convert_salinity: Practical - Absolute Salinity Conversions

In marelac: Tools for Aquatic Sciences

Description

Conversion from practical to absolute salinity and vice versa.

Usage

convert_PStoAS(S = 35, p = max(0, P - 1.013253), P = 1.013253,
  lat = NULL, lon = NULL, DSi = NULL,
  Ocean = c("Global", "Atlantic", "Pacific", "Indian", "Southern"))

convert_AStoPS(S = 35, p = max(0, P - 1.013253), P = 1.013253,
  lat = NULL, lon = NULL, DSi = NULL,
   Ocean = c("Global","Atlantic","Pacific","Indian","Southern"))

Arguments

S	Salinity, either practical salinity (convert_PStoAS), dimensionless or absolute salinity (convert_AStoPS, g/kg)
p	gauge or applied pressure, pressure referenced against the local atmospheric pressure, bar
P	true pressure, bar
lat	latitude (-90 to +90)
lon	longitude (0 to 360)
DSi	the silicate concentration, in micromol/kg
Ocean	the ocean in which the measurement was taken; only used if DSi is not NULL

Details

Absolute salinity (g kg-1) is estimated from Practical salinity as:

AS= 35.16504 /35 * PS + delt()

where delt is the absolute salinity anomaly. There are two ways in which to estimate the salinity anomaly

1. If DSi is not given a value, then the anomaly is estimated as a function of longitude lon, latitude lat and pressure p, using the lookup table as in sw_sfac.

2. If DSi is given a value, then a regression on it is used, based on the values of Ocean and -except for the "global" ocean- the latitute lat:

"Global"

a global estimate is used,

delt= 9.824e-5 *DSi,

"Southern"

the Southern Ocean (lat < -30),

delt= 7.4884e-5 *DSi,

"Pacific"

the Pacific Ocean ,

delt= 7.4884e-5 *(1 + 0.3622[lat/30 + 1])*DSi,

"Indian"

the Indian Ocean ,

delt= 7.4884e-5 *(1 + 0.3861[lat/30 + 1])*DSi,

"Atlantic"

the Atlantic Ocean ,

delt= 7.4884e-5 *(1 + 1.0028[lat/30 + 1])*DSi,

Note that for the Pacific, Indian and Atlantic Ocean regression, the latitude is needed. If lat is NULL then the Global regression will be used.

Value

The absolute salinity (convert_PStoAS) or practical salinity (convert_AStoPS).

Author(s)

Karline Soetaert <[e-mail]>

References

Millero FJ, Feistel R, Wright DG and McDougall TJ, 2008. The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale, Deep-Sea Res. I, 55, 50-72.

McDougall TJ, Jackett DR and Millero FJ, 2009. An algorithm for estimating Absolute Salinity in the global ocean. Ocean Science Discussions 6, 215-242. http://www.ocean-sci-discuss.net/6/215/2009/

Uses the Fortran code written by David Jackett. http://www.marine.csiro.au/~jackett/TEOS-10/

See Also

convert_RtoS, convert_StoR, convert_StoCl, convert_p, convert_T,

Examples

# check values: should be 35.7
convert_PStoAS(S = 35.52764437773386, p = 102.3, lon = 201, lat = -21)

# check values: should be 35.52764437773386
convert_AStoPS(S = 35.7, p = 102.3, lon = 201, lat = -21)

#
convert_PStoAS(S = 35)
convert_AStoPS(S = 35)
convert_PStoAS(S = 35, lat = 10, lon = 10, p = 0)

# Based on Si concentration
DSi <- seq(from = 0, to = 200, by = 10)
Global   <-  convert_PStoAS(30, DSi = DSi, Ocean = "Global")
Atlantic <-  convert_PStoAS(30, DSi = DSi, Ocean = "Atlantic", lat = 0)
Pacific  <-  convert_PStoAS(30, DSi = DSi, Ocean = "Pacific", lat = 0)
Indian   <-  convert_PStoAS(30, DSi = DSi, Ocean = "Indian", lat = 0)
Southern <-  convert_PStoAS(30, DSi = DSi, Ocean = "Southern")

matplot(x = DSi, y = cbind(Global, Atlantic, Pacific, Indian, Southern),
  pch = 1, xlab = "DSi, micromol/kg", ylab = "Absolute salinity (PS=30)")
legend("topleft",c("Global", "Atlantic", "Pacific", "Indian", "Southern"),
       col = 1:5, pch = 1)

Example output

Loading required package: shape
[1] 35.7
[1] 35.52764
[1] 35.16504
[1] 34.83573
[1] 35.16504

marelac documentation built on Feb. 12, 2020, 3 a.m.