varwg.meteo.meteox2y.lw2clouds

varwg.meteo.meteox2y.lw2clouds(lw, temp, rh=None, dew=None, e=None, site='low')

Cloud cover from incident long wave radiation (Iziomon et al (2003)[Rd8835ed535f1-1]_)

As input is required: incident long wave radiation (lw), air temperature (temp) and EITHER relative humidity (rh) OR dewpoint (dew) OR vapour pressure (e)

Parameters:

lwfloat or numpy.array of floats

incident longwave radiation [W/m**2]

tempfloat or numpy.array of floats

air temperature [deg C]

rhfloat or numpy.array of floats or None

relative humidity with values between 0 and 1 [-]

dewfloat or numpy.array of floats or None

dewpoint [deg C]

efloat or numpy.array of floats or None

vapour pressure [hPa]

site{‘low’, ‘high’}

parameterisation for lowland or highland site

Returns:

cloudsfloat or numpy.array of floats

cloud cover with values between 0 and 1 [-]

See also

iziomon

incident long wave radiation from air temperature, cloud cover and humidity

Notes

Resulting cloud cover is always between 0 and 1. Gives 0 for unrealistic low and 1 for unrealistic high values of lw.

References

[1]

Iziomon, M.G., Mayer H, Matzarakis A. (2003): Downward atmospheric longwave irradiance under clear and cloudy skies: Measurement and parameterization, Journal of Atmospheric and Solar-Terrestrial Physics 65 (2003) 1107 - 1116

Examples

>>> lw2clouds(328., 15., rh=0.9)
0.49959967427213553

>>> lw = np.array((225.5, 235.1, 279, 267, 321.2))
>>> temp = np.array((0.0, 2.5, 5.0, 7.5, 10.0))
>>> e = np.array((5.5, 5.8, 6.1, 6.2, 6.5))
>>> lw2clouds(lw,temp,e=e)
array([0.0555659 ,  0.1020956 ,  0.79983929,  0.49550839,  0.99289638])