Atmospheric Density

This function provides a utility function for calculating and retrieving atmospheric density using the US Standard Atmosphere 1976 model (USSA1976).

import numpy as np
import ussa1976
ds = ussa1976.compute()

  • ussa1976 is a third-party or custom module that computes and provides data based on the 1976 Standard Atmosphere model.

  • The function ussa1976.compute() returns a data structure that includes physical quantities (e.g., temperature, density, pressure) at various altitudes.

def atmos_ussa1976_rho(altitude):
    # Find the closest index to altitude in metres
    idx = np.argmin(np.abs(ds["z"].values - altitude))

    # Return pressure, temperature, and density
    return ds["rho"].values[idx]

  • Purpose: Given an altitude (in meters), it returns the standard atmospheric density (rho).

  • Parameters:

    • altitude: A float or integer in meters representing the altitude at which to query atmospheric density.

  • Implementation:

    • Computes the absolute difference between the input altitude and all standard altitude levels in the dataset.

    • Uses np.argmin() to find the index of the closest altitude.

    • Returns the density value corresponding to that altitude index.