gsw (version 1.0-5)

gsw_Nsquared: Calculate Brunt Vaisala Frequency squared

Description

The result is computed based on first-differencing a computed density with respect pressure, and this can yield noisy results with CTD data that have not been smoothed and decimated. It also yields infinite values, for repeated adjacent pressure (e.g. this occurs twice with the ctd dataset provided in the oce package).

Usage

gsw_Nsquared(SA, CT, p, latitude = 0)

Arguments

SA

Absolute Salinity [ g/kg ]

CT

Conservative Temperature [ degC ]

p

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

latitude

latitude in decimal degrees, positive to the north of the equator. (This is called lat in the TEOS-10 Matlab code.)

Value

list containing N2 [ 1/s^ ] and mid-point pressure p_mid [ dbar ]

Details

The present R function works with a wrapper to a C function contained within the GSW-C system (Version 3.05-4 dated 2017-08-07, available at https://github.com/TEOS-10/GSW-C, as git commit '5b4d959e54031f9e972f3e863f63e67fa4f5bfec'), which stems from the GSW-Fortran system (https://github.com/TEOS-10/GSW-Fortran) which in turn stems from the GSW-Matlab system (https://github.com/TEOS-10/GSW-Matlab). Consult http://www.teos-10.org to learn more about these software systems, their authorships, and the science behind it all.

References

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

Examples

# NOT RUN {
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)
latitude <- 4
r <- gsw_Nsquared(SA, CT, p, latitude=4)
expect_equal(r$N2*1e3, c(0.060843209693499, 0.235723066151305, 0.216599928330380,
                       0.012941204313372, 0.008434782795209))
expect_equal(r$p_mid, c(30, 87.5, 187.5, 425, 800))
# }