R/decibar2depth.r

In AtlanticR/bio.utilities: Package that interacts with bio providing base-level generic routines to make your life easier.

#' @export
#' @title decibar2depth
#' @description This function calculates depth in meters from pressure in decibars using Saunders and Fofonoff's method
#' @param \code{P} = pressure, in decibars
#' @param \code{lat} = degrees latitude
#' @param \code{Del} = geopotential anomaly (defaults to 0)
#' @param \code{method} = valid values include"default", "seabird", and "unesco", although they all appear to be treated the same
#' @return \code{DEPTH} = depth in M
#' @author  unknown, \email{<unknown>@@dfo-mpo.gc.ca}
#' @examples
#' decibar2depth(10000,30,0)
#' [1] 9712.653
#' @note 
#' 
# DEEP-SEA RES., 1976, 23, 109-111.
#' / UNITS:
#' //   PRESSURE     P      DECIBARS
#' //   LATITUDE     LAT    DEGREES
#' //   DEPTH        DEPTH  METERS
#' //   DTN. HEIGHT  DEL    DYN. METERS (geopotenial anomaly in J/kg:: assume 0) 
#' // CHECKVALUE:
#' //   1.) DEPTH = 9712.653 M for P=10000 DECIBARS, LAT=30 DEG, DEL=0
#' //   ABOVE FOR STANDARD OCEAN: T=0 DEG CELSIUS; S=35 (PSS-78)
#' // ----------------------------------------------------------
#' // Original fortran code is found in:
#' //   UNESCO technical papers in marine science 44 (1983) -
#' //   'Algorithms for computation of fundamental properties of seawater'
#' @references \url{http://www.code10.info/index.php?option=com_content&view=article&id=67:calculating-the-depth-from-pressure&catid=54:cat_coding_algorithms_seawater&Itemid=79}, \url{http://www.code10.info/index.php?option=com_content&view=article&id=67:calculating-the-depth-from-pressure&catid=54:cat_coding_algorithms_seawater&Itemid=79}
#' @family physical and chemical properties
#' @export

      decibar2depth = function( P, lat, Del=0, method="default" ) {
        
        if (method %in% c("default", "seabird", "unesco" ) ) {
            
          X = (sin( lat * pi / 180 ))^2 # convert degree decimal to RADs

          # GR=GRAVITY VARIATION WITH LATITUDE: ANON (1970) BULLETIN GEODESIQUE
          GR = 9.780318 * (1.0 + (5.2788E-3 + 2.36E-5 * X) * X) + 1.092E-6 * P
          DepthTerm = (((-1.82E-15 * P + 2.279E-10) * P - 2.2512E-5) * P + 9.72659) * P ## assuming (35 psu, 0 C, and P=pressure in decibars )
          DEPTH = DepthTerm / GR + Del / 9.8
          return (DEPTH)
        }

      

      }