source: trunk/src/d2m_to_q2m_erai.pro @ 79

;+
;
; .. _d2m_to_q2m_erai.pro:
;
; ===================
; d2m_to_q2m_erai.pro
; ===================
;
; Conversion of d2m to q2m on OAFLUX grid
;
; :file:`${PROJECT_OD}/erai_d2m_19890101_20091231_oafluxgrid.nc` have been 
; produced by :ref:`interp_erai_dewt_1989_2009.pro`.
;
; :file:`${PROJECT_OD}/erai_t2m_19890101_20091231_oafluxgrid.nc` have been 
; produced by :ref:`interp_erai_t2m_1989_2009.pro`.
;
; :file:`${PROJECT_OD}/erai_msl_19890101_20091231_oafluxgrid.nc` have been 
; produced by :ref:`interp_erai_msl_1989_2009.pro`.
;
; q2m on OAFLUX grid is written in
; :file:`${PROJECT_OD}/q2m_erai_19890101_20091231_oafluxgrid.nc`
; if this file not already exists.
;
; This file will be used by :ref:`q2m_correction_ncdf.pro`.
;
;     .. graphviz::
;
;        digraph d2m_to_q2m_erai {
;           graph [
;           rankdir="LR",
;           ]
;
;           file_d2m [shape=ellipse,fontname=Courier,label="${PROJECT_OD}/erai_d2m_19890101_20091231_oafluxgrid.nc"];
;           file_t2m [shape=ellipse,fontname=Courier,label="${PROJECT_OD}/erai_t2m_19890101_20091231_oafluxgrid.nc"];
;           file_msl [shape=ellipse,fontname=Courier,label="${PROJECT_OD}/erai_msl_19890101_20091231_oafluxgrid.nc"];
;           file_q2m [shape=ellipse,fontname=Courier,label="${PROJECT_OD}/q2m_erai_19890101_20091231_oafluxgrid.nc"];
;
;           d2m_to_q2m_erai [shape=box,
;           fontname=Courier,
;           color=blue,
;           URL="http://forge.ipsl.jussieu.fr/tropflux/browser/trunk/src/d2m_to_q2m_erai.pro",
;           label="${PROJECT}/src/d2m_to_q2m_erai.pro"];
;
;           {file_d2m file_t2m file_msl} -> {d2m_to_q2m_erai} -> {file_q2m}
;        }
;
; SEE ALSO
; ========
;
; :ref:`project_profile.sh`
;
; :ref:`mooring_corrections`
;
; :ref:`interp_erai_dewt_1989_2009.pro`
; :ref:`interp_erai_msl_1989_2009.pro`
; :ref:`interp_erai_t2m_1989_2009.pro`
;
; :ref:`q2m_correction_ncdf.pro`
;
; :func:`rh_to_spechum`
; :func:`initncdf <saxo:initncdf>`
; :func:`read_ncdf <saxo:read_ncdf>`
; :func:`julday <saxo:julday>`
; :func:`ncdf_quickwrite <saxo:ncdf_quickwrite>`
;
; EXAMPLES
; ========
;
; ::
;
;  IDL> d2m_to_q2m_erai
;
; TODO
; ====
;
; es0 undefined
;
; coding rules
;
; EVOLUTIONS
; ==========
;
; $Id$
; 
; $URL$
;
; - fplod 20110809T154249Z aedon.locean-ipsl.upmc.fr (Darwin)
;
;   * typo
;
; - fplod 20110808T120234Z cratos (Linux)
;
;   * usage of ${PROJECT_OD}
;   * complete description
;   * remove return statement
;
; - fplod 20101215T162933Z aedon.locean-ipsl.upmc.fr (Darwin)
;
;   * graph correction
;
; - fplod 20101215T093141Z aedon.locean-ipsl.upmc.fr (Darwin)
;
;   * add graph in header
;
; - fplod 20101214T093615Z aedon.locean-ipsl.upmc.fr (Darwin)
;
;   * minimal header
;
; - pbk 2008
;
;   * creation
;
;-
pro d2m_to_q2m_erai
;
@cm_4cal
@cm_4data
@cm_4mesh
@cm_4data
@cm_project
;
; test if ${PROJECT_OD} defined
CASE project_od_env OF
  '' : BEGIN
         msg = 'eee : ${PROJECT_OD} is not defined'
         ras = report(msg)
       STOP
       END
  ELSE: BEGIN
          msg = 'iii : ${PROJECT_OD} is ' + project_od_env
          ras = report(msg)
        END
 ENDCASE
;
; check if output data will be possible
iodirout = isadirectory(project_od_env)
;
; existence and protection for reading
IF (FILE_TEST(iodirout, /DIRECTORY, /EXECUTABLE, /READ) EQ 0) THEN BEGIN
   msg = 'eee : the directory' + iodirout  + ' is not accessible.'
   ras = report(msg)
   STOP
ENDIF
;
; existence and protection for writing
IF (FILE_TEST(iodirout, /DIRECTORY, /WRITE) EQ 0) THEN BEGIN
    msg = 'eee : the directory' + iodirout  + ' was not found.'
    ras = report(msg)
    STOP
ENDIF
;
d1=19881001 & d2=20101231
;
; build d2m filename
filename_d2m='erai_d2m_19890101_20091231_oafluxgrid.nc'
;
; check if this file exists
fullfilename_d2m = isafile(iodirout + filename_d2m, NEW=0, /MUST_EXIST)
IF fullfilename_d2m[0] EQ '' THEN BEGIN
   msg = 'eee : the file ' + fullfilename_d2m + ' was not found.'
   ras = report(msg)
   STOP
ENDIF
;
; build t2m filename
filename_t2m='erai_t2m_19890101_20091231_oafluxgrid.nc'
;
; check if this file exists
fullfilename_t2m = isafile(iodirout + filename_t2m, NEW=0, /MUST_EXIST)
IF fullfilename_t2m[0] EQ '' THEN BEGIN
   msg = 'eee : the file ' + fullfilename_t2m + ' was not found.'
   ras = report(msg)
   STOP
ENDIF
;
; build msl filename
filename_msl='erai_msl_19890101_20091231_oafluxgrid.nc'
;
; check if this file exists
fullfilename_msl = isafile(iodirout + filename_msl, NEW=0, /MUST_EXIST)
IF fullfilename_msl[0] EQ '' THEN BEGIN
   msg = 'eee : the file ' + fullfilename_msl + ' was not found.'
   ras = report(msg)
   STOP
ENDIF
;
; build output filename
filename_out = 'q2m_erai_19890101_20091231_oafluxgrid.nc'
fullfilename_out = iodirout + filename_out
; in order to avoid unexpected overwritten
IF (FILE_TEST(fullfilename_out) EQ 1) THEN BEGIN
   msg = 'eee : the file ' + fullfilename_out  + ' already exists.'
   ras = report(msg)
   STOP
ENDIF
;
; reading erai dew point temperature
initncdf, fullfilename_d2m
td=read_ncdf("d2m", d1,d2, file=fullfilename_d2m,/nostr)

; reading erai air temperature
initncdf, fullfilename_t2m
t=read_ncdf("t2m", d1,d2, file=fullfilename_t2m,/nostr)
tt=time &jpt=n_elements(time)
help, t, td

;;since the t2m and d2m are already in K, no need for conversion

e=es0*exp((25.e5/461.5)*((1/273.15)-(1/td)))
es=es0*exp((25.e5/461.5)*((1/273.15)-(1/t)))

rh=(e/es)*100

;; conversion of relative humidity to sp. humidity
;; Ref.1 -  Gill, Appendix 4,
;; Ref.2 - http://efdl.cims.nyu.edu/project_aomip/forcing_data/atmosphere/humidity.html

t=t-273.15

initncdf, fullfilename_msl
P=read_ncdf("msl", d1, d2, file=fullfilename_msl,/nostr)
help, P
q2m=rh_to_spechum(rh,t,P)

;writing field
ncfile='!' + fullfilename_out
time=timegen(7670, units='days', start=julday(1,1,1989)) & jpt=n_elements(time)
cda0=string(jul2date(time(0)),format='(i8.8)')
cda1=string(jul2date(time(jpt-1)),format='(i8.8)')

tt=time-julday(1,1,1950,00,00,00)
xlon=reform(glamt(*,0) ) & ylat=reform(gphit(0,*))
valmask=1.e20

lon_attr={units:'degrees_east',long_name:'Longitude'}
lat_attr={units:'degrees_north',long_name:'Latitude'}
q2m_attr={units:'kg/kg',missing_value:valmask,long_name:'Surface specific humidity at 2m ',short_name:'q2m',axis:'TYX'}
time_attr={units:'days since 1950-01-01 00:00:00',long_name:'Time axis',time_origin:' 1950-JAN-01 00:00:00'}
globattr={source:'Surface specific humidity at 2m calculated from dew point temperature',timerange:cda0+' - '+cda1}

ncfields = 'q2m[longitude,latitude,time]=q2m:q2m_attr; ' $
                      + 'longitude[]=xlon:lon_attr; ' $
                      + 'latitude[]=ylat:lat_attr; ' $
                      + 'tt[*time]=tt:time_attr ' $
                      + ' @ globattr'

@ncdf_quickwrite
end