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Printable version (final update: 21 June 2019): PDF. Please be aware that the programme will be printed out for the registered participants in the workshop.

TimeMonday – 17th JuneTime

Tuesday – 18th June

TimeWednesday – 19th JuneThursday – 20th JuneFriday – 21st June

Location: Allen Laboratory (no. 48 on the map)
Location: Sutcliffe lecture theatre, room GU01, Department of Meteorology (no. 58 on the map)
9:00

Registration

8:30

Registration



Chair: Robert Plant
Chair: Peter Bechtold
Chair: Nedjeljka Žagar Chair: Christian M. Grams Chair: Gabriella Szépszó
10:00

Robert Plant (University of Reading, UK)

Welcome

9:00

Paul Williams (University of Reading, UK)

Andy Brown (ECMWF, UK)

Opening

BrownA_opening.pdf

9:00

Mark Rodwell (ECMWF, UK) – solicited

 Challenges and limits in ensemble weather prediction

Mark Rodwell

ECMWF, UK

Some days, the atmosphere is less predictable than on average. This is partly because the rate of growth of certainty (the result of Chaos) is dependent on the atmospheric flow itself. For example, moist processes are almost always implicated during investigations of very poor forecasts for Europe (so-called "forecast busts"). These moist processes might be associated with, for example, warm conveyor-belts along the cold-fronts of a cyclonic systems, meso-scale convective situations, or the extra-tropical transition of tropical cyclones.

Such moist situations also present a particular challenge for data assimilation. For example, satellite observation operators are highly non-linear in cloudy situations. The result is that the ensemble distribution of initial conditions is less constrained by the available observations.

Furthermore, these moist situations present challenges for the model. For example, the model's parametrized "deterministic physics" is very active in these situations, and biases are likely to have a large impact on the forecast. In order to maintain the "spread-error" relationship of the ensemble, additional "stochastic physics" is required to adequately represent the effects of sub-grid-scale uncertainty in these moist processes.

Hence such moist situations represent, almost literally, a "perfect storm" for forecasting. Progress can be made on some aspects, but the inherent large uncertainty growth-rates will remain.

This talk will illustrate these various aspects with some emphasis on the case-study of the transition of tropical cyclone Karl, which was well observed during the recent NAWDEX field campaign.

Full version: RodwellM_challenges_full.pdf
Printable version: RodwellM_challenges_print.pdf

Keith Williams (Met Office, UK) – solicited

 The impact of parametrized diabatic processes on weather forecasts

Keith Williams

Met Office, UK

This presentation will discuss the sensitivity of weather forecasts to parametrizations, with a focus on moist processes. A range of examples from the Met Office Unified Model will be given including discussion of the role of convection, cloud and boundary layer processes. Diagnostic techniques to identify the likely source of sensitivity will also be discussed. Global examples of the Impacts on both the large scale circulation and local weather will be presented.

WilliamsK_ParametrizedDia.pdf

Victoria Sinclair (University of Helsinki, Finland) – solicited

 Meridional moisture transport by extra-tropical cyclones in the Southern Hemisphere

Victoria Sinclair1, Helen Dacre2

1University of Helsinki, Finland
2University of Reading, UK

Extra-tropical cyclones are known to be responsible for a large proportion of the poleward moisture transport in the mid-latitudes. However, not all cyclones are equal; some transport significantly more moisture polewards than others. The aim of the work presented here is to identify which cyclone characteristic (genesis latitude, maximum vorticity and poleward propagation speed), leads to the greatest variability in meridional moisture transport per cyclone. We use ERA-Interim reanalysis combined with an objective cyclone tracking algorithm (TRACK), a cyclone masking method and cyclone composites. Interestingly, the results show that cyclone intensity, quantified by maximum vorticity, has a weaker influence on how much moisture a cyclone can transport than other cyclone characteristics. This result suggests that studies considering how extra-tropical cyclones will change in the future should focus on cyclone track as well as cyclone intensity and number.

SinclairV_moisture.pdf

10:10

Marcus Köhler (ECMWF, UK)

OpenIFS: A portable version of IFS for research and education and an outreach activity at ECMWF

KoehlerM_OpenIFS.pdf

9:40

Heini Wernli (ETH, Switzerland) – solicited

 Diabatic processes in extratropical cyclones

Heini Wernli

ETH, Switzerland

The prediction of the track, intensity and structure of extratropical cyclones is of key importance for accurately forecasting surface weather and its extremes. In addition to classical baroclinic instability typically induced by an upper-level cyclonic potential vorticity (PV) anomaly, moist diabatic processes that occur in saturated ascending airstreams are essential for the evolution of cyclones, the associated surface weather, and the downstream flow evolution. Results from studies that are mainly based on the analysis of IFS analyses and forecasts, will be shown to illustrate that (i) the diabatic PV production in the low troposphere is essential for the formation of intense extratropical cyclones, (ii) diabatic processes are particularly intense in so-called warm conveyor belts, i.e., in moist ascending airstreams associated with extratropical cyclones, (iii) different microphysical processes in and below clouds contribute to the diabatic formation of PV anomalies in cyclones, and (iv) exceptionally poor global model medium-range weather forecasts (so-called forecast busts) in Europe are often associated with errors in the representation of warm conveyor belts. The presentation will also provide a selection of first results from the recent field experiment NAWDEX, which was dedicated to observing diabatic processes in mid-latitude weather systems.

WernliH_diabatic.pdf

9:40

Christian M. Grams (Karlsruher Institut für Technologie, Germany) – solicited

 The impact of moist processes on the large-scale extratropical circulation

Christian M. Grams

Karlsruher Institut für Technologie, Germany

The large-scale extratropical circulation is dominated by Rossby wave activity along the upper-level midlatitude wave guide. Recent research revealed that moist processes can be as important in the evolution of Rossby wave packets as dry dynamics. This is primarily due to latent heat release in ascending air streams, i.e. warm conveyor belts (WCBs). Thereby moist warm air is transported poleward and ascends slantwise along the midlatitude baroclinic zone. Latent heat release due to condensation enhances this ascent and results in a net transport of air mass into the upper troposphere. This so-called diabatic outflow deflects the wave guide poleward, accelerates the jet stream, and an upper-level ridge builds or amplifies that might ultimately become a blocking anticyclone. Rossby wave activity in the Atlantic-European region often occurs in preferred quasi-stationary, persistent, and recurrent states called weather regimes. These explain most of the atmospheric variability on sub-seasonal time scales. However, current numerical weather prediction models struggle in correctly predicting weather regime life cycles.

This presentation will focus on the role of diabatic outflow in the life cycle of Atlantic-European weather regimes and how diabatic outflow affects predictability of the large-scale extratropical circulation. In the period prior to the onset of regimes characterized by blocking important changes of the location and frequency of WCBs occur. WCB activity increases significantly upstream of the incipient blocking anticyclone even before blocking is detectable. Diabatic outflow persists over the blocked region later. Thus diabatic outflow is key for the onset and maintenance of blocked regimes in the Atlantic-European region. The misrepresentation of WCB activity and associated diabatic outflow can result in severe forecast busts due to upscale error growth. Thereby the physical processes within a WCB might communicate and amplify small initial condition error to the large-scale extratropical circulation. This is exemplified for recent cases of regime onset.

Further reading:

Ferranti, L., S. Corti, M. Janousek, 2015: Flow-dependent verification of the ECMWF ensemble over the Euro-Atlantic sector. Q.J.R. Meteorol. Soc., 141, 916–924, https://doi.org/10.1002/qj.2411.

Grams, C.M., H.M. Archambault, 2016: The key role of diabatic outflow in amplifying the midlatitude flow: a representative case study of weather systems surrounding western North Pacific extratropical transition. Mon. Wea. Rev., 144, 3847–3869, https://doi.org/10.1175/MWR-D-15-0419.1.

Grams, C.M., R. Beerli, S. Pfenninger, I. Staffell, H. Wernli, 2017: Balancing Europe’s wind-power output through spatial deployment informed by weather regimes. Nature Climate Change, 7, 557–562, https://doi.org/10.1038/nclimate3338.

Joos, H., H. Wernli, 2012: Influence of microphysical processes on the potential vorticity development in a warm conveyor belt: a case-study with the limited-area model COSMO. Q.J.R. Meteorol. Soc., 138, 407–418, https://doi.org/10.1002/qj.934.

Martínez-Alvarado, O., E. Madonna, S.L. Gray, H. Joos, 2016: A route to systematic error in forecasts of Rossby waves. Q.J.R. Meteorol. Soc., 142, 196–210, https://doi.org/10.1002/qj.2645.

Michel, C., G. Rivière, 2011: The link between Rossby wave breakings and weather regime transitions. J. Atmos. Sci., 68, 1730–1748, https://doi.org/10.1175/2011JAS3635.1.

Pfahl, S., C. Schwierz, M. Croci-Maspoli, C.M. Grams, H. Wernli, 2015: Importance of latent heat release in ascending air streams for atmospheric blocking. Nature Geosci, 8, 610–614, https://doi.org/10.1038/ngeo2487.

Vautard, R., 1990: Multiple weather regimes over the North Atlantic: analysis of precursors and successors. Mon. Wea. Rev., 118, 2056–2081, https://doi.org/10.1175/1520-0493(1990)118<2056:MWROTN>2.0.CO;2.

GramsCM_MoistProcesses.pdf

John Methven (University of Reading, UK) – solicited

 Mechanisms for diabatic influence on the jet stream

John Methven1, Ben Harvey1, Andreas Schäfler1, Suzanne Gray1, Leo Saffin2, Maarten Ambaum1

1University of Reading, UK
2University of Oxford, UK

The jet stream has a major influence on the development of weather systems across the North Atlantic and weather across Europe. Forecast busts in Europe have been associated with a particular precursor configuration of waves on the jet stream linked with active weather systems over the eastern USA 5 days beforehand. It has been conjectured that misrepresentation of cloud processes and latent heat release in those systems is responsible for the poor forecasts downstream. However, is it true? How might these diabatic processes influence the jet stream structure, Rossby wave disturbances and the dynamics of weather systems? The North Atlantic Waveguide and Downstream Impacts Experiment set out to answer these questions by making new high resolution measurements exploring jet stream structure and influences on development. One finding was that the tropopause potential vorticity gradient and the peak jet stream winds are much sharper than represented in global analyses and furthermore the gradient decreases with forecast lead time. Evidence for diabatic processes acting to increase the PV contrast across the tropopause is presented, and the consequences for Rossby wave propagation and forecasts are explored.

MethvenJ_mechanisms.pdf

David Wallom (University of Oxford, UK)

Results from OpenIFS@home (20 min.)

WallomD_results.pdf

10:40

Andreas Müller (ECMWF, UK) – solicited

Spectral transform

MuellerA_spectral.pdf

Group presentations (10-15 min. each), discussion
11:00

Andreas Müller (ECMWF, UK) – solicited

Practical exercise on spectral method


10:20
 Poster introductions (2 minutes and max. 2 slides each)

1. Jake Bland (University of Reading, UK)

 UTLS humidity biases during NAWDEX

Jake Bland1, Suzanne Gray1, John Methven1, Richard Forbes2

1University of Reading, UK
2ECMWF, UK

Lower stratospheric moisture influences Rossby wave evolution through radiative induced temperature changes. Therefore it is expected that misrepresentation of moisture in models leads to forecast errors, which may propagate downstream and affect future system development. That the IFS exhibits a large moist bias in the lower stratosphere and an associated temperature bias is known, but the causes of this, and the impact on cyclone evolution are not. Work has been done to characterise these biases and investigate their behaviour in different conditions through comparisons of operational model data to radiosonde observations. This will be used to inform modelling studies to further investigate these biases in the IFS and their influence on cyclone development.

2. Yun Chen (National Meteorological Center of China)

 Impact of moist progress on the short-term forecast of rainfall brought by Yagi to China in 2018

Yun Chen, Jun Xu

National Meteorological Center of China

Yagi, the No. 14 typhoon that made its landfall in Zhejiang province on August 12, 2018, brought severe rainstorms to northern China on August 13 and 14, with its maximum daily precipitation over 300mm and its maximum hourly precipitation over 120mm. This event, however, was not well forecasted. The 24-h rain-area forecast, made based on forecasts of ECWMF IFS, was west to the observation by more than 100 kilometers. With an analysis on the circulation and precipitation fields, we found that this bias in heavy-rain region forecast was caused by both biases in typhoon track and precipitation pattern. The forecast of typhoon track was sensitive to initial fields and moist progress. Our sensitivity analysis of ECWMF ensemble forecast revealed that subtropical high being north to the observation and a weaker-than-observation upper trough near Baikal in initial field will lead to a track forecast west to the observation. Without these two biases, only in Member 18 of ECWMF ensemble forecast, the forecast of heavy rainfall region was closer to the observation.

The bias in the precipitation pattern was related to the bias in simulating MCS. The rain bands developed in an environment characterized by high relative humidity, high freezing level, and moderate CAPE, favorable for high precipitation efficiency. Near the periphery of typhoon, the boundary layer was highly humid and warm. Easterly wind speed convergence within the boundary layer triggered and maintained MCS, which manifested a train effect, leading to heavy rainfall. However, ECWMF did not describe MCS well and therefore predicted much more precipitation in the north and west of typhoon while underestimated the MCS precipitation near the east. This, in turn, led to biases in the low-level wind through excessive latent heat release and further led to a bias in the track forecast.

In conclusion, this bias of landfall typhoon precipitation forecast was caused by both biases in initial errors and moist progress. But which one was more important and interaction between them need to do further research work.

3. Guokun Dai (Fudan University, China)

 Arctic influence on the predictability of the cold surge occurred in China during January 2016

Guokun Dai

Fudan University, China

An extreme cold event occurred during 21-25 January 2016, which affected most areas in China, especially eastern China. Arctic influence on the predictability of the extreme cold event has been investigated with OpenIFS model. First, control experiments with different initial conditions are conducted and results show that integration with ERA-Interim reanalysis initial conditions performs better than that with ERA operational analysis. Diagnostic analyses have found that integration with ERA-Interim initial conditions has a better forecast of the Ural Blocking and Siberian High, which are crucial for the extreme cold event prediction.

Subsequently, sensitive experiments are conducted to verify the influence of Arctic initial conditions on the predictability of the extreme cold event. Integrations with hybrid initial conditions, which remove the Arctic analysis errors from the ERA operational initial conditions, show an improved forecast skill of the cold event. Further investigations reveal that a more accurate Arctic initial condition can result in a better prediction of Ural Blocking and Siberian High, so that the forecast skill of the cold event improves.

DaiG_poster.pdf

4. Mokhliss El-azaar (EHTP, Morocco)

 A coupled shallow and deep convection closure in OpenIFS

Noureddine Semane1, Siham Sbii2, Hannachi Abdel3, Mokhliss El-azaar1, Yamna Ghabbar1

1EHTP, Morocco
2Moroccan Meteorological Service
3University of Stockholm, Sweden

The conventional convective available potential energy (CAPE) closure is based on the balance between the rate of CAPE change due to large-scale forcing and that due to deep convection, which is valid particularly for long time scales. Nonequilibrium convection, which is prominent at subdiurnal timescales, is well covered, however, when the CAPE closure incorporates the rate of CAPE change due to boundary layer forcing yielding nonequilibrium convection closure. This closure consists of subtracting from the total mass flux a fraction of the shallow cumulus contribution that is supposed to approximately balance the boundary layer forcing. The latter is newly parametrized here based on the moist static energy budget taking into account the enthalpy radiative tendency in the shallow convection layer.

5. Jian-Feng Gu (University of Reading, UK)

 Intensification variability of tropical cyclones in directional shear flows

Jian-Feng Gu1, Zhe-Min Tan2, Xin Qiu2

1University of Reading, UK
2 Nanjing University , China

The coupling of vortex tilt and convection, and their effects on the intensification variability of tropical cyclones (TCs) in directional shear flows is investigated. Balanced response to the height-dependent vortex tilt controls TC structural differences in clockwise (CW) and counter-clockwise (CC) hodographs during their initial stage of development. Moist convection may enhance the coupling between displaced vortices at different levels and thus reduce the vortex tilt amplitude and enhance precession of the overall vortex tilt during the early stage of development. However, differences in the overall vortex tilt between CW and CC hodographs are further amplified by a feedback from convective heating and therefore result in much higher intensification rates for TCs in CW hodographs than in CC hodographs.

In CW hodographs, convection organization in the left-of-shear region is favored because the low-level vortex tilt is ahead of the overall vortex tilt and the TC moves to the left side of the deep-layer shear. This results in a more humid mid-troposphere and stronger surface heat flux on the left side (azimuthally downwind) of the overall vortex tilt. The convective heating plays a leading role in assisting the vortex precession, thus providing a positive feedback and supporting continuous precession of the vortex tilt into the up-shear-left region.

In CC hodographs, convection tends to organize in the right side (azimuthally upwind) of the overall vortex tilt because the low-level vortex tilt is behind the overall vortex tilt and the TC moves to the right side of the deep-layer shear. In addition, convection organizes radially outward near the down-shear-right region, which weakens convection within the inner region. These configurations lead to a drier mid-troposphere and weaker surface heat flux in the downwind region of the overall vortex tilt and also a broader potential vorticity skirt. As a result, a negative feedback is established that prevents continuous precession of the overall vortex tilt.

6. Ben Harvey (University of Reading)

 Observations of the North Atlantic jet stream from NAWDEX

Ben Harvey1,2, John Methven2

1National Centre for Atmospheric Science, UK
2University of Reading, UK

Upper-level ridges are associated with negative potential vorticity anomalies. These arise partly from the adiabatic advection of low PV air from further south, and partly from the diabatic modification of PV by latent heating in the warm conveyor belts which feed them. The diabatic heating can, under suitable conditions, produce negative PV anomalies of sufficient magnitude that the absolute PV turns negative in the upper-troposphere, at least locally, leading to enhanced jet streak strengths and the possibility of reduced predictability associated with the presence of symmetric instability.

This study presents some recent airborne observations of negative PV values in warm conveyor belt airstreams from the NAWDEX field campaign. PV values are computed from a curtain of dropsonde profiles and shown to be robustly negative in the vicinity of the jet stream. The conditions under which negative PV can arise and the structure of the resulting negative PV structures are then examined. Finally, the representation of these negative PV structures in an operational NWP model is investigated, and the physical processes responsible are identified using online PV tracer diagnostics.

HarveyB_poster.pdf

7. Sam Hatfield (University of Oxford, UK)

 Raspberry PiPS: the Raspberry Pi Planet Simulator

Sam Hatfield, Milan Kloewer, Joshua Dorrington

University of Oxford, UK

The Raspberry Pi is a credit card sized computer designed to be easy to setup and use. To teach the general public about numerical weather prediction and parallel computing we have designed a small cluster of Raspberry Pis for running OpenIFS simulations.

On only 4 nodes we are able to achieve a time step of around 3 seconds for 1 hour of simulation at T95 resolution. The system is roughly comparable in computational power to the Cray Y-MP system used operationally at ECMWF in the early 90s. However, the power consumption of our system is around 6,000 times lower. This demonstrates the vast strides in computing power than Moore's Law has afforded us.

We hope our system will encourage others to consider simple and cheap systems like the Raspberry Pi for live demonstrations of other Earth-System models in future.

8. Ying Li (Chinese Academy of Meteorological Sciences)

 An ensemble analysis on abrupt northward turning of typhoon Meranti (2010) under the influence of an upper tropospheric cold low

Ying Li

Chinese Academy of Meteorological Sciences

The sudden change of typhoon track is one of challenges in typhoon forecast. Typhoon Meranti (2010) experienced an abrupt northward turning when it moved westward to the south of Taiwan Island. Ensemble forecast outputs from the European Medium Range Weather Forecasts (ECMWF) presented a large random for the north turning. The good group consisting of 8 members which predicted the abrupt northward turning well is compared to the poor group including 8 members which did not predict the unusual track, to investigate the main influence factors on the northward turning of typhoon Meranti. Results show that: 1) An upper tropospheric cold low (UTCL) cut from tropical upper-tropospheric trough (TUTT) is an important factor impacting the typhoon track change. The abrupt northward turning of typhoon Meranti is related to the coupling between Meranti and the nearby UTCL in north-south direction. 2) The UTCL can change the upper tropospheric environmental flow around the typhoon, and then influence the typhoon steering flow. When the UTCL moved to the north of Meranti, the southerly component of steering flow for typhoon movement was enhanced, which is helpful to the movement northward of Meranti. 3) The northward turning of Meranti is also associated with the vertical structure of UTCL. The UTCL with wide and deep cyclonic circulation in vertical direction is more favorable to the track change. 4) The diagnostic analysis on the potential vorticity tendency equation showed that, under the coupling between Meranti and UTCL in north-south direction, the potential vorticity horizontal advection in the north of typhoon is strengthened, which is helpful for the northward movement of Meranti. And the asymmetric wind advection of potential vorticity has a major contribution to the north track under the influence of UTCL.

LiY_poster.pdf

9. Federico Serva (CNR-ISMAR, Italy)

 The stratospheric dynamics simulated by the OpenIFS model

Federico Serva

CNR-ISMAR, Italy

The variability in the stratosphere is coupled with surface climate and weather, and in recent years, many studies highlighted the need of a well-resolved stratosphere in numerical models, in order to improve their results. Including stratospheric processes in climate models is however computationally expensive, and also many phenomena are very sensitive to the models' resolution and parameterized physics.

Since the stratosphere is an important element of the long-term climate variability, it is important that its realistic representation is included in climate models, supported by extensive testing and sensitivity studies. We present the objectives of a recently started ECMWF Special Project, aiming to gain a better understanding of stratospheric dynamical processes in the OpenIFS' model, and their sensitivity to the model configuration. The outcomes of this work could be beneficial for the future inclusion of the OpenIFS model in a comprehensive Earth System Model.

ServaF_posterintro.pdf

10. Lorenzo Silvestri (CIRIAF-CRC, University of Perugia, Italy)

 OpenIFS Held-Suarez test: an educational application of the statistical equilibrium concept

Lorenzo Silvestri, Paolina Bongioannini Cerlini

CIRIAF-CRC, University of Perugia, Italy

The Held Suarez paper (1994) proposed a solution to the problem of testing the models dynamical core results given the fact that there are no exact solutions of the primitive equations with realistic forcing. The OpenIFS model has among other tests of the code, the Held Suarez case where physics parametrization schemes of the full model are replaced by prescribed forcing and dissipation. The radiative equilibrium solution that is found, simulates a circulation that is reasonably realistic in many aspects without the burden of physical parametrizations.

During classes the Open-IFS model gives the students the possibility to run this case and one other test that start from the same idea but with different initial equilibrium temperature, modified by Williamson et al. (1998) to include stratospheric structures so to give increasing temperature in the Tropics, where the radiative equilibrium solution produces bias using different numerical schemes of the GCM that was tested.

The conceptual framework of the Held-Suarez case with the various options, allows to introduce the idea of running a test to understand the theoretical dynamics and the way it is build within the OpenIFS code, and to understand how the initial conditions can change the model equilibrium. The equilibrium that is found can be then studied statistically using the run with different initial conditions in order to evaluate its sensitivity and internal variability.

This case has been run at University of Perugia to teach applications of the general circulation primitive equations and to train the teacher and PhD students in configuring and running in a local environment the 3D version of the OpenIFS model.

Further reading:

Held, I.M., M.J. Suarez, 1994: A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models. Bull. Amer. Meteor. Soc., 75, 1825-1830.

Williamson D.L., J.G. Olson, B.A Boville, 1998: A comparison of semi-Lagrangian and Eulerian tropical climate simulations. Mon. Wea. Rev., 126, 1001-1012.

SilvestriL_posterintro.pdf

11. Irina Statnaia (University of Helsinki, Finnish Meteorological Institute)

 OpenIFS simulations for sudden stratospheric warming 2018

Irina Statnaia1,2, Alexey Karpechko2, Victoria Sinclair1, Heikki Järvinen1

1University of Helsinki, Finland
2Finnish Meteorological Institute

In mid-latitudes, and also in Europe, forecasts typically lose their skill after about 10 days. This occurs due to chaotic nature of weather processes. In turn, weather predictability is variable and there are situations when weather becomes more predictable. For the mid-latitudes during boreal winter a major source of sub-seasonal predictability is variability of the stratospheric polar vortex.

Stratospheric circulation affects development and growth of cyclones and storm tracks beneath. In extreme case, when stratospheric polar vortex breaks down in an event called Sudden Stratospheric Warming (SSW), tropospheric storm tracks are typically shifted southward making northern and central Europe affected by cold Arctic air masses. Ability to predict SSW can extend weather predictability beyond 2 weeks.

In this study, we investigate the SSW case that took place on 12 February 2018 (SSW2018), its predictability and surface climate impacts by using the OpenIFS model, initialised with different model setups (lead time, resolution, timestep). In order to better understand the sources of uncertainties, to detect model biases and investigate whether there are windows of opportunity within which the model may be more skilful, we make sensitivity experiments with different parameterization schemes. The results obtained with the OpenIFS forecast data are compared with the ECMWF’s reanalysis ERA-Interim (ERA-I) and ERA-5.

The analysis of the OpenIFS forecasts obtained within different sensitivity experiments shows the impact of orographic and non-orographic gravity wave drag, which affects the lead-time of a successful forecast and strength of the SSW2018 event. Hence, tuning of the parameterisation schemes can contribute to enhanced predictability, but the model performance should also be studied beyond a small number of case studies of individual extreme events.

StatnaiaI_poster.pdf

12. Lauri Tuppi (University of Helsinki, Finland)

 On extracting information from closure parameter convergence tests using OpenIFS

Lauri Tuppi1, Madeleine Ekblom1, Pirkka Ollinaho2, Marko Laine2, Vladimir Shemyakin3, Heikki Järvinen1

1University of Helsinki, Finland
2Finnish Meteorological Institute
3Lappeenranta University of Technology, Finland

Algorithmic methods designed for tuning of numerical weather prediction (NWP) models are gaining popularity since manual tuning is a laborious task. Automation of the tuning process would save the model developers’ time. In this study, we will study the performance of two algorithms in a realistic ensemble prediction system using OpenIFS. The methods are the original distribution based Ensemble Prediction and Parameter Estimation System (EPPES) (Järvinen et al. 2012, Laine et al. 2012) and its population based variant Differential Evolution EPPES (DE-EPPES) (Shemyakin and Haario 2018).

A necessary prerequisite for successful optimization is a successful convergence test. Convergence test is an optimization experiment where the reference state (usually analysis) has been replaced with a control forecast with known fixed parameters. As the truth is known, one can see from the results when the convergence is successful, and the algorithm is working correctly. The convergence tests begin with slightly wrong parameter values and too large uncertainty. The target is to find those known parameter values of the control forecast.

We chose to use two parameters from the convection scheme of OpenIFS in our convergence tests. We explore different experimental set-ups (ensemble size, forecast length, different algorithms) and their effect on the convergence of the parameters to find the most efficient model tuning set-up.

Further reading:

Järvinen, H. et al., 2012: http://dx.doi.org/10.1002/qj.923.

Laine, M. et al., 2012: http://dx.doi.org/10.1002/qj.922.

Shemyakin, V., Haario, H., 2018: https://doi.org/10.1007/s11071-018-4239-5.

TuppiL_poster.pdf

13. Jun Xu (National Meteorological Center of China)

 Impact of moist convective progress on extreme frontal rainstorm forecast using ECMWF IFS

Jun Xu

National Meteorological Center of China

Forecast of frontal rainstorm remains a big challenge for forecasters and NWP when moist convective processes are considered, although the influencing synoptic systems are well predicted. Using ECMWF IFS forecast, we selected a case of extreme frontal rainstorm with obvious convection attacked North China on April 21 2018 to study the predictability and causes of biases.

Influenced by the heat and moisture transport brought by extremely strong low-level jet, warm sector rain band, narrow rain-band and wide rain-band were included in the frontal precipitation, which was consist with the typical frontal precipitation pattern proposed by Houze. The narrow rain-band was the center of precipitation; it was featured by significant moist convection and long-lasting precipitation. Though 24-h accumulated precipitation threat score in 36-h forecast reached 0.36, ECMWF IFS underestimated the narrow rain-band precipitation while overestimated the grid-scale precipitation at the back of front. The excessive low-level latent heat feedback associated with the excessive grid-scale precipitation in turn led to stronger and slowly-moving synoptic vortex systems in the model, resulting in significant large-scale bias within the 36-h forecast.

Predictability research showed that initial errors were distributed from meso-scale to synoptic scale. Before the onset of the main moist convection, the errors had been concentrated in waves with length of 500-1000km. Besides deficiency of convective parameter, forecast of a weaker synoptic scale wind speed fluctuation and a lower surface temperature could also lead to the underestimation of moist convection and overestimation of grid-scale precipitation. After the 15-hour-long moist process, the errors concentrated at scales larger than 1000km. Results also revealed that the rapid error growth period was in keeping with the moist convective process. In conclusion, deficiency in moist convection could lead to error growth above synoptic scale in short-term forecast, and limit ECMWF IFS predictability.

14. Sophia Schäfer (Deutscher Wetterdienst, Germany)

 How likely are cold pools to trigger new convection?

Sophia Schäfer1, Mirjam Hirt2, George Craig2, Julien Savre2

1 Deutscher Wetterdienst , Germany
2L udwig-Maximilians-University Munich , Germany

Convection presents one of the major uncertainties in current weather and climate models. In particular, spatial distribution and diurnal cycle of convection in current parametrisations deviate significantly from observations. While weather models are now able to explicitly model deep convection, they still struggle to represent the onset of new convection. One important process that is missing in current parametrisations consists of cold pools and gust fronts that form from convective precipitation and downdraughts. In their turn, these effects can trigger new convection in adjoining areas, which tends to increase convective organization and prolong convective activity. Both convective memory and spatial organisation are frequently lacking in current models. Our aim is to capture the increased probability of triggering due to cold pools and use this information to improve the spatio-temporal structure of convection triggering in both km-scale models and in the Plant-Craig stochastic convection parametrisation for global weather and climate models.

We identify and track individual cold pools and convective cells in high-resolution ICON model simulations over Germany, which allows us to determine the intensity and lifecycle of individual cold pools and associated convection. In an environment with weak to medium large-scale forcing, we find that 80% of convective precipitation is associated with cold pools. The passage of cold pool gust fronts correlates strongly with precipitation at a time delay of 30 min, confirming that the gust fronts play an important role in new triggering. The probability of new triggering correlates with cold pool intensity, especially for larger and stronger cold pools, which account for around half of the cold pool triggering. Hence, cold pool intensity provides a measure of triggering probability in parametrised convection.

While km-scale models can resolve cold pools, they miss the finer structure of the gust fronts, and as a result, the variability of vertical velocity in gust fronts, which strongly influences convection initiation probability, is significantly under-represented. Remedying this lack of variability should improve convection modeling on km-scales.

10:20

Helen Dacre (University of Reading, UK)

 Linking atmospheric rivers and warm conveyor belt airflows

Helen Dacre

University of Reading, UK

Extreme precipitation associated with extratropical cyclones can lead to flooding if cyclones track over land. However, the dynamical mechanisms by which moist air is transported into cyclones is poorly understood. We analyse airflows within a climatology of cyclones in order to understand how cyclones redistribute moisture stored in the atmosphere. This analysis shows that within a cyclones' warm sector the cyclone-relative airflow is rearwards relative to the cyclone propagation direction. This low-level airflow (termed the feeder airstream) slows down when it reaches the cold front resulting in moisture flux convergence and the formation of a band of high moisture content. One branch of the feeder airstream turns towards the cyclone centre supplying moisture to the base of the warm conveyor belt where it ascends and precipitation forms. The other branch turns away from the cyclone centre exporting moisture from the cyclone. As the cyclone travels, this export results in a filament of high moisture content marking the track of the cyclone (often used to identify atmospheric rivers). We find that both cyclone precipitation and water vapour transport increase when moisture in the feeder airstream increases, thus explaining the link between atmospheric rivers and the precipitation associated with warm conveyor belt ascent. Atmospheric moisture budgets calculated as cyclones pass over fixed domains relative to the cyclone tracks, show that continuous evaporation of moisture in the pre-cyclone environment moistens the feeder airstream. Evaporation behind the cold front acts to moisten the atmosphere in the wake of the cyclone passage, potentially preconditioning the environment for subsequent cyclone development.

Full version: DacreH_AR_full.pdf
Printable version: DacreH_AR_print.pdf

Mika Rantanen (University of Helsinki, Finland)

 The extratropical transition of Hurricane Ophelia (2017) as diagnosed with omega equation and vorticity equation

Mika Rantanen, Jouni Räisänen, Victoria Sinclair, Heikki Järvinen

University of Helsinki, Finland

Hurricane Ophelia was a category 3 hurricane which underwent an extratropical transition and made landfall in Europe as an exceptionally strong post-tropical cyclone in October 2017. In Ireland, for instance, Ophelia was the worst storm in 50 years and resulted in significant damage and loss of life.

In this study, the different physical processes affecting Ophelia’s transformation from a hurricane to a mid-latitude cyclone are studied. For this purpose, we have developed software which uses OpenIFS model output and a system consisting of a generalized omega equation and vorticity equation. By using these two equations, the atmospheric vertical motion and vorticity tendency are separated into the contributions from different physical processes: vorticity advection, thermal advection, friction, diabatic heating, and the imbalance between the temperature and vorticity tendencies.

Vorticity advection, which is often considered an important forcing for the development of mid-latitude cyclones, is shown to play a small role in the re-intensification of Ophelia as an extratropical storm. This is because the effects of divergent and non-divergent components of vorticity advection mainly cancelled each other out, resulting in a net effect close to zero. However, our results show that diabatic heating was the dominate forcing in both the tropical and extratropical phases of Ophelia.

Furthermore, we calculated in more detail the diabatic heating contributions from different model parameterizations. We find that the temperature tendency due to the convection scheme was the dominant forcing for vorticity tendency during the hurricane phase, but as Ophelia transformed into a mid-latitude cyclone, the microphysics temperature tendency gradually increased becoming the dominant forcing once the transition was complete.

RantanenM_Ophelia.pdf

Group presentations (10-15 min. each), discussion

11:30Coffee & tea break10:50 Coffee & tea break 10:40Coffee & tea break

Chair: Victoria Sinclair
Chair: Suzanne Gray
Chair: Mark Rodwell Chair: Keith Williams Chair: Marcus Köhler
12:00

Michail Diamantakis (ECMWF, UK) – solicited

 The IFS dynamical core and its new features in cycle 43r3
  • Semi-implicit, semi-Lagrangian schemes
  • New octahedral grid & implications
  • Stratospheric improvements

DiamantakisM_dynamics.pdf


11:20

David Wallom (University of Oxford, UK)

 Introducing OpenIFS@home

Sarah Sparrow1, Antje Weisheimer1,2, Andy Bowery1, Glenn Carver2, Gabriella Szépszó2, Marcus Köhler2, Florian Pappenberger2, David Wallom1

1University of Oxford, UK
2ECMWF, UK

Weather forecasts rely heavily on general circulation models of the atmosphere and other components of the Earth system. National meteorological and hydrological services and intergovernmental organisations, like ECMWF, provide routine operational forecasts on a range of spatio-temporal scales, by running these models on state-of-the-art high-performance computing systems. Such operational forecasts are very demanding in terms of computing resources. To facilitate the use of a weather forecast model for research and training purposes outside the operational environment, ECMWF provides a portable version of its numerical weather forecast model, called OpenIFS, for use by universities and other research institutes on their own computing systems.

In this contribution, we describe a new project (OpenIFS@home) that combines OpenIFS with a citizen science approach to involve the general public in helping conduct scientific experiments. We will be using volunteers from across the world to run OpenIFS on their computers at home. The infrastructure of such distributed computing experiments will be based on our experience and expertise with the climateprediction.net and weather@home systems, that successfully use versions of the Met Office Hadley Centre model for weather and climate change simulations.

In OpenIFS@home, the enormous computing resource by volunteers will be utilised to study the predictability of weather forecasts. Interesting past weather and climate events will be explored by re-running them and testing sensitivities to physical parameter choices in the model. Large ensemble simulations will be possible that will help study probabilistic forecasts in a chaotic atmospheric flow and reduce uncertainties due to nonlinear interactions. It is also planned for a later stage, to adopt the system for performing climate change experiments. It is expected that OpenIFS@home will become a valuable additional contribution to the existing range of distributed computing modelling experiments for weather impacts and climate attribution research.

WallomD_OpenIFSatHome.pdf

11:00

Nedjeljka Žagar (University of Hamburg, Germany) – solicited

 Analysis and forecast uncertainties in the tropics: why do we care?

Nedjeljka Žagar

University of Hamburg, Germany

Global numerical weather prediction (NWP) models are characterized by significant uncertainties in their initial state in the tropics. Furthermore, the largest simulated uncertainties of the global ensemble forecasts in the short range is also found in the tropics. This applies to all zonal wavenumbers and the larger the scale, the greater the uncertainty. My lecture will present evidence of these facts using the data from the ECMWF deterministic and ensemble prediction system to illustrate how these properties have evolved in recent years.

Moist processes in the tropics generate the spectrum of waves that propagate horizontally and vertically. For example, the short-term response to tropical heating anomalies resembling MJO projects predominantly on the inertio-gravity (IG) waves, especially the Kelvin wave. The equatorial IG waves make a large part of tropical variance on all scales and their role in the initial state for NWP is still not clear. This is related to complex moist dynamics, a lack of wind observations and assumptions made in data assimilation modelling. I will demonstrate that uncertainties in the forecasted IG spectra associated with moist convection are less successfully reduced on all scales than uncertainties associated with Rossby waves.

In order to explain some observed features of the NWP models and to investigate possible remedies, simplified models can be used provided they are still complex enough to capture the main dynamical and physical aspects of the phenomena of interest. I will introduce such a model for moist processes and data assimilation in the tropics and present its results that explain some observed features of full-scale NWP systems.

ZagarN_tropics.pdf

Klaus Wyser (Swedish Meteorological and Hydrological Institute) – solicited

 A first glance at EC-Earth and CMIP6

Klaus Wyser

Swedish Meteorological and Hydrological Institute

The 6th phase of the Coupled Model Intercomparison (CMIP6) has started and the EC-Earth community has started making pre-industrial, historical and future scenario experiments with the EC-Earth3 model. The data are uploaded to ESG data nodes and shared with the climate modeling community. In my talk I will briefly describe the development from the coupled IFS-NEMO model to the CMIP6 version of EC-Earth3, the tuning of the coupled model, and present an analysis of the first results from our CMIP6 simulations. The results will be put in context to other CMIP6 models in a common evaluation that will focus on the role of clouds for the climate.

WyserK_EC-Earth.pdf

Group presentations (max. 10 min. each), discussion
11:40

Terhi Laurila (Finnish Meteorological Institute)

 The extratropical transition of Hurricane Debby (1982) and its re-development into an intense windstorm Mauri over Finland

Terhi Laurila1, Victoria Sinclair2, Hilppa Gregow1

1Finnish Meteorological Institute
2University of Helsinki, Finland

On 22 September 1982, an intense windstorm Mauri led to extensive wind damage in northern Finland. Mauri was potentially related to the extratropical transition of Hurricane Debby which is an uncommon origin for a windstorm in Fenno-Scandinavia. In this study, we analyze the synoptic-dynamic evolution of Mauri to investigate the role of Debby in its development, and we examine the physical reasons for strong wind gusts over Finland. A brief synoptic overview was conducted based on ERA-Interim and a more detailed analysis was performed based on multiple OpenIFS simulations with different initialization times. We found that Debby did not immediately re-intensify when it reached the mid-latitudes due to lack of upper-level support. However, ex-Debby was able to self-maintain itself as a diabatic Rossby wave while traveling rapidly across the Atlantic. Near the UK, ex-Debby rapidly re-intensified when it interacted with an upper-level potential vorticity anomaly of another extratropical cyclone. This intensification was not captured in OpenIFS simulations initialized on 17 and 19 September since the phasing of upper and lower-level anomalies was incorrectly simulated. In the simulation from 21 September, the re-intensification of ex-Debby was captured and the wind gusts over northern Finland were stronger than in the other simulations. Strong pressure gradients caused the strong wind speeds and the wind gusts were further enhanced behind the cold front due to turbulent mixing and in the warm sector due to convectively driven downdrafts. In conclusion, Mauri was connected to Hurricane Debby but the interaction with another extratropical cyclone over the UK was critical for ex-Debby to re-develop into an intense windstorm over Finland.

LaurilaT_Debby.pdf

11:40

Bethan Harris (University of Reading, UK)

 An Available Potential Energy budget for an axisymmetric tropical cyclone

Bethan Harris, Remi Tailleux, Christopher Holloway, Pier Luigi Vidale

University of Reading, UK

Investigating the evolution of Available Potential Energy (APE) in a tropical cyclone (TC) offers the opportunity to gain greater physical insight into the effects of diabatic processes on TC intensification and maintenance. For example, when TC processes are considered in terms of entropy, irreversible processes are by definition a source of entropy and therefore reduce the efficiency of the TC heat engine; local APE theory shows that in fact irreversible processes may be either a source or sink of APE and so they could in some situations promote intensification. We present a budget of APE for the idealised axisymmetric TC model of Rotunno and Emanuel [1987], with Craig’s modified microphysics scheme. The APE density is defined for each moist air parcel as the work released when the parcel moves from its initial position to its level of neutral buoyancy with respect to a reference state. A discretised APE density and APE production efficiencies are constructed to match the model equations. In the mature stage, the chief source of APE in the TC is the advection of APE along the near-surface radial inflow, with significant additional contributions from local APE production due to surface fluxes and the microphysics scheme. The intensification phase is characterised by increasing APE production efficiencies as well as changes in diabatic forcings. We outline the link between the APE budget and TC intensification in terms of the kinetic energy budget, and question whether the choice of APE reference state affects the interpretation of diabatic processes as sources or sinks of APE. We discuss how the components of the APE budget may be useful as process-oriented diagnostics for studying the role of moisture-convection coupling in TC intensification in NWP and climate models.

HarrisB_APE.pdf

Joakim Kjellsson (GEOMAR, Germany)

 FOCI-OpenIFS: A flexible climate model for high-resolution simulations

Joakim Kjellsson, Wonsun Park, Mojib Latif

GEOMAR, Germany

We study the variations in air-sea interactions across different horizontal length scales using a climate model, FOCI, run at various resolutions. At higher horizontal and vertical resolution, the atmosphere model is capable of capturing short-lived, localised extremes in precipitation and wind speed, which impacts the air-sea exchange of momentum and freshwater. Furthermore, studies suggest that increasing the horizontal resolution of the ocean component leads to more intense air-sea fluxes of heat and freshwater.

The FOCI-OIFS v1.0 climate model is based on OpenIFS cy40r1 and NEMO/LIM v3.6 run at 1.125° and 0.5° resolution respectively, with the possibility to increase ocean resolution to 0.1° regionally using AGRIF two-way nesting. OpenIFS can be run at a variety of horizontal resolution. The development and set up of this model will be presented as discussed.

KjellssonJ_FOCI-OIFS.pdf

12:00

Chris Thorncroft (University at Albany, USA) – solicited

 A review of the structure and variability of African easterly waves including their relationship with Atlantic tropical cyclones

Chris Thorncroft, Alan Brammer, Matt Janiga

University at Albany, USA

In the first part of this talk emphasis will be given to the regional differences in the vertical structure of AEWs as they move between East Africa and the East Atlantic. The vertical structure of temperature and vorticity in the AEWs are related to regional differences in the climatological and vortex‐centred diabatic heating and diabatic potential vorticity (PV) generation profiles from three reanalysis datasets (ERA-Interim, NCEP-CFSR, MERRA). The climatological diabatic heating over East Africa peaks at 450 hPa with diabatic cooling below 750 hPa. In contrast, the convectively active West African coast and the East Atlantic have increased diabatic heating in the lower troposphere. Due to these regional differences in diabatic heating, diabatic PV generation peaks near 700 hPa over the continent and below 800 hPa over the East Atlantic. Moving westwards from East Africa to the East Atlantic, AEW composites have weaker lower tropospheric cold cores and significantly increased lower tropospheric vorticity within the convectively active troughs.In the second part of this talk emphasis is given to the factors that influence the probability that a favorable-looking AEW leaving the West African coast becomes a tropical cyclone or not. The analysis shows that favorable developing waves had significantly higher moisture content in the lower troposphere to the northwest of the trough as they exited the West African coast compared to favorable non-developing waves. Trajectory analysis for all the waves revealed that as the AEWs transition over the West African coast the troughs are typically open to the environment ahead and to the northwest of the trough. For developing waves this means that moist air is ingested into the lower levels of the system, while for non-developing waves dry air is ingested. Finally, some real time monitoring and forecast products based on this work will briefly be presented.

ThorncroftCh_EasterlyWaves.pdf

12:00

Pirkka Ollinaho (Finnish Meteorological Institute)

 Ensemble prediction with OpenIFS

Pirkka Ollinaho

Finnish Meteorological Institute

Probabilistic forecasts provide information on how predictions of the atmospheric evolution may differ from the traditional "best guess" solution, i.e. the deterministic forecast. Ensemble prediction systems generate this probabilistic information through assessing uncertainties in both the model initial state and the model itself. In order to open up ensemble prediction research for a wider research community, we have recreated all 50+1 operational IFS ensemble initial states for OpenIFS. The data set covers one year (December 2016 to November 2017) twice a day. A range of model resolutions are provided to cover different research needs (TL159, TL399 and TL639).

An open-source workflow manager, called OpenEPS, is used to launch ensemble forecast experiments from the perturbed initial conditions. The experiments are run with OpenIFS CY40R1 and examine all the provided resolutions. The probabilistic skill of the experiments is assessed through ensemble mean RMSE and ensemble spread, and the Continuous Ranked Probability Score (CRPS) for several forecast variables. We will furthermore discuss how many ensemble members are required for conducting meaningful research experiments. This is inspired by a recent paper by Leutbecher (2018), who explored the ensemble size impacts with IFS. Here we redo the same experiments with the OpenIFS ensembles.

We will also illustrate the research potential of running your own ensemble of forecasts through a case study of typhoon Damrey, which severely affected Vietnam in 2017.

Further reading:

Leutbecher M., 2018: Ensemble size: How suboptimal is less than infinity? Q. J. R. Meteorol. Soc. 2018, 1–22, https://doi.org/10.1002/qj.3387.

OllinahoP_ensemble.pdf

Xavier Yepes Arbós (Barcelona Supercomputing Center, Spain)

 A portable framework to generate initial conditions for IFS/OpenIFS from ERA reanalysis products using OpenIFS

Xavier Yepes Arbós, Etienne Tourigny, Mario Acosta Cobos, Francisco Doblas-Reyes

Barcelona Supercomputing Center, Spain

Models used in weather and climate forecasts must initialize the state of the Earth system (atmosphere, ocean, land and cryosphere) from observations. Retrospective forecasts (also called hindcasts) in weather or climate prediction mode are used to evaluate the model’s performance and are typically initialized from reanalysis products (such as ERA-Interim). However, the horizontal and vertical resolution of the reanalyses can be different and additional operations are needed to fit the grid model of the hindcast.

The EC-Earth climate model used, among others, by BSC relies on atmospheric initial conditions derived from ERA-Interim. These data must be obtained for several start dates (4 each year) for the entire period covered by the reanalysis product. Until recently, these data were generated at ECMWF HPC facilities using an IFS experiment with the prepIFS infrastructure.

The procedure used is:

  1. Download the reanalysis data at its native resolution using MARS requests.
  2. Running IFS in mode 927 to make use of FullPos, a powerful post-processing package that performs horizontal and vertical interpolations.
  3. Post-processing the result and archival on MARS.

While this procedure is robust and relatively fast, it relies on ECMWF infrastructure and support. Moreover, it is vulnerable to changes in the HPC platform used.

To overcome these shortcomings, the scripts have been simplified and adapted to run on other HPC platforms using the OpenIFS model cycle 40r1. The advantage of the new scripts is that they can be easily deployed on any machine with minimal effort by the user. Currently, the retrieval script is run on the ecgate cluster at ECMWF for efficiency and ease of implementation, relying on the MARS client, but it could be adapted to use the CDS API instead of MARS client. In addition, they are automated using the open-source Autosubmit workflow manager to minimize the user intervention as well as errors, and to optimize some processes.

The results show that the differences of the interpolated GRIB files produced by IFS on ECMWF and by OpenIFS on MareNostrum are negligible. Moreover, several configurations have been successfully interpolated, including configuration T1279L137, which takes very little time, proving that the implementation is fast.

Yepes-ArbosX_InitialConditions.pdf

12:20

Hannah Christensen (University of Oxford, UK)

 Constraining stochastic parametrisation schemes using high-resolution model simulations and the OpenIFS Single Column Model

Hannah Christensen

University of Oxford, UK

Stochastic parametrisations are used in weather and climate models to represent model error. Designing new stochastic schemes has been the target of much innovative research over the last decade, with a focus on developing physically motivated schemes. We present a technique for systematically deriving new stochastic parametrisations or for constraining existing stochastic approaches. We take a high-resolution model simulation and coarse-grain it to the desired forecast model resolution. This provides the initial conditions and forcing data needed to drive the OpenIFS Single Column Model (SCM). By comparing the SCM parametrised tendencies with the evolution of the high-resolution model, we can measure the ‘error’ in the SCM tendencies. As a case study, we use this approach to assess the physical basis of the ‘Stochastically Perturbed Parametrisation Tendencies’ (SPPT) scheme, used operationally in the ECMWF Ensemble Prediction System to represent model uncertainty. We provide justification for the multiplicative nature of SPPT, and for the large temporal and spatial scales used in the stochastic perturbations. However, we also identify issues with the SPPT scheme and motivate improvements. In particular, our results indicate that an alternative approach is needed to represent uncertainty in the convection scheme. It is hoped this new coarse-graining technique will improve both holistic and process-based approaches to stochastic parametrisation.

Further reading:

Christensen, H.M.: Constraining stochastic parametrisation schemes using high-resolution simulations. For submission to Q. J. Roy. Meteor. Soc.

Christensen, H.M., Dawson, A., Holloway, C.E., 2018: Forcing Single-Column Models Using High-Resolution Model Simulations. J. Adv. Model. Earth Syst., 10(8), 1833-1857, https://doi.org/10.1029/2017MS001189.

ChristensenH_SCM.pdf

Emma Howard (University of Oxford, UK)

 The influence of orography on synoptic weather systems in tropical Southern Africa

Emma Howard, Richard Washington

University of Oxford, UK

Precipitation underpins the lives of 150 million people in southern Africa. Shifts in rainfall can undercut agricultural production, undermine water, food and energy security, and ultimately threaten the economic viability of the region.

Tropical Lows are important rain-bearing weather systems in southern Africa, providing 33% of summer precipitation across the southern edge of the tropical rain belt. They are a means by which the ENSO signal is expressed in Southern Africa, forming less frequently and further north during the El Nino phase, which is linked to regional drought. Meanwhile, heat lows play an important role in controlling the location of the edge of the tropical rain belt in spring.

This talk will present some key findings on the synoptics of tropical lows and heat lows. The role of the steep southern African topography in the formation, maintenance and anchoring of these features will be considered by means of a novel global-regional modelling setup combining OpenIFS with WRF.

HowardE_orography.pdf

Suzanne Gray, Robert Plant (University of Reading, UK)

Summary & closure of the workshop

GrayS-PlantB_summary.pdf

13:00
Lunch – Allen Laboratory (no. 48 on the map)
13:00
Lunch – Department of Meteorology (no. 58 on the map)
12:40
Lunch – Department of Meteorology (no. 58 on the map)
Location: Allen Laboratory (no. 48 on the map)

14:00

Margarita Choulga (ECMWF, UK) – solicited

Lake model in OpenIFS

ChoulgaM_lakes.pdf

14:10

Ben Harvey (University of Reading, UK)

Introduction to the NAWDEX case study: Extratropical phase of tropical storm Karl

HarveyB_CaseOverview.pdf

13:50Practical session on the NAWDEX case
14:25

Robin Hogan (ECMWF, UK) – solicited

ecRad: A modular radiation scheme for IFS, OpenIFS, and for offline research

Full version: HoganR_ecRad_full.pdf
Printable version: HoganR_ecRad_print.pdf

15:05Comfort break
15:10

Marcus Köhler (ECMWF, UK)

 Practical exercise on introduction to OpenIFS
  • Build the model
  • Study and set the namelist
  • Running on Cray (basic commands to submit a job, check the job status etc.)
  • Run the T21 test
  • Diagnostics
  • gribapi/eccodes tools for examine GRIB files
  • GRIB 2 netCDF conversion

Tutorial

14:40Practical session on the NAWDEX case
16:10Coffee & tea break15:40 Coffee & tea break 15:40Coffee & tea break
16:30

Gabriella Szépszó (ECMWF, UK)

 Practical exercise with OpenIFS on a real case study
  • Case study: storm Desmond
  • Short study the initial conditions
  • Set the namelist
  • Run the model (T255 experiment for 3 days)
  • Post-processing
  • Collect ERA5 data for validation
  • Introduction to Metview
  • Visualization of the forecast outputs and ERA5 with Metview

Tutorial

16:00Practical session on the NAWDEX case16:00Practical session on the NAWDEX case
17:30End of the practical session
17:30 End of the practical session 17:30End of the practical session


18:00

Ice breaker and poster session

In room 1L61 at the Department of Meteorology (no. 58 on the map)

19:00

Drink & group photo & workshop dinner at ECMWF

Coach in the university car park 1a (no. 1a on the map); pick-up time: 18:45

Social event for early career researchers


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