rsaga.pisr: Potential incoming solar radiation

In RSAGA: SAGA Geoprocessing and Terrain Analysis

Potential incoming solar radiation

Description

This function calculates the potential incoming solar radiation in an area using different atmospheric models; module available in SAGA GIS 2.0.6+.

Usage

rsaga.pisr(
  in.dem,
  in.svf.grid = NULL,
  in.vapour.grid = NULL,
  in.latitude.grid = NULL,
  in.longitude.grid = NULL,
  out.direct.grid,
  out.diffuse.grid,
  out.total.grid = NULL,
  out.ratio.grid = NULL,
  out.duration,
  out.sunrise,
  out.sunset,
  local.svf = TRUE,
  latitude,
  unit = c("kWh/m2", "kJ/m2", "J/cm2"),
  solconst = 1367,
  enable.bending = FALSE,
  bending.radius = 6366737.96,
  bending.lat.offset = "user",
  bending.lat.ref.user = 0,
  bending.lon.offset = "center",
  bending.lon.ref.user = 0,
  method = c("height", "components", "lumped"),
  hgt.atmosphere = 12000,
  hgt.water.vapour.pressure = 10,
  cmp.pressure = 1013,
  cmp.water.content = 1.68,
  cmp.dust = 100,
  lmp.transmittance = 70,
  time.range = c(0, 24),
  time.step = 0.5,
  start.date = list(day = 21, month = 3),
  end.date = NULL,
  day.step = 5,
  env = rsaga.env(),
  ...
)

Arguments

in.dem	name of input digital elevation model (DEM) grid in SAGA grid format (default extension: .sgrd)
in.svf.grid	Optional input grid in SAGA format: Sky View Factor; see also local.svf
in.vapour.grid	Optional input grid in SAGA format: Water vapour pressure (mbar); see also argument hgt.water.vapour.pressure
in.latitude.grid	Optional input grid in SAGA format: Latitude (degree) of each grid cell
in.longitude.grid	see in.latitude.grid
out.direct.grid	Output grid: Direct insolation (unit selected by unit argument)
out.diffuse.grid	Output grid: Diffuse insolation
out.total.grid	Optional output grid: Total insolation, i.e. sum of direct and diffuse incoming solar radiation
out.ratio.grid	Optional output grid: Direct to diffuse ratio
out.duration	Optional output grid: Duration of insolation
out.sunrise	Optional output grid: time of sunrise; only calculated if time span is set to single day
out.sunset	Time of sunset; see out.sunrise
local.svf	logical (default: TRUE; if TRUE, use sky view factor based on local slope (after Oke, 1988), if no sky view factor grid is provided in in.svf.grid
latitude	Geographical latitude in degree North (negative values indicate southern hemisphere)
unit	unit of insolation output grids: "kWh/m2" (default) "kJ/m2", or "J/cm2"
solconst	solar constant, defaults to 1367 W/m2
enable.bending	logical (default: FALSE): incorporate effects of planetary bending?
bending.radius	Planetary radius, default 6366737.96
bending.lat.offset	if bending is enabled: latitudinal reference is "user"-defined (default), or relative to "top", "center" or "bottom" of grid?
bending.lat.ref.user	user-defined lat. reference for bending, see bending.lat.offset
bending.lon.offset	longitudinal reference, i.e. local time, is "user"-defined, or relative to "top", "center" (default) or "bottom" of grid?
bending.lon.ref.user	user-defined reference for local time (Details??)
method	specifies how the atmospheric components should be accounted for: either based on the height of atmosphere and vapour pressure ("height", or numeric code 0), or air pressure, water and dust content ("components", code 1), or lumped atmospheric transmittance ("lumped", code 0)
hgt.atmosphere	Height of atmosphere (in m); default 12000 m
hgt.water.vapour.pressure	Water vapour pressure in mbar (default 10 mbar); This value is used if no vapour pressure grid is given in argument in.vapour.grid
cmp.pressure	atmospheric pressure in mbar, defaults to 1013 mbar
cmp.water.content	water content of a vertical slice of the atmosphere in cm: between 1.5 and 1.7cm, average 1.68cm (default)
cmp.dust	dust factor in ppm; defaults to 100 ppm
lmp.transmittance	transmittance of the atmosphere in percent; usually between 60 (humid areas) and 80 percent (deserts)
time.range	numeric vector of length 2: time span (hours of the day) for numerical integration
time.step	time step in hours for numerical integration
start.date	list of length two, giving the start date in day and month components as numbers; these numbers are one-based (SAGA_CMD uses zero-based numbers internally), i.e. Jan. 1st is list(day=1,month=1)
end.date	see start.date
day.step	if days indicates a range of days, this specifies the time step (number of days) for calculating the incoming solar radiation
env	RSAGA geoprocessing environment obtained with rsaga.env(); this argument is required for version control (see Note)
...	optional arguments to be passed to rsaga.geoprocessor()

Details

According to SAGA GIS 2.0.7 documentation, "Most options should do well, but TAPES-G based diffuse irradiance calculation ("Atmospheric Effects" methods 2 and 3) needs further revision!" I.e. be careful with method = "components" and method = "lumped".

Note

This module is computationally very intensive (depending on the size of the grid and the time resolution, of course). The performance seems to have much improved in SAGA GIS 2.1.0, which by default runs this module in multicore mode (at the release candidate 1 for Windows does).

SAGA_CMD uses zero-based days and months, but this R function uses the standard one-based days and months (e.g. day 1 is the first day of the month, month 1 is January) and translates to the SAGA system.

This function uses module Potential Incoming Solar Radiation from SAGA library ta_lighting in SAGA version 2.0.6+.

Author(s)

Alexander Brenning (R interface), Olaf Conrad (SAGA module)

References

Boehner, J., Antonic, O. (2009): Land surface parameters specific to topo-climatology. In: Hengl, T. and Reuter, H. I. (eds.): Geomorphometry - Concepts, Software, Applications. Elsevier.

Oke, T.R. (1988): Boundary layer climates. London, Taylor and Francis.

Wilson, J.P., Gallant, J.C. (eds.), 2000: Terrain analysis - principles and applications. New York, John Wiley and Sons.

See Also

rsaga.hillshade(); for similar modules in older SAGA versions (pre-2.0.6) see rsaga.solar.radiation() and rsaga.insolation()

RSAGA documentation built on Dec. 10, 2022, 1:12 a.m.