Dataset of "A hierarchy of global ocean models coupled to CESM1"

Data associated with the following publication:

Hsu, T. Y., Primeau, F. W., & Magnusdottir, G. (2022). A Hierarchy of Global Ocean Models Coupled to CESM1.

Paper Abstract:

We develop a hierarchy of simplified ocean models for coupled ocean, atmosphere, and sea ice climate simulations using the Community Earth System Model version 1 (CESM1). The hierarchy has four members: a slab ocean model, a mixed-layer model with entrainment and detrainment, an Ekman mixed-layer model, and an ocean general circulation model (OGCM). Flux corrections of heat and salt are applied to the simplified models ensuring that all hierarchy members have the same climatology. We diagnose the needed flux corrections from auxiliary simulations in which we restore the temperature and salinity to the daily climatology obtained from a target CESM1 simulation. The resulting 3-dimensional corrections contain the interannual variability fluxes that maintain the correct vertical gradients of temperature and salinity in the tropics. We find that the inclusion of mixed-layer entrainment and Ekman flow produces sea surface temperature and surface air temperature fields whose means and variances are progressively more similar to those produced by the target CESM1 simulation.

We illustrate the application of the hierarchy to the problem of understanding the response of the climate system to the loss of Arctic sea ice. We find that the shifts in the positions of the mid-latitude westerly jet and of the Inter-tropical Convergence Zone (ITCZ) in response to sea-ice loss depend critically on upper ocean processes. Specifically, heat uptake associated with the mixed-layer entrainment influences the shift in the westerly jet and ITCZ. Moreover, the shift of ITCZ is sensitive to the form of Ekman flow parameterization.

Methods

Description of methods used for generation of data: 
The data is generated with EMOM, a hierarchy of ocean models that are applied in CESM1. The detailed description of the model is in the paper the dataset is presented in (i.e. A Hierarchy of Global Ocean Models Coupled to CESM1).

Methods for processing the data:

This dataset consists of a set of atmospheric and oceanic fields produced by the NCAR CESM1 climate model. The data is in NETCDF format and has been post-processed and formatted using the NCO command language (see http://nco.sourceforge.net/ for more details).

Software-specific information needed to interpret the data:
The data is in NetCDF format.

Usage Notes

This README file was generated on 20200416 by Tien-Yiao Hsu

Dataset of the paper

A Hierarchy of Global Ocean Models Coupled to CESM1

      Email: [e-mail]

      OrcID: 0000-0002-8121-1525

  Associate Contact Information

      Name: Francois Primeau

      Institution: University of California, Irvine

      Institutions ROR: [UCI = https://ror.org/04gyf1771]

      Address: 

        Department of Earth System Science

        Croul Hall

        Irvine, CA 92697-3100

      Email: [e-mail]

  Associate Contact Information

      Name: Gudrun Magnusdottir

      Institution: University of California, Irvine

      Institutions ROR: [UCI = https://ror.org/04gyf1771]

      Address: 

        Department of Earth System Science

        Croul Hall

        Irvine, CA 92697-3100

      Email: [e-mail]

3. Date of data organized : 20220201

4. Information about funding sources that supported the collection of the data:

    Funder name: Department of Energy

    Funder uri: https://www.energy.gov/

5. Contextual description of the data:

    The data used to produce the figures in the paper.

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SHARING/ACCESS INFORMATION

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Licenses/restrictions placed on the data: 

    CREATIVE COMMONS ATTRIBUTION 4.0 INTERNATIONAL CC-BY

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DATA & FILE OVERVIEW

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We separate sets of data in terms of folders. 

1. AMOC

   This directory contains the AMOC streamfunction output from 

   simulations OGCM_CTL and OGCM_EXP.

2. hierarchy_statistics

   This directory contains the statistics (mean, variability, ...)

   and diagnosed quantities (ex: EOF, heat transport) of the hierarchy

   output.

   The output of CTL run of year 21 to 120 is in CTL_21-120.

   The output of EXP run of year 81 to 180 is in EXP_81-180.

3. hierarchy_average

   This directory is similar to is similar to hierarchy_statistics, 

   containing CTL and EXP. The difference is that it is the raw, unprocessed

   mean data that contains the complete output variables.

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METHODOLOGICAL INFORMATION

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1. Description of methods used for generation of data: 

   The data is generated with EMOM, a hierarchy of ocean models that is

   applied in CESM1. The detail description of the model is in the paper

   the dataset is preseted in (i.e. A Hierarchy of Global Ocean Models 

   Coupled to CESM1).

2. Methods for processing the data:

   The output data is mostly the mean and variance of the climate variables.

3. Software-specific information needed to interpret the data:

   The data is in NetCDF format.

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: AMOC

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# Filename: MOC_[CTL|EXP].nc

Variable list:

  1. MOC

     Unit: Sv

     The monthly mean value of streamfunction of the meridional overturning

     circulation in ocean basins.

# Filename MOC_[CTL|EXP]_timeseries.nc

Variable list:

  1. AMOC_max

    Unit: Sv

    The annual maximum value of the Atlantic Meridional Overturning Circulation.

  2. AMOC_max_lat

    Unit: degree north

    The latitude of the location where AMOC_max occurs.

  3. AMOC_max_z

    Unit: m

    The depth of the location where AMOC_max occurs.

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: hierarchy_average

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In this directory, each sub-directory is of the form [MODEL_NAME]_[CTL|EXP]

where MODEL_NAME can be SOM, MLM, EMOM or POP2. A sub-directory has three

files: atm.nc, ocn.nc and ocn_regrid.nc. 

atm.nc is the averaged data of atmosphere model output of year 21-121 of each model run on f09 grid.

ocn.nc is the averaged data of ocean model output of year 21-121 of each model run on g16 grid.

ocn_regrid.nc is the regrided version ocn.nc from grid g16 onto f09.

Details of the atm.nc variables can be found in CAM4 documentation

https://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_1/hist_flds_fv_cam4_trop_bam.html

Details of the ocn.nc variables can be found in POP2 documentation

https://ncar.github.io/POP/doc/build/html/users_guide/model-diagnostics-and-output.html

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: hierarchy_statistics

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This directory conatins CTL and EXP runs folder where the statistics time

is 21-121 for CTL and 81-180 for EXP.

Each experiment folder contains sub-directories of the form [MODEL_NAME]_[CTL|EXP]

where MODEL_NAME can be SOM, MLM, EMOM or POP2. Each of these directories has

the same analysis listed below.

# Filename: atm_analysis_[AAO|AO|ENSO|NAO|PDO].nc

  Description: This file contains the derived climate variability patterns (i.e. 

               AAO, AO, ENSO, NAO, PDO). 

  Variable list:

      1. PCAs(modes, Ny, Nx)

         Unit: None

         The normalized PCAs. Different modes of the PCAs are separated according

         to the first dimension.

      2. PCAs_ts(time, modes)

         Unit: None

         The timeseries of projected PCAs onto the anomalies (i.e. the inner product of PCAs and anomalous fields).

# Filename: atm_analysis_mean_anomaly_[VARNAME].nc

  Description: This file contains the mean, standard deviation of the denoted field.

               VARNAME = [ICEFRAC|TAUX|TAUY|SST]

  Variable list:

      1. [VARNAME]_[TIMESCALE]M

         Unit: ICEFRAC = None

               TAUX    = N / m^2

               TAUY    = N / m^2

               SST     = K

         The mean values of each grid point. TIMESCALE = [M|S|A] where M stands for monthly,

         S for seaonal (MAM, JJA, SON, and DJF), A for annnual. 

      2. [VARNAME]_[TIMESCALE]A

         Unit: ICEFRAC = None

               TAUX    = N / m^2

               TAUY    = N / m^2

               SST     = K

         The anomalous values of each grid point. TIMESCALE = [M|S|A] where M stands for monthly,

         S for seaonal (MAM, JJA, SON, and DJF), A for annnual. 

      3. [VARNAME]_[TIMESCALE]ASTD

         Unit: ICEFRAC = None

               TAUX    = N / m^2

               TAUY    = N / m^2

               SST     = K

         The standard deviation of the anomalous values of each grid point. TIMESCALE = [M|S|A] 

         where M stands for monthly, S for seaonal (MAM, JJA, SON, and DJF), A for annnual. 

      4. [VARNAME]_[TIMESCALE]ASTD

         Unit: ICEFRAC = None

               TAUX    = (N / m^2)^2

               TAUY    = (N / m^2)^2

               SST     = K^2

         The variance of the anomalous values of each grid point. TIMESCALE = [M|S|A] 

         where M stands for monthly, S for seaonal (MAM, JJA, SON, and DJF), A for annnual. 

# Filename: atm_analysis_mean_var_[T|U].nc

  Description: This file contains the mean, standard deviation of the denoted field.

               VARNAME = [T|U]

  Variable list:

      1. [VARNAME]_[TIMESCALE]M

         Unit: T       = K

               U       = m / s

         The mean values of each grid point. TIMESCALE = [M|A] where M stands for monthly, A for annnual. 

      2. [VARNAME]_[TIMESCALE]ASTD

         Unit: T       = K

               U       = m / s

         The standard deviation of the anomalous values of each grid point. TIMESCALE = [M|A] 

         where M stands for monthly, A for annnual. 

      3. [VARNAME]_[TIMESCALE]AVAR

         Unit: T       = K

               U       = m / s

         The variance of the anomalous values of each grid point. TIMESCALE = [M|A] 

         where M stands for monthly, A for annnual. 

# Filename: atm_analysis_SST_CORR.nc

  Description: This file contains the year-to-year correlation of monthly anomalous SST.

  Variable list:

      1. CORR(months, Ny, Nx)

         Unit: None

         The year-to-year correlation of monthly anomalous SST.

# Filename: ice_analysis_mean_anomaly_[aice|vice].nc

  Description: This file contains the mean, standard deviation of the denoted field.

               VARNAME = [aice|vice].

               The variables are exactly of the same structure as described in 

               atm_analysis_mean_anomaly_[VARNAME].nc

               The unit for aice = None

               The unit for vice = m

# Filename: ocn_analysis_mean_anomaly_STRAT.nc

  Description: This file contains the mean, standard deviation of the denoted field.

               STRAT is the difference of mean ocean temperatures T_top - T_bot.

               T_top is the mean temperature of the top 50m of the ocean where as

               T_bot is the mean temperature of the ocean between depth 50m to 503.7m.

               The variables are exactly of the same structure as described in 

               atm_analysis_mean_anomaly_[VARNAME].nc

               The unit for STRAT = K

# Filename: atm_analysis_AHT_OHT.nc

  Description: This file contains the indirectly derived atmosphere heat transport.

  Variable list:

      1. AHT(time, lat_bnd)

         Unit: W

         The monthly atmospheric heat transport.

      2. AHT_AM(year, lat_bnd) 

         Unit: W

         The annual atmospheric heat transport.

      3. AHT_MEAN(lat_bnd) 

         Unit: W

         The time-averaged atmospheric heat transport.

      4. AHT_TFLX_CONV(time, lat) 

         Unit: W / m

         The monthly-zonally-averaged atmospheric heat convergence.

      5. AHT_TFLX_CONV_MEAN(lat) 

         Unit: W

         The time-zonally-averaged atmospheric heat convergence.

# Filename: ocn_analysis_OHT.nc

  Description: This file contains the derived ocean heat transport.

  Variable list:

      1. ADVT(time, lat)

         Unit: K / s / m^3

         The monthly vertically-integrated temperature tendency due to advection and horizontal diffusion.

      2. ADVT_MEAN(lat)

         Unit: K / s / m^3

         The time-averaged ADVT.

      3. OHT(time, lat_bnd)

         Unit: W

         The total monthly ocean heat transport.

      4. OHT_MEAN(lat_bnd)

         Unit: W

         The time-average of OHT.

      5. OHT_ADVT(time, lat_bnd)

         Unit: W

         The monthly ocean heat transport due to advection and horizontal diffusion.

      6. OHT_ADVT_MEAN(time, lat_bnd)

         Unit: W

         The time-averaged of OHT_ADVT.

      7. OHT_ADVT(time, lat_bnd)

         Unit: W

         The monthly ocean heat transport due to advection and horizontal diffusion.

      8. OHT_ADVT_MEAN(lat_bnd)

         Unit: W

         The time-averaged of OHT_ADVT.

      9. OHT_WKRSTT(time, lat_bnd)

         Unit: W

         The monthly ocean heat transport due to weak-restoring.

      10. OHT_WKRSTT_MEAN(lat_bnd)

         Unit: W

         The time-averaged of OHT_WKRSTT.

      11. SHF(time, lat)

         Unit: W

         The monthly surface heat flux.

      12. SHF_MEAN(lat)

         Unit: W

         The time-average of SHF.

      13. WKRSTT(time, lat)

         Unit: K / s / m^2

         The vertically integrated monthly weak-restoring.

      14. WKRSTT_MEAN(lat)

         Unit: W

         The time-average of WKRSTT.

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: supp/importance_of_KH

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This directory conatins the average of CAM4 and EMOM output of field during year 21-30.

The meaning of the variable can be found in official website

https://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_1/hist_flds_fv_cam4_trop_bam.html

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: supp/ocean_mean_temp

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This directory conatins the annual average of ocean mean temperature of the top 33 layers (507.33m) in

the EXP run (sea-ice loss run)

# Filename: paper2021_[MODEL_NAME]_EXP.ocn_mean_T.nc

  Description: This file contains the annual average of ocean mean temperature of the top 33 layers (507.33m).

    Variable list:

      1. TEMP(time, Nz)

         Unit: degC

         Ocean temperature.

      2. SALT(time, Nz)

         Unit: kg / m^3 (PSU)

         Ocean salinity.

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: supp/ocean_heat_content_trend

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This directory conatins the difference of the ocean state between the year 181 and year 81 of the EXP run.

# Filename: OHC_diff_[MODEL_NAME].nc

  Description: The difference of the ocean state between the year 181 and year 81 of the EXP run.

    Variable list:

      1. TEMP(time, Nz)

         Unit: degC

         Ocean temperature.

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DATA-SPECIFIC INFORMATION FOR DIRECTORY: supp/vice_target_file

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This directory conatins the sea-ice forcing used to derive Q-flux (CTL) and the

forcing applied in EXP run. 

# Filename: forcing.vice.[GRID].paper2021_[RUN]_POP2.nc

  Description: This the sea-ice forcing used in the [RUN] in the grid of [GRID].

               GRID = [f09|gx1v6]

               [RUN] = [CTL|EXP]

    Variable list:

      1. vice_target(time, nlat, nlon)

         Unit: m^3 / m^2 (volume density)

         Total ice volume.