92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Monday, 23 January 2012
Predictive Ability of Various Auroral Precipitation Models As Evaluated Using Polar UVI Global Images
Hall E (New Orleans Convention Center )
Patrick T. Newell, APL, Laurel, MD; and T. Sotirelis, K. Liou, S. Wing, and R. Redmon

Auroral precipitation models have been valuable tools for several decades, but it has been difficult to estimate their objective accuracy. Global UV imagers, which make instantaneous estimates of hemispheric auroral power, provide a way forward. Specifically, we correlated Polar UVI images with the predictions of several precipitation models, including the Hardy Kp model, the Brautigam IMF-based model, the Evans nowcast model currently used at NOAA, and OVATION Prime, a forecast model which is also in real-time operation at NOAA. To minimize dayglow, the nightside precipitating power (1800 – 0600 MLT) is considered, and only for cases where that entire region is within the Polar UVI field of view. Also, only instances where each model has a prediction are considered (i.e., there must be IMF data, and there must be a NOAA satellite pass within the last 1 h). Altogether, 27613 1-minute (“instantaneous”) images satisfied these criteria from 1996-1997. The four models investigated predict roughly half the variance in auroral power. From least to best at predicting instantaneous auroral power, the results are Brautigam-IMF model (r=0.68, r2=46%); Evans nowcast model (r=0.70, r2=49%); Hardy-Kp model (r=0.72, r2=52%); and OVATION Prime-IMF (r=0.75, r2=56%). We also considered 1-h averages of UVI images. All four models improved, but the nowcast jumped from third to first: Brautigam-IMF (r=0.69, r2=48%); Hardy-Kp (r=0.74, r2=55%); OVATION Prime-IMF (r=0.76, r2=58%); Evans nowcast (r=0.77, r2=59%). The nowcast approach benefits most from hourly averaging because at times more than one satellite pass is available. We also plan to evaluate the performance of these models under more extreme conditions, and to consider the Zhang-Paxton image-based model, said to be valid through Kp=9.

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