Towards AOD1B RL07

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

<p>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.</p> <p>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.</p>

Towards AOD1B RL07

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

<p>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.</p><p>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.</p>

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

2012 ◽  
Vol 9 (1) ◽  
pp. 25-61
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 ◽  
Model Studies

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.

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

Ocean Science ◽  
2012 ◽  
Vol 8 (5) ◽  
pp. 813-825 ◽  
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.

scholarly journals Global tide simulations with ICON-O: testing the model performance on highly irregular meshes

2020 ◽  
Vol 71 (1) ◽  
pp. 43-57
Author(s):  
Kai Logemann ◽  
Leonidas Linardakis ◽  
Peter Korn ◽  
Corinna Schrum
Keyword(s):  
General Circulation ◽  
Model Performance ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Discrete Fourier Transformation ◽  
Global Ocean ◽  
Transition Zones ◽  
Maximum Angle ◽  
Irregular Meshes

AbstractThe global tide is simulated with the global ocean general circulation model ICON-O using a newly developed tidal module, which computes the full tidal potential. The simulated coastal M2 amplitudes, derived by a discrete Fourier transformation of the output sea level time series, are compared with the according values derived from satellite altimetry (TPXO-8 atlas). The experiments are repeated with four uniform and sixteen irregular triangular grids. The results show that the quality of the coastal tide simulation depends primarily on the coastal resolution and that the ocean interior can be resolved up to twenty times lower without causing considerable reductions in quality. The mesh transition zones between areas of different resolutions are formed by cell bisection and subsequent local spring optimisation tolerating a triangular cell’s maximum angle up to 84°. Numerical problems with these high-grade non-equiangular cells were not encountered. The results emphasise the numerical feasibility and potential efficiency of highly irregular computational meshes used by ICON-O.

Comparison of the Semtner and Chervin eddy-resolving global ocean model with LUCIE and satellite observations in the Leeuwin Current region

1996 ◽  
Vol 47 (3) ◽  
pp. 509 ◽  
Author(s):  
CJC Reason ◽  
AF Pearce
Keyword(s):  
Western Australia ◽  
Satellite Data ◽  
General Circulation ◽  
Maximum Velocity ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Western Coast ◽  
Model Output ◽  
Leeuwin Current

Output from the Semtner and Chervin eddy-resolving global ocean general circulation model is compared with observations from the Leeuwin Current Interdisciplinary Experiment (LUCIE) and satellite data for the coastal waters of Western Australia. The model output is a snapshot over the domain 9-43�S, 90-120�E for a day in mid July 1987, which is during the season that the Leeuwin Current is expected to be well established along the western and southern coasts of Western Australia. Maximum Leeuwin Current velocities in the model are of the order of 60 cm s-1 and are found in the southern part of the current on the western coast and around into the Great Australian Bight. At depths below about 200 m, and centred near 400 m, there is an equatorward-flowing undercurrent with maximum velocity of order 25 cm s-1. Comparison of temperature and salinity cross-sections with LUCIE observations reveals that the model output for this day exhibits many realistic features. In particular, the model fields display a number of prominent meanders and eddies on the Leeuwin Current as well as further offshore. Consistent with observations, mesoscale features associated with the Leeuwin Current are concentrated between 25�S and the Cape Mentelle region; the flow in the northern part of the Leeuwin Current and the North West Shelf may be too weak to induce eddy-generating instabilities. Prominent in the model output are two large meanders on the Leeuwin Current between 25�S and 29�S and two anticyclonic eddies further downstream; features similar to these are evident in satellite data during winter 1987.

scholarly journals Formation Mechanism for Isopycnal Temperature–Salinity Anomalies Propagating from the Eastern South Pacific to the Equatorial Region

2007 ◽  
Vol 20 (7) ◽  
pp. 1305-1315 ◽  
Author(s):  
Masami Nonaka ◽  
Hideharu Sasaki
Keyword(s):  
Formation Mechanism ◽  
General Circulation ◽  
Circulation Model ◽  
South Pacific ◽  
Ocean General Circulation Model ◽  
Equatorial Region ◽  
Sea Surface ◽  
Global Ocean ◽  
Decadal Time Scale ◽  
Isopycnal Surface

Abstract Equatorward propagation of temperature–salinity (or spiciness) anomalies on an isopycnal surface emanating from the eastern subtropical South Pacific and their formation mechanism are investigated based on a hindcast simulation with an eddy-resolving quasi-global ocean general circulation model. Because of density-compensating meridional distributions of temperature and salinity, the meridional density gradient is weak at the sea surface in the eastern subtropical South Pacific. With these mean fields, cool sea surface temperature anomalies (SSTAs) can make the outcrop line of an isopycnal surface migrate equatorward more than 5° and induce warm and salty anomalies on the isopycnal surface. Subducted warm, salty anomalies propagate to the equatorial region over approximately 5 yr and may influence equatorial isopycnal temperature–salinity anomalies. Although the associated effects are unclear, if these anomalies could further induce warm eastern equatorial SSTAs that are positively correlated with eastern South Pacific SSTAs, opposite sign temperature–salinity anomalies would be formed in the subtropical South Pacific, and a closed cycle having a decadal time scale might be induced.

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