Daniel Reinert’s research while affiliated with Deutscher Wetterdienst and other places


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Publications (37)


Evolution of MSP and MWS over the 10 d simulation period for the 50 km grid spacing.
Wind–pressure relationship in the simulated TCs at all time steps for the 50 km grid spacing. MWS and MSP from Fig. were used in this calculation. Second-order polynomial functions are fit using a least-squares method.
Radial profiles of 1 km wind speed and surface pressure averaged from days 4–10 of the 50 km simulation. Values in the radial profiles are azimuthally averaged.
Azimuthally averaged vertical wind composite of the simulated TCs from days 4–10 of the 50 km simulation.
Evolution of MSP and MWS over the 10 d simulation period. Grid spacings of 50 km (dashed line) and 25 km (solid line) are shown for participating models.

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DCMIP2016: the tropical cyclone test case
  • Article
  • Full-text available

April 2024

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82 Reads

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2 Citations

Geoscientific Model Development
Justin L. Willson

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Christiane Jablonowski

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This paper describes and analyzes the Reed–Jablonowski (RJ) tropical cyclone (TC) test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). This intermediate-complexity test case analyzes the evolution of a weak vortex into a TC in an idealized tropical environment. Reference solutions from nine general circulation models (GCMs) with identical simplified physics parameterization packages that participated in DCMIP2016 are analyzed in this study at 50 km horizontal grid spacing, with five of these models also providing solutions at 25 km grid spacing. Evolution of minimum surface pressure (MSP) and maximum 1 km azimuthally averaged wind speed (MWS), the wind–pressure relationship, radial profiles of wind speed and surface pressure, and wind composites are presented for all participating GCMs at both horizontal grid spacings. While all TCs undergo a similar evolution process, some reach significantly higher intensities than others, ultimately impacting their horizontal and vertical structures. TCs simulated at 25 km grid spacings retain these differences but reach higher intensities and are more compact than their 50 km counterparts. These results indicate that dynamical core choice is an essential factor in GCM development, and future work should be conducted to explore how specific differences within the dynamical core affect TC behavior in GCMs.

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List of DCMIP2016 symbols used in model initialization (Ullrich et al., 2016).
List of constants used for the Idealized Tropical Cyclone test (Ullrich et al., 2016).
Information about models that submitted RJ TC test case simulations in DCMIP2016 and were analyzed in this study.
Additional information about the models used in this study. Three dynamical cores are present: spectral element (SE), finite differ- ence (FD), and finite volume (FV). More information can be found in Ullrich et al. (2017)
DCMIP2016: the tropical cyclone test case

May 2023

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145 Reads

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1 Citation

This paper describes and analyzes the Reed-Jablonowski (RJ) tropical cyclone (TC) test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). The intermediate complexity test case analyzes the evolution of a weak vortex into a TC in an idealized tropical environment. Simulations from 9 general circulation models (GCMs) that participated in DCMIP2016 are analyzed in this study at 50 km horizontal grid spacing, with 5 of these models also providing simulations at 25 km grid spacing for an analysis on the impact of finer grid spacing. Evolution of minimum surface pressure (MSP) and maximum 1 km azimuthally averaged wind speed (MWS), the wind-pressure relationship, radial profiles of wind speed and surface pressure, and wind composites are documented for all participating GCMs at both horizontal grid spacings. While results are generally similar between all models, some GCMs reach significantly higher storm intensities than others, ultimately impacting specific characteristics of their horizontal and vertical structure. TCs simulated at 25 km grid spacings retained these differences, but reach higher intensities and are more compact than their 50 km counterparts. These results indicate dynamical core choice is an essential factor in GCM development, and future work should be conducted to explore how specific differences within the dynamical core affect TC behavior in GCMs.


Grid refinement in ICON v2.6.4

September 2022

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5 Reads

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3 Citations

This article describes the implementation of grid refinement in the ICOsahedral Nonhydrostatic (ICON) modeling system. It basically follows the classical two-way nesting approach known from widely used mesoscale models like MM5 or WRF, but it differs in the way feedback from fine grids to coarser grids is applied. Moreover, the ICON implementation supports vertical nesting in the sense that the upper boundary of a nested domain may be lower than that of its parent domain. Compared to the well-established implementations on quadrilateral grids, new methods had to be developed for interpolating the lateral boundary conditions from the parent domain to the child domain(s). These are based on radial basis functions (RBFs) and partly apply direct reconstruction of the prognostic variables at the required grid points, whereas gradient-based extrapolation from parent to child grid points is used in other cases. The runtime flow control is written such that limited-area domains can be processed identically to nested domains except for the lateral boundary data supply. To demonstrate the functionality and quality of the grid nesting in ICON, idealized tests based on the Jablonowski–Williamson test case and the Schär mountain wave test case are presented. The results show that the numerical disturbances induced at the nest boundaries are small enough to be negligible for real applications. This is confirmed by experiments closely following the configuration used for operational numerical weather prediction at DWD, which demonstrate that a regional refinement over Europe has a significant positive impact on the forecast quality in the Northern Hemisphere.


The ICON-A model for direct QBO simulations on GPUs (version icon-cscs:baf28a514)

September 2022

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164 Reads

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19 Citations

Classical numerical models for the global atmosphere, as used for numerical weather forecasting or climate research, have been developed for conventional central processing unit (CPU) architectures. This hinders the employment of such models on current top-performing supercomputers, which achieve their computing power with hybrid architectures, mostly using graphics processing units (GPUs). Thus also scientific applications of such models are restricted to the lesser computer power of CPUs. Here we present the development of a GPU-enabled version of the ICON atmosphere model (ICON-A), motivated by a research project on the quasi-biennial oscillation (QBO), a global-scale wind oscillation in the equatorial stratosphere that depends on a broad spectrum of atmospheric waves, which originates from tropical deep convection. Resolving the relevant scales, from a few kilometers to the size of the globe, is a formidable computational problem, which can only be realized now on top-performing supercomputers. This motivated porting ICON-A, in the specific configuration needed for the research project, in a first step to the GPU architecture of the Piz Daint computer at the Swiss National Supercomputing Centre and in a second step to the JUWELS Booster computer at the Forschungszentrum Jülich. On Piz Daint, the ported code achieves a single-node GPU vs. CPU speedup factor of 6.4 and allows for global experiments at a horizontal resolution of 5 km on 1024 computing nodes with 1 GPU per node with a turnover of 48 simulated days per day. On JUWELS Booster, the more modern hardware in combination with an upgraded code base allows for simulations at the same resolution on 128 computing nodes with 4 GPUs per node and a turnover of 133 simulated days per day. Additionally, the code still remains functional on CPUs, as is demonstrated by additional experiments on the Levante compute system at the German Climate Computing Center. While the application shows good weak scaling over the tested 16-fold increase in grid size and node count, making also higher resolved global simulations possible, the strong scaling on GPUs is relatively poor, which limits the options to increase turnover with more nodes. Initial experiments demonstrate that the ICON-A model can simulate downward-propagating QBO jets, which are driven by wave–mean flow interaction.


List of model configurations for the Jablonowski-Williamson test.
Grid Refinement in ICON v2.6.4

May 2022

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77 Reads

This article describes the implementation of grid refinement in the ICOsahedral Nonhydrostatic (ICON) modeling system. It basically follows the classical two-way-nesting approach known from widely used mesoscale models like MM5 or WRF, but differs in the way how feedback from fine grids to coarser grids is applied. Moreover, the ICON implementation supports vertical nesting in the sense that the upper boundary of a nested domain may be lower than that of its parent domain. Compared to the well-established implementations on quadrilateral grids, new methods had to be developed for interpolating the lateral boundary conditions from the parent domain to the child domain(s). These are based on radial basis functions (RBFs) and partly apply direct reconstruction of the prognostic variables at the required grid points, whereas gradient-based extrapolation from parent to child grid points is used in other cases. The technical implementation on the unstructured ICON grid is based upon sorting the boundary interpolation points at the beginning of the grid-point index vector, so that computations on boundary interpolation points can be excluded by appropriate start indices without the need of IF masks. The run-time flow control is written such that limited-area domains can be processed identically to nested domains except for the lateral boundary data supply. To demonstrate the functionality and quality of the grid nesting in ICON, idealized tests based on the Schär mountain wave test case (Schär et al., 2002) and the Jablonowski-Williamson test case (Jablonowski and Williamson,2006) are presented. The results show that the numerical disturbances induced at the nest boundaries are small enough to be negligible for real applications. This is confirmed by experiments closely following the configuration used for operational numerical weather prediction at DWD, which demonstrate that a regional refinement over Europe has a significant positive impact on the forecast quality in the northern hemisphere.


The ICON-A model for direct QBO simulations on GPUs (version icon-cscs:baf28a514)

April 2022

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67 Reads

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5 Citations

Classical numerical models for the global atmosphere, as used for numerical weather forecasting or climate research, have been developed for conventional central processing unit (CPU) architectures. This now hinders the employment of such models on current top performing supercomputers, which achieve their computing power with hybrid architectures, mostly using graphics processing units (GPUs). Thus also scientific applications of such models are restricted to the lesser computer power of CPUs. Here we present the development of a GPU enabled version of the ICON atmosphere model (ICON-A) motivated by a research project on the quasi-biennial oscillation (QBO), a global scale wind oscillation in the equatorial stratosphere that depends on a broad spectrum of atmospheric waves, which origins from tropical deep convection. Resolving the relevant scales, from a few km to the size of the globe, is a formidable computational problem, which can only be realized now on top performing supercomputers. This motivated porting ICON-A, in the specific configuration needed for the research project, in a first step to the GPU architecture of the Piz Daint computer at the Swiss National Supercomputing Centre, and in a second step to the Juwels-Booster computer at the Forschungszentrum Jülich. On Piz Daint the ported code achieves a single node GPU vs. CPU speed-up factor of 6.3, and now allows global experiments at a horizontal resolution of 5 km on 1024 computing nodes with 1 GPU per node with a turnover of 48 simulated days per day. On Juwels-Booster the more modern hardware in combination with an upgraded code base allows for simulations at the same resolution on 128 computing nodes with 4 GPUs per node and a turnover of 133 simulated days per day. Additionally, the code still remains functional on CPUs as it is demonstrated by additional experiments on the Levante compute system at the German Climate Computing Center. While the application shows good weak scaling making also higher resolved global simulations possible, the strong scaling on GPUs is relatively weak, which limits the options to increase turnover with more nodes. Initial experiments demonstrate that the ICON-A model can simulate downward propagating QBO jets, which are driven by wave meanflow interaction.


Case study of a moisture intrusion over the Arctic with the ICOsahedral Non-hydrostatic (ICON) model: resolution dependence of its representation

January 2022

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167 Reads

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11 Citations

The Arctic is warming faster than the global average and any other region of a similar size. One important factor in this is the poleward atmospheric transport of heat and moisture, which contributes directly to the surface and air warming. In this case study, the atmospheric circulation and spatio-temporal structure of a moisture intrusion event is assessed, which occurred from 5 to 7 June 2017 over the Nordic seas during an intensive measurement campaign over Svalbard. This analysis focuses on high-spatial-resolution simulations with the ICON (ICOsahedral Non-hydrostatic) model which is put in context with coarser-resolution runs as well the ERA5 reanalysis. A variety of observations including passive microwave satellite measurements is used for evaluation. The global operational ICON forecasts from the Deutscher Wetterdienst (DWD) at 13 km horizontal resolution are used to drive high-resolution Limited-Area Mode (LAM) ICON simulations over the Arctic with 6 and 3 km horizontal resolutions. The results show the skilful capacity of the ICON-LAM model to represent the observed spatio-temporal structure of the selected moisture intrusion event and its signature in the temperature, humidity and wind profiles, and surface radiation. In several aspects, the high-resolution simulations offer a higher accuracy than the global simulations and the ERA5 reanalysis when evaluated against observations. One feature where the high-resolution simulations demonstrated an advanced skill is the representation of the changing vertical structure of specific humidity and wind associated with the moisture intrusion passing Ny-Ålesund (western Svalbard); the humidity increase at 1–2 km height topped by a dry layer and the development of a low-level wind jet are best represented by the 3 km simulation. The study also demonstrates that such moisture intrusions can have a strong impact on the radiative and turbulent heat fluxes at the surface. A drastic decrease in downward shortwave radiation by ca. 500 W m-2 as well as an increase in downward longwave radiation by ca. 100 W m-2 within 3 h have been determined. These results highlight the importance of both moisture and clouds associated with this event for the surface energy budget.



Figure 3. Top row shows the integrated contents of water vapour (IWV, a)) and liquid (CRWP, b)) and solid hydrometeor content (ISGWP, c)) from the 6 km ICON-LAM simulation for the 6 th June 2017 12:00 UTC. In panels d)-f) the forward simulated TB at 183.31±1, 183.31±3, and 190.31 GHz based on ICON-LAM on the 6km resolution are shown. g) to i) show the observations from MHS for an overpass between
Figure 10. Time series of specific humidity in g kg -1 (color shading), air temperature in K (isolines) and wind speed in m s -1 (orange isolines) profiles at Shojna from ICON-LAM6 (a) and specific humidity difference between ICON-LAM6 and ICON-LAM3 (b, ICON-LAM3 remapped onto the ICON-LAM6 grid resolution), from 5 th June 2017 00:00 UTC to 8 th June 2017 00:00 UTC.
Figure 12. Surface map of sensible (a) and latent (b) heat fluxes (W m -2 , color shading) from ICON-LAM 6 km, on 6 th June 2017 12:00 UTC. Positive/negative signs indicate a downward/upward flux to/from the surface. Regions of IWV > 20 kg m -2 (red line), precipitation > 5 mm (pink line) and sea-ice fraction > 0.15 (black hatching) are included.
Case study of a moisture intrusion over the Arctic with the ICON model: resolution dependence of its representation

July 2021

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126 Reads

The Arctic is warming faster than the global average and any other region. One important factor for this is the poleward atmospheric transport of heat and moisture, which contributes directly to the surface and air warming. In this case study, the atmospheric circulation and spatio-temporal structure of a moisture intrusion event is assessed, which occurred during the 5th to 7th June 2017 over the Nordic Seas during an intensive measurement campaign over Svalbard. This analysis focuses on high-spatial resolution simulations with the ICON (ICOsahedral Non-hydrostatic) model which is put in context with coarser resolution runs as well the ERA5 reanalysis. A variety of observations including passive microwave satellite measurements is used for evaluation. The global operational ICON forecasts from the German Weather Service DWD at 13 km horizontal resolution are used to drive high resolution Limited Area Mode (LAM) ICON simulations over the Arctic with 6 km and 3 km horizontal resolutions. The results show the skillfull capacity of the ICON-LAM model to represent the observed spatio-temporal structure of the selected moisture intrusion event and its signature in the temperature, humidity and wind profiles, and surface radiation. The high resolution simulations offer a higher accuracy than the global simulations and the ERA5 reanalysis, compared to observations. This is especially demonstrated in the representation of the changing vertical structure of specific humidity and wind associated with the moisture intrusion passing Ny-Ålesund (western Svalbard). Namely, the humidity increase in 1–2 km height topped by a dry layer and the development of a low-level wind jet is best represented by the 3 km simulation. The study also demonstrates that such moisture intrusions can have a strong impact on the radiative and turbulent heat fluxes at the surface. A drastic decrease of downward shortwave radiation by ca. 500 W m−2 and an increase of downward longwave radiation by ca. 100 W m−2 within 3 hours are determined, which highlight the importance of both moisture and clouds associated with this event for the surface energy budget.


The upper-atmosphere extension of the ICON general circulation model (version: ua-icon-1.0)

August 2019

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402 Reads

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49 Citations

How the upper-atmosphere branch of the circulation contributes to and interacts with the circulation of the middle and lower atmosphere is a research area with many open questions. Inertia–gravity waves, for instance, have moved in the focus of research as they are suspected to be key features in driving and shaping the circulation. Numerical atmospheric models are an important pillar for this research. We use the ICOsahedral Non-hydrostatic (ICON) general circulation model, which is a joint development of the Max Planck Institute for Meteorology (MPI-M) and the German Weather Service (DWD), and provides, e.g., local mass conservation, a flexible grid nesting option, and a non-hydrostatic dynamical core formulated on an icosahedral–triangular grid. We extended ICON to the upper atmosphere and present here the two main components of this new configuration named UA-ICON: an extension of the dynamical core from shallow- to deep-atmosphere dynamics and the implementation of an upper-atmosphere physics package. A series of idealized test cases and climatological simulations is performed in order to evaluate the upper-atmosphere extension of ICON.


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Citations (28)


... The core of the horizontal ICON grid structure is a projection of a regular icosahedron onto the sphere of the earth. The horizontal resolution of ICON is easily variable (Zängl et al., 2022). For the tracer transport in the standard ICON model, a mass consistent finite volume approach with fractional steps (operator splitting) is employed (Reinert, 2020;Reinert and Zängl, 2021); this transport scheme was not used for the ICON/MESSy-CLaMS simulations of N 2 O transport in focus here. ...

Reference:

Lagrangian transport based on the winds of the icosahedral nonhydrostatic model (ICON)
Grid refinement in ICON v2.6.4

... This robust framework efficiently detects, tracks, and scientifically analyzed various features within climate datasets, unhindered by spatial or temporal resolution limitations. TempestExt has been serving as a reliable tool for accurately identifying and tracking tropical cyclones (TCs), subtropical cyclones, atmospheric rivers, Indian summer monsoon low-pressure systems, as well as mesoscale convective systems (Pinheiro et al 2019, Vishnu et al 2020, Ullrich et al 2021, Tang et al 2022, Willson et al 2024, Wu et al 2024. TempestExt may also serve as a promising tool for identifying the SWV. ...

DCMIP2016: the tropical cyclone test case

... As a starting point to overcome this parameterization deadlock, Giorgetta et al. (2022) presented the first direct simulation of QBO jets over a short period of 48 days in a very high resolution GCM (∼5 km horizontal, ∼400 m vertical) that no longer employs a parameterization of deep convection and GWs. This type of GCMs is commonly referred to as global storm-resolving models (GSRMs) (e.g., Satoh et al., 2019;Stevens et al., 2019). ...

The ICON-A model for direct QBO simulations on GPUs (version icon-cscs:baf28a514)

... Theis and Wong, 2017), HPC 15 systems are increasingly relying on specialized hardware architectures such as graphics processing units (GPUs) to increase throughput while maintaining a reasonable power envelope (Strohmaier et al., 2015). This has led to a number of efforts to port existing weather and climate models to run on such heterogeneous architectures, for example by adding OpenACC directives (Lapillonne et al., 2017;Clement et al., 2019;Giorgetta et al., 2022). Today, there is a handful of successful productive 2. Performance development: adapting the implementation to a set of given hardware architecture, optimization to reach useful simulation time. ...

The ICON-A model for direct QBO simulations on GPUs (version icon-cscs:baf28a514)

... Of the 33 CMIP6 models we investigated, over one third of the models displayed this serious deficiency. One possible reason is that the model spatial resolution is too coarse to represent high mountains 39,40 , and thus the terrain blocking. However, this explanation is insufficient. ...

Case study of a moisture intrusion over the Arctic with the ICOsahedral Non-hydrostatic (ICON) model: resolution dependence of its representation

... However, the advantage of ICON is its good performance at high resolution due to the scalability of the code and the use of non-hydrostatic equations for the atmosphere that allow high resolution convection permitting simulations (Stevens et al. 2019). Another advantage is the availability of adaptive grids as well for the atmosphere (Maurer et al. 2022) as for the ocean (Logemann et al. 2021;Korn et al. 2022). The role of such improvements for seasonal and near-term predictions will be investigated in forthcoming studies. ...

Domain Nesting in ICON and its Application to AMIP Experiments with Regional Refinement
  • Citing Preprint
  • August 2021

... The need to understand the TI system in the context of its interactions with the lower atmosphere has motivated the development of numerical models spanning the whole atmosphere region, from Earth surface to the upper thermosphere, that can simulate the radiative, chemical, dynamical, and electrodynamical processes. A review of whole atmosphere modeling was given in the work by Akmaev (2011), and model capabilities have advanced further since then, including enhanced thermospheric and ionospheric physics (Borchert et al., 2019;Jin et al., 2011;Verronen et al., 2016;Wu et al., 2021) and whole atmosphere data assimilation (Pedatella et al., , 2020Wang et al., 2011). Most of the whole atmosphere models, however, have horizontal resolutions irrelevant for resolving mesoscale processes and gravity waves. ...

The upper-atmosphere extension of the ICON general circulation model (version: ua-icon-1.0)

... The splitting supercell test of DCMIP2016 (Klemp et al., 2015;Zarzycki et al., 2019) emphasizes the importance of scrutinizing nonhydrostatic model simulations of small-scale dynamics, especially as models approach spatial resolutions on the (sub-)kilometre scale. This test utilized the smallplanet testing framework (Wedi and Smolarkiewicz, 2009), a cost-effective approach by scaling down Earth's radius by a factor of 120. ...

DCMIP2016: the splitting supercell test case

... Over the last two decades a number of nonhydrostatic atmospheric models used in weather and climate applications have been modified to integrate the deep-atmosphere equations that accommodate the generalizations mentioned above. These models include, for example, one of the earliest global nonhydrostatic models NICAM (Satoh et al. 2008), the Met Office model ENDGAME (Wood et al. 2014) and the research model MCore (Ullrich et al. 2014, and references therein), and the ICON model (Borchert et al. 2019). Although very few tests exist to validate deep-atmosphere equations solvers, all these models except NICAM (unreported) were evaluated with a baroclinic wave test case (Ullrich et al. 2014), where shallow and deep configurations are tested on spheres of both Earth radius and a reduced radius. ...

The upper-atmosphere extension of the ICON general circulation model

Geoscientific Model Development Discussions

... Meanwhile, different weather and climate models have the water isotopologues and the relevant physical processes implemented and can provide modelled isotopologue fields on a global and regional scale at different horizontal resolutions (e.g. Yoshimura et al., 2008;Risi et al., 2010;Werner et al., 2011;Pfahl et al., 2012;Eckstein et al., 2018;Tanoue et al., 2023). This offers advanced opportunities for studying atmospheric moisture processes with water isotopologues. ...

From climatological to small-scale applications: simulating water isotopologues with ICON-ART-Iso (version 2.3)