gsw (version 1.2-0)

gsw_geo_strf_dyn_height_1: Geostrophic Dynamic Height Anomaly (provisional version)

Description

This calculates a geopotential anomaly, called either the dynamic height anomaly or the geostrophic streamfunction in the TEOS-10 document listed as [1] below.

To get the column-integrated value in meters, take the first value of the returned vector and divide by 9.7963\(m/s^2\). Note that this yields an integral with the top measured pressure (not zero) as an upper limit.

Usage

gsw_geo_strf_dyn_height_1(SA, CT, p, p_ref = 0, max_dp = 1, interp_method = 2)

Value

A vector containing geopotential anomaly in \(m^2/s^2\) for each level. For more on the units, see [2].

Arguments

SA

Absolute Salinity [ g/kg ]. The valid range for most `gsw` functions is 0 to 42 g/kg.

CT

Conservative Temperature [ degC ].

p

sea pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar

p_ref

reference pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar

max_dp

numeric value indicating the maximum tolerated pressure separation between levels. If any pressure step exceeds max_dp, then a uniform grid is constructed with max_dp as the interval.

interp_method

integer specifying interpolation scheme (1 for linear, 2 for pchip)

Implementation Note

This R function uses a wrapper to a C function contained within the GSW-C system as updated 2022-10-11 at https://github.com/TEOS-10/GSW-C with git commit `657216dd4f5ea079b5f0e021a4163e2d26893371`.

The C function uses data from the library/gsw_data_v3_0.mat file provided in the GSW-Matlab source code, version 3.06-11. Unfortunately, this version of the mat file is no longer displayed on the TEOS-10.org website. Therefore, in the interests of making GSW-R be self-contained, a copy was downloaded from http://www.teos-10.org/software/gsw_matlab_v3_06_11.zip on 2022-05-25, the .mat file was stored in the developer/create_data directory of https://github.com/TEOS-10/GSW-R, and then the dataset used in GSW-R was created based on that .mat file.

Please consult http://www.teos-10.org to learn more about the various TEOS-10 software systems.

Details

Because of the scheme used in the underlying C code, the pressures must be in order, and must not have any repeats. Also, there must be at least 4 pressure values. Violating any of these restrictions yields an error.

If p_ref exceeds the largest p value, a vector of zeros is returned, in accordance with the underlying C code.

References

1. http://www.teos-10.org/pubs/gsw/html/gsw_geo_strf_dyn_height.html

2. Talley et al., 2011. Descriptive Physical Oceanography, Edition 6, Elsevier.

Examples

SA <- c(34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
CT <- c(28.8099, 28.4392, 22.7862, 10.2262,  6.8272,  4.3236)
p <- c(      10,      50,     125,     250,     600,    1000)
p_ref <- 1000
dh <- gsw_geo_strf_dyn_height_1(SA, CT, p, p_ref, 1, 2)
## FIXME: The following test values fail.
## all.equal(dh, c(17.039204557769487, 14.665853784722286, 10.912861136923812,
##                 7.567928838774945, 3.393524055565328, 0))