Import Meteorology for model input

Import the meteorology data, check its format, and eventually compute missing variables.

Meteorology(file = NULL, Period = NULL, Parameters = Import_Parameters())

Arguments

file	Either the file name to read, a shell command that preprocesses the file (e.g. fread("grep filename")) or the input itself as a string, see data.table::fread(). In both cases, a length 1 character string. A filename input is passed through path.expand for convenience and may be a URL starting http:// or file://. Default to NULL to return the Aquiares() example data from the package.
Period	A vector of two POSIX dates that correspond to the min and max dates for the desired time period to be returned.
Parameters	A list of parameters: Start_Date: optional, the Posixct date of the first meteo file record. Only needed if the Date column is missing. FPAR : Fraction of global radiation corresponding to PAR radiation, only needed if either RAD or PAR is missing. Elevation : elevation of the site (m), only needed if atmospheric pressure is missing Latitude : latitude of the site (degree), only needed if the diffuse fraction of light is missing WindSpeed : constant wind speed (m s-1), only needed if windspeed is missing CO2 : constant atmospheric \(CO_2\) concentration (ppm), only needed if \(CO_2\) is missing MinTT : minimum temperature threshold for degree days computing (Celsius), see GDD() albedo : site shortwave surface albedo, only needed if net radiation is missing, see Rad_net()

Value

A daily meteorology data.frame (invisibly).

Details

The imported file is expected to be at daily time-step. The albedo is used to compute the system net radiation that is then used to compute the soil net radiation using an extinction coefficient with the plot LAI following the Shuttleworth & Wallace (1985) formulation. This computation is likely to be depreciated in the near future as the computation has been replaced by a metamodel. It is kept for information for the moment.

Var	unit	Definition	If missing
Date	POSIXct	Date in POSIXct format	Computed from start date parameter, or set a dummy date if missing
year	year	Year of the simulation	Computed from Date
DOY	day	day of the year	Computed from Date
Rain	mm	Rainfall	Assume no rain
Tair	Celsius	Air temperature (above canopy)	Computed from Tmax and Tmin
Tmax	Celsius	Maximum air temperature during the day	Required (error)
Tmin	Celsius	Minimum air temperature during the day	Required (error)
RH	%	Relative humidity	Not used, but prefered over VPD for Rn computation
RAD	MJ m-2 d-1	Incident shortwave radiation	Computed from PAR
Pressure	hPa	Atmospheric pressure	Computed from VPD, Tair and Elevation, or alternatively from Tair and Elevation.
WindSpeed	m s-1	Wind speed	Taken as constant: Parameters$WindSpeed
CO2	ppm	Atmospheric CO2 concentration	Taken as constant: Parameters$CO2
DegreeDays	Celsius	Growing degree days	Computed using GDD()
PAR	MJ m-2 d-1	Incident photosynthetically active radiation	Computed from RAD
FDiff	Fraction	Diffuse light fraction	Computed using Diffuse_d() using Spitters et al. (1986) formula
VPD	hPa	Vapor pressure deficit	Computed from RH
Rn	MJ m-2 d-1	Net radiation (will be depreciated)	Computed using Rad_net() with RH, or VPD
DaysWithoutRain	day	Number of consecutive days with no rainfall	Computed from Rain
Air_Density	kg m-3	Air density of moist air (\(\rho\)) above canopy	Computed using bigleaf::air.density()
ZEN	radian	Solar zenithal angle at noon	Computed from Date, Latitude, Longitude and Timezone

Note

It is highly recommended to set the system environment timezone to the one from the meteorology file. If not, the function try to use the Timezone from the parameter files to set it. When in doubt, set it to UTC (Sys.setenv(TZ="UTC")), as for Aquiares().

See also

DynACof()

Examples

if (FALSE) {
if(interactive()){
 Sys.setenv(TZ="UTC")
 Met_c= Meteorology()

 # Get the units of the output variables:
 attr(Met_c,"unit")
 }
}