advectionFrotation function

Rotational advection field

Provides an advection field corresponding to rotation around a specified center.

advectionFrotation(spacepoints, x0, y0, a, b)

Arguments

• spacepoints: vector of coordinates (2 x d), where d is the number of locations/grid points
• x0: x coordinate of the center of rotation
• y0: y coordinate of the center of rotation
• a: parameter controlling the x component of rotational velocity
• b: parameter controlling the y component of rotational velocity

Note

• if a > 0, b > 0: clockwise rotation around (x0, y0)
• if a < 0, b < 0: counter-clockwise rotation around (x0, y0)

Examples

library(ggquiver)
library(ggplot2)
## specify coordinates
m = 25
aux <- seq(0, m - 1, length = m)
coord <- expand.grid(aux, aux)

af <- advectionFrotation(spacepoints = coord,
                        x0 = floor(m / 2),
                        y0 = floor(m / 2),
                        a = 3,
                        b = 2)

## visualize advection field
dta <- data.frame(lon = coord[ ,1], lat = coord[ ,2], u = af[ ,1], v = af[ ,2])
ggplot(dta, aes(x = lon, y = lat, u = u, v = v)) +
geom_quiver() +
theme_light()

References

Papalexiou, S.M., Serinaldi, F., Porcu, E. (2021). Advancing Space-Time Simulation of Random Fields: From Storms to Cyclones and Beyond. Water Resources Research, 57, e2020WR029466, tools:::Rd_expr_doi("10.1029/2020WR029466")