TIEGCM

Overview

The Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) is developed by the NCAR High Altitude Observatory (HAO).

DART-TIEGCM has been used to assimilate neutral mass density retrieved from satellite-borne accelerometers and electron density obtained from ground-based and space-based GNSS signals. Unlike other ionospheric data assimilation applications, this approach allows simultaneous assimilation of thermospheric and ionospheric parameters by taking advantage of the coupling of plasma and neutral constituents described in TIEGCM. DART/TIEGCM’s demonstrated capability to infer under-observed thermospheric parameters from abundant electron density observations has important implications for the future of upper atmosphere research.

DART is designed so that the TIEGCM source code can be used with no modifications. TIEGCM and DART run as separate executables. The TIEGCM 2.0 source code and User’s Guide is available from HAO:

DART-TIEGCM namelist options

The model_nml namelist contains the TIEGCM specific options for DART. model_nml is read from the file input.nml. Namelists start with an ampersand ‘&’ and terminate with a slash ‘/’. Character strings that contain a ‘/’ must be enclosed in quotes to prevent them from prematurely terminating the namelist.

&model_nml
   tiegcm_restart_file_name    = 'tiegcm_restart_p.nc'
   tiegcm_secondary_file_name  = 'tiegcm_s.nc'
   model_res                   = 5.0
   assimilation_period_seconds = 3600
   estimate_f10_7              = .false.
   f10_7_file_name             = 'f10_7.nc'
   debug                       = 0
   variables = 'NE',    'QTY_ELECTRON_DENSITY',          '1000.0',  'NA',      'restart',    'UPDATE'
               'OP',    'QTY_DENSITY_ION_OP',            'NA',      'NA',      'restart',    'UPDATE',
               'TI',    'QTY_TEMPERATURE_ION',           'NA',      'NA',      'restart',    'UPDATE',
               'TE',    'QTY_TEMPERATURE_ELECTRON',      'NA',      'NA',      'restart',    'UPDATE',
               'OP_NM', 'QTY_DENSITY_ION_OP',            'NA',      'NA',      'restart',    'UPDATE',
               'O1',    'QTY_ATOMIC_OXYGEN_MIXING_RATIO','0.00001', '0.99999', 'secondary',  'NO_COPY_BACK',
               'O2',    'QTY_MOLEC_OXYGEN_MIXING_RATIO', '0.00001', '0.99999', 'secondary',  'NO_COPY_BACK',
               'TN',    'QTY_TEMPERATURE',               '0.0',     '6000.0',  'secondary',  'NO_COPY_BACK',
               'ZG',    'QTY_GEOMETRIC_HEIGHT',          'NA',      'NA',      'secondary',  'NO_COPY_BACK',
   /

Namelist entry

Type

Description

tiegcm_restart_file_name

character(len=256)

The TIEGCM restart template

tiegcm_secondary_file_name

character(len=256)

The TIEGCM secondary template

model_res

real(r8)

TIEGCM model resolution 5.0 or 2.5 degrees

assimilation_period_seconds

integer

This specifies the width of the assimilation window. The current model time is used as the center time of the assimilation window. All observations in the assimilation window are assimilated. BEWARE: if you put observations that occur before the beginning of the assimilation_period, DART will error out because it cannot move the model ‘back in time’ to process these observations. assimilation_period_seconds must be an integer number of TIEGCM dynamical timesteps (as specified by tiegcm.nml:STEP) AND be able to be expressed by tiegcm.nml:STOP. Since STOP has three components: day-of-year, hour, and minute, the assimilation_period_seconds must be an integer number of minutes.

estimate_f10_7

logical

Switch to specify that the f10.7 index should be estimated by augmenting the DART state vector with a scalar. The location of the f10.7 index is taken to be longitude of local noon and latitude zero.

f10_7_file_name

character(len=256)

If estimate_f107=.true. f10.7 will be part of the dart state. The variable f10_7 is read from f10_7_file_name An example f10_7.cdl file is given in the work directory

debug

integer

Set to 0 (zero) for minimal output. Successively larger values generate successively more output.

variables

character (MAX_NUM_VARIABLES * 6)

Six strings to describe the TIEGCM variables to be used in DART. A description of the six strings is given below.

 
variables = 'NAME', 'QTY', 'MIN', 'MAX', 'FILE', 'UPDATE'

NAME The variable name in the TIEGCM netCDF file.

QTY The DART quantity for the variable.

MIN The minimum bound (if any) for the variable. Enter ‘NA’ for no minimum.

MAX The a maximum bound (if any) for the variable.

FILE The tiegcm netcdf file containing the variable. ‘restart’ or ‘secondary’

UPDATE filter will update the variable in the TIEGCM netcdf file. Use NO_COPY_BACK to prevent filter from updating the variable.

Below is an example showing the namelist options necessary to add f10.7 to the DART state

&filter_nml
   input_state_file_list        = 'restart_p_files.txt', 'secondary_files.txt', 'f10.7.txt'
   output_state_file_list       = 'out_restart_p_files.txt', 'out_secondary_files.txt', 'out_f10.7.txt'

&model_nml
  estimate_f10_7 = .true.
  f10_7_file_name = 'f10_7.nc'
  variables =  'NE',    'QTY_ELECTRON_DENSITY',          '1000.0',  'NA',      'restart',    'UPDATE'
               ...
               'ZG',    'QTY_GEOMETRIC_HEIGHT',          'NA',      'NA',      'secondary',  'NO_COPY_BACK',
               'f10_7'  'QTY_1D_PARAMETER'               'NA',      'NA',      'calculate', 'UPDATE'

References

  • Matsuo, T., and E. A. Araujo-Pradere (2011), Role of thermosphere-ionosphere coupling in a global ionosphere specification, Radio Science, 46, RS0D23, doi:10.1029/2010RS004576

  • Lee, I. T., T, Matsuo, A. D. Richmond, J. Y. Liu, W. Wang, C. H. Lin, J. L. Anderson, and M. Q. Chen (2012), Assimilation of FORMOSAT-3/COSMIC electron density profiles into thermosphere/Ionosphere coupling model by using ensemble Kalman filter, Journal of Geophysical Research, 117, A10318, doi:10.1029/2012JA017700

  • Matsuo, T., I. T. Lee, and J. L. Anderson (2013), Thermospheric mass density specification using an ensemble Kalman filter, Journal of Geophysical Research, 118, 1339-1350, doi:10.1002/jgra.50162

  • Lee, I. T., H. F. Tsai, J. Y. Liu, Matsuo, T., and L. C. Chang (2013), Modeling impact of FORMOSAT-7/COSMIC-2 mission on ionospheric space weather monitoring, Journal of Geophysical Research, 118, 6518-6523, doi:10.1002/jgra.50538

  • Matsuo, T. (2014), Upper atmosphere data assimilation with an ensemble Kalman filter, in Modeling the Ionosphere-Thermosphere System, Geophys. Monogr. Ser., vol. 201, edited by J. Huba, R. Schunk, and G. Khazanov, pp. 273-282, John Wiley & Sons, Ltd, Chichester, UK, doi:10.1002/9781118704417

  • Hsu, C.-H., T. Matsuo, W. Wang, and J. Y. Liu (2014), Effects of inferring unobserved thermospheric and ionospheric state variables by using an ensemble Kalman filter on global ionospheric specification and forecasting, Journal of Geophysical Research, 119, 9256-9267, doi:10.1002/2014JA020390

  • Chartier, A., T. Matsuo, J. L. Anderson, G. Lu, T. Hoar, N. Collins, A. Coster, C. Mitchell, L. Paxton, G. Bust (2015), Ionospheric Data Assimilation and Forecasting During Storms, Journal of Geophysical Research, doi:10.1002/2014JA020799