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Data and code associated with: Two annual cycles of the Pacific cold tongue under orbital precession


Chiang, John et al. (2022), Data and code associated with: Two annual cycles of the Pacific cold tongue under orbital precession, Dryad, Dataset,


The Pacific cold tongue annual cycle in sea surface temperature is presumed to be driven by Earth’s axial tilt and thus its phasing should be fixed relative to the calendar. However, its phase and amplitude change dramatically and consistently under various configurations of orbital precession in several Earth System models. Here we undertake Earth System model simulations and simulations of an intermediate coupled model to investigate causes of this behavior. In particular, simulations of the Community Earth System Model version 1.2 are carried out spanning the space of orbital eccentricity and longitude of perihelion.  This dataset archives model output and analytical codes used in this investigation. The results are reported in Chiang et al. (2022), Two annual cycles of the Pacific cold tongue under orbital precession.  Nature,  

Usage Notes

There are 4 tar files associated with analytical codes:

  • Code_Boos_Korty.tar: Python script to implement the energy flux potential analysis of Boos and Korty (2016).  Original code was provided by William Boos (UC Berkeley), and adapted by Paul Nicknish. Code is posted with the permission from William Boos.
  • Code_Fixed_Angle.tar: Scripts to implement the fixed angle calendar correction of Pollard and Reusch (2002), specific to CESM output.  Original fortran code provided by David Pollard, and further adapted by Michael Erb.  These are the original codes and documentation as provided by Michael Erb.  Code and documentation is posted with permission from Michael Erb and Dave Pollard.
  • Code_Misc.tar: MATLAB scripts to reproduce Figure 3 and Table 1, and Extended Data Figure 6.  Code by John Chiang, except for one Matlab function - intersections.m - that was developed by Douglas M. Schwarz and redistributed with permission.
  • Code_ISM.tar:  The Battisti (1988) model as used in the manuscript.  Original code from David Battisti, and adapted by Daniel Vimont.  Code is posted with permission from David Battisti.

There are 5 tar files associated with 5 distinct model outputs:

  • Data_CESM_LOP.tar: CESM LOP runs for eccentricity = 0, 0.01, 0.02, and 0.04.
  • Data_CESM_idealized.tar: CESM1.2 'no annual cycle', 'tilt-only', 'distance-only', and 'tilt-and-distance' runs listed in Extended Data Table 1.
  • Data_HadCM3.tar: HadCM3 output used in Figure 1.
  • Data_iCESM.tar: iCESM1.2 output used in Figure 1.
  • Data_ICM.tar: contains (i) the CESM slab ocean model output used to generate the wind forcing for the intermediate coupled model; and (ii) the intermediate coupled model output.

The GFDL CM2.1 and EC-Earth model outputs also used in figure 1 of the paper can be found in these archives:

  • Erb, Michael, Broccoli, Anthony & Raney, Bryan. Idealized single-forcing GCM simulations with GFDL CM2.1. (2018) doi:10.5281/zenodo.1194480.
  • Bosmans, Joyce. Idealized orbital extreme GCM simulations with EC-Earth-2-2. (2019) doi:10.5281/zenodo.3268528.