摘要：We report progresses made by our group in the elaboration of a weather engineering technology
for generating clouds and rainfalls in specific arid and semi-arid sub-tropical regions. In these regions,
large amount of humidity can be present in the low atmosphere in Spring and Summer seasons without
leading to cloud formation. This results from a too large stability of the atmosphere that inhibits thermal
convection. The Geshem technology we are developing is based on a large solar absorbing artificial black
surface of area of about 10-12 km2 set at the ground. The upward heat flux produced by this artificial heat
island dilates the lower humid air layers flowing over the artificial surface. Rainfalls could be triggered by
this system on sunny days during which the thermal convection induced by the artificial solar captor can
overcome the atmospheric stability. The dominant wind would carry the resulting clouds over an area
behind the solar absorber that can extend up to 20-40 km far from the downwind edge of the solar
absorber. We are studying the physical feasibility of the technique by computer simulations based on
mesoscale atmospheric circulation models, theoretical models and the large amount of data gathered the
recent years on numerous existing natural or inadvertent heat islands such as Urban Heat Islands (UHI)
due to cities or dark natural ground areas located at sub-tropical and tropical latitudes. In case of proven
feasibility, the Geshem system together with appropriate water management and adapted agriculture
methods could provide a new approach for locally fighting against desertification by converting small
mesoscale arid areas into farming or forest zones.
关键词：aridity, solar energy, clouds formation, weather engineering
