Calculate the short-wave radiation

INTERFACE:

   subroutine short_wave_radiation(jul,secs,dlon,dlat,cloud,swr)

DESCRIPTION:

This subroutine calculates the short-wave net radiation based on latitude, longitude, time, fractional cloud cover and albedo. The albedo monthly values from Payne (1972) are given here as means of the values between at 30$^{\circ}$ N and 40$^{\circ}$ N for the Atlantic Ocean (hence the same latitudinal band of the Mediterranean Sea). The basic formula for the short-wave radiation at the surface, $Q_s$, has been taken from Rosati and Miyakoda (1988), who adapted the work of Reed (1977) and Simpson and Paulson (1999):

$$Q_s=Q_{tot} (1-0.62 C + 0.0019 \beta) (1-\alpha),$$ (230)

with the total radiation reaching the surface under clear skies, $Q_{tot}$, the fractional cloud cover, $C$, the solar noon altitude, $\beta$, and the albedo, $\alpha$. This piece of code has been taken the MOM-I (Modular Ocean Model) version at the INGV (Istituto Nazionale di Geofisica e Vulcanologia, see http://www.bo.ingv.it/).

USES:

   use time, only: calendar_date
   IMPLICIT NONE

INPUT PARAMETERS:

   integer, intent(in)                 :: jul,secs
   REALTYPE, intent(in)                :: dlon,dlat
   REALTYPE, intent(in)                :: cloud

OUTPUT PARAMETERS:

   REALTYPE, optional, intent(out)     :: swr

REVISION HISTORY:

   Original author(s): Karsten Bolding & Hans Burchard
   $Log: short_wave_radiation.F90,v $
   Revision 1.1  2007-09-25 10:06:10  kbk
   modularized the airsea module - added Fairall method

LOCAL VARIABLES:

   REALTYPE, parameter       :: pi=3.14159265358979323846
   REALTYPE, parameter       :: deg2rad=pi/180.
   REALTYPE, parameter       :: rad2deg=180./pi
 
   REALTYPE                  :: solar=1350.
   REALTYPE                  :: eclips=23.439*deg2rad
   REALTYPE                  :: tau=0.7
   REALTYPE                  :: aozone=0.09
 
   REALTYPE                  :: th0,th02,th03,sundec
   REALTYPE                  :: thsun,coszen,zen,dzen,sunbet
   REALTYPE                  :: qatten,qzer,qdir,qdiff,qtot,qshort
   REALTYPE                  :: albedo
   integer                   :: jab
   integer                   :: yy,mm,dd
   REALTYPE                  :: yrdays,days,hour,tjul
   REALTYPE                  :: rlon,rlat
 
   integer                   :: yday(12) = &
                 (/ 0,31,59,90,120,151,181,212,243,273,304,334 /)
 
   REALTYPE                  :: alb1(20) = &
                 (/.719,.656,.603,.480,.385,.300,.250,.193,.164, &
                   .131,.103,.084,.071,.061,.054,.039,.036,.032,.031,.030 /)
 
   REALTYPE                  :: za(20) = &
                 (/90.,88.,86.,84.,82.,80.,78.,76.,74.,70.,  &
                   66.,62.,58.,54.,50.,40.,30.,20.,10.,0.0 /)
 
   REALTYPE                  :: dza(19)
   data           dza/8*2.0, 6*4.0, 5*10.0/