1 chapman
chapman
1.1 Functions
| Name | Description |
|---|---|
| chapman | Compute the optical slant air mass accounting for the earth’s curvature |
1.1.1 chapman
chapman.chapman(mu, X=6371.0 / 8.0, method='f')Compute the optical slant air mass accounting for the earth’s curvature using the Chapman function.
1.1.1.1 Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| mu | float or array_like | Cosine of the zenith angle at the point of interest. | required |
| X | float | Ratio of altitude at the point of interest (from Earth’s centre) to the scale height of the atmospheric absorber. Default is 6371/8 ≈ 796.375, corresponding to Earth’s mean radius (6371 km) and Rayleigh scale height (8 km). | 6371.0 / 8.0 |
| method | (d, e, f) | Method for computation. Default is ‘f’. - ‘d’: Titheridge (1988, 2000) method - ‘e’: Kocifaj (1996) and Schüler (2012) method - ‘f’: Huestis(2001) method (the most accurate) | 'd' |
1.1.1.2 Returns
| Name | Type | Description |
|---|---|---|
| float or ndarray | Chapman function value(s) representing the optical slant air mass factor (ratio of slant to vertical path) for a spherical atmosphere. In plane-parallel limit this reduces to 1/mu. |
1.1.1.3 References
.. [1] Vasylyev, D. (2021). Accurate analytic approximation for the Chapman grazing incidence function. Earth Planets Space, 73, 112. https://doi.org/10.1186/s40623-021-01435-y .. [2] Huestis, D. L. (2001). Accurate evaluation of the Chapman function for atmospheric attenuation. Journal of Quantitative Spectroscopy and Radiative Transfer, 69(6), 709–721. https://doi.org/10.1016/S0022-4073(00)00107-2 .. [3] Titheridge, J. E. (1988). A non-linear theory of the Chapman graticule. Journal of Atmospheric and Solar-Terrestrial Physics, 50(3), 209-219. .. [4] Titheridge, J. E. (2000). Modelling of the basic mechanisms controlling the pre-reversal enhancement of equatorial spread F. Journal of Atmospheric and Solar-Terrestrial Physics, 62(17), 1521-1531. .. [5] Kocifaj, M. (1996). On the Chapman graticule computation revisited. Journal of Atmospheric and Solar-Terrestrial Physics, 58(16), 1819-1823. .. [6] Schüler, T. (2012). On the use of ionospheric scale heights in the Chapman function model. Radio Science, 47, RS5003.