Python interface for the NRLMSISE-00 empirical atmosphere model

This python version of the NRLMSISE00 upper atmosphere model is based on the C-version of the code, available at www.brodo.de/space/nrlmsise. The C code is imported as a git submodule from git://git.linta.de/~brodo/nrlmsise-00.git (browsable version at: https://git.linta.de/?p=~brodo/nrlmsise-00.git).

Overview

Quote from https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=MSISE:

“The MSISE model describes the neutral temperature and densities in Earth's atmosphere from ground to thermospheric heights. The NRLMSIS-00 empirical atmosphere model was developed by Mike Picone, Alan Hedin, and Doug Drob.”

Install

Requirements

• numpy - required
• pytest - optional, for testing

pynrlmsise00

There is no pip package yet, but pynrlmsise00 can be installed with pip directly from github (see https://pip.pypa.io/en/stable/reference/pip_install/#vcs-support and https://pip.pypa.io/en/stable/reference/pip_install/#git):

$ pip install [-e] git+https://github.com/st-bender/pynrlmsise00.git

The other option is to use a local clone:

$ git clone https://github.com/st-bender/pynrlmsise00.git
$ cd pynrlmsise00
$ git submodule init
$ git submodule update

and then using pip (optionally using -e, see https://pip.pypa.io/en/stable/reference/pip_install/#install-editable):

$ pip install [-e] .

or using setup.py:

$ python setup.py install

Optionally, test the correct function of the module with

$ py.test [-v]

or even including the doctests in this document:

$ py.test [-v] --doctest-glob='*.md'

Usage

The python module itself is named nrlmsise00 and is imported as usual:

>>> import nrlmsise00

Basic class and method documentation is accessible via pydoc:

$ pydoc nrlmsise00

C model interface

The C submodule directly interfaces the model functions gtd7() and gtd7d() by importing nrlmsise00._nrlmsise00. The return values are always tuples of two lists containing the densities (d[0]--d[8]), and temperatures (t[0], t[1]). The flags and ap_a value array are set via keywords, but both default to the standard setting, such that changing them should not be necessary for most use cases.

>>> from nrlmsise00._nrlmsise00 import gtd7, gtd7d
>>> # using the standard flags
>>> gtd7(2009, 172, 29000, 400, 60, -70, 16, 150, 150, 4)
([666517.690495152, 113880555.97522168, 19982109.255734544, 402276.3585712511, 3557.464994515886, 4.074713532757222e-15, 34753.12399717142, 4095913.2682930017, 26672.73209335869], [1250.5399435607994, 1241.4161300191206])

Python interface

The Python interface functions take datetime.datetime objects for convenience. The local solar time is calculated from that time and the given location, but it can be set explicitly via the lst keyword. The returned value has the same format as the C version, and because of their similarity, gtd7() and gtd7d() are selected via the method keyword, gtd7 is the default.

>>> from datetime import datetime
>>> from nrlmsise00 import msise_model
>>> msise_model(datetime(2009, 6, 21, 8, 3, 20), 400, 60, -70, 150, 150, 4, lst=16)
([666517.690495152, 113880555.97522168, 19982109.255734544, 402276.3585712511, 3557.464994515886, 4.074713532757222e-15, 34753.12399717142, 4095913.2682930017, 26672.73209335869], [1250.5399435607994, 1241.4161300191206])

A numpy compatible flat version is available as msise_flat(), it returns a 11-element numpy.ndarray with the densities in the first 9 entries and the temperatures in the last two entries.

>>> from datetime import datetime
>>> from nrlmsise00 import msise_flat
>>> msise_flat(datetime(2009, 6, 21, 8, 3, 20), 400, 60, -70, 150, 150, 4)
array([5.65085279e+05, 6.79850175e+07, 1.18819263e+07, 2.37030166e+05,
       1.32459684e+03, 2.39947892e-15, 5.32498381e+04, 1.07596246e+06,
       2.66727321e+04, 1.10058413e+03, 1.09824872e+03])

All arguments can be numpy.ndarrays, but must be broadcastable to a common shape. For example to calculate the values for three altitudes (200, 300, and 400 km) and two latitude locations (60 and 70 °N) simultaneously, one can use numpy.newaxis (which is equal to None) like this:

>>> from datetime import datetime
>>> import numpy as np
>>> from nrlmsise00 import msise_flat
>>> alts = np.arange(200, 401, 100.)  # = [200, 300, 400] [km]
>>> lats = np.arange(60, 71, 10.)  # = [60, 70] [°N]
>>> # Using broadcasting, the output will be a 2 x 3 x 11 element array:
>>> msise_flat(datetime(2009, 6, 21, 8, 3, 20), alts[None, :], lats[:, None], -70, 150, 150, 4)
array([[[1.36949418e+06, 1.95229496e+09, 3.83824808e+09, 1.79130515e+08,
         4.92145034e+06, 2.40511268e-13, 8.34108685e+04, 1.74317585e+07,
         3.45500931e-08, 1.10058413e+03, 9.68827485e+02],
        [8.40190601e+05, 3.25739060e+08, 1.82477392e+08, 5.37973134e+06,
         6.53609278e+04, 1.75304136e-14, 5.92944463e+04, 4.36516218e+06,
         1.03939126e+02, 1.10058413e+03, 1.08356514e+03],
        [5.65085279e+05, 6.79850175e+07, 1.18819263e+07, 2.37030166e+05,
         1.32459684e+03, 2.39947892e-15, 5.32498381e+04, 1.07596246e+06,
         2.66727321e+04, 1.10058413e+03, 1.09824872e+03]],
<BLANKLINE>
       [[1.10012225e+06, 1.94725472e+09, 4.08547233e+09, 1.92320077e+08,
         6.65460281e+06, 2.52846563e-13, 6.16745965e+04, 2.45012145e+07,
         5.21846603e-08, 1.13812434e+03, 1.00132640e+03],
        [6.83809952e+05, 3.42643970e+08, 2.13434661e+08, 6.43426889e+06,
         1.01162173e+05, 1.95300073e-14, 4.36031132e+04, 6.70490625e+06,
         1.59911615e+02, 1.13812434e+03, 1.12084651e+03],
        [4.65787225e+05, 7.52160226e+07, 1.51795904e+07, 3.13560147e+05,
         2.32541183e+03, 2.76353370e-15, 3.92811827e+04, 1.73321928e+06,
         4.12296154e+04, 1.13812434e+03, 1.13580463e+03]]])

This module also provides "flat" variants of the C functions as gtd7_flat() and gtd7d_flat(). For example using gtd7() the same way as above:

>>> import numpy as np
>>> from nrlmsise00 import gtd7_flat
>>> alts = np.arange(200, 401, 100.)  # = [200, 300, 400] [km]
>>> lats = np.arange(60, 71, 10.)  # = [60, 70] [°N]
>>> # Using broadcasting, the output will be a 2 x 3 x 11 element array:
>>> gtd7_flat(2009, 172, 29000, alts[None, :], lats[:, None], -70, 16, 150, 150, 4)
array([[[1.55567936e+06, 2.55949597e+09, 4.00342724e+09, 1.74513806e+08,
         6.56916263e+06, 2.64872982e-13, 5.63405578e+04, 4.71893934e+07,
         3.45500931e-08, 1.25053994e+03, 1.02704994e+03],
        [9.58507714e+05, 4.66979460e+08, 2.31041924e+08, 6.58659651e+06,
         1.16566762e+05, 2.38399390e-14, 3.86535595e+04, 1.43755262e+07,
         1.03939126e+02, 1.25053994e+03, 1.20645403e+03],
        [6.66517690e+05, 1.13880556e+08, 1.99821093e+07, 4.02276359e+05,
         3.55746499e+03, 4.07471353e-15, 3.47531240e+04, 4.09591327e+06,
         2.66727321e+04, 1.25053994e+03, 1.24141613e+03]],
<BLANKLINE>
       [[1.31669842e+06, 2.40644124e+09, 4.21778196e+09, 1.89878716e+08,
         8.17662024e+06, 2.71788520e-13, 4.64192484e+04, 5.13265845e+07,
         5.21846603e-08, 1.24246351e+03, 1.04698385e+03],
        [8.22632403e+05, 4.52803942e+08, 2.53857090e+08, 7.50201654e+06,
         1.53431033e+05, 2.46179628e-14, 3.20594861e+04, 1.62651506e+07,
         1.59911615e+02, 1.24246351e+03, 1.20963726e+03],
        [5.73944168e+05, 1.10836468e+08, 2.19925518e+07, 4.58648922e+05,
         4.68600377e+03, 4.10277781e-15, 2.89330169e+04, 4.65636025e+06,
         4.12296154e+04, 1.24246351e+03, 1.23665288e+03]]])

Note

All functions require the solar 10.7 cm radio flux and and the geomagnetic Ap index values to produce correct results. In particular, according to the C source code:

• f107A: 81 day average of F10.7 flux (centered on the given day of year)
• f107: daily F10.7 flux for previous day
• ap: magnetic index (daily)

The f107 and f107A values used to generate the model correspond to the 10.7 cm radio flux at the actual distance of the Earth from the Sun rather than the radio flux at 1 AU. The following site provides both classes of values (outdated): ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX/

f107, f107A, and ap effects are neither large nor well established below 80 km and these parameters should be set to 150., 150., and 4. respectively.

License

This python interface is free software: you can redistribute it or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2 (GPLv2), see local copy or online version.

The C source code of NRLMSISE-00 is in the public domain, see COPYING.NRLMSISE-00.