swDynamicHeight {oce} | R Documentation |
Compute the dynamic height of a column of seawater.
swDynamicHeight(x, referencePressure = 2000, subdivisions = 500, rel.tol = .Machine$double.eps^0.25, eos = getOption("oceEOS", default = "gsw"))
x |
a |
referencePressure |
reference pressure [dbar]. If this exceeds the
highest pressure supplied to |
subdivisions |
number of subdivisions for call to
|
rel.tol |
absolute tolerance for call to |
eos |
equation of state, either |
If the first argument is a section
, then dynamic height is calculated
for each station within a section, and returns a list containing distance
along the section along with dynamic height.
If the first argument is a ctd
, then this returns just a single
value, the dynamic height.
If eos="unesco"
, processing is as follows. First, a piecewise-linear
model of the density variation with pressure is developed using
approxfun
. (The option rule=2
is used to
extrapolate the uppermost density up to the surface, preventing a possible a
bias for bottle data, in which the first depth may be a few metres below the
surface.) A second function is constructed as the density of water with
salinity 35PSU, temperature of 0degC, and pressure as in the
ctd
. The difference of the reciprocals of these densities, is then
integrated with integrate
with pressure limits 0
to referencePressure
. (For improved numerical results, the variables
are scaled before the integration, making both independent and dependent
variables be of order one.)
If eos="gsw"
, gsw_geo_strf_dyn_height
is used
to calculate a result in m^2/s^2, and this is divided by
9.7963m/s^2.
If pressures are out of order, the data are sorted. If any pressure
is repeated, only the first level is used.
If there are under 4 remaining distinct
pressures, NA
is returned, with a warning.
In the first form, a list containing distance
, the distance
[km] from the first station in the section and height
, the dynamic
height [m].
In the second form, a single value, containing the dynamic height [m].
Dan Kelley
Gill, A.E., 1982. Atmosphere-ocean Dynamics, Academic Press, New York, 662 pp.
Other functions that calculate seawater properties: T68fromT90
,
T90fromT48
, T90fromT68
,
swAbsoluteSalinity
,
swAlphaOverBeta
, swAlpha
,
swBeta
, swCSTp
,
swConservativeTemperature
,
swDepth
, swLapseRate
,
swN2
, swPressure
,
swRho
, swRrho
,
swSCTp
, swSTrho
,
swSigma0
, swSigma1
,
swSigma2
, swSigma3
,
swSigma4
, swSigmaTheta
,
swSigmaT
, swSigma
,
swSoundAbsorption
,
swSoundSpeed
, swSpecificHeat
,
swSpice
, swTFreeze
,
swTSrho
,
swThermalConductivity
,
swTheta
, swViscosity
,
swZ
## Not run: library(oce) data(section) # Dynamic height and geostrophy par(mfcol=c(2,2)) par(mar=c(4.5,4.5,2,1)) # Left-hand column: whole section # (The smoothing lowers Gulf Stream speed greatly) westToEast <- subset(section, 1<=stationId&stationId<=123) dh <- swDynamicHeight(westToEast) plot(dh$distance, dh$height, type='p', xlab="", ylab="dyn. height [m]") ok <- !is.na(dh$height) smu <- supsmu(dh$distance, dh$height) lines(smu, col="blue") f <- coriolis(section[["station", 1]][["latitude"]]) g <- gravity(section[["station", 1]][["latitude"]]) v <- diff(smu$y)/diff(smu$x) * g / f / 1e3 # 1e3 converts to m plot(smu$x[-1], v, type='l', col="blue", xlab="distance [km]", ylab="velocity [m/s]") # right-hand column: gulf stream region, unsmoothed gs <- subset(section, 102<=stationId&stationId<=124) dh.gs <- swDynamicHeight(gs) plot(dh.gs$distance, dh.gs$height, type='b', xlab="", ylab="dyn. height [m]") v <- diff(dh.gs$height)/diff(dh.gs$distance) * g / f / 1e3 plot(dh.gs$distance[-1], v, type='l', col="blue", xlab="distance [km]", ylab="velocity [m/s]") ## End(Not run)