by Yevgeni DEMIN, Cand. Sc. (Tech.), consultant/development engineer, TOO R&D center "Russian Testing of Automatic Facilities"; Viktor KUSHIN, Dr. Sc. (Tech.), laboratory head, Research Institute of Theoretical and Experimental Physics; Dmitry IOSELIANI, leading engineer of the same institute
Sahara, the largest desert of our planet that occupies a fourth of Africa's territory, is often compared to a tumor. The metaphor reflects the sad situation, what with the abnormal soil erosion and weathering-processes producing ever larger tracts of barren sands.
Yes, Sahara keeps expanding, gobbling up ever more territories. A number of untoward factors speed up desert encroachment, such as northeastern trade winds, intensive solar radiation, forest felling, trampling (with pastures devastated by cattle), and overlong droughts, especially in areas at latitude 18N. These droughts entailed disastrous consequences in the 1970s, when all of the cattle and the larger part of farm crops perished.
And yet a retrospective study of archeological evidence shows that Sahara's climate was rather humid about ten thousand years ago. During the Ice Age this land lay in the zone of normal or lower pressure. So the inhabitants could till land, go huning and even fishing! But then change set in: the atmospheric pressure started moving up, and anticyclonic processes in the atmosphere turned into a dominant factor.
Now, speaking of anticyclones: their scenario is as follows. Drawn from the cold layers of the troposphere, the air goes down and warms. The weathermen say that this process is stable in deserts which are a region of enhanced atmospheric pressure. Under like conditions (typical of Sahara and also of dry districts of California, USA, and Mexi-Articles in this rubric reflect the opinion of the authors. -Ed.
со) as good as no clouds are formed, hence there is scant precipitation. Besides, the absence of shade and the intensive reflection of solar light by sand contr ... Читать далее