Omnidirectional rain gauge

An Omnidirectional rain gauge measures an azimuth and zenith direction of flying rainwater. The Omnidirectional rain gauge includes catchment and measurement units. The catchment unit has a plural conical cylinders having individually different heights, and being overlaid so that bottom vertexes of the plural conical cylinders coincide with or come close to each other. The overlaid plural conical cylinders are partitioned by partitions, arranged radially in a plurality of horizontal azimuth directions, to form a plurality of catchment cells. Each of the plurality of partitions is shaped as semicircle following a virtual spherical outer circumference. Diameter of each of top opening parts opposite to the bottom vertexes, of the overlaid plural conical cylinders is sized to follow virtual spherical outer circumference. The measurement unit, by the rainwater caught by each of the plurality of catchment cells of the catchment unit dropping in a drop of water of a certain weight, detects the number of the dropping drops of water with respect to each of the plurality of catchment cells, and determines the amount of the rainwater caught by each of catchment cells on the basis of the total detected number of the drops of water.

FIELD OF THE INVENTION

This invention relates to a rain gauge, a certain aspect of which relates to an omnidirectional rain gage which measures separately the rainwater amount incoming from each azimuth and zenith direction.

BACKGROUND ART

As a conventional rain gauge, generally a rain gauge with a tipping bucket has been widely used.FIG. 1is a drawing for illustrating an overview of such the rain gauge with a tipping bucket.

The rain gauge with a tipping bucket is configured to have a conical funnel1A as a catchment unit for catching the dropping rainwater, and a tipping bucket1B which reserves a certain amount of the rainwater caught by conical funnel1A and tips over to any direction around a pivot point.

The tipping bucket1(B) includes catchment bucket units I and II respectively on the left and the right sides, each of which has the same specified capacity. When the catchment bucket unit I on one side reserves a specified amount of rainwater (FIG.1(A)), the catchment bucket unit I tips over by its weight around the pivot point and drains off the reserved rainwater. Then, the tipping bucket unit II on the other side starts to reserve the rainwater (FIG. 1(B)). Further, when the specified amount of the rainwater is reserved in the other catchment bucket unit II, again the catchment bucket unit II tips over and drains off the reserved rainwater, then the condition transits to as illustrated inFIG. 1(A).

Then, every time the tipping bucket1B tips over, a switch not illustrated is turned on. Thus, from the number of times of the switch being turned on in a specified period and the specified capacity of the catchment bucket units I and II, the total rainfall amount or the rainfall amount per unit time can be obtained.

Here, the conventional rain gauge with a tipping bucket illustrated inFIG. 1is configured to catch the dropping rainwater by the conical funnel1A. Therefore, inFIG. 2for explaining problems of the rain gauge with a tipping bucket, when the rainwater drops in the perpendicular direction under a windless condition (FIG.2(A)), rainfall amount can be measured accurately.

However, as illustrated inFIG. 2(B), when the rainwater drops in the inclined direction under a windy condition, the cylindrical outer shape causes inconsistency of the surrounding wind and the amount of the rainwater which cannot be caught by the catchment surface at the top of the cylinder increases. In such a case, an accurate measurement of the rainfall amount becomes difficult.

For example, on a steep inclined land, the rainwater comes flying in the horizontal direction by a wind blowing up, theretofore, an accurate measurement of the rainfall amount by the conventional rain gauge with a tipping bucket as illustrated inFIG. 1is difficult.

To address such problem, improvements on the catchment unit have been proposed (examples are illustrated in Patent documents 1 and 2).

An invention described in Patent document 1, relates to a rain gauge with a tipping bucket having a spherical catchment unit (or water gathering unit), for the place of the funnel1of the rain gauge with a tipping bucket. That is, the invention of patent document 1 has such configuration as to gather the rainwater caught by the spherical catchment unit having a circular catchment plane which can be projected as a certain circular area to all azimuth and zenith directions.

An invention described in Patent document 2 has a semispherical catchment unit, instead.

Patent Document 1: Japanese Laid-Open Patent Publication 2006-17462

Patent Document 2: Japanese Laid-Open Patent Publication 2003-21689

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Present Invention

By the inventions described in the above-mentioned Patent documents 1 and 2 having the catchment units of either spherical or semispherical shape, it is possible to catch incoming rainwater flying from all azimuth and zenith directions all together and to measure the amount of caught rainwater by a tipping bucket underneath.

However, the configurations of the inventions described in Patent documents 1 and 2 are not for measuring both of the rainfall amount and the direction which the rainwater comes from.

That is, since the rainfall amount is described as the thickness of the rainwater which drops on the horizontal surface of the ground, for converting the amount (the weight) of the caught rainwater into the thickness, the weight needs to be divided by the area of the horizontal surface (the projected area on the horizontal plane of the catchment surface), and by the density of water (the weight per unit volume).

Therefore, in order to convert the amount of the rainwater into the thickness in case that the catchment unit is not placed on the ground, information about the dropping area of the rainwater caught by the catchment unit, such as which region on the ground the rainwater drops. The reason for this is because the dropping area depends on the dropping direction (zenith angle) of the rainwater.

Nevertheless, since the above-mentioned Patent documents 1 and 2 do not have any descriptions about the measurement of the dropping area, the inventions described in Patent documents 1 and 2 are not desirable for measuring the rainfall amount.

Further, as a conventional method for measuring rainfall amount, a method for calculating the rainfall amount, as illustrated inFIG. 1, on the basis of the number of times the tipping bucket1B of a certain capacity tips over is adopted. Therefore, some errors may be observed, with regard to the accuracy of the measurement of the rainfall amount, at most in the range of the certain capacity of the tipping bucket1B.

Also, as another technology for improving the measurement accuracy by using more complicated configuration, a technology is known for measuring the rainfall intensity by a light-emitting unit generating infrared laser bundle and by detecting the light scattered by the rainwater passing between the light-emitting unit and a light-receiving lens and being exposed to the laser bundle. Or, another technology is proposed for measuring the rainfall amount by gathering the rainwater from a cylindrical catchment cylinder into a chamber, sucking the retained water by a siphon tube, and sensing the amount of the sucked water by a capacitance sensor. However, in case of using these methods, the configurations are complicated and not desirable for measuring rainwater coming from each azimuth and zenith direction.

Therefore, the objective of the present invention is to provide an omnidirectional rain gauge which can measure the rainfall amount with respect to each azimuth and zenith direction by a facilitated configuration and with high accuracy, and a method for calculating the distinct direction, which rainwater comes from, by using the omnidirectional rain gauge.

Means for Solving the Problems

To achieve the above-indicated objective, according to a first aspect of the present invention, an omnidirectional rain gauge includes a catchment unit to catch rainwater; and a measurement unit to measure the amount of the rainwater caught by the catchment unit; wherein the catchment unit includes:

a plurality of conical cylinders which have individually different heights, and are overlaid so that bottom vertexes of the plurality of conical cylinders coincide with or come close to each other;

the overlaid plurality of conical cylinders are partitioned by partitions, which are arranged radially in a plurality of horizontal azimuth directions, to form a plurality of catchment cells;

each of the plurality of partitions is shaped as semicircle following a virtual spherical outer circumference;

the diameter of each of top opening parts, which are opposite to the bottom vertexes, of the overlaid plurality of conical cylinders is sized to follow the virtual spherical outer circumference; and

the measurement unit, by the rainwater caught by each of the plurality of catchment cells of the catchment unit dropping in a drop of water of a certain weight, detects the number of the dropping drops of water with respect to each of the plurality of catchment cells, and determines the amount of the rainwater caught by each of the plurality of catchment cells on the basis of the total detected number of the drops of water.

To achieve the above-indicated objective, according to a second aspect of the present invention, a rain gauge includes a catchment unit to catch rainwater; and a measurement unit to measure the amount of the rainwater caught by the catchment unit; wherein the catchment unit comprises a plurality of funnels which have tubes of individually different diameters at the bottom parts, and are overlaid so that the tubes are inserted into one another in the order of the diameters;

the plurality of overlaid funnels are partitioned by a plurality of partitions, which are radially arranged in a plurality of horizontal azimuth directions, to form a plurality of catchment cells;

each of the plurality of partitions is shaped as semicircle following a virtual spherical outer circumference;

the diameters of the upper openings of the plurality of overlaid funnels are sized to follow the virtual spherical outer circumference; and

the measurement unit, by the rainwater caught by each of the plurality of catchment cells of the catchment unit dropping in a drop of water of a certain weight, detects the number of the dropping drops of water with respect to each of the plurality of catchment cells, and determines the amount of the rainwater caught by each of the plurality of catchment cells on the basis of the total detected number of the drops of water.

In the first aspect or the second aspect described above, the measurement unit is configured to include:

a plurality of tubes of the same diameter, each of which is connected to the inside of water pipes provided at each of the bottoms of the plurality of catchment cells;

a switch unit which has a plurality of switches each of which is provided corresponding to each of the plurality of tubes; and detects drops of water which drop from the bottom tip portion of each of the plurality of tubes; and

a processing unit which counts the number of the drops of water detected by the switch unit and converts the number into the amount of rainwater caught by each of the plurality of catchment cells

In the first aspect or the second aspect described above, the omnidirectional rain gauge is further configured to include:a second catchment unit for catching the drops of water which pass through each of the plurality of switches; and the processor unit which aggregates the amount of the drop of water caught by the second catchment unit, and determines, when there is a difference between the aggregated amount of the drop of water and total amount of rainwater caught by each of the plurality of catchment cells, that the difference is the amount of rainwater caught by a catchment cell which does not detect the amount of the drops of water.

Further, in the above aspect, each of the plurality of switches of the switch unit is featured by being configured to include a pair of electrode plates facing each other placed, with respect to each of the plurality of tubes, in the position apart by a prescribed distance from the bottom tip portions of the plurality of tubes; and the pair of electrode plates becomes conducted when a drop of water dropping from the bottom tip portion of the tube, corresponding to the pair of the electrode plate, passes between the pair of electrode plates facing each other.

Further, the pair of electrode plates facing each other can be featured by being placed so that the electrode plates are parallel in the direction of dropping of the drops of water.

Also, the pair of electrode plates facing each other can be featured by being placed so that the electrode plates are parallel in the direction of dropping of the drops of water and by including holes through which water drops pass.

EFFECTS OF THE INVENTION

The above configurations according to the present invention provide the following advantageous effects.(1) The omnidirectional rain gauge in accordance with the present invention catches the rainwater from all spatial directions, with the catch ratio of nearly 100%, and thus can measure an accurate rainfall amount. By using the rain gauge of the present invention, it will be found that all the rainfall amount measured by rain gauges used in the past all over the world were underestimated.

For example, in a wind-prone region such as the top of Mount Fuji where the rainwater comes from the horizontal direction or even from the downward direction, the conventional rain gauge cannot catch such rainwater at all, therefore installation of rain gauges has been abandoned. In contrast, the rain gauge of the present invention enables the installation and the measurement.

Also, the rainfall amount relates to an estimation of the rainfall amount in a reservoir area or to an estimation of the downpour amount or the underground filtration amount at the time of landslide disaster on slopes, and thus the rainfall amount is inevitable and the most fundamental data for planning various water resource managements, or for preventing natural disasters such as landslides etc. In this context, using the rain gauge of the present invention can replace or correct the past estimation of rainfall amount of higher accuracy in conjunction with the land topography.(2) The measurement accuracy of the rain gauge of the present invention (depending upon the weight of a drop of water passing through electrode terminals of a switch unit (approximately 0.1 g) and consistency thereof) can be significantly improved as much as more than 100 times of that of the conventional rain gauge with a tipping bucket, and thus it is possible to detect a very little rainfall (less than 0.5 mm) at the time of drizzle, which cannot be detected by the conventional rain gauge, and to measure the rainfall amount thereof.(3) By applying the present invention, the rainwater can be caught and measured, and the measured result can be converted into the rainwater amount which collides with the ground of slope with an arbitrary azimuth direction and inclination. Therefore, the rain gauge of the present invention can make a great difference in the rainwater amount colliding with the ground of the windward slope and that of the leeward slope when a typhoon hits, which cannot be given by the conventional rain gauge. Also, contribution can be expected to studies and forecasts of occurrences of many disasters such as floods, caused by heavy rainfall.

EXPLANATION OF REFERENCE NUMBERS

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are explained below with reference to accompanying drawings. The embodiments are for illustrating the present invention, however, the application of the present invention is not limited thereto.

FIG. 3is a drawing to illustrate a first configuration example of a water catchment unit of an omnidirectional rain gauge according to the present invention.FIG. 3(A)is a drawing to illustrate a picture of the configuration of the water catchment unit observed from a lateral view, andFIG. 3(B)is a drawing to illustrate a picture thereof from the above with an angle.

In the example illustrated inFIG. 3, the water catchment unit1is configured to have semicircle-plate-shaped catchment walls (referred to as “partitions” hereinafter)101-104, which are arranged radially in four horizontal azimuth directions, and three funnels111-113, which are shaped in circular truncated cone spread along the inclination in different directions, so that the partitions101-104and the funnels111-113are crossing one another.

Alternatively, the rain gauge has a plurality of funnels (conical cylinders)111-113which have individually different heights and are overlaid one another with the apexes facing the bottom coinciding with one another. The overlaid conical cylinders111-113are partitioned by the partitions101-104which are arranged radially in a plurality of horizontal azimuth directions. It can be explained that each of the partitions101-103are shapes as semicircles following the virtually spherical outer circumference, and that the diameters of the bottom planes and the diameters of the top planes of the overlaid conical cylinders are sized as to fit the virtually spherical outer circumference.

By this means, twelve catchment reservoirs (referred to as “catchment cells” (corresponding to channels CH1-CH12) hereinafter) are formed.

FIG. 4is a drawing to illustrate an external structure of the omnidirectional rain gauge in accordance with the present invention including the water catchment unit1illustrated inFIG. 3. A measurement unit2is provided underneath the catchment unit1.FIG. 4(A)is a drawing of a top view, andFIG. 4(B)is a drawing of a lateral view. The measurement unit2is configured to have tubes20, switch units21, and a processor unit22such as a data logger or the like.

The three funnels111-113are overlaid in such manner that inclined sides of the truncated cones, which are open upward, are placed in positions corresponding to opening angles of 45 degrees, 90 degrees, and 135 degrees along the zenith directions with respect to the center “O” of the virtual sphere, and that the apexes of the truncated cones coincide.

FIG. 5is a drawing to illustrate a configuration of the catchment unit1in a skeletal structure to facilitate understanding. Heavy lines indicate the catchment cell corresponding to the channel CH6, which is formed by segmentation by the funnels112and111, and the semicircle-plate-shaped partitions101and102.

At the bottom of each of the catchment cells corresponding to twelve channels CH1-CH12, a water conducting hole is provided, which is connected to each of the twelve tubes20of the same diameter. At the lower left ofFIG. 5, a cross-sectional view of a tip portion of the tubes20is illustrated.

To return toFIG. 4, a switch unit21is provided underneath the twelve tubes20.

As a practical example, the switch unit21includes switches which are conducted by drops of water dropping from the bottom tip portions of the tubes20.

FIG. 6is a schematic drawing to explain a switch of the switch unit21. In the upper part ofFIG. 6, an arrangement of the twelve channels CH1-CH12formed by the twelve tubes20is schematically illustrated in a plane view.

Further,FIG. 6illustrates a status of drops of water dropping from the tube20which is corresponding to the channel CH5among the twelve channels CH1-12.

Further, inFIG. 6, corresponding to each of tubes20for twelve channels CH1-CH12, a pair of electrode plates201aand201bis provided in a position apart downward by a distance D from each of tubes20.

The height D is set so that drops of water dropping from the tubes20are reaching the pair of electrode plates201aand201bin drops of approximately the same diameter.

The drops of water dropping from the tube20corresponding to the channel CH5become spherical shape of approximately the same size while dropping as far as the distance D, and reach the pair of electrode plates201aand201bwhich is then made electrically conducted.

Thus, the number of times of the electrical conduction of the electrode plates201aand201bcorresponds to the number of drops of water, therefore, from the weight of a single drop of water and the number of drops of water, the rainfall amount which is caught by each channel of the catchment unit1can be determined.

FIG. 7is a drawing to explain a bottom tip portion of the tubes20and a pair of electrode plates201aand201bin a partially magnified view.

Underneath the tube20, there is provided a filter20A shaped as sponge net. By this means, the rainwater dropping from the tube20can drop in the drops of water of the same diameter and thus of the same weight.

As illustrated inFIG. 7(A), the pair of electrode plates201aand201b, corresponding to a catchment cell (a channel CH) of the catchment unit1, is located in a position apart by the distance D from the bottom of the tube20, and each of the pair of electrode plates201aand201bis connected by conducting wires to a processor unit22such as a data logger or the like. And as illustrated inFIG. 7(B)which is a magnified view of the pair of electrode plates201aand201b, when drops of water drop passing between the electrode plates201aand201b, the electrode plates201aand201bbecome electrically conducted. By this means, counting the timing of the conduction by the processor unit22such as a data logger or the like is possible.

As a practical example, the diameter of each of the twelve tubes20corresponding to twelve channels was configured to be 10 mm. And water conducting tube20B which had the length of 10 mm and a diameter of 5 mm was provided underneath the filter20A. At this time, the weight of a drop of water passing between the pair of electrode plates201aand201bwas 0.14 g.

FIG. 8is a drawing to illustrate a second configuration example of the catchment unit of the omnidirectional rain gauge in accordance with the present invention.FIG. 8(A)is a diagrammatic perspective view of an external appearance of the catchment unit, illustrating a status of the catchment unit placed on a catching stage221located on the top of a measurement unit which will be explained in the following.

FIG. 8(B)is a front view observed from the direction indicated by an arrow inFIG. 8(A), andFIG. 8(C)is a top view.

In comparison with the configuration of the first practical example illustrated inFIG. 4, the feature of the second practical example is such that three-tier funnels200,201and202are provided. And water pipes200a,201a, and202aof the funnel200,201, and202, respectively, which have diameters in that order, are configured to insert into one another in a concentric fashion.

Further, the tiered funnels200,201and202are partitioned into four azimuth directions by four partitions210,212, and213.

And, the diameters of the funnels200-202and the partitions210-213are configured so that the outer rims of these are in contact with the virtually spherical outer circumference220. Therefore, as with the first example, for each azimuth and zenith direction, catchment cells are formed corresponding to the partitioned twelve different directions.

The configuration of the catchment unit, as illustrated inFIG. 8, is formed by the tiered funnels of which water pipes have different diameters, and this configuration has an advantage to facilitate the manufacturing process compared with the configuration, as previously illustrated byFIG. 4, of overlaying the apexes of truncated cones which have different heights.

FIG. 9is a drawing to illustrate in a magnified view, the water pipes200a-202aoverlaid in concentric fashion observed from the downward direction of the catchment unit, when the water pipes of different diameters of the funnels200-202are overlaid in concentric fashion.

The water pipe201aof the funnel201is inserted into the inside of the water pipe202aof the funnel202, and the water pipe200aof the funnel200is inserted into the inside of the water pipe201aof the funnel201.

Further, as illustrated inFIG. 9, inside of the water pipe200aof the innermost funnel200, bottom parts of four catchment cells are formed by four directional partitions210-213which partition the funnel200. And thin tubes (for channels Ch1-Ch4) are inserted into the holes at the bottom parts, and are connected therewith.

Inside the water pipe201aof the funnel201, between the water pipe201aand the water pipe200aof a funnel200, bottom parts of four catchment cells are formed by being partitioned by the four partitions210-213. And thin tubes (for the channels Ch5-Ch8) are inserted into the holes at the bottom parts, and are connected therewith.

In the same manner, inside the water pipe202aof the funnel202, between the water pipe202aand the water pipe201aof a funnel201, bottom parts of the four catchment cells are formed by being partitioned by four partitions210-213. And thin tubes (for the channels Ch9-Ch12)) are inserted into the holes at the bottom parts, and are connected therewith.

Thus, twelve tubes for the channels Ch1-Ch12are derived from the bottom part of the catchment unit.

FIG. 10is a schematic drawing of a cross-sectional view of the measurement unit to which the twelve tubes (for twelve channels Ch) derived from the bottom parts of the catchment unit are connected.

On the top of a cylinder-shaped outer shell220, a catching stage221of the catchment unit is provided. Further, from the top of the outer shell220, connecting units222for the twelve tubes, a switch unit223having rainwater detecting switches located in positions respectively corresponding to the twelve tubes, and a catchment funnel224for catching all the rainwater are provided in that order.

The catchment funnel224has a tube224a, and has a separate water drop detecting switch225along the tubes224a.

The detail of a practical example of each component configuring such measurement unit will be explained in the following.

FIG. 11is a drawing to explain the tube connecting unit222.FIG. 11Ais a schematic drawing of a cross-sectional view of the tube connecting unit222, andFIG. 11Bis a drawing observed from the bottom side of the tube connecting unit222.

The tube connecting unit222is disk-shaped and has twelve holes Ch1-Ch12corresponding to the twelve channels for receiving each of twelve tubes. The rainwater which passed through the twelve tubes drops respectively from these holes Ch1-Ch12.

FIG. 12is a drawing to illustrate a plane view of the tube connecting unit222for the twelve tubes, switch units223, water catchment funnel224, and the catchment switch225, in the order of the alignment on the outer shell220from the top.

FIG. 12(A)illustrates the tube connecting unit222illustrated inFIG. 11.FIG. 12(B)illustrates a plane view of the switch unit223,FIG. 12(C)illustrates a plane view of the catchment funnel224, andFIG. 12(D)illustrates a plane view of the switch225.

The switch unit223is disk-shaped and has radially arranged twelve switches223Ch1-223Ch12. And the alignment positions the switches223Ch1-223Ch12correspond to positions of the twelve holes Ch1-Ch12formed on the tube connecting unit222.

Further, the catchment switch225is placed so as to detect rainwater dropping from the tubes224aof catchment funnel224.

FIG. 13illustrates a common configuration of each switch of the twelve switches223ch1-223ch12of the switch unit223and a single catchment switch225, which are referred simply as a “switch” and explained in the following.

The switch is configured by a pair of upper and lower electrode terminals210A and210B. In one practical example, the pair of upper and lower electrode terminals210A and210B has rings210bwhich have body parts210aand through holes210c.

By such switch configuration of the pair of upper and lower electrode terminals, the detection of drops or water dropping from the tubes connected to the tube connecting unit222and from the tube224aof the catchment funnel224.

In other words, as illustrated inFIG. 13(B), drops of water, when dropping, enter into the through holes210cof the switch, and contact the pair of upper and lower electrode terminals210A and210B in the interspace between them. By this means, the electrode terminals210A and210B become electrically conducted. Thus by electrically sensing this status, the detection of dropping of the drops of water is made possible.

In such configuration of the second practical example, the rainwater is detected and counted by each of the twelve switches223Ch1-223Ch12of the switch unit223. Therefore, by the same manner as explained with regard to the former practical example, detection of the rainwater dropping with respect to all the twelve cells is possible.

Here, the reason for configuring the switch by the pair of upper and lower electrode terminals210A and210B, as illustrated inFIG. 13, is because the upper and lower electrode terminals can detect with higher certainty the drops of water compared with the example of using a pair of parallel electrode terminals as explained previously inFIG. 7, even if the position at which drops of water drop is deviated to some extent in the horizontal direction.

That is, even if a drop of water R, as illustrated inFIG. 13(B), drops on a position deviated from the center of the holes of the electrode terminals210A and210B of the switch, the drop of water R can be caught.

InFIG. 13, the configuration of the pair of upper and lower electrode terminals210A and210B having rings210bwhich have the through holes210cis explained, however, important thing here is configuring the pair of upper and lower electrode terminals, and thus the shapes of the pair of electrode terminals are not limited to the example of having the rings210bwith the through holes210c. For example, U-shape such as a part of a ring is open, or merely needle-like-shape is applicable.

Further, in the configuration of this practical example, the reason for the catchment funnel224and the switch225being provided underneath the switch unit223of twelve switches223Ch1-223Ch12is as follows.

The catchment funnel224can gather the rainwater dropping further after passing through the twelve switches223Ch1-223Ch12. And the amount of the rainwater caught by the catchment funnel224can be detected by the switch225.

Here, in case that the detection of the rainwater by any of the twelve switches223Ch1-223Ch12fails, according to the configuration of the previous practical example, the rainwater of the failed cell cannot be detected.

Contrary to this, by the configuration ofFIG. 10, in case that any of the twelve switches223Ch1-223Ch12fails, difference may occur between the total rainwater amount detected by each of twelve switches223Ch1-223Ch12and the total amount detected by the switch225of the rainwater gathered by the catchment funnel224.

In such case, the difference is the rainwater amount which could have been detected by a switch which failed in the detection among the twelve switches223ch1-223ch12.

Thus the difference in the rainwater amount can be related to the rainwater amount of the cell corresponding to the switch which failed in the detection.

In this manner, by the second practical example, even if any of the twelve switches223Ch1-223Ch12fails in the detection, the rainwater amount with respect to each azimuth and zenith direction can be detected with high accuracy.

Next, a method for determining an accurate rainfall amount by using the rain gauge explained above through specifying the azimuth direction and the zenith angle in which the rainwater drops will be explained.

Here, relation between the amount (Q) of the rainwater, which comes in the spherical catchment unit placed on the ground, and the rainfall amount (P) is examined by a schematic diagram illustrated inFIG. 14.

InFIG. 14, the amount (Q, the unit: g) of the rainwater which comes in the virtually spherical catchment unit1(radius: r) placed on the ground, and the rainfall amount (P, unit: mm) are different amounts. The relation between the amount (Q) of the rainwater which comes in the virtually spherical catchment unit1and the rainfall amount (P) is described by the following formula.
Q=ρ·P/10·πr2/cos θ  Formula 1
Here, θ indicates the zenith angle of the dropping direction in which the rainwater drops with the vertex being 0 degrees. And ρ indicates the density of a rainwater, which is 1 g/cm3.

In the calculation of the projected area S (unit: cm2) on the ground of the virtually spherical catchment unit, the projected area S differs according to the zenith angle θ. InFIG. 14, the projected areas S1, S2, and S3will be studied.

Here, the projected areas S1, S2, and S3are such that S1=πr2(=S), S2(=πr2/cos θ2), and S3=(πr2/cos θ3), with the magnitude relation such that S1<S2<S3.

On the other hand, rainfall amount P1, P2, and P3for projected areas S1, S2, and S3are described as follows.
P1=10Q/(ρ·πr2)
P2=10Q/(ρ·πr2)·cos θ2
P3=10Q/(ρ·πr2)·cos θ3
Therefore, the magnitude relation of the rainfall amounts is such that P1>P2>P3.

Here, since a 3-dimensional rain gauge in accordance with the present invention measures the dropping direction (the azimuth direction and zenith angle) and the amount (the weight) per direction of the rainwater, the amount per unit area of the rainwater which hits the surface of the arbitrary direction (an azimuth direction D, and a zenith angleθ) can be calculated. On the other hand, since a 1-dimensional rain gauge such as a rain gauge with a tipping bucket cannot measure the dropping direction of the rainwater, the amount per unit area of the rainwater which hits the surface of the arbitrary direction cannot be measured. In such aspect lies the most distinctive advantage of the 3-dimensional rain gauge in accordance with the present invention.

FIG. 15is a flow diagram of the processing procedures according to the present invention for determining the rainfall amount by considering the projected area as illustrated inFIG. 14. This process flow is performed by the processor unit22such as a data logger or the like provided with the measurement unit2illustrated inFIG. 4.

For the first, upon starting processing, a time interval of the rain gauge is set, for example, as 10 minute interval (step S1).

After that, the number of drops of water passing through the switch unit21of the measurement unit2of each cell in the preset time interval (10 minute) is counted with respect to each of the twelve cells (channel: CH), and the amount of drops of water is calculated by multiplying the count of the drops of water by the weight of a drop of water (step S2).

FIG. 16Aillustrates a conversion table, in accordance with the omnidirectional rain gauge of the present invention, which converts the one rainfall for hours measured in every 10 minutes into the number of drops of water which dropped in each cell in a 10 minute interval, and into the amount of water caught in per unit surface area of the sphere (g/cm2/10min).

InFIG. 16A, the numbers of the catchment cells CH1-CH12are illustrated in the cross direction, and the numbers of the drops of water per 10 minutes (drops/10 min) are illustrated in section I in the vertical direction.

Section II illustrates the weight of drops of water (g/10 min) corresponding to the number of drops of water, calculated by the weight of one drop of water being 0.14 g.

Section III illustrates the area (cm2) of the virtually spherical outer circumference of the catchment cell, which is equivalent to the area of curved surface corresponding to each catchment cell.

Section IV illustrates the amount of water caught in a unit spherical surface area of the catchment cell (g/cm2/10 min). Since the spherical surface areas of the catchment cell differ as illustrated in the above section III, it is converted, considering the surface area, into the amount of water caught in a unit area.

On the basis of the table data ofFIG. 16A, inFIG. 15, a distinctive dropping direction of the rainwater (the azimuth direction and in the zenith angle) is calculated from the quantitative relation of the drops of water of each cell (step S3).

FIG. 16Bis a drawing for explaining a method for calculating the distinctive dropping direction of the rainwater, and illustrating aggregated values of the observed data formatted in the table ofFIG. 16Awith respect to four horizontal directions.

That is, section[A] ofFIG. 16Billustrates a group of catchment cells CH1,5, and9corresponding to the azimuth direction of 0-90 degrees, a group of catchment cells CH2,6, and10corresponding to the azimuth direction of 90-180 degrees, a group of catchment cells CH3,7, and corresponding to the azimuth direction of 180-270 degrees, and a group of catchment cells CH4,8, and12corresponding to the azimuth direction of 270-360 degrees.

In section[B] ofFIG. 16B, the horizontal azimuth direction indicating the maximum dropping amount of drops of water is illustrated by an arrow as the rainwater dropping direction of 170 degrees.

A method for calculating the rainwater dropping azimuth direction indicating the maximum dropping amount of drops of water can be explained byFIG. 17.

FIG. 17is a drawing, on the basis ofFIG. 16B, to illustrate by bar graphs in the vertical direction, the magnitude of the numbers illustrated in FIG.16B[A] in four quadrants with respect to four directions (0-90 degrees, 90-180 degrees, 180-270 degrees, and 270-360 degrees).

FIG. 17illustrates two example methods for calculating the distinctive azimuth direction of the dropping amount of drops of water.

The first method is, on the basis of all the data in the four quadrants, by assuming that the dropping amounts of drops of water of each quadrant are normally-distributed, to determine the vertex of the assumed normal distribution curve to be the distinctive dropping direction of water ([A]).

The second method is, by plotting the numbers of the top three quadrants on the sides of an isosceles triangle, to determine the vertex of the isosceles triangle to be the distinctive dropping direction of drops of water ([B]). As illustrated in section [B] ofFIG. 16B, by either of the two methods, a direction around 170 degree, in a clockwise direction with the north direction being as 0 degrees, can be determined as the distinctive dropping azimuth direction.

On the other hand, the zenith angle of the distinctive drop is determined, on the basis ofFIG. 16C, by a method which will be explained inFIG. 18.

FIG. 16Cis a drawing to explain the method for determining the zenith angle of the distinctive drop of rainwater. In the drawing, the amounts of the rainwater caught by the six cells, including the cross-section at the distinctive dropping azimuth direction of 170 degree, are selected and aligned in the order of the zenith angle.

FIG. 18is a drawing to illustrate by bar graphs in the vertical direction the magnitude of the numbers which are illustrated in FIG.16C[A].

InFIG. 18, as in the same manner of the explanation ofFIG. 17, two example methods for determining the distinctive azimuth direction of dropping zenith angle are illustrated.

The first method is, on the basis of the data of all the cells, by assuming that the dropping amounts of the drop of water of each cell are normally distributed, to determine the vertex of simulated normal distribution curve as the distinctive dropping zenith angle ([A]).

The second method is, by plotting the numbers of the top three cells on the sides of an isosceles triangle, to determine the vertex of the isosceles triangle as the distinctive dropping zenith angle ([B]).

As illustrated in section [B] ofFIG. 16C, by either of the two methods, a direction around 42 degree, with the vertex direction being 0 degrees, can be determined as the distinctive dropping zenith angle.

As described above, by determining the distinctive dropping azimuth direction and the distinctive dropping zenith angle, the distinctive dropping direction of the rainwater can be determined.

Here, in the above explanation of practical example, on the basis of an assumption such that each cell of the rain gauges of the first and the second practical examples is circumscribed with the virtual sphere, the amount of caught water per unit spherical area is calculated.

However, in actuality, a geometric correction (step S4) is necessary on a rainwater collision amount against the virtual sphere (bundles of the rainwater passing through the sphere) which is circumscribed with the catchment cells.

FIG. 19is a drawing to explain such the geometric correction.FIG. 19illustrates case [A] such that the distinctive dropping direction of the rainwater is within a range from the vertex of 0 degree to 45 degree, and case[B] of a range from 45 degree to 180 degree.

The catchment unit1is placed on the measurement unit2. Therefore, against a virtual sphere1A which is circumscribed with the catchment unit1, a plane1B which is vertical with the distinctive dropping direction of the rainwater is assumed. There occurs a difference between a projected region1C to the plane1B which is vertical to the distinctive dropping direction, and a region1D which is capable of catching the rainwater.

That is, this difference occurs in the following two regions which are incapable of catching the rainwater.

For the first, a region at the lowermost of the virtual sphere1A placed on the measurement unit2, because of having no catchment cells, is a region1E which is incapable of catching the rainwater,

For the second, a region between the walls of the cells, because of being passed through by the rainwater coming into the virtual sphere1A, is a region1F which is incapable of catching the rainwater.

Such regions which are incapable of catching the rainwater depend on the dropping direction of the rainwater (the azimuth direction and the zenith angle). Therefore, correction values with respect to each direction (corresponding to rainwater catch ratio) can be preliminarily determined on an experimental basis and programmed. The correction values may depend on the rainfall intensity, the size of a drop of rainwater, and the wind velocity. Further, in the manufacturing process of the catchment unit1, there may occur individual validities, therefore the pre-shipping examination is necessary.

In this way, at the step S4of the processing flow of the aboveFIG. 15, a geometric correction by the preliminarily determined correction value is performed.

After that, at step S5ofFIG. 15, the rainwater collision amount is converted into a collision amount at the time the rain gauge is installed on an arbitrary installation plane (herewith the zenith angle of the horizontal plane is 0 degree), and further converted into a rainfall amount (the unit: mm) by the density of a rainwater (1g/cm3). By this means, the rain gauge of the present invention can be applied for determining the rainwater collision amount per unit area of an inclined plane of any angle.

That is, the conventional rain gauge, because of being a horizontal 2-dimensional rain gauge, can be placed only on the horizontal plane. Contrary to this, the 3-dimensional rain gauge of the present invention, because of the spherical shape, can be placed on a plane of any azimuth direction and any zenith angle (including a vertical plane), and can measure the rainwater collision amount (the unit: g/cm2) against any arbitrary inclined plane in the surroundings.

FIGS. 20A,20B, and20C correspond to step S5of the processing flow illustrated inFIG. 15, and illustrate changes of the area of the rainwater bundle when the zenith angle of a plane is rotated, with the zenith angle [1] illustrated in the upper region ofFIG. 20Aas a reference, to the positions of zenith angles of [2]-[6].

Concretely,FIG. 20Ais a drawing to illustrate the areas of the rainwater bundles at the zenith angle positions [1] and [2].FIG. 20Bis a drawing to illustrate the areas of the rainwater bundles at the zenith angle positions [3] and [4].FIG. 20Cis a drawing, corresponding to step S5of processing procedure flow ofFIG. 15, to illustrate the areas of the rainwater bundles at the zenith angle positions [5] and [6].

InFIGS. 20A and 20B, if the azimuth direction of the plane is changed, the area of the rainwater bundle decreases in the orthogonal direction from the zenith angle (100-1−100-4). Further, inFIG. 20C, when the distinctive dropping direction of the rainwater is lateral with the inclined plane, (at the zenith angle position [5]), or when the distinctive dropping direction of the rainwater corresponds to the back side of the inclined plane, the area of the rainwater bundle vanishes and thus the rainwater collision amount becomes zero.

From the above, it is understood that the amount of rainwater which collides on the plane greatly differs depending on the relation between the distinctive dropping direction of the rainwater and the direction of the plane, with the maximum collision amount on the vertical plane, zero collision amount on the parallel plane, and zero collision amount on the plane exceeding parallel position, corresponding to the back side of the plane.

Therefore, at step S5ofFIG. 15, by converting the dropping amount of the rainwater into the dropping amount on the plane on which the rain gauge placed at the time of the installation, the rainwater collision amount on the installation plane can be easily detected.

Here, the advantage of the rain gauge in accordance with the present invention over the conventional rain gauge with a tipping bucket in measurement accuracy will be examined on the basis of observation data as follows.

FIG. 21is a schematic drawing of an apparatus used for such an examination.

InFIG. 21, a component A is an omnidirectional rain gauge in accordance with the present invention, and a component B is a conventional rain gauge with tipping bucket. The omnidirectional rain gauge in accordance with the present invention (arbitrarily referred to as a “3-dimensional rain gauge” hereinafter), the component A, and the conventional rain gauge with a tipping bucket (arbitrarily referred to as a “1-dimensional rain gauge” hereinafter), the component B are placed in a lateral fashion on the same ground.

And the measured values of the 3-dimensional rain gauge (the component A) and the 1-dimensional rain gauge (the component B) are obtained by a data logger22.

FIGS. 22A and 22Bare graphic representations of measurement results, which provided the base of the 10 minute measurement data explained previously inFIG. 10A, obtained by the examination apparatus ofFIG. 21which measures the rainfall amount every 10 minutes over hours.FIG. 22Ahas a vertical axis in equal intervals, andFIG. 22Bhas a vertical axis in a logarithm scale.

The 3-dimensional rain gauge (the component A) measures the rainfall amount by aggregating the numbers of conduction of the switches (the number of pulses) of all channels in every 10 minutes, and multiplying the total by the weight of a drop of water per pulse, 0.14 g, so that the rainwater catchment amount (equivalent to the catching amount) in the unit of g/10 minutes is obtained.

On the other hand, the examined 1-dimensional rain gauge (the component B) generates a pulse per one tipping over of the tipping bucket which has a capacity of 15.7 g. Therefore, catching amount in every 10 minutes is determined by multiplying the number of pulses in the interval by the tipping bucket's capacity of 15.7 g, so that the rainwater catchment amount (equivalent to the catching amount) in the unit of g/10 minutes is obtained.

As clearly understood fromFIGS. 22A and 22B, the 1-dimensional rain gauge (the component B) tips over no more than the maximum number of 6 times/10 minutes (FIG.22A:a), on the other hand, the 3-dimensional rain gauge in accordance with the present invention counts more drops of water than 1000 drops/10 minutes in total (FIG.22B:b).

Here, rainfall time zones in and detected times at which the rain gauges perform the detection will be compared. As illustrated inFIG. 22B, the time zone of the detection of the 3-dimensional rain gauge (the component A) is from 15:40 to 20:30, that is, 210 minutes in total, on the other hand, the time zone of the detection of the 1-dimensional rain gauge (the component B) is from 15:50 to 19:00, that is, 130 minutes in total. Therefore, it is understood that the 1-dimensional rain gauge was able to perform the detection only as long as 62% of the time period in which the 3-dimensional rain gauge performed the detection.

To compare the total amounts of rainfall in one consecutive rainfall, the 3-dimensional rain gauge's catching amount is 1036.2 g, while the 1-dimensional rain gauge's catching amount is 800.7 g. Therefore, it is determined that the 1-dimensional rain gauge was able to catch only as much as 77% (=800.7/1036.72) of the rainwater amount caught by the 3-dimensional rain gauge. The reason for this is because the 1-dimensional rain gauge has difficulties in catching the rainwater coming from the diagonal angles.

Further, the wind velocity of the rainfall time zone from 15:40 to 20:30, in which the rain gauges performed the detection, is from the minimum of 1.4 m/s to the maximum of 2.4 m/s, with the average of 1.4 m/s. Such condition of wind velocity belongs to a weak wind, therefore, under conditions with stronger wind, the catching amount of rainwater by the 1-dimensional rain gauge in the comparison above is anticipated to be in smaller numbers.

Also, inFIGS. 22A and 22B, the reason for the measured values by the 1-dimensional rain gauge indicating the greater number than the measured values by the 3-dimensional rain gauge, or the reason for the measured values by the 1-dimensional rain gauge indicating one time measured value after a series of zeros is because under a condition of a little rainfall, it takes a certain long time before the rainwater of 15.7 g is retained in the tipping bucket enough for the tipping over.

As explained above about the practical examples, the present invention enables, contrary to the conventional rain gauge, the catch ratio of nearly 100% for catching the incoming rainwater. And by performing the geometric correction as illustrated in step S4ofFIG. 15, the catch ratio of 100% is possible. And the measurement accuracy, which depends on the weight of drops of water (0.14 g) passing through the electrode terminals of the switch and the consistency thereof, can be as much as 100 times of the tipping over unit (0.5 mm or 15.7 g) of the conventional rain gauge with tipping bucket.

Further, the present invention enables catching and measuring the rainfall with respect to each direction, and thus converting it into the rainwater collision amount on the plane with an arbitrary inclination. Therefore, the present invention greatly contributes to the industry, the disaster prevention, and the environmental preservation.