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18/07/2018 - Welcome Jan Wandel

We are very happy to welcome Jan Wandel as a new member of the group “Large-scale Dynamics and Predictability”. Jan got a Bachelor’s and Master’s degree in Meteorology from KIT. During his studies he was engaged in IMK’s “early weather hazards warning” (Wettergefahrenfrühwarnung). In his Masterthesis at IMK-TRO Jan studied the synoptic environment triggering hailstorms in Europe.

Jan will now take care of operational weather regime forecast products in our group and investigate the linkage of weather regimes and hailstorms in collaboration with his former group. In autumn Jan will start a PhD in the project “SPREADOUT”, in which he will investigate the predictability of diabatic outflow in operational sub-seasonal numerical weather prediction models, stratified according to critical weather regime life cycle stages and external modes of the climate system. In addition, Jan will develop operational forecast products for weather regimes on sub-seasonal time-scales. We wish Jan a great start, success and a lot of fun with his work and colleagues at IMK. Welcome!

15/06/2018 - Improving weather forecasts on sub-seasonal time scales

IR-Sat+Jet
Fig. 1: Meteorological situation during the Central European summer heat wave in July 2015, IR satellite image, blocking anticyclone (blue hatching), deflection of the jet stream (green contour), warm conveyor belt (blue-to-red trajectories).

Advances in numerical weather prediction currently push the weather forecast horizon into sub-seasonal time scales of several days to a few weeks. On these time scales so-called weather regimes – quasi-stationary, recurrent, and persistent flow patterns – govern the variability of the large-scale circulation. They modulate the character of daily weather for continent-size regions and prolonged periods. Therefore, weather regimes have strong implications for socio-economic sectors such as agriculture, transport, or renewable energies [1].

The correct prediction of weather regime life cycles still is a key challenge for current sub-seasonal forecasting systems because weather regimes are concurrently modified by processes on very different spatial and temporal scales: From a weather perspective, the life cycles of these regimes are influenced by meso- to synoptic-scale weather systems such as extratropical cyclones or convective systems. From a climate perspective, modes of the climate system such as the Madden-Julian-Oscillation or the state of the stratosphere are potential sources of sub-seasonal predictability for such regimes.

The newly established group “Large-scale Dynamics and Predictability” aims to provide a comprehensive investigation of the physical and dynamical processes that control predictability and forecast skill on sub-seasonal time scales, with a focus on the life cycle of large-scale flow regimes in the Atlantic-European region. In addition, the group explores novel probabilistic forecast products on sub-seasonal time scales in collaboration with official weather services.

An example of such a novel forecast product is shown for the “early heat wave” in Central Europe that peaked from 19. – 22. April 2018 (Figure 2). The overview regime plot indicates how likely a specific weather regime occurs within the subsequent 15 days (Figure 2a). The detailed regime product shows how well the different regimes are established in a probabilistic forecast (Figure 2b). In this case these forecast products correctly indicated – more than one week in advance – the actual transition from a “Scandinavian blocking regime” (ScBL) into a “zonal regime” (ZO) at the end of the heat wave (Figure 2c compared to Figure 2b). However, particularly such transitions from one regime to another are often not well predicted by current sub-seasonal forecast systems.

The group now investigates in detail how well sub-seasonal forecasting systems represent weather regime life cycles and their underlying physical processes on shorter synoptic time-scales as well as their modulation by slower climate modes, e.g. the Madden-Julian-Oscillation or the state of the stratosphere [2]. Working at the interface of these different spatial and temporal scales will not just improve the understanding of weather regimes but ultimately also contribute to the overarching goal of a seamless prediction of weather and climate.

The group is funded by the Helmholtz Association with a Helmholtz Young Investigator Group Grant for the project “Sub-seasonal Predictability: Understanding the Role of Diabatic Outflow” (SPREADOUT).

Link: Group: Large-scale Dynamics and Predictability http://www.imk-tro.kit.edu/english/7425.php

[1] C. M. Grams, R. Beerli, S. Pfenninger, I. Staffell, H. Wernli, Balancing Europe’s wind-power output through spatial deployment informed by weather regimes. Nature Climate Change. 7, 557–562 (2017).

[2] Papritz L., Grams C. M., Linking Low‐Frequency Large‐Scale Circulation Patterns to Cold Air Outbreak Formation in the Northeastern North Atlantic. Geophysical Research Letters. 45, 2542–2553 (2018).

[Working group: Large-scale Dynamics and Predictability]

Fig. 2: Example of novel weather regime forecast products. (a) Ensemble forecast initialised at 12 UTC 15 April 2018. Bars indicate relative number of members projecting in one of 7 weather regimes (colors) or no regime (grey). Bottom rows show the attribution of the ensemble mean, control, and high resolution (up to 240h) forecasts, respectively. (b) Ensemble distribution of projection in one of 7 weather regimes at each forecast step. Light shades indicate maximum and minimum projection, dark shades show the 75th and 25th percentile. Lines show the projection of the control forecast (bold solid), high resolution forecast (bold dashed, only up to 240h), and ensemble mean (thin dashed). (c) Actual verifying projection into 7 weather regimes in the 30day period starting on 7 April 2018.

11/06/2018 - Visit of AXPO Trading

AGGrams_Axpo
Julian Quinting, Dominik Büeler, energy meteorologist Remo Beerli, and Christian Grams in front of the AXPO main building in Baden (Switzerland).

The SPREADOUT group visited AXPO Trading in Baden (Switzerland) on 11 June 2018. The main purpose of the visit was to inform energy traders and meteorologists at AXPO about current research activities and to discuss forecast tools useful to the energy sector. After an introductory presentation on SPREADOUT by Christian Grams and Dominik Büeler, Remo Beerli (energy meteorologist at AXPO) showed us the trading floor. There we gained interesting insights in the day-to-day business of energy meteorologists and learned about the forecast products that are needed to provide reliable information to the energy traders. Future collaborations and research avenues were elaborated in a lively discussion in the afternoon.


01/06/2018 - Welcome Nadine Schittko and Seraphine Hauser

Spreadout
Dominik Büeler, Nadine Schittko, Seraphine Hauser, Christian Grams, Julian Quinting

SPREADOUT is growing further: We welcome Nadine Schittko and Seraphine Hauser who will join the group for the next year to complete their Master’s degree.

Nadine will analyse the representation of tropical cyclones in the global forecast model ICON. In the framework of the Master’s thesis, she will implement different tropical cyclone tracking algorithms to verify the intensity and motion of tropical cyclones against best track data. Some impact relevant North Atlantic Hurriances in 2016/17 will be studied in greater detail. The project is executed in close collaboration with DWD where the resulting tools may be used operationally in the future for verification purposes.

In her Master’s thesis, Seraphine is going to analyse “The effect of the El Nino Southern Oscillation on Australian climate variability from a weather system perspective”. Using a novel data set of objectively identified weather systems, the goal of the first part of the project is to develop a conceptual picture on how different states of the El Nino Southern Oscillation are related to the occurrence frequency of subtropical and midlatitude weather systems. The results will then be used to attribute the observed variability in temperature and precipitation to these weather systems.

We wish Nadine and Seraphine great success and a lot of fun with their work!


01/03/2018 - Welcome

We welcome Dominik Büeler as a new member of the group “Large-scale Dynamics and Predictability”. Dominik received his PhD from ETH Zurich for his thesis entitled "Potential vorticity diagnostics to quantify effects of latent heating in extratropical cyclones: methodology and application to idealized climate change simulations". Already before his PhD, Dominik gained experience both in climate and weather modelling: he analysed marine boundary layer clouds in ECHAM5-HAM and investigated the northern mid- and high-latitude climate in a climate change mitigation scenario in his Bachelor and Master thesis, respectively. During a one-year internship at MeteoSwiss, he worked on the potential of COSMO in predicting photovoltaic power, which offered him an insight into applied weather science. After a short PostDoc project at ETH Zurich last autumn on month-ahead predictability of European wind power, Dominik will continue research in the field of sub-seasonal predictability at KIT in the project “SPREADOUT”. He will study the representation of large-scale weather regimes in sub-seasonal numerical weather prediction models and physical processes governing weather regime life cycles. We wish Dominik a great start, success and a lot of fun with his work and colleagues at IMK.

 

15/02/2018 - Welcome

We welcome Julian Quinting as a senior scientist in the group “Large-scale Dynamics and Predictability”. Julian received his PhD from KIT for his thesis entitled “ The impact of tropical convection on the dynamics and predictability of midlatitude Rossby waves: a climatological study” His Diploma and PhD research was part of the PANDOWAE research unit. After his PostDoc time at ETH Zurich and Monash University, Melbourne, Julian is back at KIT and will work on Sub-seasonal predictability in the project “SPREADOUT”.

As a PostDoc in Zurich, Julian worked on upper-level frontogenesis, Rossby wave dynamics, and MJO teleconnections. In addition, he helped preparing the NAWDEX field campaign and in autumn 2016 contributed actively to flight planning and forecasting based in Iceland. His research focus during the last 2 years at Monash shifted to the understanding of physical processes driving extreme events in the Australian region (e.g. heat waves) and southern hemispheric Rossby wave dynamics. In SPREADOUT Julian will study the representation of physical processes in global NWP data sets, their modulation by global teleconnections (e.g. MJO, ENSO), and how they affect sub-seasonal predictability for Europe. We wish Julian great success and a lot of fun with his work and colleagues at IMK.

 

 

12/12/2017 - Statement regarding Nature Geoscience manuscript “Southward shift of the global wind energy resource under high carbon dioxide emissions”

windraeder_626px
picture: Bernhard Mühr, www.wolkenatlas.de

Based on an ensemble of 10 global climate model simulations following the RCP4.5 and RCP8.5 scenarios, this study reports a strong decrease of potential wind electricity generation in the mid-latitudes during the XXI Century (https://www.nature.com/articles/s41561-017-0029-9). The authors use a simple methodology and data with low spatio-temporal resolution, and consider an exemplary wind energy turbine for the computations. Compared to other regions of the world (notably North America), the changes for Europe are comparatively small. These projections for Europe are partially in agreement with studies based on datasets with much higher spatial and temporal resolution (e.g., Tobin et al., 2015, Reyers et al., 2016, Moemken et al., 2018). These studies reveal rather small changes of wind energy potentials for Europe on the continental scale (+/- 5%). On the other hand, they point to increased variability of wind electricity generation in multiple time scales. The differences to the Nature Geoscience study are related with the different data resolution and methodology.

In particular, an increased occurrence of low wind speed (< 3m/s) events reported in Moemken et al. (2018) may cause challenges for the energy supply across Europe. However, this challenge can be overcome with suitable mitigation strategies and updated planning. For example, Grams et al. (2017) provide evidence that the concentration of wind parks in some areas (e.g. North Sea) is problematic to warrant a reliable wind electricity generation. A pan-European management strategy and a more de-central distribution of wind parks would permit to balance the weather and climate variability and thus contribute to a more reliable energy supply. Moreover, the joint management of different renewable sources (notably solar) would further contribute to mitigate the possible changes in wind energy production in future decades.

 

References:

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

Moemken, J., M. Reyers, H. Feldmann, and J. G. Pinto, 2018: Wind speed and wind energy potentials in EURO-CORDEX ensemble simulations: evaluation and future changes, Journal of Geophysical Research: Atmospheres, in revision.

Reyers, M., J. Moemken, and J. G. Pinto, 2016: Future changes of wind energy potentials over Europe in a large CMIP5 multi-model ensemble. Int. J. Climatol., 36, 783–796, doi:10.1002/joc.4382.

Tobin, I., and Coauthors, 2015: Assessing climate change impacts on European wind energy from ENSEMBLES high-resolution climate projections. Climatic Change, 128, 99–112, doi:10.1007/s10584-014-1291-0.

Link: http://www.sek.kit.edu/kit_express_3874.php

Contact: Joaquim G. Pinto http://www.imk-tro.kit.edu/14_7131.php

Contact: Christian M. Grams http://www.imk-tro.kit.edu/14_7356.php