2008 Workshop:Ground-Space Models for Studying Atmospheric Coupling

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Ground-Space Models for Studying Atmospheric Coupling

Contents 1 Ground-Space Models for Studying Atmospheric Coupling 1.1 Location 1.2 Date/Time 1.3 Conveners 1.4 Format of the Workshop 1.5 Duration 1.6 Estimated attendance 1.7 Conflicts with other workshops 1.8 Special technology requests 1.9 Brief Initial Description 1.10 Description for Students 1.11 Workshop Summary 1.12 Presentation Resources 1.13 Forum

Location

Grindelwald

Date/Time

1300-1500 and 1600-1800 Wednesday 18 June 2008

Conveners

• Han-Li Liu
• Dave Siskind
• Bob Schunk

Format of the Workshop

scheduled short-presentations and discussions

Duration

4 hours. Co-Convener Dave Siskind has to leave on Friday.

Estimated attendance

50

Conflicts with other workshops

Coupling of Atmospheric Regions During Sudden Stratospheric Warmings.
New Understanding of Thermospheric Density and Composition Structure and Variability.
Lower and Upper Atmosphere Coupling.

Special technology requests

none

Brief Initial Description

Understanding the coupling of lower and upper atmosphere is a key element of CEDAR research, and a new CEDAR initiative, Integrative Aeronomy, aims to focus specifically on the physics and chemistry of the upper atmosphere and its integrative role in planetary atmosphere-space systems. To understand the coupling mechanisms, address issues in integrative aeronomy, and to support the CEDAR community research, numerical models from the ground to the upper atmosphere have been developed in recent years. We feel it would be timely to have a workshop reviewing the current status of such models and to discuss model development, validation, model inter-comparison, research application of these models, and integration with the CEDAR observational community. Specific topics will include, but not limited to,

1. Determine major dynamics, physics, chemistry modules used in these models.
2. Climatological comparisons (temperature, winds, composition, tides, planetary and gravity waves, semi-annual oscillation, quasi-biennial oscillation) and long term trends.
3. Meteorological case studies
   1. CAWSES-related tidal studies,
   2. Stratospheric warmings and associated mesospheric coolings,
   3. Polar mesospheric clouds,
   4. Perturbations from solar activity/space weather effects
4. Error growth and data assimilation.
5. Coupling of the neutral atmosphere to the ionosphere.
6. Possible impacts on the middle and lower atmosphere by upper atmospheric processes.

The unifying theme of the above topics is that they should consider the atmosphere from the troposphere into the thermosphere.

Description for Students

The upper atmosphere of the Earth responds to forcing from two external sources. The first, the solar wind, has been known for some time.. During geomagnetic storms, an increase in the solar wind speed acts to induce a large-scale current in the upper atmosphere. The energy that is deposited in the upper atmosphere at high latitudes not only leads to bright auroral displays, but acts to excite atmospheric gravity waves that propagate from high to low latitudes. In addition, during both quiet and disturbed times, it is now recognized that the upper atmosphere is affected by planetary, tidal, and gravity waves that propagate upwards from the lower and middle atmosphere (troposphere, stratosphere, and mesosphere), and they provide a significant source of momentum and energy for the upper atmosphere. The role that these waves play in the dynamics and energetics of the upper atmosphere is an exciting and relatively new area of research. An important part of this CEDAR Workshop will be devoted to understanding the coupling of the lower and upper atmosphere via waves and to the interaction of lower atmospheric waves with waves generated at high latitudes using newly developed numerical models.

Workshop Summary

In recent years there has been rapid development of general circulation models extending from the ground to the thermosphere. It is timely for the CEDAR community to learn the status of such model development, and to discuss issues in developing and validating these models, application of the models in studying atmospheric coupling, and whole atmosphere and/or upper atmosphere data assimilation.

Steve Eckermann presented the recent development of the NOGAPS-ALPHA, which now extends from the ground to ~100 km and includes non-LTE heating and cooling, prognostic ozone, H2O, CH4, and N2O, and parameterization of non-orographic gravity waves. The NOGAPS data assimilation system (NAVDAS) uses 3DVar methods and has been extended to assimilate upper atmosphere data (Aura MLS and TIMED/SABER). It also has the capability to ingest single-point measurements, which is valuable for CEDAR. The first results from an assimilation to support the AIM Small Explorer Mission were presented. Han-Li Liu reported that the NCAR WACCM has recently been extended to include the thermosphere and ionosphere (without electrodynamics). The model resolves compositional, temperature, and wind structures from the ground to the upper thermosphere in a self-consistent way. These fields and their seasonal variability compare well with climatology, and strong short-term variability is seen in the thermosphere.

Bob Schunk reported on a study of short-term variability in the ionosphere by incorporating fields from NOGAPS and WACCM as boundary conditions at 90 km in GAIM. Short-term variability with planetary-wave periods (2-20 days) is also identified in TEC and magnetometer data, and the need to study their sources using a whole atmosphere model was identified by Art Richmond and Wenbin Wang. Wenbin Wang also demonstrated that solar wind bear variability with periods between 5-15 days, which induces ionosphere/thermosphere variability with similar periods. A whole atmosphere model will be valuable in delineating the relative roles of lower atmospheric driving and solar wind driving. Variability on smaller and shorter time scales due to gravity waves needs to be simulated by regional models, and Larry Gardner described the development of one such model. This model extends from the ground to 600 km altitude and 600 km in the horizontal direction.

Most global models assume hydrostatic equilibrium, which is a valid assumption on global scales. As the model resolution increases, we are now approaching scales where such assumption is becoming questionable. Deng/Ridley used GITM, which is a non-hydrostatic global model, to demonstrate that the vertical wind due to intensive auroral heating could reach 60m/s around 250 km, comparable to FPI measurements of the thermospheric wind. As a comparison, TIEGCM simulation with the same amount of auroral heating yields vertical wind less than 5m/s.

The development of whole atmosphere models pose unique challenges, for example, the dominant physical processes and the respective temporal scales can be quite different at different atmosphere regions. Art Richmond pointed out the need to solve electrodynamics equations along magnetic field lines due to the significant anisotropy in electric conductivity, thus the need for conversion between the geomagnetic and geographic coordinate systems.

Results from whole atmosphere models could be very sensitive to the gravity wave parameterization used in the model. Dave Siskind showed that the mesospheric and thermospheric responses during a stratospheric sudden warming (SSW) are very sensitive to the both the orographic and non-orographic schemes used in the model, and observational constraints are needed to reduce the uncertainty in gravity waves. Constraints on gravity wave by observations during SSW were also discussed in another workshop, Coupling of Atmospheric Regions during Stratospheric Sudden Warmings.

It is critical to validate the climatology from whole atmosphere models against observations and empirical models. Preliminary validations have been conducted on WACCM and NOGAPS-ALPHA results. The community is now actively involved in validating the model results with observations. Tao Yuan presented a comparison of climatological winds and temperature from WACCM, HAMMONIA, and TIME-GCM with those obtained from multiple years of lidar measurement at CSU. Loren Chang compared migrating diurnal tide observed by multiple ground-based sites during the CAWSES tidal campaigns with that from CMAM, WACCM, and TIME-GCM/ECMWF. Larisa Goncharenko reported on the progress in the inter-comparison of observed tides during the CAWSES tidal campaigns.

The NRL-HWM has often been used to provide thermospheric wind climatology, and Doug Drob reported that it has been recently updated to include HRDI/WINDII winds. TIME-GCM results have been used where no data is available (e.g. polar region and night time in the lower thermosphere).

Chaotic error growth determines the predictability of a model system, and Han-Li Liu showed that in WACCM the error growth is the largest in the MLT and winter stratosphere--regions where planetary waves are strong. The error growth in WACCM is generally controlled by the error growth in the troposphere, which is likely associated with baroclinic/barotropic instability. Tomoko Matsuo's research in applying ensemble Kalman filter (EnKF) to MLT data assimilation signifies the importance of error growth in a forecast model.

EnKF data assimilation technique is being applied to physics based ionosphere models. Ludger Scherliess reported the development of a full-physics based GAIM model using EnKF, which can be used to determine the ionospheric drivers at low to mid-latitudes and global electron density distribution. Dave Pawlowski showed results from GITM EnKF data assimilation experiments and demonstrated improvement of TEC calculation by applying the EnKF technique.

From the presentations and discussions of this four-hour workshop, it is found:

1. There is a clear need to validate whole atmosphere models with observations and empirical models so that the right baseline climatology can be obtained from these models. This will also help reduce uncertainties in model parameterizations. CEDAR is already playing an active role in the process.
2. Better quantification of thermosphere/ionosphere variability demands whole atmosphere modeling.
3. Regional scale models are needed to understand large variabilities on "weather" scales in the upper atmosphere.
4. The predictability of the upper atmosphere is strongly influenced by the predictability of the troposphere. Its implication for data assimilation of the whole atmosphere should be further explored.
5. For data sparse systems, such as the ionosphere, ensemble Kalman filter technique applied to physics-based models proves to be a valuable tool in quantifying the variability of the systems.

Presentation Resources

Ground to Space Models: Introduction Slides

Forum

Comments, Questions, Discussion Forum

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