@article{Owens:2017:10.1007/s11207-017-1090-7,
author = {Owens, MJ and Riley, P and Horbury, TS},
doi = {10.1007/s11207-017-1090-7},
journal = {Solar Physics},
title = {Probabilistic Solar Wind and Geomagnetic Forecasting Using an Analogue Ensemble or "Similar Day" Approach},
url = {http://dx.doi.org/10.1007/s11207-017-1090-7},
volume = {292},
year = {2017}
}

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TY  - JOUR
AB  - Effective space-weather prediction and mitigation requires accurate forecastingof near-Earth solar-wind conditions. Numerical magnetohydrodynamic models of the solarwind, driven by remote solar observations, are gaining skill at forecasting the large-scalesolar-wind features that give rise to near-Earth variations over days and weeks. There remainsa need for accurate short-term (hours to days) solar-wind forecasts, however. In thisstudy we investigate the analogue ensemble (AnEn), or “similar day”, approach that wasdeveloped for atmospheric weather forecasting. The central premise of the AnEn is thatpast variations that are analogous or similar to current conditions can be used to provide agood estimate of future variations. By considering an ensemble of past analogues, the AnEnforecast is inherently probabilistic and provides a measure of the forecast uncertainty. Weshow that forecasts of solar-wind speed can be improved by considering both speed anddensity when determining past analogues, whereas forecasts of the out-of-ecliptic magneticfield [BN] are improved by also considering the in-ecliptic magnetic-field components. Ingeneral, the best forecasts are found by considering only the previous 6 – 12 hours of observations.Using these parameters, the AnEn provides a valuable probabilistic forecast forsolar-wind speed, density, and in-ecliptic magnetic field over lead times from a few hoursto around four days. For BN, which is central to space-weather disturbance, the AnEn onlyprovides a valuable forecast out to around six to seven hours. As the inherent predictabilityof this parameter is low, this is still likely a marked improvement over other forecast methods.We also investigate the use of the AnEn in forecasting geomagnetic indices Dst and Kp.The AnEn provides a valuable probabilistic forecast of both indices out to around four days.We outline a number of future improvements to AnEn forecasts of near-Earth solar-windand geomagnetic conditions.
AU  - Owens,MJ
AU  - Riley,P
AU  - Horbury,TS
DO  - 10.1007/s11207-017-1090-7
PY  - 2017///
SN  - 0038-0938
TI  - Probabilistic Solar Wind and Geomagnetic Forecasting Using an Analogue Ensemble or "Similar Day" Approach
T2  - Solar Physics
UR  - http://dx.doi.org/10.1007/s11207-017-1090-7
UR  - http://hdl.handle.net/10044/1/51012
VL  - 292
ER  - 

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