NCEP.M.Groundspeed {RNCEP}

Calculate flow-assistance according to equation 'M.Groundspeed'

Description

This function calculates flow-assistance according to equation M.Groundspeed and determines the speed of forward and sideways movement if an animal behaves according to the rules of equation M.Groundspeed.

Usage

NCEP.M.Groundspeed(u, v, direction, p.airspeed,...)

Arguments

u

A numeric value indicating the U (i.e. zonal or east/west) flow component in meters per second, toward east being positive. Values must describe the direction into which the flow is moving.

v

A numeric value indicating the V (i.e. meridional or north/south) flow component in meters per second, toward north being positive. Values must describe the direction into which the flow is moving.

direction

A numeric value indicating the preferred direction of movement in degrees from North.

p.airspeed

A numeric value indicating the animal's preferred speed relative to the flow (i.e. airspeed) in meters per second. See Details.

...

Any extra arguments passed to the flow-assistance equation.

Details

This function calculates flow-assistance and forward and sideways movement according to equation M.Groundspeed. Equation M.Groundspeed stipulates that an animal maintains a speed relative to the fixed Earth (i.e. groundspeed) in the specified direction equal to its preferred airspeed (i.e. p.airspeed) plus the component of the flow parallel to the preferred direction by altering its actual airspeed and heading. Note that, the actual airspeed that a animal must exhibit, following these assumptions, can be very different from its preferred airspeed.

Value

A data.frame containing flow-assistance (‘fa’), the animal's forward speed (‘forward.move’ which includes the animal's own airspeed), the animal's sideways speed (‘side.move’ which includes the animal's own airspeed), the component of the flow parallel to preferred direction of movement(‘tailwind’), the component of the flow perpendicular to the preferred direction of movement (‘sidewind’), the animal's speed relative to the flow (‘airspeed’), and the animal's speed relative to the fixed Earth (‘groundspeed’) each in meters per second, presuming u, v, and airspeed were given in meters per second.

Author(s)

Michael U. Kemp [e-mail]

References

To cite package 'RNCEP' in publications use:

Kemp, M. U., van Loon, E. E., Shamoun-Baranes, J., and Bouten, W. 2011. RNCEP:global weather and climate data at your fingertips. – Methods in Ecology and Evolution. DOI:10.1111/j.2041-210X.2011.00138.x.

For more information on flow-assistance and equation M.Groundspeed see:

Kemp, M.U., Shamoun-Baranes, J., van Loon, E. E., and Bouten, W. 2012. Quantifying flow-assistance and implications for movement research. – Journal of Theoretical Biology. In prep.

Examples

library(RNCEP)
## Using NCEP.M.Groundspeed to calculate flow-assistance ##
tst <- NCEP.M.Groundspeed(u=-2, v=-1, direction=225, p.airspeed=12)