*************************** ** THE GEM MESSENGER ** *************************** Volume 23, Number 25 August 28, 2013 ---------------------------------------------------------------------- 1. 2013 Workshop Report from The Metrics and Validation Focus Group ---------------------------------------------------------------------- From: Timothy Guild, Lutz Rastaetter, Howard Singer The GGCM Metrics and Validation Focus Group held three well-attended sessions at this past GEM workshop in Snowmass, CO, on Thursday and Friday, June 20-21, 2013. The sessions represented a wide range of community contributions on all aspects of model / data comparisons, understanding model / data discrepancies, and new validation studies and metrics. The sessions included varied presentations from 18 attendees, representing 13 institutions and 3 countries. The detailed agenda was posted to the GEM wiki in advance (http://aten.igpp.ucla.edu/gemwiki/index.php/FG:_Metrics_and_Validatio n). The first Metrics and Validation (M&V) session was entitled "New Validation Results and Methods." It solicited short presentations focusing on all aspects of data-model comparisons. We welcomed themes which included geospace model validation using regional ground magnetometer indices, model responses to dynamic magnetopause boundaries, long-term "climatological" model validation, using multi- variate metrics to assess model performance, or any related contribution. This session included contributions from 9 research teams (F. Toffoletto, L. Rastaetter and H. Singer, A. Glocer, V. Veibell and R. Weigel, G. Facsko, R. Katus and M. Liemohn, H. Korth, J. Rigler, and A. Pembroke) discussing the state-of-the-art validation results from MHD/Ring current coupled models, calculation and comparison of ground magnetic perturbations from global simulations, data/model comparisons from climatological-scale simulations (months- to-years), and multi-variate techniques for global validation studies. We also had a presentation offering a new, unique dataset of precipitating particle properties, ready for use in validation of global MHD models. The session was so well subscribed that presentations from this session overflowed into the follow-on sessions, in order to enable adequate discussion time and participation from the audience. The second session sponsored by the M&V focus group was titled "How Validation Studies Guide Model Improvements." This solicitation gets at the heart of the M&V focus group, attempting to understand data/model differences from validation studies to improve the underlying physics of geospace models, and thus enabling a more complete GGCM with improved prediction efficiencies. In this session we had contributions from H. Singer, D. Welling, M. Chen, A. Samsonov, S. Merkin, and L. Rastaetter. The session was initiated with a presentation on the lessons learned from solar wind research regarding the merits of ensemble forecasting that can provide confidence bounds and uncertainties on model solutions. We also heard about model performance related to the GEM Dst Challenge and the GEM Magnetopause Challenge, the influence of polar wind on Dst, and the need for a multi-fluid approach in MHD models where each fluid has separate densities, velocities and temperatures. The role of uncertainties in model results that can be attributed to boundary conditions rather than missing physical processes was discussed, as well as vortices in the inner magnetosphere and the influence of inner magnetosphere boundaries on the creation of these structures. We discussed new opportunities for data-model comparisons, including results from comparisons between MHD models and the Active Magnetosphere and Polar Electrodynamics Response Experiment (AMPERE) observations. The last session organized by the M&V focus group was titled "Validation of MHD models coupled with other modules such as the Ring Current and Polar Outflow." It solicited recent advances in the development of coupled models of the magnetosphere, inner magnetosphere, the plasmasphere/polar wind, and the ionosphere/thermosphere. In this session modelers presented recent advances in coupled models: J. Raeder (OpenGGCM-RCM), M. Wiltberger (multi-fluid LFM) and B. Zhang (LFM, studying polar outflow and polar cap position). Wrapping up the M&V sessions, we began a discussion on studying the magnetopause position in a future metrics and validation study. The role of statistical models in lieu of actual observations during an event (which are sparse) was debated. More discussion is planned for the mini-GEM in San Francisco in December. One recurrent theme within the three sessions of the M&V focus group this year was the organized, validation of GGCM component models subject to uncertain initial and boundary conditions. A technique to quantitatively understand model behavior subject to these conditions, ensemble modeling, was recently borrowed from the tropospheric weather modeling community for quiet time solar/heliospheric modeling [Riley et al., 2013, doi:10.1002/jgra.50156]. Many presentations at this year's GEM workshop echoed this theme in one way or another. After discussion in the focus group sessions, it was decided that ensemble modeling was a worthwhile method for the focus group to investigate, and could potentially illuminate model shortcomings in a more rigorous and less biased way than is currently done. We plan to continue this theme in upcoming workshops. +-------------------------------------------------------------------+ | The GEM Messenger is the electronic newsletter for the | | NSF GEM Program and Workshops. | | | | Editor: Peter Chi, GEM Communications Coordinator | | E-mail: | | | | To subscribe GEM Messengers, send an e-mail message to: | | | | with the following command in the body of your e-mail: | | subscribe gem | | To remove your e-mail address from the list, the command is: | | unsubscribe gem | | | | GEM Messenger is also posted online (via NewsFeed) at | | http://heliophysics.blogspot.com and | | http://www.facebook.com/heliophysics | | | | Back issues are available at ftp://igpp.ucla.edu/scratch/gem/ | | | | URL of GEM Home Page: http://aten.igpp.ucla.edu/gemwiki | | Workshop Information: http://www.cpe.vt.edu/gem/index.html | +-------------------------------------------------------------------+