Top NWP experts mark Research Director’s departure

Raymond Pierrehumbert, Halley Professor of Physics at the University of Oxford, gave a talk on planetary wave resonance and multiple equilibria. He pointed out that the issue of resonance in planetary atmospheric waves has still not been fully resolved decades after it was first raised.

Simplified models imply the possibility of such resonance leading to an infinite amplitude. The issue of how, in the real atmosphere, such amplitudes are damped continues to be the subject of research.

Nedjeljka Žagar, Professor of Meteorology at the University of Ljubljana, spoke about the role of tropical analysis uncertainties in global predictability. She explained that uncertainties in the initial conditions of forecasts in the tropics also affect forecast skill in the mid-latitudes.

One reason for the uncertainties is a lack of weather observations. New wind data, such as from the Aeolus satellite to be launched at the end of this year, could help to address the problem.

Hans Huang, the Head of Weather Modelling and Prediction at the Centre for Climate Research Singapore, talked about convective-scale NWP in Singapore. He said forecasts in Singapore are difficult because tropical weather systems are complex, develop rapidly, are short-lived and are driven by variable winds.

Successive model upgrades have, however, improved the prediction of rainfall and storm cells. A collaborative effort will be needed to make further improvements.

Professor Belcher gave a talk on climate science post-COP21. He said the drivers of climate science after the Paris Agreement would include the global energy balance; mitigation strategies; weather and climate hazards; and the impacts and opportunities of mitigation and adaptation.

The energy balance problem is more fundamental than rising near-surface temperatures, which are a symptom. Studies show that energy continues to accumulate in the deep ocean.

Dr Burridge, a member of staff from the start and ECMWF Director from 1991 to 2004, took the audience on a whistle-stop tour of the history of NWP and of ECMWF. He pointed out that, within four years of creating the Centre, a step change in global numerical weather prediction had been achieved.

However, this had only been possible with a lot of help from visitors and other institutions. Dr Burridge concluded by wishing ECMWF good luck with the new ten-year Strategy adopted in 2016.

Professor Källén emphasised the role of collaboration in his overview of some of the main items on ECMWF’s research agenda. He said a lot of work remains to be done in data assimilation and modelling to further improve medium-range weather forecasts.

ECMWF’s strategy to achieve this includes an Earth system approach to modelling and analysing the state of the atmosphere; probabilistic predictions using ensemble forecasts at a horizontal resolution of 5 km by 2025; and scalability across the NWP chain.

Dr Rabier said ECMWF had played a unique role over the last four decades by addressing the most difficult problems in NWP that no single country could resolve on its own. She said the Earth system approach being pursued by the Centre means more coupled processes will be included.

Another major aspect of ECMWF’s new ten-year Strategy is an emphasis on ensemble forecasts. Dr Rabier, who “once was a deterministic girl”, made it clear that these will become the Centre’s main output.