Seminars

Seminars / Informal seminars / Lectures by ECMWF Staff and Invited Lecturers

Seminars contribute to our ongoing educational programme and are tailored to the interests of the ECMWF scientific community.

Informal seminars are held throughout the year on a range of topics. Seminars vary in their duration, depending on the area covered, and are given by subject specialists. As with the annual seminar, this may be an ECMWF staff member or an invited lecturer.

The following is a listing of seminars/lectures that have been given this year on topics of interest to the ECMWF scientific community.  See also our past informal seminars

2020

18 June
at 10:30

VIRTUAL - please join meeting a few minutes before start time (name to be provided and approved)

http://tiny.cc/ecPoint-seminar

 

“ecPoint” - a Post-processing Tool that improves Forecasts and highlights Systematic Model Errors

Speaker: Timothy Hewson

Abstract

In April 2019 ECMWF introduced a new, experimental, “point rainfall” forecast product onto its ecCharts web display platform, based on the post-processing package “ecPoint”, to give site-specific forecasts for everywhere in the world up to day 10. Prior to this development forecasters had access to just raw ensemble output in ecCharts, which provides gridbox average totals. ecPoint aims to incorporate probabilistically the expected sub-grid variability, and simultaneously apply gridscale bias corrections. Both these adjustments depend critically on “gridbox-weather-type”.

This presentation will describe the meteorology-based calibration rationale that underpins ecPoint, how this is different to pre-existing post-processing methods, and how it can also be applied to other surface variables such as 2m temperature. Numerous benefits will be highlighted.

The conditional verification concepts underpinning the calibration allow one to identify weather-situation-dependent gridscale biases. Examples will illustrate the diagnostic power of this approach, showing where and when rainfall is typically under- and over-forecast, providing pointers for future model improvements. And using an open source GUI one can apply the calibration code to data from other models, and thereby intercompare performance in different weather situations.

The forecast improvements that then arise will be discussed, using both long term global verification up to day 10, and illustrative case studies, with a focus on how extreme localised rainfall, that might lead to flash floods, is better handled. It will be shown how the post-processing can usefully shift the emphasis for warning issue from one region to another, when one compares with raw ensemble output.

There will be brief reference, from collaborative work, to how ecPoint output seems to compare favorably with the post-processed output of convection-resolving limited area ensembles.

The talk will conclude by discussing, in the context of ongoing and potential projects, numerous future applications of ecPoint, such as bias-corrected inputs to hydrological models, point rainfall re-analyses and tests of theories such as city impact on rainfall. Avenues for improving the methodology will also be highlighted.

28 April
at 10:00

VIRTUAL

Can approximations of the CRPS help us better understand why the skill changes?

Martin Leutbecher and Thomas Haiden

Abstract

Ensemble verification of scalar variables often involves the use of the continuous ranked probability score (CRPS). The talk looks at a Gaussian approximation of the CRPS with the aim to improve our understanding of score changes. The approximation permits to express the CRPS of an ensemble as a function of the variance of the error of the ensemble mean, the mean error of the ensemble mean and the ensemble variance. The methodology will be applied to direct model output from medium-range ensemble forecasts as well as postprocessed ensemble forecasts. We will examine how well this approximation works and whether it might be suitable to complement information we see for instance in scorecards.

14 February
at 10:30

Room: LT

Aircraft Weather Observations and their Use (current and future)

Speaker: Steve Stringer (Met Office and EUMETNET) and Siebren de Haan/Jan Sondij (KNMI and EMADDC)

Abstract

Aircraft based weather observations (ABO) have increasingly become a very valuable input into the global weather forecasting process, with some independent assessments showing their impact on NWP to be second only to that of satellite data. An international workshop on Aircraft Based-Observations (ABO) is to be hosted at ECMWF, 12th/13th February 2020, bringing together ABO data users and ABO data providers to share their experience of aircraft data use and to recommend any necessary changes to procedures in the provision or use of aircraft data in the future. The seminar will provide an overview of the current status ABO data provision, plans for the future, together with outcomes and recommendations from the ABO Workshop. An overview of European plans to implement an operational centre and service for the  delivery of quality controlled Mode-S derived aircraft observations will be also included.  (Mode-S reports are derived from air traffic management messages and provide very high resolution data, particularly winds, over parts of Europe and potentially elsewhere.  They are not yet processed at ECMWF.)  

11 February
at 14:00

Room: LT

The relationship between the circumglobal teleconnection, the Indian monsoon and European summer weather

Speaker: Jonathan Beverley (University of Reading, University of Exeter)

 Abstract

Recent research has led to improvements in European winter seasonal forecasts, however summer forecast skill remains relatively low. One potential source of predictability for Europe is the Indian summer monsoon, which can influence the weather across many parts of the northern hemisphere via a global wave train known as the “circumglobal teleconnection” (CGT). Here I assess the ability of the ECMWF coupled seasonal forecast model to represent this teleconnection mechanism. To understand how errors in its representation are related to errors in summer forecast skill over Europe, results from relaxation and thermal forcing experiments, as well as barotropic model experiments, will be presented. These experiments were designed to identify possible causes of errors in the teleconnection pathway, and to explore the impact of improving the representation of the CGT on European summer forecast skill.

23 January
at 14:00

Room: LT

Can GNSS Polarimetric Radio Occultations (GNSS  PRO) contribute to better understanding, monitoring or predicting extreme events?

Speaker: Estel Cardellach (ICE-CSIC/IEEC, Spain)

Abstract

The GNSS Polarimetric Radio Occultations (GNSS PRO) is a new measurement concept being proved aboard the PAZ satellite, operating since May 2018. The technique is based on the 'traditional' GNSS Radio Occultations (GNSS RO), widely used for atmospheric profiling of thermodynamic parameters and assimilated in operational NWP. Adding polarimetric capabilities to the RO system enables to sense hydrometeors, especially big rain droplets in heavy rain, and frozen particles. The system, thus, is the first technique with joint and synchronous sensitivity to both types of parameters: thermodynamic and hydrometeor profiling. Whereas the geophysical content of the GNSS RO signals to infer the 'traditional' products lays on the bending of the signal propagation (atmosphere acting as a lens because of its vertical gradients in T, p and q), the physical principle to sense hydrometeors is the excess propagation delay of the horizontally polarized signal with respect to the vertically polarized one. These are two independent sensing principles obtained from a single set of data.

Can GNSS PRO contribute to better understanding, monitoring or predicting extreme events? We are not ready to provide a full answer to this question, yet. But the seminar will present the technique, the facts demonstrated during the PAZ mission so far, the current identified limitations, and potential areas of interest and opportunities for scientists at ECMWF working on precipitation, micro-physics modeling and large scale convective systems -- elements towards improved understanding, monitoring and prediction of some extreme events.

   

LT = Lecture Theatre, LCR = Large Committee Room, MZR = Mezzanine Committee Room,
CC = Council Chamber