NASA/NOAA MOU Annex Final Report: Evaluating Model Advancements for Predicting CME Arrival Time

TL;DR

The paper tackles CME arrival time forecast accuracy by integrating time-dependent inner boundary driving using the ADAPT flux transport model, fed by GONG magnetograms, into the WSA-ENLIL framework and comparing results against the operational (non-ADAPT) configuration. It evaluates 38 historical events across multiple years with a large suite of simulations to quantify replication fidelity, the impact of magnetogram corrections, and potential gains from time-dependent driving and ADAPT ensembles. The findings indicate that time-dependent, zero-point corrected magnetogram inputs generally reduce arrival-time errors, with notable improvements for the 2017–2019 subset where magnetogram corrections are more reliable, underscoring the value of ensemble-based approaches and robust validation. The work highlights practical challenges in CME arrival detection, the importance of detailed documentation and software management across interagency collaborations, and points to future avenues for ensemble validation and model recalibration to maximize forecast utility.

Abstract

The purpose of this project was to assess improvements in CME arrival time forecasts at Earth using the Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model driven by data from the Global Oscillation Network Group (GONG) ground observatories. These outputs are then fed into the coupled Wang-Sheeley-Arge (WSA) - ENLIL model and compared to an operational version of WSA-ENLIL (without ADAPT). SWPC selected a set of 38 historical events over the period of five years from 2012--2014 (33 events) and 2017--2019 (5 events). The overall three-year project consisted of multiple simulation validation studies for the entire event set (1292 simulations): (a) benchmark single map (operational version prior to May 2019) (b) time-dependent sequence of GONG maps driving WSA-ENLIL with 4 different model settings (c) single test simulation of a time-dependent sequence of GONG maps driving ADAPT-WSA-ENLIL (d) single GONG map driving ADAPT-WSA-ENLIL (e) time-dependent sequence of GONG maps driving ADAPT-WSA-ENLIL. We report that for all 38 events, within each model version/settings combination, the CME arrival time error decreased by 0.2 to 0.9 hours when using a sequence of time-dependent zero-point corrected magnetograms compared to using single magnetogram input. Overall, for all events, when using the older uncorrected magnetograms, the CME arrival time error increased for all new model versions/settings combination compared to the benchmark. Notably for the 5 events in the period 2017--2019 when more reliable zero-point corrected magnetograms were available, the ADAPT-WSA-ENLIL (median arrival realization) CME arrival time error decreased against all benchmarks. In this report we also discuss replicating the operational model, challenges in detecting CME arrival in simulations, and comparing zero-point corrected and uncorrected magnetogram inputs.

Figures (18)

• Figure 1: Example of replication results at Earth for Event #1 in Table \ref{['tbl:subset']}.
• Figure 2: Model output time-series of speed, density, magnetic field, and temperature for different resolution settings for the 4 events (of the 7 events listed in Table \ref{['tbl:subset']}). Low resolution--purple, medium resolution--orange, high resolution--green, high$\times$2 resolution--grey.
• Figure 3: Comparison of WSA version 2.2 and ENLIL version 2.9f speed, density, magnetic field, and temperature results (blue) at Earth when using zero-point corrected maps corobs=gongz (left) and uncorrected maps (right) compared to OMNI observations (red).
• Figure 4: Arrival time error for each event and simulation setting (the color for each setting is defined in the legend). Symbols: hollow black squares=SWPC operational arrival times, squares=benchmark single-map driven arrival times, triangles=time-dependent arrival times. The grey bars show the distance between the (a) single map benchmark and (e) ADAPT time-dependent map driven arrival times, showing the greatest improvement in arrival time error. The error bars show the range of arrival time errors from the ADAPT ensembles.
• Figure 5: GONG-WSA-ENLIL radial velocity contour plots for event 1 (2012-01-23 04:00 UT) showing the (panel a) constant Earth HEEQ latitude plane, (panel b) meridional plane of Earth, and (panel c) 1 AU sphere in cylindrical. The single map driven benchmark (a) simulation (top) shows the CME arrival around 2012-01-24 16:01 UT, while the CME has not yet arrived in the time-dependent driven (b) simulation (bottom) at the same timestamp. For this event, the CME propagates just inside the front of a high speed stream that has a slower speed in the time-dependent driven simulation, causing the CME to arrive later compared to the benchmark.