Satellite and Universal Time (SATUT) Sampling of the NCAR TIEGCM, TIME-GCM, and GSWM Models for CEDAR and TIMED Related Studies

Overview Sampling Description Model Descriptions Data Availability Rules of the Road and Data Access References Example Plots Contact

Overview

The instruments on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and a complement of ground based NSF Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) instruments provide invaluable diagnostics of MLTI forcings, dynamics, and energetics. The interpretation of these diagnostics and elucidation of the impact of the associated processes on the MLTI requires complementary modeling initiatives. Many of our colleagues in the TIMED and CEDAR communities will use the NCAR/HAO models for both proposed and already established investigations. We make samples of the Thermosphere - Ionosphere - Electrodynamics General Circulation Model (TIEGCM), of the Thermosphere - Ionosphere - Mesosphere - Electrodynamics General Circulation Model (TIME-GCM), and of the Global Scale Wave Model (GSWM) available to the community in netCDF format. In order to facilitate direct comparisons with the TIMED instruments, the model ouputs are sampled along the measurement tracks from the Sounding the Atmosphere using Broadband Emission Radiometry (SABER) instrument, from the TIMED Doppler Interferometer (TIDI, see also TIDI at HAO), and from the Global Ultraviolet Imager (GUVI). An analogous product for the CEDAR ground-based component of TIMED is also provided.

Sampling Description

The basic idea of the model sampling is to provide the winds, temperatures, and trace constituents that would be measured by GUVI, TIDI and SABER if TIMED flew through the model atmosphere. Some additional (= not measured by the instruments) model fields are also provided. Universal time (UT) and locations (latitude and longitude) of the instrument tangent points (footprints) are extracted from SABER level 2a data files as provided by the SABER web page, and from the TIDI vector data files as provided by the TIDI web page. GUVI sampling is currently based on the TIMED spacecraft position (1 minute resolution) and therefore approximates the GUVI nadir measurements. The model histories (see Model Descriptions) are linearly interpolated in space and time to the instrument footprints. Missing or "bad" instrument data are treated as missing values and are not included in the sampled model files. The locations and UT's of each height scan in the sampled model files are altitude independent. They correspond to an instrument tangent height of approximately 100 km. The sampled model results are written to daily netCDF files. TIME-GCM and TIEGCM results are provided in log-pressure coordinates. GSWM tidal perturbations are on the geometric height scale. The altitude coverage of the sampled model data is usually larger than the instrument coverage.

SABER

The sampling for SABER is based upon the level 2a orbit-by-orbit data files in data version 01 (preliminary). Locations and UT's for each height scan used for the sampling correspond to the tangent point altitude in the middle between the lowermost and uppermost altitudes in this scan (roughly 100 km).

TIDI

The sampling for TIDI is based upon the daily vector (VEC) data files in data version 01 (preliminary). UT's and locations correspond to the nominal tangent point altitude provided in the TIDI vector files.

GUVI

The sampling for GUVI is based upon the generic TIMED spacecraft position, recorded every 1 minute. It therefore approximates the GUVI nadir measurements.

Ground stations

GSWM results at specified locations can be accessed from the GSWM web page. (See also the TIMED at CU web page.) For TIEGCM and TIME-GCM results at selected ground stations check the Data Availability section.

Model Descriptions

GSWM

The sampled GSWM model results (0-124 km) provide tidal perturbations of temperature (T), zonal wind (U), meridional wind (V), and vertical wind (W) for the locations and UT's of the SABER and TIDI measurements. Each data field is a linear superposition (with respect to the relative phasing) of 28 tidal components (14 diurnal components and 14 semidiurnal components). GSWM-00 provides the radiative forced migrating diurnal and semidiurnal tides. GSWM-02 provides the migrating tides and 12 nonmigrating components (w6 to e6 without the migrating tides) for diurnal and semidiurnal periods respectively that are forced by tropospheric latent heat release associated with deep convective systems in the tropics. The reader is refered to the Hagan et al. and Hagan and Forbes papers in the References section and to the GSWM web page for details. Note, that GSWM is a linear model. No non-linear tidal forcing mechanisms, such as wave-wave interactions, are included. There is also no radiative forcing of nonmigrating tidal components included. Because GSWM tides are monthly climatologies, the model tides (amplitudes and phases) are linearly interpolated to the day-of-year of the TIMED measurements before the tidal perturbations for the SABER and TIDI UT's and locations are computed.

TIME-GCM

A general overview of TIME-GCM can be found here. There is currently one model run available.

TIME-GCM/AMIE

Selected time periods (e.g. the April 2002 solar storm period) include the assimilative mapping of ionospheric electrodynamics (AMIE) procedure. An overview of the TIME-GCM/AMIE simulation for the April 2002 storm period including some animations is available here. The full TIME-GCM/AMIE output entering the model sampling procedure is on the 5 deg x 5 deg model grid at al 45 pressure levels (~30-500 km) every 10 minutes. There is no lower boundary NCEP forcing included in this run. Available model fields:

SABER	TIDI	GUVI	CEDAR ground based component of TIMED
TN, UN, VN, W, CO2, O3, O2, O, OH, NO, RHO, Z (geopotential)	TN, UN, VN, W, UI, VI, WI, O3, O2, O, RHO, Z (geopotential)	TN, O, O2, N2, O/N2, NE, RHO, Z (geopotential)	TN, UN, VN, WN, UI, VI, WI, TE, TI, NE, RHO, Z (geopotential)

TIEGCM

A general overview of TIEGCM can be found here. There is currently no sampled TIEGCM model run available.

Data Availability

These instrument/model combinations and time periods (YYYYDDD) are currently available. Additional time periods and instrument/model pairs will be added soon. Example plots can be found here. To access the data, go to the **Rules of the Road**.
	TIEGCM	TIME-GCM	GSWM
SABER	NOT YET	2002106-2002112 (TIME-GCM/AMIE)	2002091-2002120
TIDI	NOT YET	2002106-2002111 (TIME-GCM/AMIE)	2002078-2002365
GUVI	NOT YET	2002106-2002112 (TIME-GCM/AMIE)	NOT AVAILABLE
CEDAR ground-based component of TIMED	NOT YET	2002106-2002112 (TIME-GCM/AMIE, 10 minutes time resolution, List of sampled locations)	ALL, data access from GSWM web page

Rules of the Road

The sampled model results are made available here for the benefit of the scientific community. However, many aspects of these results have not been published. If users are planning to use the sampled model results in a publication or presentation, they are kindly requested to contact Dr. Maura Hagan (hagan at ucar.edu) and discuss with her opportunities for collaboration and co-authorship.

If you agree with these Rules of the Road, please enter your email address in the field below and press the "I agree" button for data access. Your email address will be stored.

Developed by Jens Oberheide (jenso@ucar.edu): 19 December 2002
Last update by Jens Oberheide: 26 August 2003
Copyright 2002, NCAR