DOI: 10.5061/dryad.r4xgxd2nw
title: Data from: The Relationship between the Southern Ocean and the Eastern tropical Pacific in unforced and forced climate model simulations

description: The sea surface temperature (SST) over the eastern tropical Pacific
 significantly influences global-mean climate feedback and may be driven in
 part by the SST over the Southern Ocean. Previous studies demonstrated a
 teleconnection from the Southern Ocean to the eastern tropical Pacific by
 perturbing the Southern Ocean climate. We investigate if this
 teleconnection holds in a fully coupled, freely running climate system
 using CMIP6 models. We assess the relationship between the Southern Ocean
 (SO) and the eastern tropical Pacific (SEP) by calculating correlations
 between SO and SEP SST timeseries within each model and regressions
 between mean SO and SEP SSTs across models. We show robust, positive
 SO-SEP relationships in an unforced climate using pre-industrial SSTs, in
 a forced climate using SST anomalies between pre-industrial and quadrupled
 CO2 simulations, and in the SST pattern of the forced response relative to
 the global-mean SST anomaly. The strength of SO-SEP correlations is
 positively related to the stratocumulus cloud feedback off the west coast
 of South America, and negatively related to ocean heat uptake in the same
 region. As both shortwave cloud feedback and ocean heat uptake are
 underestimated in climate models, understanding their effects on SO-SEP
 teleconnections and their interactions is crucial for determining the
 strength of SO-SEP teleconnection in the real world and its
 trustworthiness in climate model projection.
description: The original data for SST and for calculating the radiative
 restoration strength, shortwave cloud feedback, and ocean heat uptake are
 downloaded from https://aims2.llnl.gov/search.
   The original monthly data has been
 converted to annual data and re-grided to 2.5<sup>o</sup> x
 2.5<sup>o</sup> spatial resolution.
   SST anomalies are calculated for each
 grid by subtracting the linear regression fit of timeseries of piControl
 simulations from abrupt-4xCO2 simulations.
   The main SST pattern used in the study
 is calculated by dividing SST anomalies at each grid point by the
 global-mean SST anomalies at each timestep. Other SST patterns are
 calculated by subtracting local SST anomalies at each grid point from the
 global-mean SST anomalies at each timestep, by regressing local SST
 anomalies at each grid point onto the global-mean SST anomalies across the
 entire timeseries (150 years), and by applying principal component
 analysis (PCA) to the three-dimensional SST anomalies.
   The climatological total wind
 advection is calculated using climatological zonal and meridional winds by
 √(U<sup>2</sup> + V<sup>2</sup>) in pre-industrial
 control simulations across the entire timeseries (150 years). 
   The anomalous total wind advection is
 calculated by subtracting the climatological total winds from the forced
 total winds that calculated in abrupt4xCO2 simulations across the entire
 timeseries.   The
 wind-evaporation-SST (WES) feedback is calculated using the surface upward
 latent heat flux (LH), the wind advection, SSTs, and sea-level air
 pressure. Regressing surface upward latent heat flux, SSTs, sea-level air
 pressure, zonal (u) and meridional winds onto normalized SST averaged over
 a small region in the southeast Pacific (19°S–15°S, 103°W–107°W) in
 pre-industrial simulations provides a spatial pattern of WES feedback
 mechanism in an unforced climate.   
 The WES feedback on SST pattern is calculated by regressing
 anomalous surface upward latent heat flux, SSTs, sea-level air pressure,
 zonal and meridional winds onto normalized SST patterns averaged over a
 small region in the southeast Pacific (19°S–15°S,
 103°W–107°W).   The WES
 parameter (WESp) in pre-industrial control simulation is calculated based
 on WESp = LH · u / wind_bar<sup>2</sup>. wind_bar accounts for
 submonthly wind variance and is calculated by √(U<sup>2</sup>
 + V<sup>2</sup> + w_hat<sup>2</sup>), where w_hat
 is set to 4m/s.   The
 changes in WESp is calculated by subtracting WESp in pre-industrial
 control simulation from WESp in abrupt4xCO2 simulations.
   Radiative restoration strength is
 calculated by regressing the local shortwave cloud radiative effect onto
 local SST in pre-industrial control simulations across the entire
 timeseries (150 years). The shortwave cloud radiative effect is the
 difference between the outgoing shortwave flux at the top-of-atmosphere
 and the outgoing shortwave flux at top-of-atmosphere when there are no
 clouds (clear sky).  
 Shortwave cloud feedback is calculated by regressing anomalies
 of the local shortwave cloud radiative effect onto local SST anomalies
 across the entire timeseries (150 years). The anomalies of the shortwave
 cloud radiative effect are calculated by subtracting the linear regression
 fit of timeseries of piControl simulations from abrupt-4xCO2
 simulations.   Ocean heat
 uptake is represented by the net surface downward heat flux, which is the
 difference between surface downward longwave flux, surface upward longwave
 flux, surface downward shortwave flux, surface upward shortwave flux,
 surface upward sensible heat flux, and surface upward latent heat
 flux.   Changes in ocean
 heat uptake are calculated by subtracting the linear regression fit of
 timeseries of piControl simulations from abrupt-4xCO2
 simulations.
description: # Data from: The Relationship between the Southern Ocean and the eastern
 tropical Pacific in unforced and forced climate model simulations
 [https://doi.org/10.5061/dryad.r4xgxd2nw](https://doi.org/10.5061/dryad.r4xgxd2nw) This dataset contains multi-model simulations (in total, 53 models are used) from CMIP6 archive that serve our analyses of finding the connections between the Southern Ocean and the eastern tropical Pacific. The original CMIP6 model outputs are downloaded from [https://aims2.llnl.gov/search](https://aims2.llnl.gov/search), which then went through processes that convert the monthly data to annual data and re-grid different spatial resolutions of different models to a 2.5° x 2.5° resolution. This dataset generally contains five variables (sea surface temperature, wind, wind-evaporation-SST feedback, shortwave cloud feedback, and ocean heat uptake) under three conditions (unforced pre-industrial condition, forced condition, and the pattern of the forced condition). File information in the following content is ordered in accordance with the figures in the associated article. The specific model names are hidden for concision. ## Format of data file: .nc and .txt ## File Information: *grid.nc:*  Grid cell area with the same spatial resolution as all other NetCDF files. This file is used for calculating the area-weighted average. *tos_piControl/tos_regrid_ann_\*_piControl.nc:*  Three-dimensional (time x latitude x longitude) sea surface temperature (SST) in unforced pre-industrial simulations, behind Fig.1. *tos_anomaly/tos_regrid_ann_\*_anomaly.nc:* Three-dimensional SST anomaly, behind Fig.2. *tos_pattern/division/tos_regrid_ann_\*_pattern.nc:* Three-dimensional SST pattern, behind Fig.3 and Fig.4. *tos_pattern/subtraction/tos_regrid_ann_\*_pattern_s.nc* *tos_pattern/regression/tos_regrid_ann_\*_pattern_r.nc* *tos_pattern/PCA/tos_regrid_ann_\*_pattern_PCA.nc* Three-dimensional SST pattern calculated by three other methods in the same models, behind Fig.5. "pattern_s" represents SST pattern calculated by subtraction; "pattern_r" represents SST pattern calculated by regression; "pattern_PCA" represents SST pattern calculated by PCA. *Wind/uas_regrid_ann_\*_piControl.nc* *Wind/vas_regrid_ann_\*_piControl.nc* *Wind/wind_regrid_ann_\*_piControl.nc* *Wind/uas_regrid_ann_\*_anomaly.nc* *Wind/vas_regrid_ann_\*_anomaly.nc* *Wind/wind_regrid_ann_\*_anomaly.nc* *WES/WES_\*_piControl.nc* *WES/WES_\*_pattern.nc* *cloudFeedback/RS_regrid_ann_\*_piControl.nc* *cloudFeedback/CF_regrid_ann_\*_anomaly.nc* *OHU/OHU_regrid_ann_\*_piControl.nc* *OHU/dOHU_regrid_ann_\*_anomaly.nc* Three-dimensional surface zonal wind (uas), surface meridional wind (vas), and surface total wind (wind) in pre-industrial simulations and their anomalies, two-dimensional WES feedback-related variables in pre-industrial control simulations and using anomalies, two-dimensional radiative restoration strength in pre-industrial simulations (RS), two-dimensional shortwave cloud feedback using anomalies (CF), three-dimensional ocean heat uptake in pre-industrial simulations (OHU), and three-dimensional changes in ocean heat uptake between unforced and forced simulations (dOHU) behind Fig.6. The two-dimensional WES feedback-related netCDF files contain five physical variables, of which the calculations are shown in Method section and are repeated here: * In piControl files: 1. WES_LH: regressing the surface upward latent heat flux (LH) from pre-industrial simulations onto normalized SST averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W) from pre-industrial simulations. 2. WES_SST: regressing the SSTs from pre-industrial simulations onto normalized SST averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W) from pre-industrial simulations. 3. WES_SLP: regressing the sea-level air pressure (SLP) from pre-industrial simulations onto normalized SST averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W) from pre-industrial simulations. 4. WES_U (V): regressing the zonal (meridional) winds from pre-industrial simulations onto normalized SST averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W) from pre-industrial simulations. * In pattern files: 1. WES_LH: regressing the anomalous LH onto normalized SST pattern averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W). 2. WES_SST: regressing the anomalous SSTs onto normalized SST pattern averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W). 3. WES_SLP: regressing the anomalous SLP onto normalized SST pattern averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W). 4. WES_U (V): regressing the anomalous zonal (meridional) winds onto normalized SST pattern averaged over a small region in the southeast Pacific (19°S–15°S, 103°W–107°W). *Wind_wSA.txt* *dWind_wSA.txt* *WESp.txt* *dWESp.txt* *RS_wSA.txt* *CF_wSA.txt* *OHU_wSA.txt* *dOHU_wSA.txt* Wind advection in pre-industrial simulations and anomalies averaged over a box off the west coast of South America (42S-10S, 85W-70W). WES parameter in pre-industrial simulations and its change between pre-industrial and abrupt4xCO2 simulations averaged over a triangular region near the central South Pacific ((10S,180), (10S,100W), (30S,100W)). Radiative restoration strength and shortwave cloud feedback averaged over a box off the west coast of South America (35S-10S, 100W-71W), and ocean heat uptake and its changes averaged over a box off the west coast of South America (40S-15S, 82W-70W), behind Fig.7. ## Version changes 10/24/2024: added variables related to wind and WES feedback, including a folder named "Wind" that contains three-dimensional surface zonal, meridional, and total wind advection for each climate model, and a folder named "WES" that contains two-dimensional WES-related variables. In addition, area-weighted average of wind and WES feedback in pre-industrial control simulations and using anomalies are included in files "Wind_wSA.txt", "dWind_wSA.txt", "WESp.txt", and "dWESp.txt".