== Radiation Parameters ==
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Since r1551 an interface for use of radiation models is available in PALM. Currently, PALM offers one built-in radiation model for clear-sky conditions, calculating the net radiation at the surface.

All parts of the radiation code are modularized in module [/browser/palm/trunk/SOURCE/radiation_model.f90 radiation_model_mod]. In this context, a new Fortran NAMELIST {{{radiation_par}}} was added, containing all radiation-related steering parameters. The radiation module is automatically activated when a {{{radiation_par}}} is set in the parameter file ({{{_p3d}}}).

\\\\\\\\\\\\
'''NAMELIST group name: radiation_par''' \\\\

||='''Parameter Name'''  =||='''[../fortrantypes FORTRAN Type]'''  =||='''Default Value'''  =||='''Explanation'''  =||
|----------------
{{{#!td style="vertical-align:top"
[=#albedo '''albedo''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
0.2
}}}
{{{#!td
Surface albedo (value of 0-1).
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#albedo_type '''albedo_type''']
}}}
{{{#!td style="vertical-align:top"
I
}}}
{{{#!td style="vertical-align:top"
5
}}}
{{{#!td
This parameter controls the choice of the surface albedos for direct/diffuse/broadband albedo for a solar angle of 80° according to the following list of-predefined land surfaces. For radiation_scheme = 'rrtmg' the shortwave and longwave albedo values are used and the actual albedos are then calculated based on the current solar angle after Briegleb (1992). Setting on or more of the parameters [#albedo_lw_dif albedo_lw_dif], [#albedo_lw_dir albedo_lw_dir], [#albedo_sw_dif albedo_sw_dif], [#albedo_sw_dir albedo_sw_dir] will overwrite the respective values set by albedo_type. By default, [#albedo_lw_dif albedo_lw_dif] = [#albedo_lw_dir albedo_lw_dir] and [#albedo_sw_dif albedo_sw_dif] = [#albedo_sw_dir albedo_sw_dir]. Moreover, [#constant_albedo constant_albedo] = .T. will keep the albedos constant during the simulation. For radiation_scheme = 'clear-sky' the broadband albedo is used and does not vary in the course of the simulation.

||= '''albedo_type'''=||='''Description'''   =||='''shortwave''' =||='''longwave''' =||='''broadband''' =||
||  0|| user defined                          ||     -||    - ||    - ||
||  1|| ocean                                 || 0.06 || 0.06 || 0.06 ||
||  2|| mixed farming, tall grassland         || 0.09 || 0.28 || 0.19 ||
||  3|| tall/medium grassland                 || 0.11 || 0.33 || 0.23 ||
||  4|| evergreen shrubland                   || 0.11 || 0.33 || 0.23 ||
||  5|| short grassland/meadow/shrubland      || 0.14 || 0.34 || 0.25 ||
||  6|| evergreen needleleaf forest           || 0.06 || 0.22 || 0.14 ||
||  7|| mixed deciduous forest                || 0.06 || 0.27 || 0.17 ||
||  8|| deciduous forest                      || 0.06 || 0.31 || 0.19 ||
||  9|| tropical evergreen broadleaved forest || 0.06 || 0.22 || 0.14 ||
|| 10|| medium/tall grassland/woodland        || 0.06 || 0.28 || 0.18 ||
|| 11|| desert, sandy                         || 0.35 || 0.51 || 0.43 ||
|| 12|| desert, rocky                         || 0.24 || 0.40 || 0.32 ||
|| 13|| tundra                                || 0.10 || 0.27 || 0.19 ||
|| 14|| land ice*                             || 0.90 || 0.65 || 0.77 ||
|| 15|| sea ice                               || 0.90 || 0.65 || 0.77 ||
|| 16|| snow                                  || 0.95 || 0.70 || 0.82 ||
(* land ice is treaded differently than sea ice)
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#albedo_lw_dif '''albedo_lw_dif''']
}}}
{{{#!td style="vertical-align:top"
I
}}}
{{{#!td style="vertical-align:top"
depending on [#albedo_type albedo_type]
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#albedo_lw_dir '''albedo_lw_dir''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
depending on [#albedo_type albedo_type]
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#albedo_sw_dif '''albedo_sw_dif''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
depending on [#albedo_type albedo_type]
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#albedo_sw_dir '''albedo_sw_dir''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
depending on [#albedo_type albedo_type]
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#constant_albedo '''constant_albedo''']
}}}
{{{#!td style="vertical-align:top"
L
}}}
{{{#!td style="vertical-align:top"
.F.
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#day_init '''day_init''']
}}}
{{{#!td style="vertical-align:top"
I
}}}
{{{#!td style="vertical-align:top"
172
}}}
{{{#!td
Day of the year (1-365) at model start. The default value is 172 (June 21).
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#dt_radiation '''dt_radiation''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
0.0
}}}
{{{#!td
Timestep of the radiation model (in s).
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#lambda '''lambda''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
0.0
}}}
{{{#!td
Geographical longitude (in degrees). 

Note that the radiation scheme also requires information on the geographical latitude (see [wiki:doc/app/inipar#phi phi]).
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#lw_raditaion '''lw_radiation''']
}}}
{{{#!td style="vertical-align:top"
L
}}}
{{{#!td style="vertical-align:top"
.T.
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#net_radiation '''net_radiation''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
0.0
}}}
{{{#!td
Net radiation at the surface in W/m². This parameter is only used in case of [#radiation_scheme radiation scheme]{{{= 'constant'}}}.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#radiation_scheme '''radiation_scheme''']
}}}
{{{#!td style="vertical-align:top"
C*10
}}}
{{{#!td style="vertical-align:top"
'clear-sky'
}}}
{{{#!td
Radiation scheme to be used.

The user can choose between the following schemes:

'' 'constant' ''

A constant net radiation at the surface is prescribed (see [#net_radiation]).


'' 'clear-sky' ''

A simple clear sky model is used to calculate the radiation fluxes at the surface (shortwave incoming, shortwave outgoing, longwave incoming, longwave outgoing) and consequently the net radiation at the surface. This scheme requires setting of [#albedo albedo], [#day_init day_init], [#lambda lambda], [wiki:doc/app/inipar#phi phi], and [#time_utc_init time_utc_init].


'' 'rrtmg' ''

The [http://rtweb.aer.com/rrtm_frame.html RRTMG model] is used to calculate the radiative heating rates for each model column. This scheme requires setting of [#day_init day_init], [#lambda lambda], [wiki:doc/app/inipar#phi phi], [#time_utc_init time_utc_init]. The folling parameters can be set optionally: [#albedo_type albedo_type] (and/or [#albedo_lw_dif albedo_lw_dif], [#albedo_lw_dir albedo_lw_dir], [#albedo_sw_dif albedo_sw_dif], [#albedo_sw_dir albedo_sw_dir]). [#constant_albedo constant_albedo] can be used to fix the albedo during the simualation. It is also possible to use the switches [#lw_radiation lw_radiation] and [#sw_radiation sw_radiation].

}}}
|----------------
{{{#!td style="vertical-align:top"
[=#sw_raditaion '''sw_radiation''']
}}}
{{{#!td style="vertical-align:top"
L
}}}
{{{#!td style="vertical-align:top"
.T.
}}}
{{{#!td
Text goes here.
}}}
|----------------
{{{#!td style="vertical-align:top"
[=#time_utc_init '''time_utc_init''']
}}}
{{{#!td style="vertical-align:top"
R
}}}
{{{#!td style="vertical-align:top"
43200.0
}}}
{{{#!td
UTC time at model start in seconds starting from midnight, The default value is {{{43200.0}}} (12 p.m., noon).
}}}