calcMeteoParam: calcMeteoParam calculates the meteorological parameters based...

In gisma/aRps: Analyzing and visualizing Arps model runs output

Description

calcMeteoParam converts, and derives meterorlogical parameters from the ARPS netCDF modelrun result file.

• pressure (hPa)

• exner pressure (hPa)

• air temperature in degree Celsius (C)

• dew point temperature (C)

• water vapor saturation pressure (hPa)

• water vapor pressure (hPa)

• relative air humidity (

• u component of the horizontal windvector (m/s)

• v component of the horizontal windvector (m/s)

• w component of the horizontal windvector (m/s)

• windspeed (m/s)

• wind direction (deg)

Usage

x<-wind(nc)

Arguments

nc	netcdf object as opened by: nc <- open.ncdf(arpsexample)

Details

The following equations are used:

• exner pressure (Pa): e_p = (p/100000)^(R/cp)

  	p	= pressure (Pa)
  	cp	= 1005 = specific heat capacity (J/kg K)
  	R	= 287.058 0 specific gas constant (J/kg K)

• air temperature (C): tc = e_p*pt-273.15

  	pt	= potential temperature (K)
  	e_p	= exner pressure (Pa)

• air temperature (K): tk = e_p*pt

  	pt	= potential temperature (K)
  	e_p	= exner pressure (Pa)

• water vapor saturation pressure (hPa): es = 6.1078*10^((a*tc)/(b+tc))

  	a	= 7.5 (if tc >= 0)
  	b	= 237.3 (if tc >= 0)
  	a	= 9.5 (if tc < 0)
  	b	= 285.5 (if tc < 0)

• water vapor pressure (hPa): e = (p/0.622*qv)/100

  	p	= pressure (Pa)
  	qv	= Water Vapor Mixing Ratio (g/kg)

• dew point temperature (C): td = b*v/(a-v)

  	v	= log10(e/6.1078)
  	e	= water vapor pressure (hPa)
  	a	= 7.6 (if tc >= 0)
  	b	= 240.7 (if tc >= 0)
  	a	= 9.5 (if tc < 0)
  	b	= 285.5 (if tc < 0)

• relative air humidity (percent): rh=(e/es)*100

  	e	= water vapor pressure (hPa)
  	es	= water vapor saturation pressure (hPa)

• wind speed (m/s): ws=sqrt(u^2+v^2)

  	u	= zonal velocity of horizontal wind (m/s)
  	v	= meridional velocity of horizontal wind (m/s)

• wind direction (m/s): wd=180+atan2(u,v)*57.295

  	u	= zonal velocity of horizontal wind (m/s)
  	v	= meridional velocity of horizontal wind (m/s)
  	atan2	the use of atan2 avoids the quadrant search for calculating the correct angle

• For all operations is valid:

  	pt	= potential temperature (K)
  	p	= air pressure (Pa)
  	qv	= water vapor mixing ratio (g/kg)
  	u,v	the horizontal windvector components (m/s) are directly derived from the model inputfile

Value

The function wind returns a list of the the unstaggered wind components (u,v,ws,wd). the other function are returning the requested type of calculated data Be careful this data Arrays can be VERY big.

Author(s)

Chris Reudenbach and Hanna Meyer,

See Also

If you want to use this data in a GIS or otherwise georeferenced you need to extract the projection and domain extent according to the reference system that was used by ARPS getRefInfo

Examples

#### Examples how  to use the function in calcMeteoParam:
 ###  (1) provide a valid netcdf file
 ##   (2) open it
 #    (3) use it (i.e. air pressure)
 arps.ncfile=system.file("kili.nc", package="aRps")
 nc <- nc_open(arps.ncfile)
 pr<-airpressure(nc)

gisma/aRps documentation built on May 17, 2019, 5:27 a.m.