Impact of air–sea coupling on the simulated global tropical cyclone activity in the high-resolution Community Earth System Model (CESM)

Abstract. High-resolution sea ice modeling is becoming widely available for both operational forecasts and climate studies. In traditional Eulerian grid-based models, small-scale sea ice kinematics represent the most prominent feature of high-resolution simulations, and with rheology models such as viscous–plastic (VP) and Maxwell elasto-brittle (MEB), sea ice models are able to reproduce multi-fractal sea ice deformation and linear kinematic features that are seen in high-resolution observational datasets. In this study, we carry out modeling of sea ice with multiple grid resolutions by using the Community Earth System Model (CESM) and a grid hierarchy (22, 7.3, and 2.4 km grid stepping in the Arctic). By using atmospherically forced experiments, we simulate consistent sea ice climatology across the three resolutions. Furthermore, the model reproduces reasonable sea ice kinematics, including multi-fractal spatial scaling of sea ice deformation that partially depends on atmospheric circulation patterns and forcings. By using high-resolution runs as references, we evaluate the model's effective resolution with respect to the statistics of sea ice kinematics. Specifically, we find the spatial scale at which the probability density function (PDF) of the scaled sea ice deformation rate of low-resolution runs matches that of high-resolution runs. This critical scale is treated as the effective resolution of the coarse-resolution grid, which is estimated to be about 6 to 7 times the grid's native resolution. We show that in our model, the convergence of the elastic–viscous–plastic (EVP) rheology scheme plays an important role in reproducing reasonable kinematics statistics and, more strikingly, simulates systematically thinner sea ice than the standard, non-convergent experiments in landfast ice regions of the Canadian Arctic Archipelago. Given the wide adoption of EVP and subcycling settings in current models, it highlights the importance of EVP convergence, especially for climate studies and projections. The new grids and the model integration in CESM are openly provided for public use.

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Multi-Scale Sea Ice Kinematics Modeling with a Grid Hierarchy in Community Earth System Model (version 1.2.1)

10.5194/gmd-2020-160 ◽

2020 ◽

Author(s):

Shiming Xu ◽

Jialiang Ma ◽

Lu Zhou ◽

Yan Zhang ◽

Jiping Liu ◽

...

Keyword(s):

High Resolution ◽

Sea Ice ◽

Earth System Model ◽

System Model ◽

The Arctic ◽

Earth System ◽

Multi Scale ◽

Kinematics Modeling ◽

Community Earth System Model ◽

Climate Studies

Abstract. High-resolution sea ice modeling is becoming widely available for both operational forecasts and climate studies. Sea ice kinematics is the most prominent feature of high-resolution simulations, and with rheology models such as Viscous-Plastic, current models are able to reproduce multi-fractality and linear kinematic features in satellite observations. In this study, we carry out multi-scale sea ice modeling with Community Earth System Model (CESM) by using a grid hierarchy (22 km, 7.3 km, and 2.5 km grid stepping in the Arctic). By using atmospherically forced experiments, we simulate consistent sea ice climatology across the 3 resolutions. Furthermore, the model reproduces reasonable sea ice kinematics, including multi-fractal deformation and scaling properties that are temporally changing and dependent on circulation patterns and forcings (e.g., Arctic Oscillation). With the grid hierarchy, we are able to evaluate the model's effective spatial resolution regarding the statistics of kinematics, which is estimated to be about 6 to 7 times that of the grid's native resolution. Besides, we show that in our model, the convergence of the Elastic-Viscous-Plastic (EVP) rheology scheme plays an important role in reproducing reasonable kinematics statistics, and more strikingly, simulates systematically thinner sea ice than the standard, non-convergent experiments in landfast ice regions of Canadian Arctic Archipelago. Given the wide adoption of EVP and subcycling settings in current models, it highlights the importance of EVP convergence especially for climate studies and projections. The new grids and the model integration in CESM are openly provided for public use.

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P-CSI v1.0, an accelerated barotropic solver for the high-resolution ocean model component in the Community Earth System Model v2.0

Geoscientific Model Development ◽

10.5194/gmd-9-4209-2016 ◽

2016 ◽

Vol 9 (11) ◽

pp. 4209-4225 ◽

Cited By ~ 8

Author(s):

Xiaomeng Huang ◽

Qiang Tang ◽

Yuheng Tseng ◽

Yong Hu ◽

Allison H. Baker ◽

...

Keyword(s):

High Resolution ◽

Ocean Model ◽

Original Method ◽

Earth System Model ◽

System Model ◽

Global Ocean ◽

Global Communication ◽

Earth System ◽

Communication Time ◽

Community Earth System Model

Abstract. In the Community Earth System Model (CESM), the ocean model is computationally expensive for high-resolution grids and is often the least scalable component for high-resolution production experiments. The major bottleneck is that the barotropic solver scales poorly at high core counts. We design a new barotropic solver to accelerate the high-resolution ocean simulation. The novel solver adopts a Chebyshev-type iterative method to reduce the global communication cost in conjunction with an effective block preconditioner to further reduce the iterations. The algorithm and its computational complexity are theoretically analyzed and compared with other existing methods. We confirm the significant reduction of the global communication time with a competitive convergence rate using a series of idealized tests. Numerical experiments using the CESM 0.1° global ocean model show that the proposed approach results in a factor of 1.7 speed-up over the original method with no loss of accuracy, achieving 10.5 simulated years per wall-clock day on 16 875 cores.

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Multidecadal preconditioning of the Maud Rise polynya region

Ocean Science ◽

10.5194/os-16-1443-2020 ◽

2020 ◽

Vol 16 (6) ◽

pp. 1443-1457

Author(s):

René M. van Westen ◽

Henk A. Dijkstra

Keyword(s):

High Resolution ◽

Southern Ocean ◽

Large Scale ◽

Heat Content ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Model Resolution ◽

Community Earth System Model ◽

Maud Rise

Abstract. In this paper, we consider Maud Rise polynya formation in a long (250-year) high-resolution (ocean 0.1∘, atmosphere 0.5∘ horizontal model resolution) of the Community Earth System Model. We find a dominant multidecadal timescale in the occurrence of these Maud Rise polynyas. Analysis of the results leads us to the interpretation that a preferred timescale can be induced by the variability of the Weddell Gyre, previously identified as the Southern Ocean Mode. The large-scale pattern of heat content variability associated with the Southern Ocean Mode modifies the stratification in the Maud Rise region and leads to a preferred timescale in convection through preconditioning of the subsurface density and consequently to polynya formation.

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Introducing the new Regional Community Earth System Model, R-CESM

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-20-0024.1 ◽

2021 ◽

pp. 1-53

Author(s):

Dan Fu ◽

Justin Small ◽

Jaison Kurian ◽

Yun Liu ◽

Brian Kauffman ◽

...

Keyword(s):

High Resolution ◽

Earth System Model ◽

Model Systems ◽

System Model ◽

Earth System ◽

Regional Ocean Modeling System ◽

Ocean Atmosphere ◽

Community Earth System Model ◽

Regional Community ◽

The Impact

AbstractThe development of high-resolution, fully-coupled, regional Earth system model systems is important for improving our understanding of climate variability, future projections, and extreme events at regional scales. Here we introduce and present an overview of the newly-developed Regional Community Earth System Model (R-CESM). Different from other existing regional climate models, R-CESM is based on the Community Earth System Model version 2 (CESM2) framework. We have incorporated the Weather Research and Forecasting (WRF) model and Regional Ocean Modeling System (ROMS) into CESM2 as additional components. As such, R-CESM can be conveniently used as a regional dynamical downscaling tool for the global CESM solutions or/and as a standalone high-resolution regional coupled model. The user interface of R-CESM follows that of CESM, making it readily accessible to the broader community. Among countless potential applications of R-CESM, we showcase here a few preliminary studies that illustrate its novel aspects and value. These include: 1) assessing the skill of R-CESM in a multi-year, high-resolution, regional coupled simulation of the Gulf of Mexico; 2) examining the impact of WRF and CESM ocean-atmosphere coupling physics on tropical cyclone simulations; and 3) a convection-permitting simulation of submesoscale ocean-atmosphere interactions. We also discuss capabilities under development such as i) regional refinement using a high-resolution ROMS nested within global CESM; and ii) “online” coupled data assimilation. Our open-source framework (publicly available at https://github.com/ihesp/rcesm1) can be easily adapted to a broad range of applications that are of interest to the users of CESM, WRF, and ROMS.

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Review of "P-CSI v1.0, an accelerated barotropic solver for the high-resolution ocean model component in the Community Earth System Model v2.0"

10.5194/gmd-2016-135-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

High Resolution ◽

Ocean Model ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Model Component ◽

Community Earth System Model

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Tropical Cyclone Genesis Factors in a Simulation of the Last Two Millennia: Results from the Community Earth System Model

Journal of Climate ◽

10.1175/jcli-d-15-0054.1 ◽

2015 ◽

Vol 28 (18) ◽

pp. 7182-7202 ◽

Cited By ~ 7

Author(s):

Qing Yan ◽

Robert Korty ◽

Zhongshi Zhang

Keyword(s):

Tropical Cyclone ◽

North Pacific ◽

Western North Pacific ◽

Large Scale ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Entire Interval ◽

Community Earth System Model ◽

The Last Two Millennia

Abstract Using a coupled global climate model, Community Earth System Model (CESM), the authors investigate the response of tropical cyclone (TC) genesis factors (i.e., potential intensity, vertical wind shear, midtropospheric moisture content, and absolute vorticity) to external forcings in the last two millennia (L2M). They then examine how the large-scale conditions that favor TC activity varied using a genesis potential index (GPI). These large-scale genesis factors generally exhibit no long-term trend in the simulation of the L2M prior to the industrial revolution, and the spread in the interannual variability lies within a small window. The estimated TC activity is highly variable from region to region on multidecadal time scales. Conditions appear to be more favorable for TC genesis in the twentieth century in the Northern Hemisphere relative to earlier centuries of the L2M. Additionally, conditions in this simulation are not more favorable for TC formation during the Medieval Climate Anomaly (AD 1000–1200) relative to the Little Ice Age (AD 1500–1700) except in the eastern North Pacific and south Indian Ocean. Although a comparison of conditions simulated in the model with proxy-based reconstructions of prehistoric storm activity finds agreement during several active periods in the western North Pacific, the time series of simulated genesis factors does not match that of proxy reconstructions over the entire interval in either the western North Pacific or North Atlantic; this discrepancy likely arises from uncertainties in both the model and reconstructions.

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Optimizing High-Resolution Community Earth System Model on a Heterogeneous Many-Core Supercomputing Platform (CESM-HR_sw1.0)

10.5194/gmd-2020-18 ◽

2020 ◽

Author(s):

Shaoqing Zhang ◽

Haohuan Fu ◽

Lixin Wu ◽

Yuxuan Li ◽

Hong Wang ◽

...

Keyword(s):

High Resolution ◽

Graphics Processing Units ◽

Earth System Model ◽

System Model ◽

Processing Element ◽

Earth System ◽

Central Processing ◽

Community Earth System Model ◽

Sunway Taihulight ◽

Many Core

Abstract. With the semi-conductor technology gradually approaching its physical and heat limits, recent supercomputers have adopted major architectural changes to continue increasing the performance through more power-efficient heterogeneous many-core systems. Examples include Sunway TaihuLight that has four Management Processing Element (MPE) and 256 Computing Processing Element (CPE) inside one processor and Summit that has two central processing units (CPUs) and 6 graphics processing units (GPUs) inside one node. Meanwhile, current high-resolution Earth system models that desperately require more computing power, generally consist of millions of lines of legacy codes developed for traditional homogeneous multi-core processors and cannot automatically benefit from the advancement of supercomputer hardware. As a result, refactoring and optimizing the legacy models for new architectures become a key challenge along the road of taking advantage of greener and faster supercomputers, providing better support for the global climate research community and contributing to the long-lasting society task of addressing long-term climate change. This article reports the efforts of a large group in the International Laboratory for High-Resolution Earth System Prediction (iHESP) established by the cooperation of Qingdao Pilot National Laboratory for Marine Science and Technology (QNLM), Texas A & M University and the National Center for Atmospheric Research (NCAR), with the goal of enabling highly efficient simulations of the high-resolution (25-km atmosphere and 10-km ocean) Community Earth System Model (CESM-HR) on Sunway TaihuLight. The refactoring and optimizing efforts have improved the simulation speed of CESM-HR from 1 SYPD (simulation years per day) to 3.4 SYPD (with output disabled), and supported several hundred years of pre-industrial control simulations. With further strategies on deeper refactoring and optimizing for a few remaining computing hot spots, we expect an equivalent or even better efficiency than homogeneous CPU platforms. The refactoring and optimizing processes detailed in this paper on the Sunway system should have implications to similar efforts on other heterogeneous many-core systems such as GPU-based high-performance computing (HPC) systems.

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