WO2000033638A1

WO2000033638A1 - Artificially prepared surface for inducing rainfall

Info

Publication number: WO2000033638A1
Application number: PCT/US1999/029180
Authority: WO
Inventors: Arthur R. Cogswell; Lawson P. Wynne; Peter J. Robinson
Original assignee: Cogswell Arthur R; Wynne Lawson P; Robinson Peter J
Priority date: 1998-12-10
Filing date: 1999-12-09
Publication date: 2000-06-15
Also published as: AU2047900A; WO2000033638A9

Abstract

Artificially prepared surface for inducing rainfall. A size, shape, and placement is determined for a dark pattern (20, 22, 24, 26) to be applied to terrain surface (11). A darkening agent is applied to form the dark pattern (20, 22, 24, 26). Its size, shape and placement are calculated to enable it, by its higher temperature due to increased absorption of solar energy, to heat air flowing over it sufficiently to cause a convection current (18). The current penetrates a low altitude, temperature inversion (16) and allows moist surface air to rise so that precipitation can be formed by normal atmospheric mechanisms.

Description

ARTIFICIALLY PREPARED SURFACE FOR INDUCING RAINFALL

DESCRIPTION

Technical Field This invention is related to the use of a surface prepared on the terrain to induce convection currents or upward air movement to influence climate. Typically these currents are induced to penetrate a temperature inversion layer, thus permitting natural mechanisms to cause rainfall; however, other uses are possible.

Background Art

In regions along the 30^th Parallel of latitude low-lying temperature inversions prevent atmospheric mechanisms from producing rainfall. The temperature inversions are formed when air which has been heated over the equator rises into the stratosphere. It returns to earth along the 30^th Parallel replacing air which is flowing towards the equator to be heated and repeats the cycle. This creates the summer trade winds flowing from the Northeast toward the Southwest. As the falling air encounters the air mass near the Earth's surface, the interface between them is heated by several degrees by friction and compression. This forms the inversion as shown in FIG. 1. In FIG. 1 , air temperature 13 decreases with altitude. The increased reflecting tempera- ture inversion 16 can be seen. Descending air 10 from the stratosphere encounters surface air mass 12 and forms temperature inversion 16 which has been warmed by compression and friction. Thus it is warmer than rising most air 17 rising from the desert floor 11. Thus inversion 16 blocks rising moist air 17 from rising further. Where rainfall has been scant for reasons like those illustrated above, there have been attempts in the past to induce precipitation. Primarily these have been by seeding clouds with particles around which moisture will coalesce into raindrops. These attempts have been at times quite successful over very limited geographic ar- eas. A disadvantage is that these attempts are generally dependent upon the presence of existing cumulus formations and the results are fairly localized.

In the 18^th and 19^th centuries there were attempts at causing rainfall by discharging cannon into cloud formations. Any results were presumably coincidental. So far as is known, there has been no system developed heretofore that will induce rain- fall reliably, predictably, and repeatedly.

Disclosure of Invention This invention makes it practical to modify the trade wind inversion in order to force cloud formation and rainfall. According to the invention, a surface air mass is heated to induce convection by first determining a size, shape, and placement for a dark pattern to be applied to a terrain surface. The determination is made by observing the terrain surface and observing local climate conditions. A darkening agent is applied to the terrain surface to form the dark pattern on the terrain surface. The size and shape of the dark pattern is selected so that solar energy absorbed by the dark- ening agent causes the surface air mass to be heated to a temperature at which convection, or an upward draft, results. Thus, an apparatus is formed from the darkening agent that causes convection or updraft air currents. To produce rain, the convection must be sufficient to penetrate the inversion layer so that normal atmospheric conditions operate to produce rainfall. Ideally, the dark pattern is substantially trapezoidal in shape and is aligned so that its longest axis is substantially parallel to the direction of the local, seasonal, prevailing winds. To produce rain across a region, a plurality of these dark patterns are installed which produce overlapping rainfall so that an entire region is transformed and arid land can be reclaimed. Earlier methods, such as cloud seeding, could not accomplish this. When multiple patterns are used in this way, the size, shape, and placement of each is calculated, either prior to applying any darkening agent, or in the field as the patterns are formed.

This invention provides a reliable method of artificially inducing rainfall in areas where prevailing low altitude temperature inversions inhibit the natural processes which produce rainfall elsewhere. The results of implementing the invention include: increasing vegetation; increased consumption of carbon dioxide, reversal of desertifi- cation of some areas; and, significant stimulus for economies of areas depressed by drought and famine. It is also possible to use the induced convection currents for other purposes than producing rainfall, such as the dispersal of smog over heavily populated areas.

Brief Description of Drawings

FIG. 1 shows, in section, the air descending from the stratosphere to encounter the surface air mass, forming an inversion which blocks upward air movement. FIG. 2 shows air flows when the invention is employed, where moist air flows over the darkened pattern and is heated, sufficiently to enable it to penetrate the inversion.

FIG. 3 shows a generalized shape of the darkened pattern.

FIG. 4 shows a modified shape of a darkened pattern.

FIG. 5 shows another modified shape of a darkened pattern.

FIG. 6 shows another modified shape of a darkened pattern, this time with irregular sides.

Best Mode for Carrying Out the Invention It is the purpose of this invention to provide a means of penetrating the prevail- ing temperature inversion in order to permit the natural atmospheric mechanisms to generate rainfall. Specifically, a darkening agent is applied to selected areas of the desert where extensive bare rock is exposed. The darkening agent is composed of a formulation that absorbs solar energy. Any black substance will do well. Numerous paints and coating which are commercially available can be used. This will reduce albedo, or reflectivity, of the surface relative to the surrounding area. This will cause the stony surface to be heated under the influence of daytime solar radiation significantly more than it would be if it were not dark. It, in turn, will superheat the air flowing over it. In FIG. 2, we see that darkened area 28 placed on desert floor 11 superheats rising air 18. This provides required temperature differential 15 between normal air temperature 13 and superheated air temperature 14. Thus superheated air 18 is warm enough when it encounters inversion 16 (formed by descending air 10) to pene- trate it. As a result, the normal atmospheric mechanisms resume: the air continues to rise, cool, and reach its dew point when condensation results. Latent heat is then released and the upward air motion is further accelerated. The end result is a thunderstorm at altitude.

The invention is a sharp-edged pattern of dark color as shown in Figures 3, 4, 5, and 6, placed on bare rock or gravel surface in the desert. The area of the pattern shown in FIG. 3 is in the range of 3 to 50 square kilometers or more. All of the dimensions are variable according to local meteorological conditions. These will be individually calculated in the field for each site from locally prevailing wind speed, wind direction, relative humidity, and other factors for optimum effect. Referring to FIG. 3, the general case, the pattern 20 is two-dimensional except for following the contours of the rocky terrain upon which it is placed, and consists of dark material placed on the rocky desert floor. FIG. 4 shows a rectangular pattern 22. In the preferred embodiment, it is aligned parallel to the seasonal prevailing winds. It is also two-dimensional, with the sides composed of straight lines, irregular lines, and arcs and of the same nature as in FIG. 3.

Figures 5 and 6 show patterns 24 and 26, respectively. These exhibit a tapered modification of that shown in FIG. 4, with FIG. 6 demonstrating a similar pattern but with irregular and inexact boundaries. A dark pattern is established on the rocky surface of the desert, the shape and extent of which is related to the local conditions of wind direction and speed, humidity, and other meteorological factors as described. When sunlight strikes the pattern, it is heated because of its dark color to a higher temperature than is the surrounding ter- rain of lighter color. The air passing over it is in turn heated sufficiently to offset partially the cooling which occurs naturally as air rises. As a result, when the rising warm air mass encounters the temperature inversion above it the air is still of a higher temperature than the inversion. Consequently, the rising air passes through it and continues to rise unimpeded and the natural sequence of cooling, cloud formation, and precipitation then ensues.

Making reference again to Fig. 3, Fig. 4, Fig. 5, and Fig. 6, the pattern would be established on the earth's surface generally as shown. Each will reflect modifications in the shape, angle of taper or in the dimensions of width and length to allow for local meteorological conditions. Placement of the pattern would be accomplished most conveniently by aerial spraying utilizing a darkening material. The applied material would be so then as to be substantially two-dimensional. Thickness could be anywhere from less than 1 mil to several tens of mills, but would typically be from 1 to several mills.

There are extensive areas in the earth's deserts where bare windswept rock surface is exposed and it will be in such areas that these patterns will be placed. A location where wind has scoured the surface clean and has exposed bare rock or stony debris over a wide area is preferable. Such areas are to be found in a number of locations along the 30th Parallel. The area to be prepared is in the range of 3-50 square kilometers in extent and has a shape as described above. Especially favored will be sites which are so located as to receive moist surface winds flowing from the sea and have the appropriate ground conditions described above.

The darkening substance is applied in as uniform a covering as can be practically achieved and with as sharp an edge as can be achieved. As the air moves longitudinally over the pattern it will begin to rise slightly and cooler air will begin to move in from the sides at the surface allowing the warmed air to begin to rise.

In the general case, the darkened area has an area in excess of three square kilometers but may be considerably larger to suit individual local conditions. The dark- ening need not be absolutely uniform nor need it be extremely dark. It is important that the edges be relatively sharp so that there will be a marked localized differential in surface heating between the darkened surface and the adjacent untreated surface. If this is so, it will be possible for relatively cool air from the sides to sweep in beneath the heated air mass and release it from the surface. This will enable the heated air then to rise as a vigorous updraft and penetrate the temperature inversion above it. This moist air will continue to rise through the inversion, accelerating when condensation releases latent heat at dew point until precipitation results at a higher altitude.

In order to understand the process proposed here, it is important to visualize what happens as the surface air mass flows over the darkened area throughout any given summer day. On most days at this season in, for example, North African field of operation, the air is moving generally from the northeast toward the southwest. Typical windspeed is approximately 20-25 kilometers per hour in a relatively constant flow. It will, at this rate, take several minutes to pass completely over the darkened area. It will in that time become superheated relative to the adjacent air mass which is flowing over a surface that has not been darkened. Then as the air mass begins to rise in temperature it will begin lifting from the surface. Cooler air from the sides will sweep in to replace the heated air at the surface, permitting the heated air to continue to rise. The superheated air will assume a linear shape, a ridge of hot air slanting upward to the southwest from the desert floor to form a plume of cloud some miles downwind. This will resolve itself into a line of thunderstorms generally parallel to the direction of the wind as the hot spot continues to pump warm moist air up through the inversion throughout the day. If other conditions are favorable rainfall will be gener- ated many kilometers downwind from the darkened spot lasting through the daylight hours into the early evening.

The Sahara in North Africa is a desert and Central Africa is ravaged by drought and famine because the usual mechanisms which produce rain elsewhere are blocked there. A prevailing temperature inversion, as described above, prevents rain even though there is moisture in the winds from the north. This inversion, or thin warm layer of air, is formed when air flows down toward the earth near the 30th parallel. This then moves toward the equator to replace air which has been heated by the sun and is rising into the upper atmosphere. This descending air mass encounters the air flowing over the earth's surface, also toward the Equator, and the interface between them is heated by several degrees by a combination of friction and compression, forming the inversion. Then when moist air flowing over the desert from the sea is heated and rises, it cannot continue to rise and form rain clouds because the inversion is warmer than the rising air and blocks its upward motion. Thus for this region the prevailing northerly winds may be moist, but no clouds can form and no rain can fall because of this overlying temperature inversion. Rising air associated with the Intertropical Convergence Zone over the Equator where these northerly winds meet their southerly counterpart can induce precipitation in low lati- tudes near the Equator. However, in recent years this precipitation has not been able to reach north from the Equator into the area of the Sahel where drought has been a problem.

This invention will establish the practicality of modifying the trade wind inversion in order to force cloud formation and rainfall by placing artificially darkened sharp- edged patterns on areas of windswept rocky desert. It is recognized that many areas on the desert floor are already dark in color, but typically the dark color fades from dark to light too gradually to induce the strong vertical air movement required to induce precipitation. Eventually, a line of these sharp-edged patterns could be placed every 30 kilometers or so across North Africa from the Atlantic to the Red Sea. These could create vigorous updrafts to penetrate the inversion over a wide area, carry the moisture aloft and induce precipitation over mid-Saharan mountain ranges and over famine-ridden regions of the northern Sahel.

This will make it possible to bring rain to the northern desert as well as to areas now and in Sub-Saharan Africa and make them again food producing regions with re- liable rainfall. In addition, large areas of forest and arable land should be created on the northern slopes of the Saharan mountain ranges. Further effects of this invention may include:

(1 ) a contribution to total global vegetation, (2) consequent increased consumption of carbon dioxide with beneficial effects upon the C02 balance worldwide,

(3) a reversal of desertification

(4) a significant stimulus for the economies of nations currently depressed by drought and famine

(5) possible applications elsewhere along the 30^th Parallel, north and south.

(6) the dispersal of smog over heavily populated areas

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the darkening agent can have a fibrous admixture added which will make it adaptable to terrain surfaces other than rock. In addition, the technique may be employed in shallow water or on snow for other purposes. The technique is applicable in many parts of the world.

Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than exclusively by the examples given.

We claim:

Claims

CLAIMS 1. A method of heating a surface air mass to induce convection, the method comprising the steps of: determining, by observing a terrain surface (11) and local climate condi- tions, a size, shape, and placement for a dark pattern (20, 22, 24, 26) to be ap- plied to a terrain surface (11); and applying a darkening agent to the terrain surface (11) to form the dark pattern (20, 22, 24, 26) on the terrain surface (11) of the size and shape so that solar energy absorbed by the darkening agent causes the surface air mass to be heated to a temperature at which convection results.

2. The method of claim 1 wherein the convection current is sufficient to pene- trate an inversion layer (16) so that normal atmospheric conditions operate to produce rainfall.

3. The method of claim 1 wherein the dark pattern (24) is substantially trape- zoidal in shape and is aligned so that its longest axis is substantially parallel to the di- rection of the local, seasonal, prevailing winds.

4. The method of claim 2 wherein the dark pattern (24) is substantially trape- zoidal in shape and is aligned so that its longest axis is substantially parallel to the di- rection of the local, seasonal, prevailing winds.

5. A method of inducing rainfall in a normally arid region, the method compris- ing the steps of: determining, by observing a terrain surface (11) and local climate condi- tions, a size, shape, and placement for a dark pattern (20, 22, 24, 26) to be ap- plied to the terrain surface (11); applying a darkening agent to the terrain surface (11) to form the dark pattern (20, 22, 24, 26) on the terrain surface (11) of the size and shape so that solar energy absorbed by the darkening agent causes the surface air mass to be heated to a temperature where convection results; and repeating the determining and applying steps to form a plurality of dark patterns (20, 22, 24, 26) across a portion of a region so that convection current (18) is sufficient to penetrate an inversion layer (16) so that normal atmospheric conditions operate to produce rainfall across the region.

6. The method of claim 5 wherein at least one dark pattern (24) is substantially trapezoidal in shape and is aligned so that its longest axis is substantially parallel to the direction of the local, seasonal, prevailing winds.

7. Apparatus for heating a surface air mass to induce convection, the appara- tus comprising: a darkening agent applied to a terrain surface (11) to form a dark pattern (20, 22, 24, 26) on the terrain surface (11) of a size and shape so that, given the local climate conditions, solar energy absorbed by the darkening agent causes the surface air mass to be heated to a temperature where convection results.

8. The apparatus of claim 7 wherein the convection current (18) is sufficient to penetrate an inversion layer (16) so that normal atmospheric conditions operate to produce rainfall.

9. The apparatus of claim 7 wherein the dark pattern (24) is substantially trape- zoidal in shape and is aligned so that its longest axis is substantially parallel to the di- rection of the local, seasonal, prevailing winds.

10. The apparatus of claim 8 wherein the dark pattern (24) is substantially trapezoidal in shape and is aligned so that its longest axis is substantially parallel to the direction of the local, seasonal, prevailing winds.

11. Apparatus for inducing rainfall in a normally arid region, the apparatus comprising: a plurality of dark patterns (20, 22, 24, 26) disposed across a re- gion, each dark pattern (20, 22, 24, 26) further comprising a darkening agent applied to a terrain surface (11) to form a dark pattern (20, 22, 24, 26) on the terrain surface (11) of a size and shape so that, given the local climate condi- tions, solar energy absorbed by the darkening agent causes the surface air mass to be heated to a temperature where convection results, the number of dark patterns (20, 22, 24, 26) sufficient so that so that the convection current (18) penetrates an inversion layer (16) so that normal atmospheric conditions operate to produce rainfall across the region

12. The apparatus of claim 11 wherein at least one dark pattern (24) is sub- stantially trapezoidal in shape and is aligned so that its longest axis is substantially parallel to the direction of the local, seasonal, prevailing winds.