Halo 22 Degree Ice Crystal Checker
Compare observed angular radius to ideal 60-degree hexagonal ice-prism minimum deviation under caller index/tolerance; angular agreement does not prove ice crystal habit, visible halo or sun-viewing safety.
Description
An ideal hexagonal ice prism has a 60-degree apex angle.
An ideal hexagonal ice prism has a 60-degree apex angle. Its minimum-deviation angle can be compared with an observed halo radius using a declared measurement tolerance.1
Compare observed angular radius to ideal 60-degree hexagonal ice-prism minimum deviation under caller index/tolerance; angular agreement does not prove ice crystal habit, visible halo or sun-viewing safety.
When to use Halo 22 Degree Ice Crystal Checker
Use this tool to compare observed angular radius to ideal 60-degree hexagonal ice-prism minimum deviation under caller index/tolerance; angular agreement does not prove ice crystal habit, visible halo or sun-viewing safety.
Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
How to use Halo 22 Degree Ice Crystal Checker and understand its results
- Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
- Enter relativeIceRefractiveIndex, observedHaloRadiusDegrees, callerAngularToleranceDegrees using the field table and calculation rules, then run the tool.
- Read hexagonalPrismMinimumDeviationDegrees, observedMinusPrismAngleDegrees, withinCallerAngularTolerance. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| relativeIceRefractiveIndex | Relative ice refractive index | number | Required |
| observedHaloRadiusDegrees | Observed halo radius degrees | number | Required |
| callerAngularToleranceDegrees | Caller angular tolerance degrees | number | Required |
Supply relative index in (1,2), a nonnegative observed radius and nonnegative angular tolerance in degrees. Report the model angle, signed observed-minus-model difference and whether its absolute value is at most the tolerance.
minimum deviation = 2asin(n/2) × 180/π − 60 degrees Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| hexagonalPrismMinimumDeviationDegrees | Hexagonal prism minimum deviation degrees | number |
| observedMinusPrismAngleDegrees | Observed minus prism angle degrees | number |
| withinCallerAngularTolerance | Within caller angular tolerance | boolean |
{
"input": {
"relativeIceRefractiveIndex": 1.31,
"observedHaloRadiusDegrees": 22,
"callerAngularToleranceDegrees": 1
},
"output": {
"hexagonalPrismMinimumDeviationDegrees": 21.839299909773032,
"observedMinusPrismAngleDegrees": 0.16070009022696752,
"withinCallerAngularTolerance": true
}
}Limitations and assumptions
Angular agreement does not establish crystal habit or a visible halo. The calculation has no brightness or atmospheric population model.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Rainbow Primary 42 Degree Angle: Compute stationary single internal-reflection spherical-drop rainbow ray under caller wavelength-specific refractive index; not a fixed 42 degree lookup or visible bow forecast. For a complementary task, use Double Rainbow Secondary 51 Degree: Compute stationary double internal-reflection spherical-drop rainbow ray under caller wavelength-specific refractive index; not a fixed 51 degree lookup or visible bow forecast.
References
-
Halo 22 Degree Ice Crystal Checker — tool.io
Similar or alternative tools
- Rainbow Primary 42 Degree Angle
Compute stationary single internal-reflection spherical-drop rainbow ray under caller wavelength-specific refractive index; not a fixed 42 degree lookup or visible bow forecast.
- Double Rainbow Secondary 51 Degree
Compute stationary double internal-reflection spherical-drop rainbow ray under caller wavelength-specific refractive index; not a fixed 51 degree lookup or visible bow forecast.