saar: Global SA lookup file

In gsw: Gibbs Sea Water Functions

Global SA lookup file

Description

This dataset is not intended for users, but rather for internal use within the gsw package. The dataset stores the 1.4M lookup table defined in the 8.3M file src/gsw_saar_data.c in the C library. (The .c file exceeds CRAN limitations on size.)

Details

The data are designed to replace C elements defined as below in src/gsw_saar_data.c:

    static int	gsw_nx=91, gsw_ny=45, gsw_nz=45;
    static double	longs_ref[91];
    static double	lats_ref[45];
    static double	p_ref[45];
    static double	ndepth_ref[4095];
    static double	saar_ref[184275];
    static double	delta_sa_ref[184275];

R storage is in a list named saar, with elements named as in the C code, i.e. gsw_nx etc.

C storage for these variables is allocated as needed, and the data are inserted, when gsw is launched. Thus, the existing C library code "knows" about the data as local storage, which keeps alterations to the C library to a minimum.

The saar dataset was created by the following R code. The netcdf file used in this code comes from the GSW-Fortran repository (at commit baa0c09ffc7ed1f74972a1a2902d8754caa5b4cb) and its md5 value is dacb3f981e8e710ac2e83477701b3905.

  library(ncdf4)
  nc <- nc_open("~/git/GSW-Fortran/test/gsw_data_v3_0.nc")
  ## Use as.vector() since these will all get handed into C, which does not understand matrices.
  p_ref <- as.vector(ncvar_get(nc, "p_ref"))
  lats_ref <- as.vector(ncvar_get(nc, "lats_ref"))
  longs_ref <- as.vector(ncvar_get(nc, "longs_ref"))
  ndepth_ref <- as.vector(ncvar_get(nc, "ndepth_ref"))
  ndepth_ref[!is.finite(ndepth_ref)] <- -9e99
  saar_ref <- as.vector(ncvar_get(nc, "SAAR_ref"))
  saar_ref[!is.finite(saar_ref)] <- -9e99
  delta_sa_ref <- as.vector(ncvar_get(nc, "deltaSA_ref"))
  delta_sa_ref[!is.finite(delta_sa_ref)] <- -9e99
  saar <- list(gsw_nx=gsw_nx, gsw_ny=gsw_ny, gsw_nz=gsw_nz,
               longs_ref=longs_ref, lats_ref=lats_ref, p_ref=p_ref, ndepth_ref=ndepth_ref,
               saar_ref=saar_ref, delta_sa_ref=delta_sa_ref)
  save(saar, file="saar.rda")
  tools::resaveRdaFiles("saar.rda")
  nc_close(nc)

gsw documentation built on Oct. 16, 2022, 5:06 p.m.