Summarize a time series of wind fields into a wind rose

This function converts a wind_field_ts into a wind_rose object summarizing the distribution of wind speed and direction observations in each grid cell. The result is a set of eight raster layers giving the average wind conductance toward each of a cell's 'queen' neighbors.

Usage

wind_rose(x, trans = 1, ...)

Arguments

x

Data set of class `wind_series`.

trans

Either a function, or a positive number indicating the power to raise windspeeds to; see details.

...

Additional arguments passed to `terra::app`, e.g. 'filename'.

Value

A wind_rose object. This is an 8-layer raster stack, where each layer is wind conductance from the focal cell to one of its neighbors (clockwise starting in the SW). If input windspeeds are in m/s and `trans = 1`, values are in (1 / hours)

Details

The `trans` parameter defines the transformation function used to convert wind speed into conductance. If a numeric value is supplied, the function speed^trans is used. A value of trans = 0 will ignore speed, assigning weights based on direction only; trans = 1 assumes conductance is proportional to windspeed, trans = 2 assumes it's proportional to aerodynamic drag, and trans = 3 assumes it's proportional to force. Any intermediate value can also be used. Any function that transforms a numeric vector can also be supplied; for example, to model seed dispersal for a species that only releases seeds when winds exceed 10 m/s, we could specify a threshold function `trans = function(x)x[x < 10] <- 0; return(x)`.