scholarly journals Adaptive Wavelet Methods for Earth Systems Modelling

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 236
Author(s):  
Nicholas K.-R. Kevlahan
Keyword(s):  
Adaptive Mesh Refinement ◽  
Climate Models ◽  
Adaptive Mesh ◽  
Mass Conservation ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Climate Modelling ◽  
Exact Mass ◽  
Adaptive Wavelet ◽  
Wavelet Methods

This paper reviews how dynamically adaptive wavelet methods can be designed to simulate atmosphere and ocean dynamics in both flat and spherical geometries. We highlight the special features that these models must have in order to be valid for climate modelling applications. These include exact mass conservation and various mimetic properties that ensure the solutions remain physically realistic, even in the under-resolved conditions typical of climate models. Particular attention is paid to the implementation of complex topography in adaptive models. Using wavetrisk as an example, we explain in detail how to build a semi-realistic global atmosphere or ocean model of interest to the geophysical community. We end with a discussion of the challenges that remain to developing a realistic dynamically adaptive atmosphere or ocean climate models. These include scale-aware subgrid scale parameterizations of physical processes, such as clouds. Although we focus on adaptive wavelet methods, many of the topics we discuss are relevant for adaptive mesh refinement (AMR).

scholarly journals Adaptive Wavelet Methods for Earth Systems Modelling

2021 ◽  
Author(s):  
Nicholas Kevlahan
Keyword(s):  
Adaptive Mesh Refinement ◽  
Climate Models ◽  
Adaptive Mesh ◽  
Mass Conservation ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Climate Modelling ◽  
Exact Mass ◽  
Adaptive Wavelet ◽  
Wavelet Methods

This paper reviews how dynamically adaptive wavelet methods can be designed to simulate atmosphere and ocean dynamics in both flat and spherical geometries. We highlight the special features that these models must have in order to be valid for climate modelling applications. These include exact mass conservation and various mimetic properties that ensure the solutions remain physically realistic, even in the under-resolved conditions typical of climate models. Particular attention is paid to the implementation of complex topography in adaptive models. Using \textsc{wavetrisk} as an example, we explain in detail how to build a semi-realistic global atmosphere or ocean model of interest to the geophysical community. We end with a discussion of the challenges that remain to developing a realistic dynamically adaptive atmosphere or ocean climate models. These include scale-aware subgrid scale parameterizations of physical processes, such as clouds. Although we focus on adaptive wavelet methods, many of the topics we discuss are relevant for adaptive mesh refinement (AMR).

The NEMO (Nucleus for European Modelling of the Ocean) numerical ocean platform

2020 ◽  
Author(s):  
Guillaume Samson ◽  
Claire Levy ◽  
Nemo System Team
Keyword(s):  
Adaptive Mesh Refinement ◽  
State Of The Art ◽  
Adaptive Mesh ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Ice Shelves ◽  
Model Code ◽  
Set Up ◽  
Climate Studies

<p>The Nucleus for European Modelling of the Ocean (NEMO) is a state-of-the art modelling platform for oceanographic research, operational oceanography, sesonnal forecasts and climate studies. NEMO includes three major components; the blue ocean (dynamics), the white ocean (sea-ice), the green ocean (ocean biogeochemistry). It also allows coupling through interfaces with atmosphere (through OASIS software), waves, ice-shelves, so as nesting through the adaptive mesh refinement software AGRIF. Some reference configurations and test cases allowing to explore, to set-up and to validate the applications, and a set of tools to use the platform are also available to the community. The whole platform and its documentation are available under free licence.</p><p>The evolution and reliability of NEMO are organised and controlled by a European Consortium between CMCC (Italy), CNRS (France), MOI France), NOC (UK), UKMO (UK).</p><p>Consortium members agree on long term strategy and yearly plans, sharing expertise and efforts within the NEMO System Team: the core team of NEMO developers in order to ensure the successful and sustainable development of the NEMO System as a well-organised, state-of-the-art ocean model code system suitable for both research and operational work</p>

scholarly journals Extending legacy climate models by adaptive mesh refinement for single-component tracer transport: a case study with ECHAM6-HAMMOZ (ECHAM6.3-HAM2.3-MOZ1.0)

2021 ◽  
Vol 14 (5) ◽  
pp. 2289-2316
Author(s):  
Yumeng Chen ◽  
Konrad Simon ◽  
Jörn Behrens
Keyword(s):  
Adaptive Mesh Refinement ◽  
Climate Models ◽  
Climate Model ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Mass Conservation ◽  
Atmospheric Model ◽  
Transport Processes ◽  
Tracer Transport ◽  
Dust Transport

Abstract. The model error in climate models depends on mesh resolution, among other factors. While global refinement of the computational mesh is often not feasible computationally, adaptive mesh refinement (AMR) can be an option for spatially localized features. Creating a climate model with AMR has been prohibitive so far. We use AMR in one single-model component, namely the tracer transport scheme. Particularly, we integrate AMR into the tracer transport module of the atmospheric model ECHAM6 and test our implementation in several idealized scenarios and in a realistic application scenario (dust transport). To achieve this goal, we modify the flux-form semi-Lagrangian (FFSL) transport scheme in ECHAM6 such that we can use it on adaptive meshes while retaining all important properties (such as mass conservation) of the original FFSL implementation. Our proposed AMR scheme is dimensionally split and ensures that high-resolution information is always propagated on (locally) highly resolved meshes. We utilize a data structure that can accommodate an adaptive Gaussian grid. We demonstrate that our AMR scheme improves both accuracy and efficiency compared to the original FFSL scheme. More importantly, our approach improves the representation of transport processes in ECHAM6 for coarse-resolution simulations. Hence, this paper suggests that we can overcome the overhead of developing a fully adaptive Earth system model by integrating AMR into single components while leaving data structures of the dynamical core untouched. This enables studies to retain well-tested and complex legacy code of existing models while still improving the accuracy of specific components without sacrificing efficiency.

scholarly journals Extending Legacy Climate Models by Adaptive Mesh Refinement for Single Component Tracer Transport: A Case Study with ECHAM6-HAMMOZ (ECHAM30-HAM23-MOZ10)

2020 ◽  
Author(s):  
Yumeng Chen ◽  
Konrad Simon ◽  
Jörn Behrens
Keyword(s):  
Adaptive Mesh Refinement ◽  
Climate Models ◽  
Climate Model ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Mass Conservation ◽  
Atmospheric Model ◽  
Transport Processes ◽  
Tracer Transport ◽  
Dust Transport

Abstract. Model error in climate models depends on mesh resolution among other factors. While global refinement of the computational mesh is often not feasible computationally, Adaptive Mesh Refinement (AMR) can be an option for spatially localized features. Creating a climate model with AMR has been prohibitive so far. We use AMR in one single model component, namely the tracer transport scheme.M Particularly, we integrate AMR into the tracer transport module of the atmospheric model ECHAM6 and test our implementation in several idealized scenarios and in a realistic application scenario (dust transport). To achieve this goal, we modify the Flux-Form Semi-Lagrangian (FFSL) transport scheme in ECHAM6 such that we can use it on adaptive meshes while retaining all important properties such as mass conservation of the original FFSL implementation. Our proposed AMR scheme is dimensionally split and ensures that high-resolution information is always propagated on (locally) highly resolved meshes. We also introduce a data structure that can accommodate an adaptive Gaussian grid. We demonstrate that our AMR scheme improves both accuracy and efficiency compared to the original FFSL scheme. More importantly, our approach improves the representation of transport processes in ECHAM6 for coarse resolution simulations. Hence, this paper suggests that we can overcome the overhead of developing a fully adaptive earth system model by integrating AMR into single components while leaving data structures of the dynamical core untouched. This enables studies to retain well-tested and complex legacy code of existing models while still improving the accuracy of specific components, without sacrificing efficiency.

scholarly journals Contrasting the modelled sensitivity of the Amundsen Sea Embayment ice streams

2016 ◽  
Vol 62 (233) ◽  
pp. 552-562 ◽  
Author(s):  
ISABEL J. NIAS ◽  
STEPHEN L. CORNFORD ◽  
ANTONY J. PAYNE
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Mass Conservation ◽  
Physical Parameters ◽  
Ice Streams ◽  
Amundsen Sea ◽  
West Antarctic ◽  
Grounding Line

AbstractPresent-day mass loss from the West Antarctic ice sheet is centred on the Amundsen Sea Embayment (ASE), primarily through ice streams, including Pine Island, Thwaites and Smith glaciers. To understand the differences in response of these ice streams, we ran a perturbed parameter ensemble, using a vertically-integrated ice flow model with adaptive mesh refinement. We generated 71 sets of three physical parameters (basal traction coefficient, ice viscosity stiffening factor and sub-shelf melt rate), which we used to simulate the ASE for 50 years. We also explored the effects of different bed geometries and basal sliding laws. The mean rate of sea-level rise across the ensemble of simulations is comparable with current observed rates for the ASE. We found evidence that grounding line dynamics are sensitive to features in the bed geometry: simulations using BedMap2 geometry resulted in a higher rate of sea-level rise than simulations using a rougher geometry, created using mass conservation. Modelled grounding-line retreat of all the three ice streams was sensitive to viscosity and basal traction, while the melt rate was more important in Pine Island and Smith glaciers, which flow through more confined ice shelves than Thwaites, which has a relatively unconfined shelf.

scholarly journals A perspective on sustained marine observations for climate modelling and prediction

2014 ◽  
Vol 372 (2025) ◽  
pp. 20130340 ◽  
Author(s):  
Nick J. Dunstone
Keyword(s):  
Climate Models ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Climate Modelling ◽  
The North ◽  
Near Term ◽  
The Impact ◽  
Ocean Observations ◽  
Ocean Observing

Here, I examine some of the many varied ways in which sustained global ocean observations are used in numerical modelling activities. In particular, I focus on the use of ocean observations to initialize predictions in ocean and climate models. Examples are also shown of how models can be used to assess the impact of both current ocean observations and to simulate that of potential new ocean observing platforms. The ocean has never been better observed than it is today and similarly ocean models have never been as capable at representing the real ocean as they are now. However, there remain important unanswered questions that can likely only be addressed via future improvements in ocean observations. In particular, ocean observing systems need to respond to the needs of the burgeoning field of near-term climate predictions. Although new ocean observing platforms promise exciting new discoveries, there is a delicate balance to be made between their funding and that of the current ocean observing system. Here, I identify the need to secure long-term funding for ocean observing platforms as they mature, from a mainly research exercise to an operational system for sustained observation over climate change time scales. At the same time, considerable progress continues to be made via ship-based observing campaigns and I highlight some that are dedicated to addressing uncertainties in key ocean model parametrizations. The use of ocean observations to understand the prominent long time scale changes observed in the North Atlantic is another focus of this paper. The exciting first decade of monitoring of the Atlantic meridional overturning circulation by the RAPID-MOCHA array is highlighted. The use of ocean and climate models as tools to further probe the drivers of variability seen in such time series is another exciting development. I also discuss the need for a concerted combined effort from climate models and ocean observations in order to understand the current slow-down in surface global warming.

scholarly journals LGM climate forcing and ocean dynamical feedback and their implications for estimating climate sensitivity

2020 ◽  
Author(s):  
Jiang Zhu ◽  
Christopher J. Poulsen
Keyword(s):  
Ocean Circulation ◽  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Climate Models ◽  
Model Simulation ◽  
Ice Sheets ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
True Value ◽  
Climate Forcings

Abstract. Equilibrium climate sensitivity (ECS) has been directly estimated using reconstructions of past climates that are different than today’s. A challenge to this approach is that temperature proxies integrate over the timescales of the fast feedback processes (e.g. changes in water vapor, snow, and clouds) that are captured in ECS as well as the slower feedback processes (e.g. changes in ice sheets and ocean circulation) that are not. A way around this issue is to treat the slow feedbacks as climate forcings and independently account for their impact on global temperature. Here we conduct a suite of Last Glacial Maximum (LGM) simulations using the Community Earth System Model version 1.2 (CESM1.2) to quantify the forcing and efficacy of land ice sheets (LIS) and greenhouse gases (GHG) in order to estimate ECS. Our forcing and efficacy quantification adopts the effective radiative forcing (ERF) and adjustment framework and provides a complete accounting for the radiative, topographic, and dynamical impacts of LIS on surface temperatures. ERF and efficacy of LGM LIS are −3.2 W m−2 and 1.1, respectively. The larger-than-unity efficacy is caused by the relatively larger temperature changes over land and the Northern Hemisphere subtropical oceans than those in response to a doubling of atmospheric CO2. The subtropical SST response is linked to LIS-induced wind changes and feedbacks in ocean-atmosphere coupling and clouds. ERF and efficacy of LGM GHG are −2.8 W m−2 and 0.9, respectively. The lower efficacy is primarily attributed to a smaller cloud feedback at colder temperatures. Our simulations further demonstrate that the direct ECS calculation using the forcing, efficacy, and temperature response in CESM1.2 overestimates the true value in the model by 25 % due to the neglect of slow ocean dynamical feedback. This is supported by the greater cooling (6.8 °C) in a fully coupled LGM simulation than that (5.3 °C) in a slab ocean model simulation with ocean dynamics disabled. The majority (67 %) of the ocean dynamical feedback is attributed to dynamical changes in the Southern Ocean, where interactions between ocean stratification, heat transport, and sea-ice cover are found to amplify the LGM cooling. Our study demonstrates the value of climate models in the quantification of climate forcings and the ocean dynamical feedback, which is necessary for an accurate direct ECS estimation.

scholarly journals OpenArray v1.0: A Simple Operator Library for the Decoupling of Ocean Modelling and Parallel Computing

2019 ◽  
Author(s):  
Xiaomeng Huang ◽  
Xing Huang ◽  
Dong Wang ◽  
Qi Wu ◽  
Shixun Zhang ◽  
...  
Keyword(s):  
Parallel Computing ◽  
Climate Models ◽  
Automatic Parallelization ◽  
Ocean Model ◽  
Computational Techniques ◽  
Climate Modelling ◽  
Ocean Modelling ◽  
Parallel Efficiency ◽  
Strong Scaling ◽  
Simple Operator

Abstract. The increasing complexity of climate models combined with rapidly evolving computational techniques introduces a large gap in climate modelling. In this work, we design a simple computing library to decouple the work of ocean modelling from the work of parallel computing. The library provides twelve basic operators that feature user-friendly interfaces, effective programming and automatic parallelization. We further implement a highly readable and efficient ocean model that contains only 1860 lines of code but achieves a 91 % parallel efficiency in strong scaling and 99 % parallel efficiency in weak scaling with 4096 Intel CPU cores. This ocean model also exhibits excellent scalability on the Sunway TaihuLight supercomputer. This work presents a valuable example for the development of the next generation of ocean models.

scholarly journals Adaptive wavelet simulation of global ocean dynamics

2015 ◽  
Vol 8 (7) ◽  
pp. 5265-5313 ◽  
Author(s):  
N. K.-R. Kevlahan ◽  
T. Dubos ◽  
M. Aechtner
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Solid Wall ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Adaptive Wavelet ◽  
Wall Boundary Conditions ◽  
Rotating Shallow Water ◽  
Rotating Shallow Water Equations

Abstract. In order to easily enforce solid-wall boundary conditions in the presence of complex coastlines, we propose a new mass and energy conserving Brinkman penalization for the rotating shallow water equations. This penalization does not lead to higher wave speeds in the solid region. The error estimates for the penalization are derived analytically and verified numerically for linearized one dimensional equations. The penalization is implemented in a conservative dynamically adaptive wavelet method for the rotating shallow water equations on the sphere with bathymetry and coastline data from NOAA's ETOPO1 database. This code could form the dynamical core for a future global ocean model. The potential of the dynamically adaptive ocean model is illustrated by using it to simulate the 2004 Indonesian tsunami and wind-driven gyres.

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