world.

Equally someone with 30" of rain in low latitudes and high daytime
insolation and temperatures and with much of it coming erratically in a
few summer cloudbursts is going to be very arid indeed.

--
Oz
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