Model-consistent ocean data assimilation for seasonal to decadal climate prediction

2020 ◽  
Author(s):  
Sebastian Brune ◽  
Holger Pohlmann ◽  
Kristina Fröhlich ◽  
Johanna Baehr
Keyword(s):  
Data Assimilation ◽  
Large Scale ◽  
Climate Model ◽  
Climate Prediction ◽  
Meridional Overturning Circulation ◽  
Atmospheric Variability ◽  
Decadal Time Scale ◽  
Sense Data ◽  
Ocean Data Assimilation ◽  
Assimilation Scheme

<p>In Earth's climate system, the slowly varying ocean represents an important source of memory for predictions on the seasonal to decadal time scale. The ocean picks up atmospheric variability on a broad range of scales and feeds back on the large-scale atmospheric circulation. While today’s comprehensive Earth system models (ESMs) used in climate prediction are able to simulate this atmosphere-ocean feedback in a broad sense, data assimilation - which brings the climate model close to the observed state – allows the use of ESMs for climate predictions. We propose that the quality of climate predictions can be improved by initializing the ESMs using a model-consistent assimilation of observations resulting in (1) an initialization of the ESM with a model state close to the observed one, while (2) minimizing a potential initialization shock resulting from a mismatch between the simulated climate state and observations.<br />Here we demonstrate our approach towards a model-consistent assimilation of two ESMs used in climate prediction at Universität Hamburg and Deutscher Wetterdienst: MPI-ESM and ICON-ESM. Central to our approach is a weakly coupled assimilation setup, consisting of an Ensemble Kalman filter assimilation scheme in the ocean component (MPI-ESM, ICON-ESM) and a nudging assimilation scheme in the atmospheric component (MPI-ESM). We show that our approach facilitates a large part of atmosphere-ocean interaction already within the assimilation, allowing for a quick adaption of the assimilation in case of unrealistic behaviour of key processes. For two key large-scale oceanic processes, Atlantic meridional overturning circulation and oceanic Rossby waves, we analyze how sensitive they are to the degree of atmosphere-ocean interaction allowed for during assimilation and what this implies for the respective climate predictions. </p>

scholarly journals Pengaruh Central Pacific dan eastern Pacific El Nino terhadap variabilitas curah hujan di Sulawesi

2018 ◽  
Vol 15 (2) ◽  
pp. 73
Author(s):  
Budi Prasetyo ◽  
Nikita Pusparini
Keyword(s):  
Data Assimilation ◽  
El Niño ◽  
El Nino ◽  
Climate Prediction ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Eastern Pacific El Niño ◽  
Ocean Data Assimilation ◽  
Ep El Niño ◽  
Climate Prediction Center

Pulau Sulawesi dipengaruhi oleh fenomena Central Pacific (CP) dan Eastern Pacific (EP) El Niño. Curah hujan Sulawesi mencakup ketiga pola hujan yang ada di Indonesia yaitu Monsunal, equatorial, dan lokal. Variabilitas ketiga pola curah hujan tersebut akan memberikan respon yang berbeda terhadap pengaruh dari kedua tipe El Niño tersebut. Maka, Kajian ini akan membahas pengaruh dari kedua tipe El Niño  terhadap curah hujan Sulawesi. Penelitian ini Menggunakan data curah hujan bulanan berasal dari Climate Prediction Center (CPC) National Oceanic and Atmospheric Administration (NOAA), Suhu Permukaan Laut (SPL) bulanan dari System Ocean Data Assimilation (SODA) versi 2.2.4 dan oceanic Niño Indeks (ONI) dengan periode  Januari 1950 hingga Desember 2010 (60 tahun). Perhitungan statistik sederhana berupa perata-rataan, korelasi, dan analisa komposit digunakan dalam kajian ini. Penentuan tipe El Niño menggunakan tiga buah indeks yang berbeda. Hasilnya diperoleh bahwa Curah hujan Sulawesi berkurang saat kedua tipe El Niño. Penurunan curah hujan akibat EP El Niño berkisar antara 5 – 20 mm sedangkan akibat CP El Niño berkisar antara 2-12 mm. Wilayah Sulawesi dengan pola curah hujan monsunal merupakan wilayah yang mengalami penurunan curah hujan terbesar akibat kedua tipe El Niño tersebut, kemudian diikuti dengan pola curah hujan equatorial dan terakhir Lokal.

scholarly journals DESIGN AND IMPLEMENTATION OF THE OCEANOGRAPHIC MODELING AND OBSERVATION NETWORK (REMO) FOR OPERATIONAL OCEANOGRAPHY AND OCEAN FORECASTING

2013 ◽  
Vol 31 (2) ◽  
pp. 210 ◽  
Author(s):  
Jose Antonio Moreira Lima ◽  
Renato Parkinson Martins ◽  
Clemente Augusto Souza Tanajura ◽  
Afonso De Moraes Paiva ◽  
Mauro Cirano Cirano ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Atlantic Ocean ◽  
Large Scale ◽  
Integrated Approach ◽  
Global Ocean ◽  
Assimilation Experiment ◽  
In Situ Data ◽  
Ocean Data Assimilation ◽  
Observation Network ◽  
Ocean Forecasting

ABSTRACT. This paper is concerned with the planning, implementation and some results of the Oceanographic Modeling and Observation Network (REMO) for Brazilian regional waters. Ocean forecasting has been an important scientific issue over the last decade due to studies related to climate change as well as applications related to short-range oceanic forecasts. It is a challenge to design an ocean forecasting system for a region with poor observational coverage of in situ data such as the South Atlantic Ocean. An integrated approach is proposed here in which the large-scale circulation in the Atlantic Ocean is modeled in a first step, and gradually downscaled into higher resolution regional models. This approach is able to resolve important processes such as the Brazil Current and associated meso-scale variability, continental shelf waves, local and remote wind forcing, and others. This article presents the overall strategy to develop the models using a network of Brazilian institutions and their related expertise along with international collaboration. This work has some similarity with goals of the international project Global Ocean Data Assimilation Experiment OceanView (GODAE OceanView), in which REMO takes part.Keywords: ocean models, ocean measurements, data assimilation. RESUMO. Este artigo apresenta o planejamento, implementação e alguns resultados da Rede de Modelagem e Observação Oceanográfica, com acrônimo REMO, para águas territoriais brasileiras. A previsão de condições oceânicas tem sido um importante tópico de pesquisa científica ao longo da última década, devido a estudos relacionados com mudanças climáticas assim como interesse por previsões sinóticas de curto prazo de variáveis tais como correntes marinhas e temperatura da água. É um desafio realizar o projeto de um sistema de previsão para uma região oceânica com baixa disponibilidade de medições, como o Oceano Atlântico Sul. Uma proposta de desenvolvimento integrado é apresentada neste trabalho, onde um modelo de circulação oceânica de todo Oceano Atlântico foi implementado como passo inicial, e gradualmente foram aninhados modelos regionais com maior resolução espacial. Este artigo apresenta a estratégia de desenvolvimento destes modelos oceânicos utilizando o conhecimento científico disponibilizado por pesquisadores de uma rede de instituições brasileiras, com eventual colaboração de pesquisadores internacionais. Esta iniciativa brasileira possui pontos comuns com um projeto de cooperação científica internacional, denominado Global Ocean Data Assimilation Experiment OceanView (GODAE OceanView), da qual a REMO faz parte.Palavras-chave: oceanografia operacional, modelagem oceânica, sensoriamento remoto, medições oceanográficas, assimilação de dados.

scholarly journals Simulated pre-industrial climate in Bergen Climate Model (version 2): model description and large-scale circulation features

2009 ◽  
Vol 2 (2) ◽  
pp. 197-212 ◽  
Author(s):  
O. H. Otterå ◽  
M. Bentsen ◽  
I. Bethke ◽  
N. G. Kvamstø
Keyword(s):  
Sea Ice ◽  
Observational Data ◽  
Mixed Layer ◽  
Large Scale ◽  
Climate Model ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Model Description ◽  
Sea Ice Extent ◽  
Large Scale Circulation

Abstract. The Bergen Climate Model (BCM) is a fully-coupled atmosphere-ocean-sea-ice model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate. Here, a pre-industrial multi-century simulation with an updated version of BCM is described and compared to observational data. The model is run without any form of flux adjustments and is stable for several centuries. The simulated climate reproduces the general large-scale circulation in the atmosphere reasonably well, except for a positive bias in the high latitude sea level pressure distribution. Also, by introducing an updated turbulence scheme in the atmosphere model a persistent cold bias has been eliminated. For the ocean part, the model drifts in sea surface temperatures and salinities are considerably reduced compared to earlier versions of BCM. Improved conservation properties in the ocean model have contributed to this. Furthermore, by choosing a reference pressure at 2000 m and including thermobaric effects in the ocean model, a more realistic meridional overturning circulation is simulated in the Atlantic Ocean. The simulated sea-ice extent in the Northern Hemisphere is in general agreement with observational data except for summer where the extent is somewhat underestimated. In the Southern Hemisphere, large negative biases are found in the simulated sea-ice extent. This is partly related to problems with the mixed layer parametrization, causing the mixed layer in the Southern Ocean to be too deep, which in turn makes it hard to maintain a realistic sea-ice cover here. However, despite some problematic issues, the pre-industrial control simulation presented here should still be appropriate for climate change studies requiring multi-century simulations.

scholarly journals Pacific Shallow Meridional Overturning Circulation in a Warming Climate

2011 ◽  
Vol 24 (24) ◽  
pp. 6424-6439 ◽  
Author(s):  
Daiwei Wang ◽  
Mark A. Cane
Keyword(s):  
Surface Layer ◽  
Large Scale ◽  
Climate Model ◽  
Surface Wind ◽  
Meridional Overturning Circulation ◽  
First Century ◽  
Western Boundary ◽  
Warming Climate ◽  
Meridional Overturning ◽  
Twenty First Century

Abstract By analyzing a set of the Coupled Model Intercomparison Project phase 3 (CMIP3) climate model projections of the twenty-first century, it is found that the shallow meridional overturning of the Pacific subtropical cells (STCs) show contrasting trends between two hemispheres in a warming climate. The strength of STCs and equivalently the STC surface-layer transport tend to be weakening (strengthening) in the Northern (Southern) Hemisphere as a response to large-scale surface wind changes over the tropical Pacific. The STC pycnocline transport convergence into the equatorial Pacific Ocean from higher latitudes shows a robust weakening in the twenty-first century. This weakening is mainly through interior pathways consistent with the relaxation of the zonal pycnocline tilt, whereas the transport change through western boundary pathways is small and not consistent across models. It is found that the change of the western boundary pycnocline transport is strongly affected by the shoaling of the pycnocline base. In addition, there is a robust weakening of the Indonesian Throughflow (ITF) transport in a warming climate. In the multimodel ensemble mean, the response to greenhouse warming of the upper-ocean mass balance associated with the STCs is such that the weakening of the equatorward pycnocline transport convergence is balanced by a weakening of the poleward surface-layer transport divergence and the ITF transport of similar amounts.

The ocean response to changes of the Greenland Ice sheet in a warming climate

2020 ◽  
Author(s):  
Marianne S. Madsen ◽  
Shuting Yang ◽  
Christian Rodehacke ◽  
Guðfinna Aðalgeirsdóttir ◽  
Synne H. Svendsen ◽  
...  
Keyword(s):  
Mass Loss ◽  
Ocean Circulation ◽  
Large Scale ◽  
Climate Model ◽  
Variable Mass ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Model System ◽  
Meridional Overturning Circulation ◽  
The Arctic

<p>During recent decades, increased and highly variable mass loss from the Greenland ice sheet has been observed, implying that the ice sheet can respond to changes in ocean and atmospheric conditions on annual to decadal time scales. Changes in ice sheet topography and increased mass loss into the ocean may impact large scale atmosphere and ocean circulation. Therefore, coupling of ice sheet and climate models, to explicitly include the processes and feedbacks of ice sheet changes, is needed to improve the understanding of ice sheet-climate interactions.</p><p>Here, we present results from the coupled ice sheet-climate model system, EC-Earth-PISM. The model consists of the atmosphere, ocean and sea-ice model system EC-Earth, two-way coupled to the Parallel Ice Sheet Model, PISM. The surface mass balance (SMB) is calculated within EC-Earth, from the precipitation, evaporation and surface melt of snow and ice, to ensure conservation of mass and energy. The ice sheet model, PISM, calculates ice dynamical changes in ice discharge and basal melt as well as changes in ice extent and thickness. Idealized climate change experiments have been performed starting from pre-industrial conditions for a) constant forcing (pre-industrial control); b) abruptly quadrupling the CO<sub>2</sub> concentration; and c) gradually increasing the CO<sub>2</sub> concentration by 1% per year until 4xCO<sub>2</sub> is reached.  All three experiments are run for 350 years.</p><p>Our results show a significant impact of the interactive ice sheet component on heat and fresh water fluxes into the Arctic and North Atlantic Oceans. The interactive ice sheet causes freshening of the Arctic Ocean and affects deep water formation, resulting in a significant delay of the recovery of the Atlantic Meridional Overturning Circulation (AMOC) in the coupled 4xCO<sub>2</sub> experiments, when compared with uncoupled experiments.</p>

Impact of Lateral Boundary Conditions on Regional Analyses

2017 ◽  
Vol 145 (4) ◽  
pp. 1361-1379 ◽  
Author(s):  
Kamel Chikhar ◽  
Pierre Gauthier
Keyword(s):  
Data Assimilation ◽  
Boundary Conditions ◽  
Large Scale ◽  
Climate Model ◽  
Systematic Errors ◽  
Global Climate Models ◽  
Lateral Boundary ◽  
Time Frequency ◽  
Lateral Boundary Conditions ◽  
Regional Analyses

Abstract Regional and global climate models are usually validated by comparison to derived observations or reanalyses. Using a model in data assimilation results in a direct comparison to observations to produce its own analyses that may reveal systematic errors. In this study, regional analyses over North America are produced based on the fifth-generation Canadian Regional Climate Model (CRCM5) combined with the variational data assimilation system of the Meteorological Service of Canada (MSC). CRCM5 is driven at its boundaries by global analyses from ERA-Interim or produced with the global configuration of the CRCM5. Assimilation cycles for the months of January and July 2011 revealed systematic errors in winter through large values in the mean analysis increments. This bias is attributed to the coupling of the lateral boundary conditions of the regional model with the driving data particularly over the northern boundary where a rapidly changing large-scale circulation created significant cross-boundary flows. Increasing the time frequency of the lateral driving and applying a large-scale spectral nudging significantly improved the circulation through the lateral boundaries, which translated in a much better agreement with observations.

The Response of Large-Scale Circulation to Obliquity-Induced Changes in Meridional Heating Gradients

2014 ◽  
Vol 27 (14) ◽  
pp. 5504-5516 ◽  
Author(s):  
Damianos F. Mantsis ◽  
Benjamin R. Lintner ◽  
Anthony J. Broccoli ◽  
Michael P. Erb ◽  
Amy C. Clement ◽  
...  
Keyword(s):  
Heat Transport ◽  
Large Scale ◽  
Climate Model ◽  
Hadley Circulation ◽  
Heat Fluxes ◽  
Meridional Overturning Circulation ◽  
Hadley Cell ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Summer Hemisphere ◽  
Insolation Change

Abstract The inter- and intrahemispheric climate responses to a change in obliquity are investigated using the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1. (GFDL CM2.1). Reduced obliquity causes a weakening of the seasonal insolation contrast between the summer and winter hemispheres and a strengthening of the meridional insolation gradient within the summer hemisphere. The interhemispheric insolation change is associated with weakening of the cross-equatorial Hadley circulation and reduced heat transport from the summer hemisphere to the winter hemisphere, in both the ocean and atmosphere. In contrast, the intrahemispheric insolation change is associated with increased midlatitude summer eddy activity as seen by the increased atmospheric heat transport at those latitudes. Analysis of the zonal mean atmospheric meridional overturning circulation on isentropic surfaces confirms the increase of the midlatitude eddy circulation, which is driven by changes of sensible and latent heat fluxes, as well as changes in the stratification or distribution of entropy. It is suggested that the strengthening of this circulation is associated with an equatorward shift of the ascending branch of the winter Hadley cell.

scholarly journals Coupled atmosphere–ocean data assimilation experiments with a low-order climate model

2013 ◽  
Vol 43 (5-6) ◽  
pp. 1631-1643 ◽  
Author(s):  
Robert Tardif ◽  
Gregory J. Hakim ◽  
Chris Snyder
Keyword(s):  
Data Assimilation ◽  
Climate Model ◽  
Ocean Data Assimilation ◽  
Low Order

scholarly journals A multiscale ocean data assimilation approach combining spatial and spectral localisation

Ocean Science ◽  
2019 ◽  
Vol 15 (2) ◽  
pp. 443-457 ◽  
Author(s):  
Ann-Sophie Tissier ◽  
Jean-Michel Brankart ◽  
Charles-Emmanuel Testut ◽  
Giovanni Ruggiero ◽  
Emmanuel Cosme ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Large Scale ◽  
Spectral Domain ◽  
Small Scale ◽  
Error Statistics ◽  
The North ◽  
Ocean Data Assimilation ◽  
Wide Range ◽  
Spatial Localisation ◽  
Operational Systems

Abstract. Ocean data assimilation systems encompass a wide range of scales that are difficult to control simultaneously using partial observation networks. All scales are not observable by all observation systems, which is not easily taken into account in current ocean operational systems. The main reason for this difficulty is that the error covariance matrices are usually assumed to be local (e.g. using a localisation algorithm in ensemble data assimilation systems), so that the large-scale patterns are removed from the error statistics. To better exploit the observational information available for all scales in the assimilation systems of the Copernicus Marine Environment Monitoring Service, we investigate a new method to introduce scale separation in the assimilation scheme. The method is based on a spectral transformation of the assimilation problem and consists in carrying out the analysis with spectral localisation for the large scales and spatial localisation for the residual scales. The target is to improve the observational update of the large-scale components of the signal by an explicit observational constraint applied directly on the large scales and to restrict the use of spatial localisation to the small-scale components of the signal. To evaluate our method, twin experiments are carried out with synthetic altimetry observations (simulating the Jason tracks), assimilated in a 1/4∘ model configuration of the North Atlantic and the Nordic Seas. Results show that the transformation to the spectral domain and the spectral localisation provides consistent ensemble estimates of the state of the system (in the spectral domain or after backward transformation to the spatial domain). Combined with spatial localisation for the residual scales, the new scheme is able to provide a reliable ensemble update for all scales, with improved accuracy for the large scale; and the performance of the system can be checked explicitly and separately for all scales in the assimilation system.

Sign in / Sign up

Export Citation Format

Share Document