Computational Efficiency and Accuracy of Methods for Asynchronously Coupling Atmosphere-Ocean Climate Models. Part II: Testing with a Seasonal Cycle

1986 ◽  
Vol 16 (1) ◽  
pp. 11-24 ◽  
Author(s):  
L. D. Danny Harvey
Keyword(s):  
Computational Efficiency ◽  
Seasonal Cycle ◽  
Climate Models ◽  
Ocean Climate

scholarly journals Genesis and Decay of Mesoscale Baroclinic Eddies in the Seasonally Ice-Covered Interior Arctic Ocean

2021 ◽  
Vol 51 (1) ◽  
pp. 115-129
Author(s):  
Gianluca Meneghello ◽  
John Marshall ◽  
Camille Lique ◽  
Pål Erik Isachsen ◽  
Edward Doddridge ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Seasonal Cycle ◽  
Climate Models ◽  
Baroclinic Instability ◽  
Temporal Distribution ◽  
Arctic Basin ◽  
Ocean Model ◽  
The Arctic ◽  
Origin And Evolution

AbstractObservations of ocean currents in the Arctic interior show a curious, and hitherto unexplained, vertical and temporal distribution of mesoscale activity. A marked seasonal cycle is found close to the surface: strong eddy activity during summer, observed from both satellites and moorings, is followed by very quiet winters. In contrast, subsurface eddies persist all year long within the deeper halocline and below. Informed by baroclinic instability analysis, we explore the origin and evolution of mesoscale eddies in the seasonally ice-covered interior Arctic Ocean. We find that the surface seasonal cycle is controlled by friction with sea ice, dissipating existing eddies and preventing the growth of new ones. In contrast, subsurface eddies, enabled by interior potential vorticity gradients and shielded by a strong stratification at a depth of approximately 50 m, can grow independently of the presence of sea ice. A high-resolution pan-Arctic ocean model confirms that the interior Arctic basin is baroclinically unstable all year long at depth. We address possible implications for the transport of water masses between the margins and the interior of the Arctic basin, and for climate models’ ability to capture the fundamental difference in mesoscale activity between ice-covered and ice-free regions.

scholarly journals On the Extraction of Microseismic Ground Motion from Analog Seismograms for the Validation of Ocean-Climate Models

2020 ◽  
Vol 91 (3) ◽  
pp. 1518-1530 ◽  
Author(s):  
Thomas Lecocq ◽  
Fabrice Ardhuin ◽  
Fabienne Collin ◽  
Thierry Camelbeeck
Keyword(s):  
Ground Motion ◽  
North Sea ◽  
Climate Models ◽  
North Atlantic Ocean ◽  
Wave Model ◽  
Ocean Wave ◽  
Good News ◽  
Flood Event ◽  
Ocean Climate ◽  
The North

Abstract We report on a pilot demonstration of the usefulness of analog seismograms to improve the database of ocean storms before the 1980s by providing additional data for the quantitative validation of ocean wave modeling, in particular for extreme events. We present a method for automatic digitization of paper seismograms to extract microseismic ground-motion periods and amplitudes. Each minute of the original paper records is scanned and vectorized. The amplitudes are calibrated based on the original metadata taken from official bulletins. The digitized time series is processed to extract power spectral densities, which are compared with modeled microseisms levels computed using a numerical ocean wave model. As a case study, we focus on one month of data recorded at the Royal Observatory of Belgium (ROB) from January to February 1953, around the “Big Flood” event, a tragic storm surge that flooded the lowlands of England, the Netherlands, and Belgium on 1 February 1953. The reconstructed spectrograms for the three components of ground motion show clear storm signatures that we relate to specific sources in the North Atlantic Ocean. However, our models of the Big Flood event based on these data do not result in the expected amplitudes as modeled compared to the observational data when the storm reached its maximum in the southern North Sea. We suggest that the source of microseisms recorded at ROB is related to the primary microseism generated in the North Sea, at periods of 7–8 s. Other discrepancies identified suggest small modifications of the source locations or energy. Reconstructed horizontal and vertical ground motions are coherent. This is a good news for the purpose of present-day analyses of constructing twentieth century ocean-climate models, especially as during much of that time only horizontal seismographs were installed at observatories.

scholarly journals Climate Model Biases in the Width of the Tropical Belt

2016 ◽  
Vol 29 (5) ◽  
pp. 1935-1954 ◽  
Author(s):  
Nicholas Davis ◽  
Thomas Birner
Keyword(s):  
Seasonal Cycle ◽  
Climate Models ◽  
Climate Model ◽  
Large Fraction ◽  
Horizontal Resolution ◽  
Hadley Cell ◽  
Second Phase ◽  
Cell Width ◽  
Mean Width ◽  
The Mean

Abstract Earth’s arid subtropics are situated at the edges of the tropical belt, which encircles the planet along the equator and covers half of its surface area. The climate of the tropical belt is strongly influenced by the Hadley cells, with their subsidence and easterly trade winds both sustaining the aridity at the belt’s edges. The understanding of Earth’s past, present, and future climates is contingent on understanding the dynamics influencing this region. An important but unanswered question is how realistically climate models reproduce the mean state of the tropical belt. This study augments the existing literature by examining the mean width and seasonality of the tropical belt in climate models from phase 5 of CMIP (CMIP5) and experiments from the second phase of the Chemistry–Climate Model Validation (CCMVal-2) activity of the Stratospheric Processes and Their Role in Climate (SPARC) project. While the models overall reproduce the structure of the tropical belt width’s seasonal cycle, they underestimate its amplitude and cannot consistently reproduce the seasonal cycle lag between the Northern Hemisphere Hadley cell edge and subtropical jet latitudes found in observations. Additionally, up to 50% of the intermodel variation in mean tropical belt width can be attributed to model horizontal resolution, with finer resolution leading to a narrower tropical belt. Finer resolution is associated with an equatorward shift and intensification of subtropical eddy momentum flux convergence, which via the Coriolis torque explains essentially all of the grid-size bias and a large fraction of the total intermodel variation in Hadley cell width.

Modelling the Antarctic Ice Sheet in the warm Mid-Pliocene

2020 ◽  
Author(s):  
James O'Neill ◽  
Tamsin Edwards ◽  
Lauren Gregoire ◽  
Niall Gandy ◽  
Aisling Dolan ◽  
...  
Keyword(s):  
Sea Level ◽  
Climate Models ◽  
Phase 1 ◽  
Ice Sheet ◽  
Latin Hypercube Design ◽  
Antarctic Ice Sheet ◽  
Sea Levels ◽  
Ocean Climate ◽  
Parameter Values ◽  
The Antarctic

<p>The Antarctic ice sheet is a deeply uncertain component of future sea level under anthropogenic climate change. To shed light on the ice sheets response to warmer climates in the past and its’ response to future warming, periods in Earth’s geological record can serve as instructive modelling targets. The mid-Pliocene warm period (3.3 – 3.0 Ma) is characterised by global mean surface temperatures ~2.7-4<sup>o</sup>C above pre-industrial, atmospheric CO<sub>2</sub> concentrations of ~400ppm and eustatic sea level rise on the order of ~10-30m above modern. The mid-Pliocene sea level record is subject to large uncertainties. The upper end of this record implies a significant contribution from Antarctica and possible collapse of regions of the ice sheet, driven by marine ice sheet instabilities.</p><p>We present a suite of BISICLES ice sheet model simulations, forced with a subset of Pliocene Modelling Intercomparison Project (PlioMIP phase 1) coupled atmosphere-ocean climate models, that represent the Pliocene Antarctic ice sheet. This ensemble captures a range of possible ice sheet model responses to a warm Pliocene-like climate under different parameter choices, sampled in a Latin hypercube design. Modelled Antarctic sea level contribution is compared to reconstructions of Pliocene sea level, to explore the extent to which available data with large uncertainties can constrain the model parameter values.</p><p>Our aim with this work is to provide insights on Antarctic contribution to sea level in the warm mid-Pliocene. We seek to characterise the role of ice-ocean, ice-atmosphere and ice-bedrock parameter uncertainty in BISICLES on the ice sheet sea level contribution range, and whether cliff instability processes are necessary in reproduce high Pliocene sea levels in this ice sheet model.</p>

scholarly journals Drake Passage Oceanic pCO2: Evaluating CMIP5 Coupled Carbon–Climate Models Using in situ Observations

2014 ◽  
Vol 27 (1) ◽  
pp. 76-100 ◽  
Author(s):  
ChuanLi Jiang ◽  
Sarah T. Gille ◽  
Janet Sprintall ◽  
Colm Sweeney
Keyword(s):  
Seasonal Cycle ◽  
Climate Models ◽  
Dissolved Inorganic Carbon ◽  
Coupled Model ◽  
Co2 Flux ◽  
Drake Passage ◽  
Polar Front ◽  
Intercomparison Project ◽  
Opposing Effects ◽  
Mixed Layers

Abstract Surface water partial pressure of CO2 (pCO2) variations in Drake Passage are examined using decade-long underway shipboard measurements. North of the Polar Front (PF), the observed pCO2 shows a seasonal cycle that peaks annually in August and dissolved inorganic carbon (DIC)–forced variations are significant. Just south of the PF, pCO2 shows a small seasonal cycle that peaks annually in February, reflecting the opposing effects of changes in SST and DIC in the surface waters. At the PF, the wintertime pCO2 is nearly in equilibrium with the atmosphere, leading to a small sea-to-air CO2 flux. These observations are used to evaluate eight available Coupled Model Intercomparison Project, phase 5 (CMIP5), Earth system models (ESMs). Six ESMs reproduce the observed annual-mean pCO2 values averaged over the Drake Passage region. However, the model amplitude of the pCO2 seasonal cycle exceeds the observed amplitude of the pCO2 seasonal cycle because of the model biases in SST and surface DIC. North of the PF, deep winter mixed layers play a larger role in pCO2 variations in the models than they do in observations. Four ESMs show elevated wintertime pCO2 near the PF, causing a significant sea-to-air CO2 flux. Wintertime winds in these models are generally stronger than the satellite-derived winds. This not only magnifies the sea-to-air CO2 flux but also upwells DIC-rich water to the surface and drives strong equatorward Ekman currents. These strong model currents likely advect the upwelled DIC farther equatorward, as strong stratification in the models precludes subduction below the mixed layer.

scholarly journals Modeling Seasonal Sudden Stratospheric Warming Climatology Based on Polar Vortex Statistics

2017 ◽  
Vol 30 (24) ◽  
pp. 10101-10116 ◽  
Author(s):  
Matthew F. Horan ◽  
Thomas Reichler
Keyword(s):  
Statistical Model ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Climate Models ◽  
Polar Vortex ◽  
General Circulation Models ◽  
Late Winter ◽  
Sudden Stratospheric Warming ◽  
Main Factors ◽  
Observational Record

This study investigates the climatological frequency distribution of sudden stratospheric warmings (SSWs). General circulation models (GCMs) tend to produce SSW maxima later in winter than observations, which has been considered as a model deficiency. However, the observed record is short, calling into question the representativeness of the observational record. To study the seasonality of SSWs and the factors behind it, the authors use observations, a long control simulation with a stratosphere resolving GCM, and also a simple statistical model that is based on the climatological seasonal cycle of the polar vortex winds. From the combined analysis, the authors conclude that the late-winter SSW maximum seen in most climate models is realistic and that observations would also have a late-winter SSW maximum if more data were available. The authors identify the seasonally varying strengths of the polar vortex and stratospheric wave driving as the two main factors behind the seasonal SSW distribution. The statistical model also indicates that there exists a continuum of weak polar vortex states and that SSWs simply form the tail of normally distributed stratospheric winds.

A General Filter for Stretched-Grid Models: Application in Cartesian Geometry

2011 ◽  
Vol 139 (5) ◽  
pp. 1637-1653 ◽  
Author(s):  
Dorina Surcel ◽  
René Laprise
Keyword(s):  
Computational Efficiency ◽  
Climate Models ◽  
Dynamical Downscaling ◽  
Global Climate ◽  
Effective Means ◽  
Computational Cost ◽  
Global Climate Models ◽  
Limited Area ◽  
Area Of Interest ◽  
Cartesian Geometry

Global climate models with variable resolution are effective means to represent regional scales over an area of interest while avoiding the nesting issues of limited-area models. The stretched-grid approach provides a dynamical downscaling approach that naturally allows two-way interactions between the regional and global scales of motion. Concentrating the resolution over a subset of the earth’s surface increases computational efficiency and reduces the computational costs compared to global uniform high-resolution models; however, it does not come free of some problems related to the variation of resolution. To address the issues associated with the stretching and anisotropy of the computational grid, a general convolution filter with a flexible response function is developed. The main feature of this filter is to locally remove scales shorter than a user-prescribed spatially varying length scale. The filtering effectiveness and computational efficiency of the filter can be custom tailored by an appropriate compromise between the filtering response and the width of the convolution stencil. This approach has been tested in one- and two-dimensional Cartesian geometry. It is shown that an effective filter can be obtained using a limited spatial stencil for the convolution to reduce computational cost, and that an adjustable spatially variable and nearly isotropic response can be obtained for application on variable grids.

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