Rnl {MeTo} | R Documentation |
Net longwave radiation (Rnl)
Description
Net longwave radiation (Rnl).
Usage
Rnl(
x,
Tmax = NULL,
Tmin = NULL,
Rhmax = NULL,
Rhmin = NULL,
Rs = NULL,
lat.rad = NULL,
lat.deg = NULL,
long.deg = NULL,
elev,
actVP = NULL,
tl,
Tmean = NULL,
Rhmean = NULL,
control = list()
)
Arguments
x |
date-time object or day of the year (must be date-time object if calculation period is shorter than a day) |
Tmax |
maximum temperature [degreeC] during 24-hour period (for daily values) |
Tmin |
minimum temperature [degreeC] during 24-hour period (for daily values) |
Rhmax |
daily maximum of air humidity [percent] (for daily values) |
Rhmin |
daily minimum of air humidity [percent] (for daily values) |
Rs |
incoming solar radiation [MJ/(m2 time)] |
lat.rad |
latitude [rad]. Use either lat.rad or lat.deg. Latitude is positive for the northern hemisphere and negative for the southern hemisphere |
lat.deg |
latitude [degree]. Use either lat.deg or lat.rad. Latitude is positive for the northern hemisphere and negative for the southern hemisphere |
long.deg |
see |
elev |
station elevation above sea level [m] |
actVP |
Actual vapor pressure [kPa]. If Rhmax, Rhmin and Rhmean are NULL |
tl |
length of calculation period [hour] (1 for hourly period, 0.5 for a 30-minute period or 24 for daily period). Only needed if length of x is date-time object with length of 1. |
Tmean |
mean temperature [degreeC] during the time period (for periods shorter than a day) |
Rhmean |
Mean air humidity [percent] (for periods shorter than a day or if Rhmax and Rhmin are missing) |
control |
list for control parameters and empirical factors (see Details and |
Details
- x:
-
must be provided as.numeric (1-366) or as a common date-time object (e.g, POSIXct, POSIXlt or Date objects). All formats for which is.timepoint from the lubridate package returns TRUE can be used
- control:
-
Lz:
longitude of the centre of the local time zone (degrees west of Greenwich)
- 0 for Greenwich
- 345 for Germany
- 330 for Cairo (Egypt)
- 255 for Bangkok (Thailand)
- 75, 90, 105 and 120 for Eastern, Central, Rocky Mountain and Pacific time zones (United States)
Lz is only needed if calculation period is shorter 1 day.
est.ratio.Rs.Rso:
Rs/Rso is used to represent cloud cover. For hourly or shorter periods during the nighttime, the ratio Rs/Rso is set equal to the Rs/Rso calculated for a time period occurring 2-3 hours before sunset. If single values during nighttime are calculated Rs/Rso ration 2-3 hours before sunset can not be calculated and an approximation is needed. Following Allen (1999) one can assume Rs/Rso = 0.4 to 0.6 during nighttime periods in humid and subhumid climates and Rs/Rso = 0.7 to 0.8 in arid and semiarid climates. A value of Rs/Rso = 0.3 presumes total cloud cover.
Value
Rnl net outgoing longwave radiation [MJ(/m2 time)]
Note
eq. 39 of reference
References
Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. FAO, Rome, 300(9).