JPH0627872B2 - Measuring device of plane projected rainfall on a slope - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for measuring the amount of projected rainfall on a slope.

(Prior Art) A rain gauge is used to measure precipitation. As is well known, the rain gauge has a cylindrical shape with a diameter of 20 cm, and measures the amount of precipitation received by a built-in rain gauge on a regular basis. That is, if it is assumed that there is no outflow and no inflow from the surroundings at the measurement site, it is to see how many millimeters of rainwater accumulate there.

Most of the conventional measurements of precipitation have come from the above-mentioned rain gauges, but it is pointed out that the measured values of rainfall on slopes such as mountains may not reflect the actual situation. For example, it is a point based on inconsistency with phenomena such as abnormal increase of river water or flash flood, although the measured value of rain gauge is not so high. A problem with such conventional rain gauge data is that the measured values on slopes such as mountains are considered to be particularly small.

A meteorologist, a person who is involved in meteorological observation, or a person who is involved in the manufacture of meteorological instruments, such as the applicant of the present invention, has carried out various studies on this problem, and has been trying to find the cause. Various papers have been published and attempts have been made to improve the equipment, but no convincing answer has been obtained yet. Among them, the effect of wind is considered to be the first cause of the error in slope rainfall. It is rather common for rain to be accompanied by some wind as a meteorological phenomenon, especially in mountainous areas. This fact is the basis for the conventional theory that the cause of insufficient measurement values is the wind. Those in this position have proposed various experiments by proposing to direct the rain gauge toward the wind, that is, to make the rain gauge opening face the wind direction.

However, if there is a wind effect, it should be the same on flat land. However, there are not many indications that the error due to the wind direction of the level rainfall is so large that it is a problem, and it seems that there is no such fact. As shown in FIG. 1, since the opening surface B of the rain gauge A and the flat surface C that is the measurement surface are parallel to each other, the projection of the opening surface B onto the flat surface C is prevented regardless of the direction D of rain. It is thought that this can be explained by the fact that the water receiving area S _O is always constant. Actually, although the capture rate slightly decreases in the leeward part, it can be considered that there is no difference in the amount of water received by the wind on flat land.

However, when the rain gauge is installed on the slope E by the same method as in the flat ground, the water receiving area changes depending on the wind direction (Fig. 2). Since the opening surface B of the rain gauge A and the slope E that is the measurement surface are not parallel, the projected shape of the opening surface B differs depending on the wind direction, and the water receiving areas S ′, S ″ ... It will decrease if there is.

It can be understood that the above facts suggest that the plane projection rainfall is important in hydrological analysis regardless of the level or slope. Here, the plane projection rainfall amount (R _P ) is the rainfall amount when the water receiving area on the slope E is projected on the horizontal plane as shown in FIG.

As a result of such a study, the present inventor has found that when measuring rainfall on a slope, the water receiving area S, which is a projection of the opening B onto the slope, is the same as in the case of a rain gauge on a flat land. As shown in Figure 3, it was concluded that it should always be constant regardless of the wind direction. However, the method of making the rain gauge vertical to the slope must be avoided because it reduces the effective area for rainfall other than that direction.

(Technical problem) The present invention has been made on the basis of the above-mentioned findings, and the problem is that the plane projection rainfall required as basic data for hydrological analysis on a slope is based on the actual situation as much as possible. It is to remove the cap from the phenomenon side.

(Technical Means) In order to solve the above problems, the present invention comprises a cylindrical body for measuring the amount of precipitation captured therein, which has a predetermined diameter, and the central axis of the cylindrical body is vertical. As described above, a means for providing a water inlet which is installed on a slope and whose opening surface is formed to be substantially parallel to the slope is provided at the upper end of the cylinder.

(Operation) In the measuring device according to the present invention configured as described above,
As it has a slope parallel to the water inlet as shown in the figure,
The water receiving area S in which the water receiving port is projected on the slope is constant regardless of the direction of precipitation. The fact that the water receiving area S increases from the flat surface in accordance with the slope inclination reflects that when the unit area of the slope is considered, it becomes larger than the area projected on the flat surface.

The plane projection rainfall amount R _P by the measuring device according to the present invention is the fourth
As shown in the figure, if the amount of rainfall captured in the water inlet 2 is R, the slope inclination is 30 °, and the rainfall inclination angle is 45 °, it can be expressed as Rcos 30 °. The amount R _P represented by this R cos 30 ° is the same as when the inclination angle of the water inlet is 0 °, that is, in the case of a flatland rain gauge. The fact that the above findings are correct will be supported from now on.

On the other hand, in the case of slope rainfall measurement using a flat rain gauge,
According to FIG. 4, assuming that the horizontal rainfall on the opening surface of the water receiving area S _O is R _O , the inclination angle, and the slope are the same as those described above, the rainfall R
_S is R _S = R _O · cos 45 ° · sec 15 ° = 0.732R _O Plane projection rainfall R _P is R _P = R _S · cos 30 ° = 0.634R _O , which is actually two-thirds It can be seen that the amount of rainfall that is less than is captured. The relationship between the wind speed and the inclination angle of rainfall is as shown in Fig. 7, and the minimum catch rate of the slope of the conventional rain gauge according to the change of the slope of the slope and the inclination angle of rainfall is as shown in the following table.

(Example) Hereinafter, description will be given with reference to the drawings.

A measuring device according to the present invention is illustrated in FIG. 5, 1 is a cylindrical body having an inner diameter of 20 cm, 2 is a water inlet formed at the upper end thereof, and at an angle θ from a plane orthogonal to the central axis of the cylindrical body 1. It has a rising slope. The angle θ is set according to an angle representative of the slope of the slope E on which the measuring device is installed. The device of the present invention is characterized in that the opening surface of the water receiving port 2 is configured to be substantially parallel to the slope E. In this case, “substantially parallel” is a virtual angle that is considered to represent the entire slope in some cases, and in some cases is an average value of the slope around the measurement site. Is a state obtained by setting, and does not necessarily mean that the measurement site and the water inlet 2 are parallel to each other.

To provide such a water inlet 2, an adapter 3 attached to the opening edge of an existing rain gauge can be used. An example thereof is illustrated in FIG. 6, and the illustrated one integrally has a connecting ring 5 having an inner peripheral portion 6 fitted to the tip inner peripheral portion 4 of the water inlet 2 at the lower end, A stopper plate 7 that is locked below is attached to the connecting ring 5 with a set screw 8 and has a detachable structure. According to this adapter type water receiving port, various types having different angles θ of the water receiving port opening surface can be prepared, and can be selected according to the slope, and the orientation can be easily set.

In the one shown in FIG. 5, 9 is a funnel which is arranged at a required height lower than the water receiving port, 10 is the rainwater, and then rainwater is tumbled, 11 is a drainage tank, 12 and 13 are tumbled. Drainage outlets for draining water from, 14 and 15 fall down 11 Left and right stoppers, 16 are their bases, 17 are legs.

(Effects) Since the present invention is configured and operates as described above, the plane projection rainfall on a slope is grasped at a degree according to the inclination, and it is easy to grasp the actual state of the rainfall on the slope, and Since it is possible to eliminate the gap between the measured value and the measured value, it has a remarkable effect in preventing damage due to heavy rain in the mountains.

[Brief description of drawings]

The drawings relate to an embodiment of a measuring apparatus according to the present invention, and FIGS. 1, 2, and 3 are explanatory views for understanding a conventional rain gauge or the measuring apparatus according to the present invention, and FIG. Explanatory diagram showing the difference between the measured values of the rain gauge and the measuring device according to the present invention, FIG. 5 is a sectional view of the measuring device according to the present invention, FIG. 6 is a sectional view of a modified example, and FIG. It is a graph which shows the relationship with the inclination angle of rainfall.

Claims (3)

[Claims] 1. A cylinder having a predetermined diameter and for measuring the amount of precipitation trapped therein, said cylinder being installed on an inclined surface such that its central axis is vertical, and the cylinder upper end. An apparatus for measuring a projected rainfall on a slope, characterized in that it has a water inlet whose opening surface is formed to be substantially parallel to the slope. 2. The apparatus for measuring rainfall on a flat surface according to claim 1, wherein the opening surface at the upper end of the cylindrical body forms an inclination angle representative of the installation slope. 3. The inclined surface according to claim 1, wherein the cylindrical body has an adapter attached to an opening surface orthogonal to the central axis of the cylindrical body and having a water inlet whose angle is substantially parallel to the installation inclined surface. A device for measuring the amount of rainfall projected on a plane.