The NCAR TGCM's are three-dimensional, time-dependent models of the EARTH's neutral upper atmosphere. The model uses a finite differencing technique to obtain a self-consistent solution for the coupled, nonlinear equations of hydrodynamics, thermodynamics, continuity of the neutral gas and for the coupling between the dynamics and the composition.
Recent models in the series include a self-consistent aeronomic scheme for the coupled Thermosphere/Ionosphere system, the Thermosphere Ionosphere Electrodynamic General Circulation Model(TIEGCM), and an extension of the lower boundary from 97 to 30 km, including the physical and chemical processes appropriate for the Mesosphere and upper Stratosphere, the Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM).
The output of the TIME-GCM consists of 30 fields on a three-dimensional latitude, longitude, pressure grid. Geographic longitude begins at -180 degrees west and continues around the globe with a 5 degree resolution. Geographic latitude resolution is also 5 degrees, from -87.5 south to +87.5 north. The vertical dimension is in a log pressure scale (ln(p0/p)) from -17.0 at the bottom (approximately 30 km) to 5.0 at the top (varying in altitude up to about 400 km). The vertical resolution is 0.5, for a total of 45 pressures.
NCL can be used to visualize TGCM and TIME-GCM output. There are master scripts that produced tgcmproc-like output, and do-it yourself scripts which allow for user customization.
TIEGM October 1995 Storm Simulation Results
Images and Animations
On October 18, 1995, an interplanetary magnetic cloud encountered the Earth
and consequently induced a major magnetic storm as well as massive substorms
(with the maximum magnitude of Dst reaching 120 nT and AE reaching 1600 nT).
The realistic time-dependent high-latitude ionospheric convection and auroral
precipitation patterns derived from the AMIE procedure was used as inputs to
the NCAR-TIEGCM to simulate the ionospheric/thermospheric response
to the storm. The TIEGCM ran in a 5-min time step, and the TIEGCM history
volumes were recorded every 10 mins. For the period of October 18-19, 1995,
the 2-day average solar radiation index Sa was 80x10^-22 W/m^2Hz.
Movies Made for the 1999 Space Weather Workshop
The AMIE procedure was used to derive realistic global distributions of ionospheric convection and auroral particle precipitation for the GEM campaign March 28-29, 1992. These patterns were used as input to the TIEGCM. Neutral winds/temperature and energy flux/ion drift are shown in this (8.2Mb Mpeg, 5.7Mb Quicktime) visualization.
Post-model processors may be used to obtain data and graphics of model output. There is a batch-mode type processor which runs on the NCAR Cray machines, and an interactive workstation based IDL processor which reads netCDF files made from model histories. These processors read histories made from tigcm, tiegcm, and time-gcm histories.
TIME-GCM history output fields
NEUTRAL TEMPERATURE (DEG K)
NEUTRAL ZONAL WIND (M/S)
NEUTRAL MERIDIONAL WIND (M/S)
MOLECULAR OXYGEN (O2)
OX (O+O3)
N4S
NOZ (NO+NO2)
CARBON MONOXIDE (CO)
CARBON DIOXIDE (CO2)
WATER VAPOR (H2O)
MOLECULAR HYDROGEN (H2)
HOX (OH+HO2+H)
O+ ionized atomic oxygen
METHANE (CH4)
O21D
NITROUS OXIDE (NO2)
NITRIC OXIDE (NO)
OZONE (O3)
ATOMIC OXYGEN (O1)
OH HYDROXYL
HO2
HYDROGEN (H)
N2D
ION TEMPERATURE (DEG K)
ELECTRON TEMPERATURE (DEG K)
ELECTRON DENSITY (NE)
O2 density+ (CM3)
VERTICAL WIND UP) (M/S)')")
HEIGHT (KM)
ELECTRIC POTENTIAL (VOLTS)
MOLECULAR NITROGEN (N2)
Many other fields are available via post-model processing, including
ion velocities, fof2, hmf2, emissions and airglow fields, etc.
Modelling the Mars and Venus Thermospheres
Comparative Terrestrial Planet Thermospheres
-Revised 14 January 1999 by foster@ucar.edu.