hourlyNCEP: Interpolate NCEP data for running microclima to hourly
In ilyamaclean/microclima: microclimate modelling with R

hourlyNCEP

R Documentation

Interpolate NCEP data for running microclima to hourly

Description

hourlyNCEP optionally downloads the required NCEP climate and radiation forcing data required for running microclima and interpolates 4x daily data to hourly.

Usage

hourlyNCEP(ncepdata = NA, lat, long, tme, reanalysis2 = FALSE)

Arguments

`ncepdata`	an optional data frame of climate variables as returned by `get_NCEP()`.
`lat`	the latitude of the location for which data are required. Ignored if `ncepdata` provided.
`long`	the longitude of the location for which data are required. Ignored if `ncepdata` provided.
`tme`	a POSIXlt object covering the duration for which data are required. Ignored if ⁠ncepdata`` provided. Hourly data are returned irrespective of the time interval of ⁠tme`⁠.Ignored if ⁠`ncepdata' provided.
`reanalysis2`	Logical. Should data be obtained from the Reanalysis II dataset (default) or from Reanalysis I (data prior to 1979). Ignored if `ncepdata` provided.

Details

If ncepdata is not provided, then get_NCEP() is called and data are downloaded from NCEP Atmospheric Model Intercomparison Project (Kanamitso et al 2002). Six-hourly data are interpolated as follows. Pressure, humidity and the u and v wind vectors are converted to hourly using spline interpolation. Wind speeed and direction and then calculated and adjusted to give values at 1 m using windheight(). The diffuse radiation proportion is calculated using difprop(), and hourly obtained by adusting for the direction of the solar beam and airmass thickness using functions siflat() and airmasscoef(). Hourly temperature are derived using hourlytemp() and longwave radiation by splining emissivity values.

Value

a dataframe with the following variables:

obs_time: POSIXlt object of times in UTC
temperature: emperatures at 2m (ºC)
humidity: specific humidity at 2m (Kg / Kg)
pressure: surface pressure (Pa)
windspeed: wind speed at 2m (metres per second
winddir: wind direction (degrees from N)
emissivity: emissivity of the atmosphere (0 - 1, downlong / uplong)
netlong: Net longwave radiation (MJ m^-2 hr^-1)
uplong: Upward longwave radiation (MJ m^-2 hr^-1)
downlong: Downward longwave radiation (MJ m^-2 hr^-1)
rad_dni: Direct radiation normal to the solar beam (MJ m^-2 hr^-1)
rad_dif: Diffuse radiation (MJ m^-2 hr^-1)
szenith: the zenith angle (degrees)
cloudcover: cloud cover (Percentage)

Examples

tme <- as.POSIXlt(c(0:30) * 24 * 3600, origin ="2015-01-15 00:00", tz = "UTC")
# NB takes a while to download data
hdata<- hourlyNCEP(NA, 50, -5, tme)
head(hdata)
plot(temperature ~ as.POSIXct(obs_time), data = hdata, type = "l", xlab = "Month")
plot(rad_dif ~ as.POSIXct(obs_time), data = hdata, type = "l", xlab = "Month")

ilyamaclean/microclima documentation built on Sept. 5, 2024, 8:37 p.m.