Calculate Brunt Vaisala Frequency squared
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).
gsw_Nsquared(SA, CT, p, latitude = 0)
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 |
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.
list containing N2 [ 1/s^ ] and mid-point pressure p_mid [ dbar ]
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))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.