Potential incoming solar radiation SAGA 2.2.2+

Description

This function calculates the potential incoming solar radiation in an area using different atmospheric models; This function reflects changes to the module with SAGA 2.2.2+. For SAGA versions 2.0.6 to 2.2.1 please see rsaga.pisr.

Usage

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rsaga.pisr2(in.dem, in.svf.grid = NULL, in.vapour.grid = NULL,
  in.linke.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, location = c("latitude", "grid"),
  latitude = 53, unit = c("kWh/m2", "kJ/m2", "J/cm2"), solconst = 1367,
  method = c("height", "components", "lumped", "hofierka"),
  hgt.atmosphere = 12000, 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 = 31, month = 10, year = 2015),
  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), for use with method = "height"; default 10 mbar

in.linke.grid

Optional input grid in SAGA format: Linke turbidity coefficient, for use with method = "hofierka"; default 3.0

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

location

specified whether to use constant latitude supplied by latitude below ("latitude" or code 0; default) or as calculated from the grid system ("grid" or code 1)

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

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 2), or by the method of Hofierka and Suri, 2009 ("hofierka", code 3). Default: "lumped".

hgt.atmosphere

Height of atmosphere (in m); default 12000 m. For use with method = "height"

cmp.pressure

atmospheric pressure in mbar, defaults to 1013 mbar. For use with method = "components"

cmp.water.content

water content of a vertical slice of the atmosphere in cm: between 1.5 and 1.7cm, average 1.68cm (default). For use with method = "components"

cmp.dust

dust factor in ppm; defaults to 100 ppm. For use with method = "components"

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 three, giving the start date in day, month, and year components as numbers; month is one-based (SAGA_CMD uses zero-based numbers internally), i.e. Jan. 1st 2015 is list(day=1,month=1,year=2015)

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

SAGA_CMD uses zero-based months, but this R function uses the standard one-based 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+. Changes to the module with SAGA 2.2.2+ include adding year to the *.date arguments to allow calculation across years. The method of Hofierka and Suri (2009) is added, which uses the Linke turbidity coefficient. Duration of insolation ("out.duration") is only calculated when the time period is set to a single day.

Author(s)

Alexander Brenning & Donovan Bangs (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.

Hofierka, J., Suri, M. (2002): The solar radiation model for Open source GIS: implementation and applications. International GRASS users conference in Trento, Italy, September 2002

See Also

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

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