How to handle negative cosine of Solar Zenith Angle while calculating clear-sky UV Index?

Asked by: Christian Williams

Can a zenith angle be negative?

Yes. cos 0° = 1, cos 90° = 0. More than 90° will be negative.

How do you solve for zenith angle?

The zenith angle is the angle between the sun and the vertical. The zenith angle is similar to the elevation angle but it is measured from the vertical rather than from the horizontal, thus making the zenith angle = 90° – elevation.

What is the maximum zenith angle?

Thus, θ + ϕ + 90° = 180° Therefore, θ = 90° – ϕ

What is zenith in reference to solar time?

The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction. It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane.

Can solar zenith angle be greater than 90?

On the equator, a day of the equinox, the elevation angle equals 90°, and the zenith angle equals 0° at solar noon. In the day, the solar elevation angle and zenith angle are always between 0° and 90°. If the elevation is negative, it means it is dark.

What does a small zenith angle mean?

Solar zenith angle, the angle between the zenith (vertical) and the sun, is useful in determining whether the sun is rising or setting and in predicting solar effects on radio communications.The smaller the solar zenith angle, the higher the sun is in the sky.

What is azimuth angle and zenith angle?

The solar azimuth and solar zenith express the position of the sun. The solar azimuth is the angle of the direction of the sun measured clockwise north from the horizon. The solar zenith is the angle measured from the local zenith and the line of sight of the sun.

Is zenith same as latitude?

The distance of the Celestial Equator from the zenith is equal to your latitude. If the distance is south of the zenith, you are north of the equator, and vice versa.

How do you calculate solar angle?

The optimum tilt angle is calculated by adding 15 degrees to your latitude during winter, and subtracting 15 degrees from your latitude during summer. For instance, if your latitude is 34°, the optimum tilt angle for your solar panels during winter will be 34 + 15 = 49°.

Can elevation angle be negative?

The angle is measured between an imaginary line between the observer and the sun and the horizontal plane the observer is standing on. The altitude angle is negative when the sun drops below the horizon.

What is satellite zenith angle?

When observing a given point on the Earth’s surface from a satellite-based instrument, the Solar Zenith Angle (SZA) is the angle between the local zenith (i.e. directly above the point on the ground) and the line of sight from that point to the sun.

How does zenith and azimuth apply to seasonal surface sunlight?

The solar azimuth angle is the azimuth (horizontal angle with respect to north) of the Sun’s position. This horizontal coordinate defines the Sun’s relative direction along the local horizon, whereas the solar zenith angle (or its complementary angle solar elevation) defines the Sun’s apparent altitude.

What is the difference between the zenith angle and internal angle?

Quote from video: So in other words if you have your Zenith angle if your points straight up would be zero degrees if you're coming straight over to the horizontal. It would be 90 degrees. And if we're farther.

What is the difference between vertical and zenith angle?

A vertical angle is formed by two intersecting lines in a vertical plane, one of these lines horizontal. A zenith angle is the complementary angle to the vertical angle and is formed by two intersecting lines in a vertical plane, one of these lines directed toward the zenith.

Can you have a negative degree angle?

Angle measure can be positive or negative, depending on the direction of rotation.

Can you have a negative angle in a triangle?

Negative angle measurement don’t exist. Sorry. In a geometric figure like a triangle all angles have positive measurement. So in a triangle our angles could have measures of 30o,60o,90o or π/6,π/3,π/2 if you like.

Can an angle in radians be negative?

Quote from video: And we move in a clock excuse me a counter clockwise direction now we can have negative radians all it means is that we're gonna be moving in a clockwise direction.

What does a negative angle mean?

Definition of negative angle



: an angle generated in a direction opposite to an arbitrarily chosen usually clockwise direction.

What do you do if you get a negative angle?

For a negative angle, you simply need to rotate in the other direction (i.e., clockwise instead of anti-clockwise). This means that for an angle of −40∘, you end up at the same point (and with the same values of sin and cos as an angle of 320∘.

How do you make a negative angle positive?

Given a negative angle, we add 360 to get its corresponding positive angle. When an angle is -360°, it implies that the object made more than one cycle in clockwise direction.