Read surface currents as table

Read meridional and zonal components of surface currents (m/s) from altimetry products. Input is optional, with date and xylim. As with the grid reading functions read_ugos_daily and read_vgos_daily this by default will return the latest data available and for the entire world.

table_uvgos(
  date,
  xylim = NULL,
  ...,
  xy = TRUE,
  cell = FALSE,
  na.rm = TRUE,
  latest = TRUE,
  res = NULL
)

Arguments

date

dates to read

xylim

extent of data to read

...

arguments passed to read functions (only lon180 relevant)

xy

include coordinates of cell in the output, TRUE by default

cell

include cell index in the output, FALSE by default

na.rm

by default missing values are removed, set to FALSE to keep all

Value

data frame of u, v, x,y (longitude,latitude), cell, and date

Details

Please note that the coordinates are in longitude latitude, but the velocity components are in m/s. You cannot meaningfully transform the x,y coordinates and use the velocity components without taking into account rotation in the transformation (we might write some helpers for this ...).

Argument lon180 may be used to specify Pacific or Atlantic orientation.

Examples

uv <- table_uvgos("2001-01-01", xylim = extent(60, 120, -60, -10))
plot(range(uv$x), range(uv$y), type = "n", asp = 1.1)
scal <- function(x) (x - min(x, na.rm = TRUE))/diff(range(x, na.rm = TRUE))
nn <- 56
arrows(uv$x, uv$y, uv$x + uv$u, uv$y + uv$v, col = grey.colors(nn)[scal(sqrt(uv$u^2 + uv$v^2)) * (nn-1) + 1], length = 0)