solarindex: Calculates the solar index
In ilyamaclean/microclima: microclimate modelling with R

solarindex

R Documentation

Calculates the solar index

Description

solarindex is used to calculate the proportion of direct beam radiation incident on an inclined surface at a specified time and location.

Usage

solarindex(
  slope = NA,
  aspect,
  localtime,
  lat = NA,
  long,
  julian,
  dtm = array(0, dim = c(1, 1)),
  reso = 1,
  merid = round(long/15, 0) * 15,
  dst = 0,
  shadow = TRUE
)

Arguments

`slope`	a single value, raster object, two-dimensional array or matrix of slopes (º). If an array or matrix, then orientated as if derived using `is_raster()`. I.e. `⁠[1, 1]⁠` is the NW corner.
`aspect`	a single value, raster object, two-dimensional array or matrix of aspects (º). If an array or matrix, then orientated as if derived using `is_raster()`. I.e. `⁠[1, 1]⁠` is the NW corner.
`localtime`	a single numeric value representing local time (decimal hour, 24 hour clock).
`lat`	a single numeric value representing the mean latitude of the location for which the solar index is required (decimal degrees, -ve south of the equator).
`long`	a single numeric value representing the mean longitude of the location for which the solar index is required (decimal degrees, -ve west of Greenwich meridian).
`julian`	a single integer representing the Julian day as returned by `julday()`.
`dtm`	an optional raster object, two-dimensional array or matrix of elevations (m). If not a raster, orientated as if derived from a raster using `is_raster()`. I.e. `⁠[1, 1]⁠` is the NW corner.
`reso`	a single numeric value representing the spatial resolution of `dtm` (m).
`merid`	an optional numeric value representing the longitude (decimal degrees) of the local time zone meridian (0 for GMT). Default is `round(long / 15, 0) * 15`
`dst`	an optional numeric value representing the time difference from the timezone meridian (hours, e.g. +1 for BST if `merid` = 0).
`shadow`	an optional logical value indicating whether topographic shading should be considered (TRUE = Yes, FALSE = No).

Details

If slope is unspecified, and dtm is a raster, slope and aspect are calculated from the raster. If slope is unspecified, and dtm is not a raster, the slope and aspect are set to zero. If lat is unspecified, and dtm is a raster with a coordinate reference system defined, lat and long are calculated from the raster. If lat is unspecified, and dtm is not a raster, or a raster without a coordinate reference system defined, an error is returned. If dtm is specified, then the projection system used must be such that units of x, y and z are identical. Use projectRaster() to convert the projection to a Universal Transverse Mercator type projection system. If dtm is a raster object, a raster object is returned.

Value

If shadow is TRUE, a raster object or a two-dimensional array of numeric values representing the proportion of direct beam radiation incident on an inclined surface, accounting for topographic shading.

If shadow is FALSE, a raster object or a two-dimensional array of numeric values representing the proportion of direct beam radiation incident on an inclined surface, not accounting for topographic shading.

If no dtm is provided, a vector, array or single numeric value of the proportion of direct beam radiation incident on the inclined surfaces specified by slope and aspect, and topographic shading is ignored.

Examples

library(raster)
jd <- julday (2010, 6, 21) # Julian day
# slope, aspect, lat & long calculated from raster
si1 <- solarindex(localtime = 8, julian = jd, dtm = dtm1m)
si2 <- solarindex(localtime = 8, julian = jd, dtm = dtm1m, shadow = FALSE)
par(mfrow = c(2, 1))
plot(si1, main = "Solar index with topographic shadowing")
plot(si2, main = "Solar index without topographic shadowing")
ll <- latlongfromraster(dtm1m)
solarindex(0, 0, 8, lat = ll$lat, long = ll$long, jd)

ilyamaclean/microclima documentation built on Oct. 31, 2023, 11:41 p.m.