from Wiktionary, Creative Commons Attribution/Share-Alike License.
- adjective climatology Extremely
arid, with an aridity index of less than 0.05.
from Wiktionary, Creative Commons Attribution/Share-Alike License
These include geological formations of notable interest as scenery and as the record of a fossil hydrographic system from fluvial to hyperarid conditions; and wildlife which includes 28 plant species rare in Algeria; one, the rare endemic cypress Cupressus dupreziana, being one of twelve critically endangered plants chosen by the Species Survival Commission of the IUCN to highlight serious threats to species around the world.
The plateau is hyperarid, very exposed and barren, but there are sheltered more humid microclimates where relict Mediterranean fauna and flora survive.
During that period there were roughly four glacial cycles and, although Egypt itself was ice-free, the local climate oscillated from hyperarid to semi-arid as the Earth's orbital position drove changes in the location of the tropical rainfall belts.
Signs of the Times 2010
The map shows drylands as defined by the U.N. Convention to Combat Desertification, namely lands where annual precipitation is less than two thirds of potential evapotranspiration — from dry sub-humid areas (ratio ranges 0.50 – 0.65) through semiarid, arid, and hyperarid (ratio
"We know from literature that the human occupation of this region ended about 5,000 years ago, with the onset of hyperarid conditions.