NCEP.PartialSpeed: Calculate flow-assistance according to equation...

In RNCEP: Obtain, Organize, and Visualize NCEP Weather Data

Description

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

Usage

NCEP.PartialSpeed(u, v, direction, airspeed, f=0.5,...)

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.
airspeed	The animal's speed relative to the flow in meters per second.
f	A numeric value between zero and one describing the proportion of the lateral component of the flow for which the animal will compensate.
...	Any extra arguments passed to the flow-assistance equation.

Details

This function calculates flow-assistance and forward and sideways movement according to equation PartialSpeed. Equation PartialSpeed stipulates that the animal compensates for a proportion (specified by f) of the flow lateral to the preferred direction by altering its heading and speed relative to the fixed Earth (i.e. groundspeed). If, with its given airspeed, the animal is incapable of compensating for the specified proportion of the lateral component of the flow, the equation produces no real solution.

Setting f to zero specifies no compensation (cf. link{NCEP.Tailwind}), while setting f to one specifies complete compensation (cf. link{NCEP.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 PartialSpeed 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.PartialSpeed to calculate flow-assistance ##
tst <- NCEP.PartialSpeed(u=-2, v=-1, direction=225, airspeed=12)

RNCEP documentation built on July 1, 2020, 7:10 p.m.