betaks {raytracing}

Calculates Beta and Ks

Description

betaks ingests the time-mean zonal wind (u), transform it in mercator coordinates (um); calculates the meridional gradient of the absolute vorticity (beta) in mercator coordinates (betam); and, finally, calculates stationary wavenumber (Ks) in mercator coordinates (ksm) (see: Hoskins and Ambrizzi, 1993). betaks returns the um, betam, and lat, for being ingested in ray or ray_source.

Usage

betaks(
  u,
  lat = "lat",
  lon = "lon",
  uname = "uwnd",
  ofile,
  a = 6371000,
  plots = FALSE,
  show.warnings = FALSE
)

Arguments

u

String indicating the input data filename. The file to be passed consists in a netCDF file with only time-mean zonal wind at one pressure level, latitude in ascending order (not a requisite), and longitude from 0 to 360. It is required that the read dimensions express longitude (in rows) x latitude (in columns). u also can be a numerical matrix with time-mean zonal wind at one pressure level, latitude in ascending order (not a requisite), and longitude from 0 to 360. It is required that the read dimensions express longitude (in rows) x latitude (in columns).

lat

String indicating the name of the latitude field. If u is a matrix, lat must be numeric.

lon

String indicating the name of the longitude field.If u is a matrix, lon must be numeric from 0 to 360.

uname

String indicating the variable name field

ofile

String indicating the file name for store output data. If missing, will not return a netCDF file

a

Numeric indicating the Earth's radio (m)

plots

Logical, if TRUE will produce filled.countour plots

show.warnings

Logical, if TRUE will warns about NaNs in sqrt(<0)

Value

list with one vector (lat) and 3 matrices (um, betam, and ksm)

Examples

{
# u is NetCDF and lat and lon characters
input <- system.file("extdata",
                     "uwnd.mon.mean_200hPa_2014JFM.nc",
                      package = "raytracing")
b <- betaks(u = input, plots = TRUE)
b$ksm[] <- ifelse(b$ksm[] >= 16 |
                  b$ksm[] <= 0, NA, b$ksm[])
cores <- c("#ff0000","#ff5a00","#ff9a00","#ffce00","#f0ff00")
graphics::filled.contour(b$ksm[, -c(1:5, 69:73)] ,
                         col = rev(colorRampPalette(cores, bias = 0.5)(20)),
                         main = "Ks")

# u, lat and lon as numeric
input <- system.file("extdata",
                     "uwnd.mon.mean_200hPa_2014JFM.bin",
                      package = "raytracing")
u <- readBin(input,
             what = numeric(),
             size = 4,
             n = 144*73*4)
lat <- seq(-90, 90, 2.5)
lon <- seq(-180, 180 - 1, 2.5)
u <- matrix(u,
            nrow = length(lon),
            ncol = length(lat))
graphics::filled.contour(u, main = "Zonal Wind Speed [m/s]")
b <- betaks(u, lat, lon)
b$ksm[] <- ifelse(b$ksm[] >= 16 |
                  b$ksm[] <= 0, NA, b$ksm[])
cores <- c("#ff0000","#ff5a00","#ff9a00","#ffce00","#f0ff00")
graphics::filled.contour(b$ksm[, -c(1:5, 69:73)] ,
                         col = rev(colorRampPalette(cores, bias = 0.5)(20)),
                         main = "Ks")
}