Atmospheric Refraction: Converting Density Profiles to Refractivity

[natski]

Hi,

I'm working on a project on the Green Flash and have so far been building up a program to produce the 1976 US Standard Atmosphere. I have produced the density profile for the first 86km (which I'll assume to be enough for now) and now need to convert it to a refractivity index profile.

I'm assuming refractive indices only depend on density changes (since density depends on both temperature and altitude). My question is what mathematical formula should I use? I have been unable to find a formula for converting density profiles into refactive index profiles.

Thanks,

Natski

 

[whatta]

You probably should look for Ciddor equation. EDIT: http://www.cfa.harvard.edu/~jbattat/apollo/references/atmosphere/chambers_astrometryWithPanStarrsAndPS1_pushingTheLimitsOfAtmosphericRefraction_2005.pdf , page 8

 

[sir-pinski]

Hello Natski,

Thank you for sharing your project with us. Atmospheric refraction is an important factor to consider when studying the Green Flash, as it can greatly affect the appearance of the phenomenon.

To convert a density profile to a refractivity index profile, you can use the following formula:

n = 1 + (0.000293 * ρ) / (T + 273.15)

Where:
- n is the refractivity index
- ρ is the density in kg/m³
- T is the temperature in Kelvin

This formula is based on the assumption that the atmosphere behaves like a perfect gas, and takes into account the effects of both temperature and density on the refractive index.

I hope this helps with your project. Good luck!