High frequency fluctuations in the heat content of an ocean general circulation model

Abstract. The transport and storage of heat by the ocean is of crucial importance because of its effect on ocean dynamics and its impact on the atmosphere, climate and climate change. Unfortunately, limits to the amount of data that can be collected and stored means that many experimental and modelling studies of the heat budget have to make use of mean datasets where the effects of short term fluctuations are lost. In this paper we investigate the magnitude of the resulting errors making use of data from OCCAM, a high resolution global ocean model. The model carries out a proper heat balance every timestep so any imbalances that are found in the analysis must result from the use of mean fields. The study concentrates on two areas of the ocean affecting the El Nino. The first is the region of tropical instability waves north of the equator. The second is in the upwelling region along the equator. It is shown that in both cases, processes with a period of less than five days can have a significant impact on the heat budget. Thus analyses using data averaged over five days or more are likely to have significant errors. It is also shown that if a series of instantaneous values is available, reasonable estimates can be made of the size of the errors. In model studies such values are available in the form of the datasets used to restart the model. In experimental studies they may be in the form of individual unaveraged observations.

Download Full-text

High frequency fluctuations in the heat content of an ocean general circulation model

Ocean Science ◽

10.5194/os-8-813-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 813-825 ◽

Cited By ~ 2

Author(s):

A. M. Huerta-Casas ◽

D. J. Webb

Keyword(s):

General Circulation ◽

Heat Budget ◽

Experimental Studies ◽

Heat Content ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Model ◽

Ocean Dynamics ◽

Global Ocean ◽

Time Step

Abstract. The transport and storage of heat by the ocean is of crucial importance because of its effect on ocean dynamics and its impact on the atmosphere, climate and climate change. Unfortunately, limits to the amount of data that can be collected and stored mean that many experimental and modelling studies of the heat budget have to make use of mean datasets where the effects of short term fluctuations are lost. In this paper we investigate the magnitude of the resulting errors by making use of data from OCCAM, a high resolution global ocean model. The model carries out a proper heat balance every time step so any imbalances that are found in the analysis must result from the use of mean fields. The study concentrates on two areas of the ocean affecting the El Nino. The first is the region of tropical instability waves north of the Equator. The second is in the upwelling region along the Equator. It is shown that in both cases, processes with a period of less than five days can have a significant impact on the heat budget. Thus, analyses using data averaged over five days or more are likely to have significant errors. It is also shown that if a series of instantaneous values is available, reasonable estimates can be made of the size of the errors. In model studies, such values are available in the form of the datasets used to restart the model. In experimental studies they may be in the form of individual unaveraged observations.

Download Full-text

Towards AOD1B RL07

10.5194/gstm2020-29 ◽

2020 ◽

Author(s):

Linus Shihora ◽

Henryk Dobslaw

Keyword(s):

General Circulation ◽

A Priori ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Temporal Variations ◽

Ocean Dynamics ◽

Global Ocean ◽

Ocean Bottom ◽

Data Set ◽

Priori Information

The Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) product provides a priori information about temporal variations in the Earth's gravity field caused by global mass variability in the atmosphere and ocean and is routinely used as background model in satellite gravimetry. The current version 06 provides Stokes coefficients expanded up to d/o 180 every 3 hours. It is based on ERA-Interim and the ECMWF operational model for the atmosphere, and simulations with the global ocean general circulation model MPIOM consistently forced with the fields from the same atmospheric data-set. We here present preliminary numerical experiments in the development towards a new release 07 of AOD1B. The experiments are performed with the TP10 configuration of MPIOM and include (I) new hourly atmospheric forcing based on the new ERA-5 reanalysis from ECMWF; (II) an improved bathymetry around Antarctica including cavities under the ice shelves; and (III) an explicit implementation of the feedback effects of self-attraction and loading to ocean dynamics. The simulated ocean bottom pressure variability is discussed with respect to AOD1B version 6 as well as in situ ocean observations. A preliminary timeseries of hourly AOD1B-like coefficients for the year 2019 that incorporate the above mentioned improvements will be made available for testing purposes.

Download Full-text

The GPU version of LASG/IAP Climate System Ocean Model version 3 (LICOM3) under the heterogeneous-compute interface for portability (HIP) framework and its large-scale application

Geoscientific Model Development ◽

10.5194/gmd-14-2781-2021 ◽

2021 ◽

Vol 14 (5) ◽

pp. 2781-2799

Author(s):

Pengfei Wang ◽

Jinrong Jiang ◽

Pengfei Lin ◽

Mengrong Ding ◽

Junlin Wei ◽

...

Keyword(s):

General Circulation ◽

Large Scale ◽

Vertical Direction ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Model ◽

Climate System ◽

Global Ocean ◽

Processing Unit ◽

Model Version

Abstract. A high-resolution (1/20∘) global ocean general circulation model with graphics processing unit (GPU) code implementations is developed based on the LASG/IAP Climate System Ocean Model version 3 (LICOM3) under a heterogeneous-compute interface for portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and three-dimensional parallelization (also partitioned in the vertical direction) is applied. The HIP version of LICOM3 (LICOM3-HIP) is 42 times faster than the same number of CPU cores when 384 AMD GPUs and CPU cores are used. LICOM3-HIP has excellent scalability; it can still obtain a speedup of more than 4 on 9216 GPUs compared to 384 GPUs. In this phase, we successfully performed a test of 1/20∘ LICOM3-HIP using 6550 nodes and 26 200 GPUs, and on a large scale, the model's speed was increased to approximately 2.72 simulated years per day (SYPD). By putting almost all the computation processes inside GPUs, the time cost of data transfer between CPUs and GPUs was reduced, resulting in high performance. Simultaneously, a 14-year spin-up integration following phase 2 of the Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing was performed, and preliminary results were evaluated. We found that the model results had little difference from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20∘ LICOM3-HIP can reproduce the observations and produce many smaller-scale activities, such as submesoscale eddies and frontal-scale structures.

Download Full-text

Global Decadal Upper-Ocean Heat Content as Viewed in Nine Analyses

Journal of Climate ◽

10.1175/2008jcli2489.1 ◽

2008 ◽

Vol 21 (22) ◽

pp. 6015-6035 ◽

Cited By ~ 55

Author(s):

James A. Carton ◽

Anthony Santorelli

Keyword(s):

Data Assimilation ◽

North Atlantic ◽

General Circulation ◽

Heat Content ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Global Ocean ◽

Warm Bias ◽

The North ◽

Ocean General Circulation

Abstract This paper examines nine analyses of global ocean 0-/700-m temperature and heat content during the 43-yr period of warming, 1960–2002. Among the analyses are two that are independent of any numerical model, six that rely on sequential data assimilation, including an ocean general circulation model, and one that uses four-dimensional variational data assimilation (4DVAR), including an ocean general circulation model and its adjoint. Most analyses show gradual warming of the global ocean with an ensemble trend of 0.77 × 108 J m−2 (10 yr)−1 (=0.24 W m−2) as the result of rapid warming in the early 1970s and again beginning around 1990. One proposed explanation for these variations is the effect of volcanic eruptions in 1963 and 1982. Examination of this hypothesis suggests that while there is an oceanic signal, it is insufficient to explain the observed heat content variations. A second potential cause of decadal variations in global heat content is the uncorrelated contribution of heat content variations in individual ocean basins. The subtropical North Atlantic is warming at twice the global average, with accelerated warming in the 1960s and again beginning in the late 1980s and extending through the end of the record. The Barents Sea region of the Arctic Ocean and the Gulf of Mexico have also warmed, while the western subpolar North Atlantic has cooled. Heat content variability in the North Pacific differs significantly from the North Atlantic. There the spatial and temporal patterns are consistent with the decadal variability previously identified through observational and modeling studies examining SST and surface winds. In the Southern Hemisphere large heat content anomalies are evident, and while there is substantial disagreement among analyses on average the band of latitudes at 30°–60°S contribute significantly to the global warming trend. Thus, the uncorrelated contributions of heat content variations in the individual basins are a major contributor to global heat content variations. A third potential contributor to global heat content variations is the effect of time-dependent bias in the set of historical observations. This last possibility is examined by comparing the analyses to the unbiased salinity–temperature–depth dataset and finding a very substantial warm bias in all analyses in the 1970s relative to the latter decades. This warm bias may well explain the rapid increase in analysis heat content in the early 1970s, but not the more recent increase, which began in the early 1990s. Finally, this study provides information about the similarities and differences between analyses that are independent of a model and those that use sequential assimilation and 4DVAR. The comparisons provide considerable encouragement for the use of the sequential analyses for climate research despite the presence of erroneous variability (also present in the no-model analyses) resulting from instrument bias. The strengths and weaknesses of each analysis need to be considered for a given application.

Download Full-text

Comparison of ocean heat content from two eddy-resolving hindcast simulations with OFES1 and OFES2

10.5194/gmd-2021-95 ◽

2021 ◽

Author(s):

Fanglou Liao ◽

Xiao Hua Wang ◽

Zhiqiang Liu

Keyword(s):

Heat Transport ◽

General Circulation ◽

Large Scale ◽

Potential Temperature ◽

Heat Content ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Heat Content ◽

Global Ocean ◽

Spatial Distributions

Abstract. The ocean heat content (OHC) estimates from high-resolution hindcast simulations from the Ocean General Circulation Model for the Earth Simulator Version 1 (OFES1) and Version 2 (OFES2), and a global objective analysis of subsurface temperature observations (EN4.2.1) were compared. There was an OHC increase in most of the global ocean over a 57-year period, mainly a result of vertical displacements of neutral density surfaces. However, we found substantial differences in the temporal and meridional distributions of the OHC between the two OFES hindcasts. The spatial distributions of potential-temperature change also differed significantly, especially in the Atlantic Ocean. The spatial distributions of the time-averaged surface heat flux and heat transport from the OFES1 and OFES2 were highly correlated, but differences could be seen. However, these differences, more specifically in the heat transport, were only partially responsible for the OHC differences. The marked OHC differences may arise from the different vertical mixing schemes and may impact the large-scale pressure field, and thus the geostrophic current. The work here should be a useful reference for future OFES users.

Download Full-text

Importance of Ocean Dynamics for the Skewness of the Indian Ocean Dipole Mode*

Journal of Climate ◽

10.1175/jcli-d-11-00615.1 ◽

2013 ◽

Vol 26 (7) ◽

pp. 2145-2159 ◽

Cited By ~ 26

Author(s):

Tomomichi Ogata ◽

Shang-Ping Xie ◽

Jian Lan ◽

Xiaotong Zheng

Keyword(s):

Indian Ocean ◽

General Circulation ◽

Model Simulation ◽

Heat Budget ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Dynamics ◽

Thermocline Depth ◽

Indian Ocean Dipole Mode ◽

Budget Analysis

Abstract Interannual anomalies of sea surface temperature (SST), wind, and cloudiness in the southeastern tropical Indian Ocean (SE-TIO) show negative skewness. In this research, asymmetry between warm and cold episodes in the SE-TIO and the importance of ocean dynamics are investigated. A coupled model simulation and observations show an asymmetric relationship between SST and the thermocline depth in the SE-TIO where SST is more sensitive to an anomalous shoaling than to deepening of the thermocline. This asymmetric thermocline feedback on SST is a result of a deep mean thermocline. Sensitivity experiments with an ocean general circulation model (OGCM) show that a negative SST skewness arises in response to sinusoidal zonal wind variations that are symmetric between the westerly and easterly phases. Heat budget analysis with an OGCM hindcast also supports the importance of ocean dynamics for SST skewness off Sumatra and Java.

Download Full-text

Formulation of a new explicit tidal scheme in ocean general circulation model

10.5194/gmd-2021-441 ◽

2022 ◽

Author(s):

Jiangbo Jin ◽

Run Guo ◽

Minghua Zhang ◽

Guangqing Zhou ◽

Qingcun Zeng

Keyword(s):

Sea Level ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Model ◽

Tidal Mixing ◽

Global Ocean ◽

The North ◽

Tidal Constituents

Abstract. Tides play an important role in ocean energy transfer and mixing, and provide major energy for maintaining thermohaline circulation. This study proposes a new explicit tidal scheme and assesses its performance in a global ocean model. Instead of using empirical specifications of tidal amplitudes and frequencies, the new scheme directly uses the positions of the Moon and Sun in a global ocean model to incorporate tides. Compared with the traditional method that has specified tidal constituents, the new scheme can better simulate the diurnal and spatial characteristics of the tidal potential of spring and neap tides as well as the spatial patterns and magnitudes of major tidal constituents (K1 and M2). It significantly reduces the total errors of eight tidal constituents (with the exception of N2 and Q1) in the traditional explicit tidal scheme. Relative to the control simulation without tides, both the new and traditional tidal schemes can lead to better dynamic sea level (DSL) simulation in the North Atlantic, reducing significant negative biases in this region. The new tidal scheme also shows smaller positive bias than the traditional scheme in the Southern Ocean. The new scheme is suited to calculate regional distributions of sea level height in addition to tidal mixing.

Download Full-text

The GPU version of LICOM3 under HIP framework and its large-scale application

10.5194/gmd-2020-323 ◽

2020 ◽

Author(s):

Pengfei Wang ◽

Jinrong Jiang ◽

Pengfei Lin ◽

Mengrong Ding ◽

Junlin Wei ◽

...

Keyword(s):

Graphics Processing Units ◽

General Circulation ◽

High Performance ◽

Large Scale ◽

Data Transfer ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Model ◽

Global Ocean ◽

Almost All

Abstract. A high-resolution (1/20°) global ocean general circulation model with Graphics processing units (GPUs) code implementations is developed based on the LASG/IAP Climate system Ocean Model version 3 (LICOM3) under Heterogeneous-compute Interface for Portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and 3-dimensional parallelization is applied. The HIP version of the LICOM3 (LICOM3-HIP) is 42 times faster than what the same number of CPU cores dose, when 384 AMD GPUs and CPU cores are used. The LICOM3-HIP has excellent scalability; it can still obtain speedup of more than four on 9216 GPUs comparing to 384 GPUs. In this phase, we successfully performed a test of 1/20° LICOM3-HIP using 6550 nodes and 26200 GPUs, and at the grand scale, the model’s time to solution can still obtain an increasing, about 2.72 simulated years per day (SYPD). The high performance was due to putting almost all of computation processes inside GPUs, and thus greatly reduces the time cost of data transfer between CPUs and GPUs. At the same time, a 14-year spin-up integration following the phase 2 of Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing has been conducted, and the preliminary results have been evaluated. We found that the model results have little differences from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20° LICOM3-HIP can not only reproduce the observations, but also produce much smaller scale activities, such as submesoscale eddies and frontal scales structures.

Download Full-text

Evaluation of a near-global eddy-resolving ocean model

Geoscientific Model Development ◽

10.5194/gmd-6-591-2013 ◽

2013 ◽

Vol 6 (3) ◽

pp. 591-615 ◽

Cited By ~ 80

Author(s):

P. R. Oke ◽

D. A. Griffin ◽

A. Schiller ◽

R. J. Matear ◽

R. Fiedler ◽

...

Keyword(s):

Sea Level ◽

Seasonal Cycle ◽

General Circulation ◽

Mixed Layer Depth ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean Model ◽

Ocean Dynamics ◽

Future Version ◽

Volume Transports

Abstract. Analysis of the variability of the last 18 yr (1993–2012) of a 32 yr run of a new near-global, eddy-resolving ocean general circulation model coupled with biogeochemistry is presented. Comparisons between modelled and observed mean sea level (MSL), mixed layer depth (MLD), sea level anomaly (SLA), sea surface temperature (SST), and {\\chla} indicate that the model variability is realistic. We find some systematic errors in the modelled MLD, with the model generally deeper than observations, which results in errors in the {\\chla}, owing to the strong biophysical coupling. We evaluate several other metrics in the model, including the zonally averaged seasonal cycle of SST, meridional overturning, volume transports through key straits and passages, zonally averaged temperature and salinity, and El Niño-related SST indices. We find that the modelled seasonal cycle in SST is 0.5–1.5 °C weaker than observed; volume transports of the Antarctic Circumpolar Current, the East Australian Current, and Indonesian Throughflow are in good agreement with observational estimates; and the correlation between the modelled and observed NINO SST indices exceeds 0.91. Most aspects of the model circulation are realistic. We conclude that the model output is suitable for broader analysis to better understand upper ocean dynamics and ocean variability at mid- and low latitudes. The new model is intended to underpin a future version of Australia's operational short-range ocean forecasting system.

Download Full-text

Towards AOD1B RL07

10.5194/egusphere-egu21-1981 ◽

2021 ◽

Author(s):

Linus Shihora ◽

Henryk Dobslaw

Keyword(s):

General Circulation ◽

A Priori ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Temporal Variations ◽

Ocean Dynamics ◽

Global Ocean ◽

Data Set ◽

Ice Shelves ◽

Priori Information

The Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) product provides a priori information about temporal variations in the Earth's gravity field caused by global mass variability in the atmosphere and ocean and is routinely used as background model in satellite gravimetry. The current version 06 provides Stokes coefficients expanded up to d/o 180 every 3 hours. It is based on ERA-Interim and the ECMWF operational model for the atmosphere, and simulations with the global ocean general circulation model MPIOM consistently forced with the fields from the same atmospheric data-set.We here present preliminary numerical experiments in the development towards a new release 07 of AOD1B. The experiments are performed with the TP10 configuration of MPIOM and include (I) new hourly atmospheric forcing based on the new ERA-5 reanalysis from ECMWF; (II) an improved bathymetry around Antarctica including cavities under the ice shelves and the consideration of shielding effects of the ice cover; and (III) an explicit implementation of the feedback effects of self-attraction and loading to ocean dynamics.

Download Full-text