Anthropogenic influence on the 2018 summer warm spell in Europe: the impact of different spatio-temporal scales
Bulletin of the American Meteorological Society American Meteorological Society 101:S1 (2020) S41-S46
Abstract:
We demonstrate that, in attribution studies, events defined over longer time scales generally produce higher probability ratios due to lower interannual variability, reconciling seemingly inconsistent attribution results of Europe’s 2018 summer heatwaves in reported studies.Optimising the use of ensemble information in numerical weather forecasts of wind power generation
Environmental Research Letters IOP Publishing 14:12 (2019) 124086-124086
An interdecadal shift of the extratropical teleconnection from the tropical Pacific during boreal summer
Geophysical Research Letters American Geophysical Union 46:22 (2019) 13379-13388
Abstract:
The extratropical teleconnection from the tropical Pacific in boreal summer exhibits a significant shift over the past 70 years. Cyclonic circulation anomalies over the North Atlantic and Eurasia associated with El Niño in the later period (1978‐2014) are absent in the earlier period (1948‐1977). An initialised atmospheric model ensemble, performed with prescribed sea surface temperature (SST) boundary conditions, replicates some key features of the shift in the teleconnection, providing clear evidence that this shift is not simply due to internal atmospheric variability or random sampling. Additional ensemble simulations, one with detrended tropical SSTs and another with constant external forcing are analysed. In the model, the teleconnection shift is associated with climatological atmospheric circulation changes, which are substantially reduced in the simulation with detrended tropical SSTs. These results demonstrate that the climatological atmospheric circulation and associated teleconnection changes are largely forced by tropical SST trends.Seasonal predictability of the winter North Atlantic Oscillation from a jet stream perspective
Geophysical Research Letters Wiley 46:16 (2019) 10159-10167
Abstract:
The winter North Atlantic Oscillation (NAO) has varied on interannual and decadal timescales over the last century, associated with variations in the speed and latitude of the eddy driven jet stream. This paper uses hindcasts from two operational seasonal forecast sys tems (the European Centre for Medium-range Weather Forecasts (ECMWF)’s seasonal forecast system, and the UK Met Office global seasonal forecast system) and a century long atmosphere-only experiment (using the ECMWF’s Integrated Forecasting System model) to relate seasonal prediction skill in the NAO to these aspects of jet variability. This shows that the NAO skill realised so far arises from interannual variations in the jet, largely associated with its latitude rather than speed. There likely remains further potential for predictability on longer, decadal timescales. In the small sample of mod els analysed here, improved representation of the structure of jet variability does not trans late to enhanced seasonal forecast skill.SEAS5: the new ECMWF seasonal forecast system
GEOSCIENTIFIC MODEL DEVELOPMENT 12:3 (2019) 1087-1117