cliBrtSunDurFrcGrid {macroBiome}

Estimator for Fraction of Bright Sunshine Duration

Description

Estimates monthly averages for daily fraction of bright sunshine duration, for a given region and year, by using the monthly time series of temperature and precipitation, and the elevation data.

Usage

cliBrtSunDurFrcGrid(
  rs.temp,
  rs.prec,
  rl.elv,
  sc.year = 2000,
  aprchSIM = c("Solar123", "SPLASH"),
  filename = "",
  ...
)

Arguments

rs.temp

multi-layer Raster*/SpatRaster object with one-year time series of monthly mean air temperature (in °C)

rs.prec

multi-layer Raster*/SpatRaster object with one-year time series of monthly precipitation sum (in mm)

rl.elv

single-layer Raster*/SpatRaster object with the elevation values (in meters above sea level)

sc.year

'numeric' scalar with the value of the year (using astronomical year numbering)

aprchSIM

'character' vector of length 1 that indicates the formula used to estimate the value of solar irradiance/irradiation for a specific day. Valid values are as follows:
(a) 'Solar123' - in this approach, first, the mean hourly solar irradiance under cloudless-sky conditions is calculated as proposed by Yin (1997b), with a minor modification, using the daytime means of optical air mass and cosine zenith; the former is computed as recommended by Yin (1997b), while the latter is estimated by using Eq 5 of Yin (1997a); however, in contrast to the original approach, where the solar constant was fixed at 4.9212 MJ m^{-2} hr^{-1}, according to Yin (1999), its value is corrected by calendar day for the variable ellipticity of the Earth's orbit, by using the scheme of Brock (1981); in the calculations, the values of solar declination and daylength are derived by using the approach of Brock (1981);
(b) 'SPLASH' - in this approach, first, under varying orbital parameters, the daily solar radiation at the top of the atmosphere is calculated (H_{0}, Eq 7 in Davis et al. (2017)), and then this value is multiplied by the atmospheric transmittivity to obtain the value of daily surface radiation; in this case as well, cloudless conditions are assumed, i.e., the transmission coefficient is taken into account with an universal value of 0.75, however, its value is modified as a function of elevation, by using the scheme of Allen (1996); the daylength is calculated via Eq 1.6.11 in Duffie and Beckman (1991), using the sunset hour angle (h_{s}, Eq 8. in Davis et al. (2017)); finally, the mean hourly surface radiation is derived as the quotient of the daily surface radiation and the daylength.

filename

output filename

...

additional arguments passed on to writeRaster

Details

See cliBrtSunDurFrcPoints.

Value

A 12-layer SpatRaster object with one-year time series of monthly mean relative sunshine duration.

Note

The objects 'rs.temp' and 'rs.prec' must be 12-layer Raster*/SpatRaster objects, while the object 'rl.elv' has to be a single-layer Raster*/SpatRaster object. These Raster*/SpatRaster objects must have the same bounding box, projection, and resolution. The object 'sc.year' has to be a single integer number.

References

Allen RG (1996) Assessing integrity of weather data for reference evapotranspiration estimation. J Irrig Drain Eng 122(2):97–106. doi:10.1061/(ASCE)0733-9437(1996)122:2(97)

Berger A, Loutre MF (1991) Insolation values for the climate of the last 10 million years. Quat Sci Rev 10(4):297-317. doi:10.1016/0277-3791(91)90033-Q

Brock TD (1981) Calculating solar radiation for ecological studies. Ecol Model 14(1–2):1-19. doi:10.1016/0304-3800(81)90011-9

Davis TW, Prentice IC, Stocker BD, Thomas RT, Whitley RJ, Wang H, Evans BJ, Gallego-Sala AV, Sykes MT, Cramer W (2017) Simple process-led algorithms for simulating habitats (SPLASH v.1.0): robust indices of radiation, evapotranspiration and plant-available moisture. Geosci Model Dev 10(2):689–708. doi:10.5194/gmd-10-689-2017

Duffie JA, Beckman WA (1991) Solar Engineering of Thermal Processes. Second Edition. Wiley-Interscience, New York, NY

Yin X (1997a) Calculating daytime mean relative air mass. Agric For Meteorol 87(2-3):85-90. doi:10.1016/S0168-1923(97)00029-4

Yin X (1997b) Optical Air Mass: Daily Integration and its Applications. Meteorol Atmos Phys 63(3-4):227-233. doi:10.1007/BF01027387

Yin X (1999) Bright Sunshine Duration in Relation to Precipitation, Air Temperature and Geographic Location. Theor Appl Climatol 64(1–2):61–68. doi:10.1007/s007040050111

Examples

library(raster)

# Loading mandatory data for the Example 'Single-Year Grid'
data(inp_exSglyGrid)
inp_exSglyGrid <- lapply(inp_exSglyGrid, crop, extent(20.15, 20.25, 46.25, 46.35))

# Estimate values of the monthly mean relative sunshine duration
# at a grid cell near Szeged, Hungary (46.3N, 20.2E), in the year 2010
with(inp_exSglyGrid, {
rs.bsdf <- cliBrtSunDurFrcGrid(temp, prec, elv, sc.year = 2010)
rs.bsdf
})