WEATHER MODIFICATION BY AIRCRAFT CLOUD SEEDING

BERYULEV G.P.

Head,
Department of Cloud Physics and
Weather Modification
Central Aerological Observatory
Rosgidromet, Russian Federation

:: Excerpt ::

Improving weather conditions and flush flood control

Throughout the halfcentury history of the artificial modification of hydrometeorological processes, which is an important direction in experimental meteorology, the focus of attention has been on designing techniques and technical aids to dissipate clouds and fogs, as well as to prevent or reduce precipitation.

In particular, it is practicable to carry out artificial weather modification operations aimed at:

A. Dissipation of stratiform clouds.
B. Destruction of cumulonimbus clouds by a dynamic technique in order to prevent shower rains and thunderstorms.
C. Inducing an early fall out of precipitation from cloud systems on the windward side of a target area through artificial seeding of these cloud systems, which leads to the formation of a ‘shadow‘ of precipitation, i.e. to precipitation reduction over the given site.

To crystallize one cubic km of supercooled cloud, it is usually enough to seed it by several hundred grams of dry ice or several grams of silver iodide. After seeding a cloud or fog by ice particles in favorable conditions an intensive cloud crystallization process begins, and in 510
minutes ice crystals are observed to fall out of the cloud.
In this case, one passage of a seeding airplane results in producing a dissipation zone with an average 35 km width. The full clearing of the target site from cloud drops and precipitation particles occurs in 35-50 minutes after seeding.

Aircraft liquid nitrogen generator of ice particles

The methods to destroy developing convective clouds differing in intensity, from cumulus congestus to cumulonimbus, using a dynamic technique, i.e. artificially generated downdrafts, were theoretically justified by scientists from the Russian Institute of Applied Geophysics and thoroughly tested under laboratory and field conditions by specialists from the CAO. It has been found out that downdrafts in the upper cloud part can be produced by an artificial air jet directed downward, through seeding powders or dispersing water mass in it.

The seeding of 30 kg or more of coarsedispersion powders (per cloud top) resulted in the destruction of singlecell isolated clouds within 10-20 minutes and frontal ones within 30-35 minutes.

Results of improving weather conditions during festivities to mark Moscow Day ( 1 September, 2001 )

The other two methods out of the four mentioned at the beginning of this section use weather modification techniques similar to that employed in the first method aimed at the dissipation of clouds and fogs. The zone of reduced precipitation is commonly referred to as “precipitation shadow”. In both cases it is possible to estimate the distance of advance seeding relative to the protected territory so as to prevent undesirable clouds and precipitation from reaching it.

In some synoptic situations, overseeding may prove to be the most appropriate procedure. This is due to its capability to reduce precipitation significantly and to its faster action facilitating the
production of an artificial crystallization zone (with reduced or no precipitation) over a protected territory, which is especially important in conditions of a complex and variable wind field. In cloud overseeding operations, the distance of seeding paths from the borders of a protected territory is chosen so as to be approximately the same as the distance of a halfhour or one hour wind transport of clouds.

The methods described can be applied with the help of instrumented aircrafts. Instrumentation includes systems to release pyrotechnic flares, devices to seed granulated dry ice, generators of ice particles, using liquefied nitrogen, and systems to introduce 25-30kg powdery material packages which open automatically after their release. All the procedures and technical aids described above were employed successfully in the activities associated with eliminating the consequences of Chernobyl disaster and improving weather condition in Moscow (November 7, 1986; May 89, 1995; September 5-7, 1997; July 13 and 19, 1998; May 9, 2000; September 23, 2000; September 12, 2001; June 12 and 15, 2002; August 31 and September 1, 2002), Tashkent (1994-2002), and Astana (June 9-10, 1998).

Source www-das.uwyo.edu/

WEATHER MODIFICATION BY CARBON DUST ABSORPTION OF SOLAR ENERGY

by w. M. Gray, W. M. Frank, M. L. Corrin and C. A. Stokes

Department of Atmospheric Science
Colorado State University
Fort Collins, Colorado
July, 1974

:: Excerpt ::

The five papers of this report have been written in an attempt to open up a new dialogue among meteorologists and other scientists on the possibility of meso-scale weather modification through carbon dust interception of solar energy...

...Most of the sun r S energy penetrates through the earth's atmosphere to the surface. A large direct atmospheric heat source would result if some of this incoming solar energy could, instead, be absorbed directly within the atmosphere...

Method of dispersion

It appears that it will be possible to manufacture small'" 0.1 micron (~) size carbon particles directly from liquid petroleum products (i.e. hydrocarbons) on aircraft or from ship or land surface sites...

...Preliminary cost analysis indicates that the cost 'of air dispersal of large amounts of carbon black from aircraft would be 2-3 times the price of the carbon black itself. Even so, the available heat per unit cost is very large. The amount of solar heating per unit cost which can be realized using a carbon dust cloud seems to be large enough to permit cost effective large scale weather modification...

...Redispersion of carbon made previously. Commercial carbon black has been taken aloft in various aircraft and has been dispersed into the air through venturi devices utilizing air flow to produce the necessary shear of particles for dispersion. This method is judged impractical for the large amount of carbon discharge required by this proj ect. Between 200 and 1000 bags per hour of beaded carbon would have to be handIed, opened, finely ground and fed through a disperser. While this might be done in a large aircraft (e.g. a Boeing 747), the cost of modifying and equipping the aircraft would be very large. A special crew of about 5 to 10 people would be required to handle the carbon in a plane. Degree of dispersion would leave much to be desired, and this alone could make this method impractical...

Use of a ram jet engine



This could be done except that such engines are not currently in use. An afterburner is in effect a ram jet added to a turbine jet engine. We mention this possibility only to indicate that it has been considered...

...It is necessary to have a stable, noncorrosive fuel which is liquid and pumpable at a reasonable temperature, preferably not much over 100F. This condition can be met with certain commerical carbon black fuels. Some of the regular aircraft fuel tanks can be used provided precautions are taken against possible damage of any rubber or plastic linings, fittings, seals, etc. by the carbon fuel...

...An ideal aircraft would be a B-52 with its 8 afterburner engines, which could be modified. Somere-piping of the fuel tanks would also required. During take off all engines would be used in the normal manner. In the air 4 engines would be switched to carbon production...

...We have concluded that by slightly modifying readily available jet engines carbon dust particles could be produced and dispersed into the air at a rate of 20-30,000 pounds per hour per engine. Roughly half of the weight of the carbon fuel would appear as carbon particles resulting in a carbon particle production cost of about 4~-6C per pound...

...A program for the development and testing of prototype carbon particle generating engines using existing jet aircraft engines and test facilities has been proposed and outlined in a feasibility study report by the author and Reed (1973)...

...This higher TRW frequency is believed to result from the terrain induced elevated heat sources which produce steeper lapse rates and enhanced upslope convergence. These elevated sources or "Hot Spots" produce more than seven times as many TRW's per unit area as the Plains region to the east. The question then arises as to whether it is possible to artificially generate similar types of elevated heat sources using carbon dust dispersed from aircraft?

Engineering and field test program

Engineering tests. Paper III discussed the technical feasibility of carbon dust generation from jet aircraft engines. No insurmountable problems are envisaged. However, much study and testing must go on before all of the engineering technicalities of the best method of carbon dust generation can be specified. In the initial development stages of this project, field programs will probably be accomplished from ground sources only. The deployment and alteration of jet aircraft is believed to be too expensive for early tests. This can be accomplished at a later date. The exact modifications to an existing jet engine required to produce the necessary sizes and amounts of carbon dust must be better determined. First, an after-burner type jet engine must be obtained and testing begun to determine the quantity, particle size, cost, etc., of the carbon generated. A sub-contractor must be found to set too engine up and test it. There are few jet engine test facilities in the United States. At certain of these facilities, such as the Naval Air Station in Trenton, New Jersey, testing would probably not be feasible because of the large smoke plume. The Air Force has test facilities at remote sites in Tennessee and at Edwards Air Force Base in California. Smoke testing is possible at these locations. Another facility is located in a jungle type region near West Palm Beach, Florida.

Design considerations

There are two types of design considerations. One is a modification required for any testing, ground or airborne; the other is the support and structural features which will be required for the modified engine ta enable it to be mounted on an aircraft. It is proposed that all questions relating to how the engine would be mounted on an aircraft be deferred until ground level testing problems have been solved.

Source ams.allenpress.com