# earth_surf: Surface of 1 dg by 1 dg Cells of the Earth In marelac: Tools for Aquatic Sciences

 earth_surf R Documentation

## Surface of 1 dg by 1 dg Cells of the Earth

### Description

`earth_surf` computes the surface of 1d by 1dg grid cells as a function of latitude.

Based on data that give the surface distance per 1 dg change in lat/lon from https://en.wikipedia.org/wiki/Latitude

`earth_dist` calculates the distance between two (lat, lon) points

### Usage

``````earth_surf(lat = 0, lon = 0)
earth_dist(alat, alon, blat, blon, method = 1)
``````

### Arguments

 `lat ` latitude (-90 - +90). `lon ` longitude - not used. `alat ` first latitude (-90 - +90). `alon ` first longitude (-180, 180). `blat ` second latitude (-90 - +90). `blon ` second longitude (-180, 180). `method ` an integer indicating the formula to use, either the spherical law of cosines (`1`) or the haversine formula (`2`)

### Value

Surface of the grid cell, in `m^2`.

Distance between the points (alat, alon), (blat, blon), m.

### Author(s)

Karline Soetaert <karline.soetaert@nioz.nl>

`Bathymetry`, `Oceans`

### Examples

``````
earth_surf(seq(0, 90, by = 15))

SURF <- outer(X = Bathymetry\$x,
Y = Bathymetry\$y,
FUN <- function(X, Y) earth_surf(Y, X))

earth_dist(10, 80, 10, 81)
earth_dist(20, 80, 20, 81)

SURF <- outer(X = Bathymetry\$x,
Y = Bathymetry\$y,
FUN <- function(X, Y) earth_surf(Y, X))

sum(SURF)                                   #is: 510,072,000  km2

# the surface of the Oceans, m2
sum(SURF*(Bathymetry\$z < 0))                  # is: 3.58e14

# the volume of the Oceans, m3
- sum(SURF*Bathymetry\$z*(Bathymetry\$z < 0))    # is: 1.34e+18

# the surface area at several depths
SurfDepth <- vector()

dseq <- seq(-7500, -250, by = 250)

for (i in 2:length(dseq)) {
ii <- which (Bathymetry\$z > dseq[i-1] & Bathymetry\$z <= dseq[i])
SurfDepth[i-1]<-sum(SURF[ii])
}

plot(dseq[-1], SurfDepth, xlab = "depth, m", log = "y",
ylab = "m2", main = "Surface at ocean depths")

``````

marelac documentation built on Sept. 25, 2023, 5:06 p.m.