Atmospheric blocking and upper-level Rossby wave forecast skill dependence on model configuration

Martinez-Alvarado, O. ORCID: https://orcid.org/0000-0002-5285-0379, Maddison, J., Gray, S. ORCID: https://orcid.org/0000-0001-8658-362X and Williams, K. (2018) Atmospheric blocking and upper-level Rossby wave forecast skill dependence on model configuration. Quarterly Journal of the Royal Meteorological Society, 144 (716). pp. 2165-2181. ISSN 1477-870X doi: 10.1002/qj.3326

Abstract/Summary

Weather models differ in their ability to forecast, at medium range, atmospheric blocking and the associated structure of upper-level Rossby waves. Here, we evaluate the effect of a model's dynamical core on such forecasts. Operational forecasts from the ensemble prediction systems (EPSs) of the European Centre for Medium-range Weather Forecasts (ECMWF), the Met Office (MO) and the Korean Meteorological Administration (KMA) are used. Northern hemisphere model output is analysed from winters before and after a major upgrade to the dynamical core of the MO-EPS. The KMA-EPS acts as a control as it uses the same model as the MO-EPS, but used the older dynamical core throughout. The confounding factor of resolution differences between the MO-EPS and the KMA-EPS is assessed using a MO forecast model hindcast experiment with the more recent dynamical core, but the operational resolution of the KMA-EPS. The introduction of the new dynamical core in the MO-EPS has led to increased forecast blocking frequency, at lead times of five and seven days, counteracting the typically-observed reduction in blocking frequency with lead time. Hit rates of blocking activity, onset and decay are also increased in the main blocking regions (without a corresponding increase in false positive rate). The previously-found reduction of upper-level ridge area and tropopause sharpness (measured by isentropic potential vorticity gradient) with lead time is also reduced with the new dynamical core. This dynamical core improvement (associated with a reduction in implicit damping) is thus demonstrated to be at least as effective as operational resolution improvements in improving forecasts of upper-level Rossby waves and associated blocking.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/76959
Identification Number/DOI	10.1002/qj.3326
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	Operational ensemble prediction systems; predictive skill; atmospheric blocking; Rossby waves
Publisher	Royal Meteorological Society
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