Probabilistic solar wind and geomagnetic forecasting using an analogue ensemble or "Similar Day" approach

Effective space-weather prediction and mitigation requires accurate forecasting of near-Earth solar-wind conditions. Numerical magnetohydrodynamic models of the solar wind, driven by remote solar observations, are gaining skill at forecasting the large-scale solar-wind features that give rise to near-Earth variations over days and weeks. There remains a need for accurate short-term (hours to days) solar-wind forecasts, however. In this study we investigate the analogue ensemble (AnEn), or “similar day”, approach that was developed for atmospheric weather forecasting. The central premise of the AnEn is that past variations that are analogous or similar to current conditions can be used to provide a good estimate of future variations. By considering an ensemble of past analogues, the AnEn forecast is inherently probabilistic and provides a measure of the forecast uncertainty. We show that forecasts of solar-wind speed can be improved by considering both speed and density when determining past analogues, whereas forecasts of the out-of-ecliptic magnetic field [ BNBN ] are improved by also considering the in-ecliptic magnetic-field components. In general, 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 for solar-wind speed, density, and in-ecliptic magnetic field over lead times from a few hours to around four days. For BNBN , which is central to space-weather disturbance, the AnEn only provides a valuable forecast out to around six to seven hours. As the inherent predictability of 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-wind and geomagnetic conditions

A verification of monthly weather forecasts in the seventies

Monthly forecasts of temperature, rainfall and sunshine have been verified during the period 1970–79. The predictions were based on seven different schemes. Of the seven methods, five refer to De Bilt (The Netherlands), one to southeast England and one to the Federal Republic of Germany. The results are not very encouraging for any of the methods. The skill is negligible except for a few schemes that predicted the monthly mean temperature 10% better than climatology

Fysische aspecten van het CO2-probleem

Via kranten en tijdschriften is zo langzamerhand bekend geworden dat het C02-gehalte van de atmosfeer toeneemt, waardoor vanwege het broeikaseffect het klimaat warmer zou worden. Van alle verdere gevolgen trekt vooral de mogelijke afsmelting van de ijskappen en de daarmee gepaard gaande stijging van de zeespiegel sterk de aandacht. Een keten van fysische oorzaken en gevolgen, waarvan alleen het eindresultaat telt. Wat werkelijk telt is echter ons inzicht in de verschillende fysische processen. Zolang dit nog onvolledig is, mogen we er niet van uitgaan dat de verschillende toekomstprojecties veel betekenis hebben. Aandacht dus voor de fysische aspecten van het C02-probleem: de meting van het C02-gehalte van de atmosfeer, het broeikaseffect, de terugkoppelingen in het klimaatsysteem, de rol van de oceanen en het gedrag van ijskappen. Ten slotte echter ook de meest recente rekenresultaten en de jacht op de primeur in het vaststellen van het C02-klimaateffect