/usr/share/ncarg/nclscripts/csm/crop.ncl is in libncarg-data 6.4.0-9.
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The actual contents of the file can be viewed below.
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; Reference:
;
; Richard G. Allen, Luis S. Pereira, Dirk Raes & Martin Smith (1998)
; Crop Evapotranspiration – Guidelines for Computing Crop Water Requirements
; FAO Irrigation and drainage paper 56. Rome, Italy: Food and Agriculture Organization of the United Nations.
; ISBN 92-5-104219-5.
; http://www.fao.org/docrep/X0490E/x0490e00.htm#Contents
; In particular: Chapters 3 & 4
; http://www.fao.org/docrep/X0490E/x0490e07.htm#chapter 3 meteorological data
; http://www.fao.org/docrep/X0490E/x0490e08.htm#chapter 4 determination of eto
; ----------------------------------------------------------------------------------
;ET is the loss of water by evaporation from both the soil and plant (evaporation + transpiration)
;
;- ET depends on several factors: solar radiation, air temperature, air vapour pressure, wind speed and surface area.
;- Potential ET (PET) is the maximum rate of ET given the current conditions. PET is not a constant value but
; varies with field conditions: it is the rate of water loss if water supply is not limiting. But often
; water supply is limited, so water loss is often smaller than PET. The rate at which water is being lost
; is known as actual ET (AET).
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("getMidMonDay")
function getMidMonDay(time:numeric)
;
; utility function
; The input 'time' (seconds/hours/days since ...") has the middle of the month
; This returns the (*approximate*) 'middle day' of the current month as an integer
; "Approximate" because day 15 is used for all months ...
; rather than 14 (Feb), 14.5 (Leap year Feb) or 15.5 (31 day months).
; This is more than adequate.
local date, yyyy, mm, dd, jday
begin
date = cd_calendar(time, 0)
yyyy = toint(date(:,0))
mm = toint(date(:,1))
dd = conform(mm, 15, -1) ; approx mid month
jday = day_of_year(yyyy, mm, dd)
copy_VarCoords(time, jday)
jday@long_name = "mid-month day of current year"
return(jday)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("getMidMonDay_yyyymm")
function getMidMonDay_yyyymm(yyyymm:numeric)
;
; utility function
; This returns the (approximate) 'middle day' of the current month as an integer
; "Approximate" because ay 15 is used for all months ...
; rather than 14 (Feb), 14.5 (Leap year Feb) or 15.5 (31 day months).
; This is more than adequate.
local date, yyyy, mm, dd, jday
begin
yyyy = toint(yyyymm/100)
mm = toint(yyyymm - (yyyy*100))
dd = conform(mm, 15, -1) ; approx mid month
jday = day_of_year(yyyy, mm, dd)
copy_VarCoords(time, jday)
jday@long_name = "mid-month day of current year"
return(jday)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; isscalar made a builtin function in 6.4.0
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
;;undef("isscalar")
;;function isscalar(x)
;;;
;;; utility function
;;; is 'x' a scalar quantity: here 'scalar' means rank=1 & size=1
;;local dimx, rankx
;;begin
;; dimx = dimsizes(x)
;; rankx = dimsizes(dimx)
;; if (rankx.eq.1 .and. dimx.eq.1) then
;; return(True)
;; else
;; return(False)
;; end if
;;end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("satvpr_temp_fao56")
function satvpr_temp_fao56(t:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Estimate saturation vapor pressure (kPa): EQN 11; Chapter 3
;
; Note_1: If t=t_dew then this calculates actual vapor pressure EQN 14 (ea)
; Note_2: if any (t.le.0) svp is undefined ==> _FillValue
; Do *not* return 0.0 because other eqns take log(satvpr)
; t could have no _FillValue BUT values <0 hence svp@_FillValue
local svp, tc, tFill
begin
if (iounit(0).lt.0 .or. iounit(0).gt.2) then ; iounit error check
print("satvpr_temp_fao56: unrecognized iounit argument: iounit="+iounit)
exit
end if
if (isatt(t,"_FillValue")) then
tFill = t@_FillValue
else
tFill = 1e20 ; t has no _FillValue BUT there could b t.le.0
end if
if (iounit(0).eq.0) then ; degC
svp = where(t.gt.0, 0.6108*exp((17.27*t)/(t+237.3)), tFill )
else if (iounit(0).eq.1) then ; degK
tc = t-273.16
svp = where(tc.gt.0, 0.6108*exp((17.27*tc)/(tc+237.3)), tFill )
else if (iounit(0).eq.2) then ; F
tc = (t-32)*0.5555556
svp = where(tc.gt.0, 0.6108*exp((17.27*tc)/(tc+237.3)), tFill )
end if ; F
end if ; K
end if ; C
svp@long_name = "saturation vapor pressure"
if (iounit(1).eq.0) then
svp = svp*10
svp@units = "hPa"
else if (iounit(1).eq.1) then
svp = svp*1000
svp@units = "Pa"
else if (iounit(1).eq.2) then
svp@units = "kPa"
end if ; kPa
end if ; Pa
end if ; hPa
svp@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
svp@info = "FAO 56; EQN 11; satvpr_temp_fao56"
if (any(t.le.0) .and. .not.isatt(svp,"_FillValue") ) then
svp@_FillValue = tFill
end if
copy_VarCoords(t, svp)
return(svp)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("satvpr_mean_fao56")
function satvpr_mean_fao56(tmin:numeric, tmax:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Estimate 'mean' saturation vapor pressure (kPa): EQN 12; Chapter 3
;
; Note_1: If t=t_dew then this calculates actual vapor pressure EQN 14 (ea)
; Note_2: if any (t.le.0) svp is undefined ==> _FillValue
; Do *not* return 0.0 because other eqns take log(satvpr)
; t could have no _FillValue BUT values <0 hence svp@_FillValue
local svp
begin
svp = (satvpr_temp_fao56(tmin, iounit) + satvpr_temp_fao56(tmax, iounit))*0.5
svp@long_name = "mean saturation vapor pressure"
svp@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
svp@info = "FAO 56; EQN 12; satvpr_mean_fao56"
copy_VarCoords(tmin, svp)
return(svp)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("satvpr_tdew_fao56")
function satvpr_tdew_fao56(tdew:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Compute actual saturation vapor pressure (kPa): EQN 14; Chapter 3
; This is the same code as 'satvpr_temp_fao56'
; Just different 'long_name' and 'info' attributes
local actsvp
begin
actsvp = satvpr_temp_fao56(tdew, iounit)
actsvp@long_name = "actual saturation vapor pressure via Tdew"
actsvp@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
actsvp@info = "FAO 56; EQN 14; satvpr_tdew_fao56"
return(actsvp)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("actvpr_tmin_fao56")
function actvpr_tmin_fao56(tmin:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Estimate actual vapor pressure (kPa) using Tmin: EQN 48; Chapter 3
; This uses the same code as 'satvpr_temp_fao56'
; Just different 'long_name' and 'info' attributes
;
; This assumes that the dew point is near the minimum temperature.
;
; NOTE:
; (a) In well watered areas Tdew >> Tmin
; (b) In arid areas Tmin >> Tdew.
; In these areas (Tmin-2) or (Tmin-3) might be better.
;
local act
begin
act = satvpr_temp_fao56(tmin, iounit)
act@long_name = "actual vapor pressure"
act@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
act@info = "FAO 56; EQN 48; actvpr_tmin_fao56"
return(act)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("tdew_actvpr_fao56")
function tdew_actvpr_fao56(actvpr:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Compute dew point temperature from actual vapor pressure via EQN 3-11; Annex 3
; actvpr - actual vapor pressure
local con, tdew, units
begin
if (iounit(0).eq.0) then ; hPa ... convert to kPa
con = 0.1
else if (iounit(0).eq.1) then ; Pa ... convert to kPa
con = 0.001
else if (iounit(0).eq.2) then ; already kPa
con = 1.0
end if
end if
end if
tdew = (116.91+237.3*log(con*actvpr))/(16.78-log(con*actvpr))
if (iounit(1).eq.0) then
units = "degC"
else if (iounit.eq.1) then
tdew = tdew+273.16
units = "degK"
else if (iounit.eq.2) then
tdew = 1.8*tdew+32
units = "F"
end if
end if
end if
tdew@long_name = "Estimated dew point temperature"
tdew@units = units
tdew@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
tdew@fao56_info= "FAO 56; Annex: EQN 3-11"
tdew@NCL = "tdew_actvpr_fao56"
copy_VarCoords(actvpr, tdew)
return(tdew)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("prsatm_z_fao56")
function prsatm_z_fao56(z:numeric, P0[1]:numeric, z0[1]:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; EQN 7, Chapter 3; This assumes 20C for a standard atmosphere
;
local con, tk0, prs, conP0
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; unit error check
print("prsatm_z_fao56: unrecognized iounit argument: iounit="+iounit)
exit
end if
con = 5.26
tk0 = 293.0 ; 273+20
conP0 = P0
if (iounit(0).eq.0) then
conP0 = conP0*0.1 ; hPa -> kPa
else
if (iounit(0).eq.1) then
conP0 = conP0*0.001 ; Pa -> kPa
end if
end if
prs = conP0*((tk0-0.0065*z)/tk0)^con
prs@long_name = "atmospheric pressure"
prs@units = "kPa"
prs@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
prs@info = "FAO 56; Chapter 3, EQN 7; prsatm_z_fao56"
copy_VarCoords(z, prs)
if (iounit(1).eq.0) then
prs = (/ prs*10.0 /) ; kPa -> hPa
prs@units = "hPa"
else
if (iounit(1).eq.1) then
prs = (/ prs*1000.0 /) ; kPa -> Pa
prs@units = "Pa"
end if
end if
return(prs)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("prsatm_tz_fao56")
function prsatm_tz_fao56(t:numeric, z:numeric, P0[1]:numeric, z0[1]:numeric, iounit[3]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; EQN 3-2; Annex 3 ... requires temperature
;
local R, g, a, con, tk0, prs, conP0
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; unit error check
print("prsatm_tz_fao56: unrecognized iounit argument: iounit="+iounit)
exit
end if
R = 287.04 ; J/(kg-degK) <==> J/(kg-degC)
g = 9.807 ; m/2
a = 0.0065 ; degK/m <==> degC/m
con = g/(a*R) ; exponent
conP0= P0
if (iounit(1).eq.0) then
conP0 = conP0*0.1 ; hPa -> kPa
else
if (iounit(1).eq.1) then
conP0 = conP0*0.001 ; Pa -> kPa
end if
end if
if (iounit(0).eq.0) then
tk0 = 273.16 + t ; degC -> degK
prs = conP0*( (tk0-a*(z-z0))/tk0 )^con
else if (iounit(0).eq.1) then ; degK
prs = conP0*( (t-a*(z-z0))/t )^con
else if (iounit(0).eq.2) then
tk0 = 273.16 + (t-32)*0.555556 ; degF -> degK
prs = conP0*( (tk0-a*(z-z0))/tk0 )^con
end if
end if
end if
prs@long_name = "atmospheric pressure"
prs@units = "kPa"
prs@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
prs@info = "FAO 56; Annex 3: EQN 3-2; prsatm_tz_fao56"
copy_VarCoords(t, prs)
if (iounit(2).eq.0) then
prs = (/ prs*10.0 /) ; kPa -> hPa
prs@units = "hPa"
else
if (iounit(2).eq.1) then
prs = (/ prs*1000.0 /) ; kPa -> Pa
prs@units = "Pa"
end if
end if
return(prs)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("u2_fao56")
function u2_fao56(uz:numeric, z:numeric, wunit[2]:integer)
; Compute 2-meter height wind
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; http://www.fao.org/docrep/x0490e/x0490e0j.htm#annex%202.%20meteorological%20tables
local u2, con
begin
con = 1.0 ; m/s
if (wunit(0).eq.1) then
con = 0.277778 ; km/hr => m/s
else if (wunit(0).eq.2) then
con = 0.44704 ; mph => m/s
end if
end if
u2 = (uz*con)*(4.87/(log(67.8*z-5.42)))
u2@long_name = "Estimated 2-meter wind speed"
u2@units = "m/s"
u2@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
u2@info = "FAO 56; EQN 47; u2_fao56"
copy_VarCoords(uz, u2)
if (wunit(1).eq.1) then
u2 = (/ (u2/0.277778) /) ; m/s => km/hr
u2@units = "m/s"
else if (wunit(1).eq.2) then
u2 = (/ (u2/0.44704) /) ; m/s => mph
u2@units = "mph"
end if
end if
return(u2)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("rhum_fao56")
function rhum_fao56(actvpr:numeric, satvpr:numeric,rhunit [1]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Compute relative humidity
local rhum, rhum_units
begin
if (any(actvpr.lt.0.0) .or. any(satvpr.le.0.0)) then
print("rhum_fao56: actvpr<0 or satvpr<=0")
exit
end if
rhum = ( actvpr/satvpr)
rhum@long_name = "Relative Humidity"
if (rhunit.eq.0) then
rhum = rhum*100
rhum@units = "%"
else
rhum@units = "fraction"
end if
rhum@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
rhum@info = "FAO 56; EQN 10; rhum_fao56"
copy_VarCoords(actvpr, rhum)
return(rhum)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("satvpr_slope_fao56")
function satvpr_slope_fao56(t:numeric, iounit[2]:integer)
; Compute slope (kPa/C) of saturation vapor pressure (svp) curve; EQN 13; Chapter 3
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; See: http://www.fao.org/docrep/x0490e/x0490e0j.htm#annex 2. meteorological tables
;
local satvpr_slope, tc, tFill
begin
if (iounit(0).lt.0 .or. iounit(0).gt.2) then ; tunit error check
print("satvpr_slope_fao56: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
exit
end if
if (iounit(1).lt.0 .or. iounit(1).gt.2) then ; tunit error check
print("satvpr_slope_fao56: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
exit
end if
if (isatt(t,"_FillValue")) then
tFill = t@_FillValue
else
tFill = 1e20
end if
if (iounit(0).eq.0) then ; degC
satvpr_slope = where(t.gt.0, 4096*(0.6108*exp((17.27*t)/(t+237.3))/(t+237.3)^2), tFill)
else
if (iounit(0).eq.1) then ; degK
tc = t-273.16
else ; F
tc = (t-32)*0.5555556
end if
satvpr_slope = where(tc.gt.0, 4096*(0.6108*exp((17.27*tc)/(tc+237.3))/(tc+237.3)^2), tFill)
end if
satvpr_slope@long_name = "slope saturation vapor pressure curve"
satvpr_slope@units = "kPa/C"
satvpr_slope@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
satvpr_slope@info = "FAO 56; EQN 13; satvpr_slope_fao56"
; if specified, change units
if (iounit(1).eq.0) then
satvpr_slope = (/ satvpr_slope*10 /) ; kPa=>hPa
satvpr_slope@units = "hPa/C"
end if
if (iounit(1).eq.1) then
satvpr_slope = (/ satvpr_slope*1000 /) ; kPa=>Pa
satvpr_slope@units = "Pa/C"
end if
if (.not.isatt(satvpr_slope,"_FillValue") .and. any(satvpr_slope.eq.tFill) ) then
satvpr_slope@_FillValue = tFill
end if
copy_VarCoords(t, satvpr_slope)
return( satvpr_slope )
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("actvpr_rhmean_fao56")
function actvpr_rhmean_fao56(tmin:numeric, tmax:numeric, rhmean:numeric, iounit[2]:integer)
;
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; http://www.fao.org/docrep/x0490e/x0490e0j.htm#annex 2. meteorological tables
; Compute 'actual' saturation vapor pressure with mean relative humidity (%): EQN 19
;
; tmin, tmax - min/max temperature (C or K)
; rmean - mean relative humidity (%)
;
local conmean, avp_rhmean, tc, tcx, tcn, tFill, tCrit, tunit, punit \
, dim_tmin, dim_tmax, dim_rhmn, rnk_tmin, rnk_tmax, rnk_rhmn
begin
if (iounit(0).lt.0 .or. iounit(0).gt.2) then ; tunit error check
print("actvpr_rhmean_fao56: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
exit
end if
if (iounit(1).lt.0 .or. iounit(1).gt.2) then ; tunit error check
print("actvpr_rhmean_fao56: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
exit
end if
tCrit = 0
tunit = iounit(0)
punit = iounit(1)
dim_tmin = dimsizes(tmin) ; size(s)
dim_tmax = dimsizes(tmax)
dim_rhmn = dimsizes(rhmean)
rnk_tmin = dimsizes(dim_tmin) ; rank
rnk_tmax = dimsizes(dim_tmax)
rnk_rhmn = dimsizes(dim_rhmn)
if (.not.(rnk_tmin.eq.rnk_tmax .and. rnk_tmin.eq.rnk_rhmn)) then
print("actvpr_rhmean_fao56: rank mismatch on input arguments")
print(" rnk_tmin="+rnk_tmin)
print(" rnk_tmax="+rnk_tmax)
print(" rnk_rhmn="+rnk_rhmn)
exit
end if
if (.not.(all(dim_tmin.eq.dim_tmax) .and. all(dim_tmin.eq.dim_rhmn))) then
print("actvpr_rhmean_fao56: dimension size mismatch on input arguments")
print(" dim_tmin="+dim_tmin+" dim_tmax="+dim_tmax+" dim_rhmn="+dim_rhmn)
exit
end if
if (isatt(tmin,"_FillValue")) then
tFill = tmin@_FillValue
else
tFill = 1e20
end if
if (all(rhmean.le.1)) then
conmean = rhmean/2.0 ; must be fractional and not %
else
conmean = rhmean/200.0
end if
if (tunit.eq.0) then ; degC; use input array
avp_rhmean = where(tmin.gt.tCrit \
,conmean*(satvpr_temp_fao56(tmax,iounit)+satvpr_temp_fao56(tmin,iounit)) \
,tFill )
avp_rhmean = where(tmin.le.tCrit .and. tmax.gt.tCrit \ ; Should this be done?
,conmean*(satvpr_temp_fao56(tmax,iounit) ) \ ; satvpr_mean_fao56(0,0)=0.0
,avp_rhmean )
avp_rhmean = where(avp_rhmean.lt.0.0, tFill, avp_rhmean)
else ; create and use temporary arrays
if (tunit.eq.1) then ; degK
tcn = tmin-273.16 ; convert to degC
tcx = tmax-273.16
else ; Farenheit
tcn = (tmin-32)*0.5555556 ; convert to degC
tcx = (tmax-32)*0.5555556
end if
avp_rhmean = where(tcn.gt.tCrit \
,conmean*(satvpr_temp_fao56(tcx,(/0,punit/))+satvpr_temp_fao56(tcn,(/0,punit/))) \
,tFill )
avp_rhmean = where(tcn.le.tCrit .and. tcx.gt.tCrit \ ; Should this be done?
,conmean*(satvpr_temp_fao56(tcx,(/0,punit/)) ) \ ; satvpr_mean_fao56(0,0)=0.0
,avp_rhmean )
avp_rhmean = where(avp_rhmean.lt.0.0, tFill, avp_rhmean)
end if
avp_rhmean@long_rhmean_name = "actual saturation vapor pressure"
avp_rhmean@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
avp_rhmean@info = "FAO 56; EQN 19: min/max t; mean rh; actvpr_rhmean_fao56"
if (punit.eq.0) then
avp_rhmean@units = "hPa"
else if (punit.eq.1) then
avp_rhmean@units = "Pa"
else if (punit.eq.2) then
avp_rhmean@units = "kPa"
end if ; kPa
end if ; Pa
end if ; hPa
if (.not.isatt(avp_rhmean,"_FillValue") .and. any(avp_rhmean.eq.tFill) ) then
avp_rhmean@_FillValue = tFill
end if
copy_VarCoords(tmin, avp_rhmean)
return( avp_rhmean )
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("actvpr_mnmx_fao56")
function actvpr_mnmx_fao56(tmin:numeric, tmax:numeric, rhmin:numeric, rhmax:numeric, iounit[2]:integer)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; http://www.fao.org/docrep/x0490e/x0490e0j.htm#annex 2. meteorological tables
; Compute 'actual' saturation vapor pressure with min/max relative humidity (%): EQN 17
; tmin, tmax - min/max temperature (C)
; rhmin, rhmax - min/max relative humidity (%)
local tunit, punit, conmin, conmax, avp_mnmx, tc, tcx, tcn, tFill \
, dim_tmin, dim_tmax, dim_rhmn, dim_rhmx, rnk_tmin, rnk_tmax, rnk_rhmn, rnk_rhmx
begin
tunit = iounit(0)
punit = iounit(1)
; check input
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; tunit error check
print("actvpr_mnmx_fao56: unrecognized iounit argument: iounit="+iounit)
exit
end if
dim_tmin = dimsizes(tmin) ; size(s)
dim_tmax = dimsizes(tmax)
dim_rhmn = dimsizes(rhmin)
dim_rhmx = dimsizes(rhmax)
rnk_tmin = dimsizes(dim_tmin) ; rank
rnk_tmax = dimsizes(dim_tmax)
rnk_rhmn = dimsizes(dim_rhmn)
rnk_rhmx = dimsizes(dim_rhmx)
if (.not.(rnk_tmin.eq.rnk_tmax .and. rnk_tmin.eq.rnk_rhmn)) then
print("actvpr_rhmean_fao56: rank mismatch on input arguments")
print(" rnk_tmin="+rnk_tmin)
print(" rnk_tmax="+rnk_tmax)
print(" rnk_rhmn="+rnk_rhmn)
print(" rnk_rhmx="+rnk_rhmx)
exit
end if
if (.not.(all(dim_tmin.eq.dim_tmax) .and. \
all(dim_tmin.eq.dim_rhmn) .and. \
all(dim_tmin.eq.dim_rhmx))) then
print("actvpr_mnmx_fao56: dimension size mismatch on input arguments")
print(" dim_tmin="+dim_tmin+" dim_tmax="+dim_tmax)
print(" dim_rhmn="+dim_rhmn+" dim_rhmx="+dim_rhmx)
exit
end if
if (isatt(tmin,"_FillValue")) then
tFill = tmin@_FillValue
else
tFill = 1e20
end if
if (all(rhmin.le.1)) then
conmin = rhmin/2.0
else
conmin = rhmin/200.0
end if
if (all(rhmax.le.1)) then
conmax = rhmax/2.0
else
conmax = rhmax/200.0
end if
; note the (min*max) and (max*min) 'cross-product'
if (tunit.eq.0) then
avp_mnmx = where(tmin.gt.0 \
,conmin*satvpr_temp_fao56(tmax,iounit) + conmax*satvpr_temp_fao56(tmin,iounit) \
,tFill)
else
if (tunit.eq.1) then ; degK
tcn = tmin-273.16 ; convert to degC
tcx = tmax-273.16
else ; Farenheit
tcn = (tmin-32)*0.5555556 ; convert to degC
tcx = (tmax-32)*0.5555556
end if
avp_mnmx = where(tcn.gt.0 \
,conmin*satvpr_temp_fao56(tcx,(/0,punit/)) + conmax*satvpr_temp_fao56(tcn,(/0,punit/)) \
,tFill)
end if
avp_mnmx@long_name = "actual saturation vapor pressure"
avp_mnmx@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
avp_mnmx@info = "FAO 56; EQN 17: min/max t & rh; actvpr_mnmx_fao56"
if (.not.isatt(avp_mnmx,"_FillValue") .and. any(avp_mnmx.eq.tFill) ) then
avp_mnmx@_FillValue = tFill
end if
if (punit.eq.0) then
avp_mnmx@units = "hPa"
else if (punit.eq.1) then
avp_mnmx@units = "Pa"
else if (punit.eq.2) then
avp_mnmx@units = "kPa"
end if ; kPa
end if ; Pa
end if ; hPa
copy_VarCoords(tmin, avp_mnmx)
return( avp_mnmx )
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("daylight_fao56")
function daylight_fao56(jday[*]:numeric, lat:numeric)
; Compute maximum day light hours; EQN 34
; http://www.fao.org/docrep/X0490E/x0490e07.htm
;
; **For abs(lat) > 55 the eqns have limited validity**
; The reason for the argtst and argval variables is an
; arbitrary attempt to minimize the effect poleward of (say) 55
local pi, pi2, con, rad, sdec, sdec, ws, pi2yr, latrad, ntim,nlat, mlon, arg \
, daylightmax, DAYLIGHTMAX, argtst, argval, FillValue
begin
if (typeof(lat).eq."double") then
pi = 4.0d*atan(1.0d)
else
pi = 4.0*atan(1.0)
end if
; constants
pi2 = 2*pi
rad = pi/180
pi2yr = pi2/365
latrad = lat*rad
con = (24/pi)
; dimensional stuff
ntim = dimsizes(jday) ; # time time steps
dimlat = dimsizes(lat)
ranklat= dimsizes(dimlat)
if (ranklat.ge.3) then
print("daylight_fao56: latitude rank exceeds 2: FATAL: ranklat="+ranklat)
exit
end if
nlat = dimlat(0)
if (ranklat.eq.2) then
mlon = dimlat(1)
end if
sdec = 0.409*sin(pi2yr*jday - 1.39) ; eq 24 [ntim]
argtst = 1 ; arbitrary value based on heuristic test
argval = 0.99999 ; arbitrary value to allow completetion
if (nlat.eq.1 .and. ntim.eq.1) then ; both input are scalar
arg := -tan(latrad)*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad)*tan(sdec)) ; eq 25 [ntim]
daylightmax = con*ws ; eq 34
else if (ranklat.eq.1) then
daylightmax = new( (/ntim,nlat/), typeof(pi), "No_FillValue")
do nl=0,nlat-1
arg = -tan(latrad(nl))*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad(nl))*tan(sdec)) ; eq 25 [ntim]
daylightmax(:,nl) = con*ws ; eq 34
end do
; handle meta data
copy_VarCoords(jday, daylightmax(:,0))
copy_VarCoords( lat, daylightmax(0,:))
else if (ranklat.eq.2) then
daylightmax = new( (/ntim,nlat,mlon/), typeof(pi), "No_FillValue")
do nl=0,nlat-1
do ml=0,mlon-1
arg = -tan(latrad(nl,ml))*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad(nl,ml))*tan(sdec)) ; eq 25 [ntim]
daylightmax(:,nl) = con*ws ; eq 34
end do
end do
; handle meta data
copy_VarCoords(jday, daylightmax(:,0,0))
copy_VarCoords( lat, daylightmax(0,:,:))
end if
end if
end if
; Change NaNs ==> 0
FillValue = totype(1e20, typeof(daylightmax))
zero = totype( 0, typeof(daylightmax))
if (any(daylightmax.lt.0)) then
daylightmax@_FillValue = FillValue
daylightmax = where(daylightmax.lt.zero, daylightmax@_FillValue, daylightmax)
end if
if (any(isnan_ieee(daylightmax))) then
daylightmax = where (isnan_ieee(daylightmax), daylightmax@_FillValue , daylightmax)
end if
daylightmax@long_name = "maximum day light hours: FAO_56"
daylightmax@units = "hours/day"
daylightmax@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
daylightmax@info = "FAO 56; EQN 34; daylight_fao56"
; force return of type 'float'
if (typeof(daylightmax).eq."float") then
return(daylightmax)
else
DAYLIGHTMAX = tofloat(daylightmax)
copy_VarMeta(daylightmax, DAYLIGHTMAX)
return(DAYLIGHTMAX)
end if
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef ("radext_fao56")
function radext_fao56(jday[*]:integer, lat:numeric, ounit[1]:integer)
; Compute extra terrestrial radiation; EQN 21 ; return as type 'float'
; http://www.fao.org/docrep/X0490E/x0490e07.htm
;
; jday - day of year
; lat - degrees_{north/south}; can be a scalar, [*], or [*][*]
; ***For abs(lat) > 55 the eqns have limited validity ***
; The reason for the argtst and argval variables is an
; arbitrary attempt to minimize the effect poleward of (say) 55
;
local pi, pi2, con, mnday, rad, gsc, rdist, ntim, nl, dimlat, ranklat \
, sdec, s, pi2yr, latrad, radextday, nlat, mlon, arg, zero, RADEXTDAY \
, argtst, argval, FillValue
begin
if (typeof(lat).eq."double") then
pi = 4.0d*atan(1.0d)
gsc = 0.0820d ; solar constant: MJ/(m2-min)
else
pi = 4.0*atan(1.0)
gsc = 0.0820 ; solar constant: MJ/(m2-min)
end if
; constants
pi2 = 2*pi
rad = pi/180
mnday = 1440 ; minutes/day (24*60)
; dimensional stuff
ntim = dimsizes(jday) ; # time time steps
dimlat = dimsizes(lat)
ranklat= dimsizes(dimlat)
if (ranklat.ge.3) then
print("radext_fao56: latitude rank exceeds 2: FATAL: ranklat="+ranklat)
exit
end if
nlat = dimlat(0)
if (ranklat.eq.2) then
mlon = dimlat(1)
end if
con = (mnday/pi) ; units conversation
pi2yr = pi2/365
latrad = lat*rad ; [nlat] or [nlat,mlon]
rdist = 1 + 0.033*cos(pi2yr*jday) ; eq 23 [ntim]
sdec = 0.409*sin(pi2yr*jday - 1.39) ; eq 24 [ntim]
argtst = 1 ; arbitrary value based on heuristic test
argval = 0.99999 ; arbitrary value to allow completetion
if (nlat.eq.1 .and. ntim.eq.1) then ; both input are scalar
arg := -tan(latrad)*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad(nl))*tan(sdec)) ; eq 25 [ntim]
radextday = con*gsc*rdist*(ws*sin(latrad)*sin(sdec) \
+cos( latrad)*cos(sdec)*sin(ws) )
else if (ranklat.eq.1) then
radextday = new( (/ntim,nlat/), typeof(pi) , "No_FillValue")
do nl=0,nlat-1
arg := -tan(latrad(nl))*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad(nl))*tan(sdec)) ; eq 25 [ntim]
radextday(:,nl) = con*gsc*rdist*(ws*sin(latrad(nl))*sin(sdec) \
+cos( latrad(nl))*cos(sdec)*sin(ws) )
end do
; handle meta data
copy_VarCoords(jday, radextday(:,0))
copy_VarCoords( lat, radextday(0,:)) ; this does not seem to work!!!
if (.not.isdimnamed(radextday,1) .and. isdimnamed(lat,0)) then
radextday!1 = lat!0 ; fix above issue
end if
else if (ranklat.eq.2) then
radextday = new( (/ntim,nlat,mlon/), "float", "No_FillValue")
do nl=0,nlat-1
do ml=0,mlon-1
arg := -tan(latrad(nl,ml))*tan(sdec)
arg = where(arg.lt.-argtst, -argval, arg)
arg = where(arg.gt. argtst, argval, arg)
ws = acos(arg) ; acos(-tan(latrad(nl,ml))*tan(sdec)) ; eq 25 [ntim]
radextday(:,nl,ml) = con*gsc*rdist*(ws*sin(latrad(nl,ml))*sin(sdec) \
+cos( latrad(nl,ml))*cos(sdec)*sin(ws) )
end do
end do
; handle meta data
copy_VarCoords(jday, radextday(:,0,0))
copy_VarCoords( lat, radextday(0,:,:))
end if ; ranklat.eq.2
end if ; ranklat.eq.1
end if ; scalar; nlat.eq.1 .and. ntim.eq.1
; Change NaNs ==> _FillValue
FillValue = totype(1e20, typeof(radextday))
zero = totype( 0 , typeof(radextday))
if (any(radextday.lt.0)) then
radextday@_FillValue = FillValue
radextday = where(radextday.lt.zero, radextday@_FillValue, radextday)
end if
if (any(isnan_ieee(radextday))) then
radextday = where (isnan_ieee(radextday), radextday@_FillValue , radextday)
end if
; Units
ra_unit = "MJ/(m2-day)" ; ounit=1
if (ounit.eq.0) then
radextday = (/ radextday*0.408 /) ; MJ/(m2-day) ==> mm/day
ra_unit = "mm/day"
end if
if (ounit.eq.2) then
radextday = (/ radextday*11.574/) ; MJ/(m2-day) ==> W/m2
ra_unit = "W/m2"
end if
radextday@long_name = "extra terrestrial radiation: FAO_56"
radextday@units = ra_unit
radextday@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
radextday@info = "FAO 56; EQN 21; radext_fao56"
;;if (isatt(radextday,"jday")) then
;; delete(radextday@jday)
;;end if
;;if (isatt(radextday,"time")) then
;; delete(radextday@time)
;;end if
; force return of type 'float'
if (typeof(radextday).eq."float") then
return(radextday)
else
RADEXTDAY = tofloat(radextday)
copy_VarMeta(radextday, RADEXTDAY)
return(RADEXTDAY)
end if
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef ("radsol_fao56")
function radsol_fao56(radext:numeric, sunhrx:numeric, sunhr:numeric, iounit[2]:integer, opt[1]:logical)
;
; Similar to 'radsol2_fao56 except that the arguments 'radext' and 'sunhrx' are input
; Avoids repetitive computations
;
; Compute solar radiation; EQN 35
; http://www.fao.org/docrep/X0490E/x0490e07.htm
;=======
; This is the 'Angstrom Formula' which relates solar radiation to extraterrestrial
; radiation and relative sunshine duration.
;
local as, bs, units, radsol, cunits, conrad
begin
as = 0.25 ; default; Chap 3, pg 23
bs = 0.50
if (opt .and. isatt(opt, "as")) then
as := opt@as
end if
if (opt .and. isatt(opt, "bs")) then
bs := opt@bs
end if
if (opt .and. isatt(opt, "as_bs") .and. dimsizes(opt@as_bs).eq.2) then
as := opt@as_bs(0)
bs := opt@as_bs(1)
end if
if (iounit(0).eq.0) then
conrad = 2.45068 ; mm/day => MJ/(m2-day)
end if
if (iounit(0).eq.1) then
conrad = 1.00 ; MJ/(m2-day)
end if
if (iounit(0).eq.2) then
conrad = 0.0864 ; W/m2 => MJ/(m2-day)
end if
; EQN 35; Rs
if (all(sunhrx.gt.0)) then
radsol = (as+bs*(sunhr/sunhrx))*(radext*conrad)
else ; avoid division by zero
sunx = where(sunhrx.le.0, 1e20, sunhrx)
sunx@_FillValue = 1e20
radsol = (as+bs*(sunhr/sunx))*(radext*conrad)
radsol = where(ismissing(radsol), 0, radsol)
end if
; EQN 35; Rs
;;;if (iounit(0).eq.0) then
;;; radsol = (as+bs*(sunhr/sunhrx))*(radext*2.45068) ; mm/day => MJ/(m2-day)
;;;else if (iounit(0).eq.1) then
;;; radsol = (as+bs*(sunhr/sunhrx))*radext ; MJ/(m2-day)
;;;else if (iounit(0).eq.2) then
;;; radsol = (as+bs*(sunhr/sunhrx))*(radext*0.0864) ; W/m2 => MJ/(m2-day)
;;; end if
;;; end if
;;;end if
if (iounit(1).eq.0) then
radsol = (/ radsol*0.408 /) ; MJ/(m2-day) => mm/day
units = "mm/day"
end if
if (iounit(1).eq.1) then
units = "MJ/(m2-day)" ; ounit=1
end if
if (iounit(1).eq.2) then
radsol = (/ radsol*11.574 /) ; MJ/(m2-day) ==> W/m2
units = "W/m2"
end if
radsol@long_name = "solar radiation: FAO_56"
radsol@units = units
radsol@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
radsol@info = "FAO 56; EQN 35; radsol_fao56"
radsol@parameters = "as="+as+" bs="+bs
copy_VarCoords(radext, radsol)
return(radsol)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef ("radsol2_fao56")
function radsol2_fao56(jday[*]:integer, lat:numeric, sunhr:numeric, ounit[1]:integer, opt[1]:logical)
; Compute solar radiation; EQN 35
; http://www.fao.org/docrep/X0490E/x0490e07.htm
;=======
; This is the 'Angstrom Formula' which relates solar radiation to extraterrestrial
; radiation and relative sunshine duration.
;=======
; For abs(lat) > 55 the eqns have limited validity
;=======
;
; julian day of current year
; lat can be a scalar, [*], or [*][*]
;
local as, bs, sunhrx, raext, radsol2, units
begin
sunhrx = daylight_fao56(jday, lat) ; max daylight/sun; hr per day
radext = radext_fao56(jday, lat, 1) ; radiation MJ/(m2-day)
as = 0.25 ; default; Chap 3, pg 23
bs = 0.50
if (opt .and. isatt(opt, "as")) then
as := opt@as
end if
if (opt .and. isatt(opt, "bs")) then
bs := opt@bs
end if
if (opt .and. isatt(opt, "as_bs") .and. dimsizes(opt@as_bs).eq.2) then
as := opt@as_bs(0)
bs := opt@as_bs(1)
end if
radsol2 = (as+bs*(sunhr/sunhrx))*radext ; MJ/(m2-day) ; EQN 35; Rs
if (ounit.eq.0) then
radsol2 = (/ radsol2*0.408 /) ; MJ/(m2-day) ==? mm/day
units = "mm/day"
end if
if (ounit.eq.1) then
units = "MJ/(m2-day)" ; ounit=1
end if
if (ounit.eq.2) then
radsol2 = (/ radsol2*11.574 /) ; MJ/(m2-day) ==> W/m2
units = "W/m2"
end if
radsol2@long_name = "solar radiation: FAO_56"
radsol2@units = units
radsol2@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
radsol2@info = "FAO 56; EQN 35; radsol2_fao56"
radsol2@parameters = "as="+as+" bs="+bs
copy_VarCoords(radext, radsol2)
return(radsol2)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("radsol3_hargreaves_fao56")
function radsol3_hargreaves_fao56(tmin:numeric, tmax:numeric, radext:numeric, krs:numeric, iounit[3]:integer)
;
; Solar radiation derived from air temp differences
; FAO 56: EQN 50
;
; Another usage is: http://dx.doi.org/10.4236/as.2013.48A008
;
; tmin, tmax - degC
; radsol - MJ/(m2-day)
;
; iounit - option for input [iounit(0)] and returned units [iounit(1)]
; iounit(0) =0: degC ; <b>input</b> units: <em>tmin/tmax</em>
; =1: degK
; =2: deg farenheit
;
; iounit(1) =0: mm/day ; <b>input</b>: <em>rex</em>
; =1: MJ/(M2-day)
; =2: W/m2
;
; iounit(2) =0: mm/day ; <b>output</b> (returned) units
; =1: MJ/(M2-day)
; =2: W/m2
;
; Allen et al [FAO-56] recommended that estimates made via this method bbe averaged over
; longer time periods, from several days to a week to a month, to remove errors
; associated with daily estimates.
;
; See also comments made in:
; Evaluation of alternative methods for estimating reference evapotranspiration
; Daniel K. Fisher1, H. C. Pringle III
; Vol.4, No.8A, 51-60 (2013) Agricultural Sciences
; http://dx.doi.org/10.4236/as.2013.48A008
;
local conext, consol, tmn, tmx, radsol_hg, units
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; iounit error check
if (iounit(0).lt.0 .or. iounit(0).gt.2) then
print("radsol3_hargreaves_fao56: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
end if
if (iounit(1).lt.0 .or. iounit(1).gt.2) then
print("radsol3_hargreaves_fao56: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
end if
if (iounit(2).lt.0 .or. iounit(2).gt.2) then
print("radsol3_hargreaves_fao56: unrecognized iounit(2) argument: iounit(2)="+iounit(2))
end if
exit
end if
; constant used to change input radext units to MJ/(m2=day)
if (iounit(1).eq.0) then
conext = 2.45068 ; mm/day ==> MJ/(m2-day)
else if (iounit(1).eq.1) then
conext = 1.0 ; no units change: MJ/(m2-day)
else if (iounit(1).eq.2) then
conext = 0.0864 ; W/m2 ==> MJ/(m2-day)
end if
end if
end if
if (iounit(0).eq.0 .or. iounit(0).eq.1) then ; degC or degK
radsol3 = sqrt(tmax-tmin)
end if
if (iounit(0).eq.2) then ; F
;;radsol3 = sqrt(((tmax-32)-(tmin-32))*0.55556)
radsol3 = sqrt((tmax-tmin)*0.55556)
end if
; radsol computation [ degC, MJ/(m2=day) ]
radsol3 = krs*radsol3*(radext*conext) ; use converted values
; change to desired output units of radsol3
if (iounit(2).eq.0) then
consol = 0.408 ; MJ/(m2-day) ==> mm/day
units = "mm/day"
else if (iounit(2).eq.1) then
consol = 1.0 ; no units change
units = "MJ/(m2-day)"
else if (iounit(2).eq.2) then
consol = 11.574 ; MJ/(m2-day) ==> W/m2
units = "W/m2"
end if
end if
end if
if (consol.ne.1.0) then
radsol3 = radsol3*consol
end if
radsol3@long_name = "solar radiation: Hargreaves"
radsol3@units = units
radsol3@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
radsol3@info = "FAQ 56: EQN 50; radsol3_hargreaves_fao56"
copy_VarCoords(tmin, radsol3)
return(radsol3)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("refevt_hargreaves_fao56")
function refevt_hargreaves_fao56(tmin:numeric, tmax:numeric, radext:numeric, iounit[3]:integer)
; Use the simple Hargreaves method to derive reference evapotranspiration (ETo; here, evt)
; This is from the FAO-56 [Food & Agriculture Organization] standard; EQN 52
; Hargreaves and Semani (1985)
;
; FAQ 56: This is an alternative to estimare ETo/evt when weather data are not avaliable.
;
; See also:
; Evaluation of alternative methods for estimating reference evapotranspiration
; Daniel K. Fisher, H. C. Pringle III
; Vol.4, No.8A, 51-60 (2013) Agricultural Sciences
; http://dx.doi.org/10.4236/as.2013.48A008
;
; NOTE: This has a tendency to underestimate evapotranspiration under high wind
; conditions (U2 > 3/m/s) and overestimate evapotranspiration under
; conditions of high humidity
;
; All input arrays (tmin, tmax, rex) must be the same size (conform).
; nomenclature:
; tmin, tmax - temperature at 2-meters (reference height)
; radext - extra-terrestrial solar radiation [mm/day]
;
; iounit - option for input [iounit(0)] and returned units [iounit(1)]
; iounit(0) =0: degC ; <b>input</b> units: <em>tmin/tmax</em>
; =1: degK
; =2: deg farenheit
;
; iounit(1) =0: mm/day ; <b>input</b>: <em>rex</em>
; =1: MJ/(M2-day)
; =2: W/m2
;
; iounit(2) =0: mm/day ; <b>output</b> (returned) units
; =1: MJ/(M2-day)
; =2: W/m2
local units, tavg, trng, conu, evt, tk0, tCrit
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; iounit error check
if (iounit(0).lt.0 .or. iounit(0).gt.2) then
print("refevt_hargreaves_fao56: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
end if
if (iounit(1).lt.0 .or. iounit(1).gt.2) then
print("refevt_hargreaves_fao56: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
end if
if (iounit(2).lt.0 .or. iounit(2).gt.2) then
print("refevt_hargreaves_fao56: unrecognized iounit(2) argument: iounit(2)="+iounit(2))
end if
exit
end if
if (isatt(tmin,"_FillValue")) then
tFill = tmin@_FillValue
else
tFill = 1e20
end if
conu = 0.0023
tk0 = 273.16 ; degK
tCrit = 0 ; degC
if (iounit(0).eq.0) then ; deC
tavg = (tmax+tmin)*0.5 ; local arrays
trng = tmax-tmin
evt = where(tmin.ge.tCrit \ ; standard formula
,conu*(tavg+17.8)*sqrt(trng)*radext, tFill)
if (any(tmin.lt.tCrit)) then ; special case; partial evt
tavg = (tmax+tCrit)*0.5
trng = tmax-tCrit
evt = where(tmin.le.tCrit .and. tmax.gt.tCrit \
,conu*(tavg+17.8)*sqrt(trng)*radext, evt)
end if
else
if (iounit(0).eq.1) then ; degK
tmn = tmin-tk0 ; convert to degC (local arrays)
tmx = tmax-tk0
else ; deg Farenheit
tmn = (tmin-32)*0.555556 ; convert to degC (local arrays)
tmx = (tmax-32)*0.555556
end if
tavg = (tmn+tmx)*0.5 ; degC
trng = tmx-tmn
evt = where(tmn.ge.tCrit \
,conu*(tavg+17.8)*sqrt(trng)*radext, tFill)
if (any(tmn.lt.tCrit)) then ; special case; partial evt
tavg = (tmx+tCrit)*0.5
trng = tmx-tCrit
evt = where(tmn.le.tCrit .and. tmx.gt.tCrit \
,conu*(tavg+17.8)*sqrt(trng)*radext, evt)
end if
end if
; units of input 'rex'
; iounit(1)=0 ... mm/day
if (iounit(1).eq.1) then
evt = evt*0.408 ; MJ/(m2-day) => mm/day
end if
if (iounit(1).eq.2) then
evt = evt*0.035 ; 1/28.4 ; W/m2 => mm/day
end if
;if (opt .and. isatt(opt,"partial_evt") .and. .not.opt@partial_evt) then
;end if
evt@long_name = "reference evapotranspiration: Hargreaves "
evt@units = "mm/day"
; standard eqn 52
if (iounit(2).eq.1) then ; 1 mm/day = 2.45 MJ/(m2-day)
evt = (/ evt*2.45098 /) ; mm/day => MJ/(m2-day)
evt@units = "MJ/(m2-day)"
end if
if (iounit(2).eq.2) then ; 1 mm/day = 28.4 W/m2
evt = (/ evt*28.4 /) ; mm/day => W/m2
evt@units = "W/m2"
end if
evt@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
evt@info = "FAO 56; EQN 52; refevt_hargreaves_fao56"
if (.not.isatt(evt,"_FillValue") .and. any(evt.eq.tFill) ) then
evt@_FillValue = tFill
end if
copy_VarCoords(tmin, evt)
return(evt)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("radsol_clrsky_fao56")
function radsol_clrsky_fao56(radext:numeric, opt[1]:logical)
;
; FAO 56: EQN 36 or 37
;
; (as+bs) => fraction of extraterrestrial radiation
; reaching earth on a clear sky day
; sunhr=sunhrx
local as, bs, z, rso, info
begin
as = 0.25
bs = 0.50
if (opt .and. isatt(opt,"as") .and. isatt(opt,"bs")) then
as = opt@as
bs = opt@bs
end if
; rso: clear sky radiation
if (opt .and. isatt(opt,"z")) then ; z = 'station' elevarion
rso = (0.75 + 2e-05*(opt@z))*radext ; EQN 37
info = "FAO 56; EQN 37"
else
rso = (as+bs)*radext ; EQN 36
info = "FAO 56; EQN 36"
end if
rso@long_name = "clear sky radiation" ; (sunhr/sunhrx)=1
rso@units = "MJ/(m2-day)"
rso@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
rso@info = info+"; radsol_clrsky_fao56"
rso@parameters = "as="+as+" bs="+bs
copy_VarCoords(radext, rso)
return(rso)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("netsw_fao56")
function netsw_fao56(radsol:numeric, albedo:numeric)
;
; Compute net solor (shortwave) radiation
; FAO 56: EQN 38
;
local netsw, wmsg
begin
if (all(albedo.le.1.0)) then
netsw = (1.0-albedo)*radsol
wmsg = ""
else
netsw = radsol
wmsg = "WARNING: albedo>1.0 encountered: netsw = radsol"
end if
netsw@long_name = "net solar (shortwave) radiation"
netsw@units = radsol@units
netsw@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
netsw@info = "FAQ 56: EQN 38; netsw_fao56"
if (wmsg.ne."") then
netsw@WARN_MSG = wmsg
end if
copy_VarCoords(radsol, netsw)
return(netsw)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("netrad_fao56")
function netrad_fao56(netsw:numeric, netlw:numeric)
;
; Compute net radiation
; FAO 56: EQN 40
;
local netrad
begin
netrad = netsw - netlw ; EQN 40
if (isatt(netsw,"units") .and. isatt(netlw,"units") .and. \
netsw@units.eq.netlw@units ) then
netrad@units = netsw@units
else
print("netrad_fao56: WARNING")
print(" units attribute not present or unit-mismatch")
print(" netsw@units="+netsw@units)
print(" netlw@units="+netlw@units)
end if
netrad@long_name = "net radiation"
netrad@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
netrad@info = "FAQ 56: EQN 40; netrad_fao56"
copy_VarCoords(netsw, netrad)
return(netrad)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("netlw_fao56")
function netlw_fao56(tmin, tmax, ea, radext, radsol, iounit[4]:integer, opt[1]:logical)
; http://www.fao.org/docrep/X0490E/x0490e07.htm
; Compute net longwave radiation ; EQN 39
;
; iounit - option for input [iounit(0)] and returned units [iounit(1)]
; iounit(0) =0: degC ; <b>input</b> units: <em>tmin/tmax</em>
; =1: degK
; =2: deg farenheit
; iounit(1) =0: hPa
; =1: Pa
; =2: kPa
; iounit(2) =0: mm/day
; =1: MJ/(m2-day)
; =2: W/m2
; iounit(3) =0: mm/day ; <b>output</b> (returned) units
; =1: MJ/(M2-day)
; =2: W/m2
local tmn, tmx, sbc, t0, eau, ru, as, bs, rso, netlw, units
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; iounit error check
print("netlw_fao56: unrecognized tunit argument: iounit="+iounit)
exit
end if
t0 = 273.16 ; K
sbc = 4.903e-09 ; MJ/(K4-m2-day) ; Stefan-Boltzmann constant
eau = (/0.10, 0.001, 1.0 /) ; ea unit convert: (0) hPa->kPa;
; (1) Pa->kPa;
; (2) kPa->kPa
ru = (/2.4507, 1.0, 0.0864/) ; rad* unit convert: (0) mm/day->MJ/(m2-day);
; (1) MJ/(m2-day)
; (2) W/m2->MJ/(m2-day)
rso = radsol_clrsky_fao56(radext, opt) ; clear sky radiation [ EQN 36 ]
ratio = radsol/rso
;;rso = radsol_clrsky_fao56(radext*ru(iounit(2), opt) ; clear sky radiation [ EQN 36 ]
;;ratio = radsol*ru(iounit(2)/rso
if (any(ratio.gt.1.0)) then
print("netlw_fao56: WARNING: ratio="+ratio+" ; radsol="+radsol+" ; rso="+rso)
print(" : WARNING: ratio = (radsol/rso) > 1.0")
ratio = ratio > 1.0 ; clip at 1.0
end if
if (iounit(0).eq.0 .or. iounit(0).eq.2) then
if (iounit(0).eq.0) then ; degC
tmn = tmin + t0
tmx = tmax + t0 ; C+t0 =>degK
else
tmn = (tmin-32)*0.5555556 + t0 ; F+t0 =>degK
tmx = (tmax-32)*0.5555556 + t0
end if
; EQN 39 ; use local converted temperature values
netlw = 0.5*sbc*(tmn^4 + tmx^4) \ ; part1: SB term
*(0.34-0.14*sqrt(ea*eau(iounit(1)))) \ ; part2: correction for humidity
*(1.35*(ratio)-0.35) ; part3: effect of cloudiness
else
; EQN 39 ; use input degK
netlw = 0.5*sbc*(tmin^4 + tmax^4) \ ; part1: SB term
*(0.34-0.14*sqrt(ea*eau(iounit(1)))) \ ; part2: correction for humidity
*(1.35*(ratio)-0.35) ; part3: effect of cloudiness
end if
if (iounit(3).eq.0) then
netlw = (/ netlw*0.408 /) ; MJ/(m2-day) ==? mm/day
units = "mm/day"
end if
if (iounit(3).eq.1) then
units = "MJ/(m2-day)"
end if
if (iounit(3).eq.2) then
netlw = (/ netlw*11.574 /) ; MJ/(m2-day) ==> W/m2
units = "W/m2"
end if
netlw@long_name = "net long wave radiation: FAO_39"
netlw@units = units
netlw@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
netlw@info = "FAO 56; EQN 39; netlw_fao56"
copy_VarCoords(tmax, netlw)
return(netlw)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("soil_heatflux_month_fao56")
function soil_heatflux_month_fao56(T:numeric, dt:numeric, dz:numeric, ndim[1]:integer, iounit[2]:integer, opt[1]:logical)
;
; Compute *monthly* soil flux
; FAO 56: EQN 41, EQN 43&44
;
; Note: Soil heat flux is small compared to net radiation.
;
; T - soil temperature (C); any dimensionality
; dt - monthly time step [ generally 1.0 ]
; dz - effective soil depth (m); for montly periods 0.5 to 2 meters; use 1.0
; ndim - number of the 'time' dimension
; iounit - units of input T: 0=degC, 1=degK, 2=F
; units of output flux: 0=mm/day; 1=MJ/(m2-day); 2=W/m2
; opt - optional arguments .. currently not used ... set to False
;
local con, units, soil_heatflux
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; iounit error check
print("netlw_fao56: unrecognized tunit argument: iounit="+iounit)
exit
end if
con = 0.14*dz
if (iounit(0).eq.1 .or. iounit(0).eq.2) then
; use converted temperatures
if (iounit(0).eq.1) then ; degK
; degK -> degC
soil_heatflux = con*center_finite_diff_n ((T-273.16),dt,False,0,ndim)
else
; F => degC
soil_heatflux = con*center_finite_diff_n ((T-32)*0.5555556,dt,False,0,ndim)
end if
else
; EQN 43 & 44 ; use input temperatures (C)
soil_heatflux = con*center_finite_diff_n (T ,dt,False,0,ndim)
end if
if (iounit(1).eq.0) then
soil_heatflux = (/ soil_heatflux*0.408 /) ; MJ/(m2-day) ==? mm/day
units = "mm/day"
end if
if (iounit(1).eq.1) then
units = "MJ/(m2-day)"
end if
if (iounit(1).eq.2) then
soil_heatflux = (/ soil_heatflux*11.574 /) ; MJ/(m2-day) == W/m2
units = "mm/day"
end if
soil_heatflux@long_name = "monthly soil heat flux"
soil_heatflux@units = units
soil_heatflux@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
soil_heatflux@info = "FAO 56; EQN 41, 43 & 44; soil_heatflux_month_fao56"
copy_VarCoords(T, soil_heatflux)
return(soil_heatflux)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("psychro_fao56")
function psychro_fao56(p:numeric, iounit[2]:integer)
;
; psychrometric constant
;
local psy, con
begin
con = 0.66474e-3 ; units: (kPa/C)
if (iounit(0).eq.0) then ; hPa -> kPa
con = con * 0.1
end if
if (iounit(0).eq.1) then ; Pa -> kPa
con = con * 0.001
end if
psy = con* p
psy@long_name = "psychrometric constant"
psy@units = "kPa/C"
psy@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
psy@info = "FAO 56; EQN 8; psychro_fao56"
if (iounit(1).eq.0) then ; (kPa/C) -> (hPa/C)
psy = (/psy*10.0/)
psy@units = "hPa/C"
end if
if (iounit(1).eq.1) then ; Pa -> kPa
psy = (/psy*1000.0/)
psy@units = "Pa/C"
end if
return(psy)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("refevt_penman_fao56")
function refevt_penman_fao56(Tmean:numeric, netrad:numeric, shflx:numeric, psychro:numeric \
,u2:numeric, vprdef:numeric, slope:numeric\
,albedo:numeric, cnumer:numeric, cdenom:numeric, ounit[1]:integer )
;
; Penman-Monteith for daily or monthly: Example 17, Chap 4
; albedo= 0.23 ; crop leaf albedo (*not* atmospheric or surface albedo)
; cnumer= 900.0 ; cdenom=0.34 short crop
; cnumer=1600.0 ; cdenom=0.38 tall crop
; or
; albedo, cnumer and cdenom are function(time, space) ; dimensionality must conform to Tmean
;
; NOTE: The 900 and 1600 are for daily or motthly;
; For hourly data use (900/24. or 1600/24.) and
; the units for 'netrad' and 'shflx' must be MJ/(m2-hour).
;
local dimT, dim_cnumer, dim_cdenom, num1, num2, dnom, refevt
begin
dimT = dimsizes(Tmean)
if (.not.isscalar(cnumer)) then
dim_cnumer = dimsizes(cnumer)
if (.not.all(dimT.eq.dim_cnumer)) then
print("refevt_penman_fao56: dimensions of cnumer do not conform the Tmean: Fatal")
exit
end if
end if
if (.not.isscalar(cdenom)) then
dim_cdenom = dimsizes(cdenom)
if (.not.all(dimT.eq.dim_cdenom)) then
print("refevt_penman_fao56: dimensions of cdenom do not conform the Tmean: Fatal")
exit
end if
end if
num1 = 0.408*(netrad-shflx)*slope ; numerator (left)
num2 = psychro*(cnumer/(Tmean+273))*u2*vprdef ; numerator (right)
dnom = slope + psychro*(1+cdenom*u2) ; denominator
refevt = (num1 + num2)/dnom
refevt@long_name = "Penman-Monteith reference evapotranspiration (month)"
refevt@units = "mm/day"
refevt@url = "http://www.fao.org/docrep/X0490E/x0490e07.htm"
refevt@info = "FAO 56; EQN 6; refevt_penman_fao56"
if (isscalar(cnumer)) then
refevt@parameters = "cnumer="+cnumer+" cdenom="+cdenom
else
refevt@parameters = "cnumer, cdenom are variable"
end if
if (ounit.eq.1) then
refevt = (/ refevt*2.45068 /)
refevt@units = "MJ/(m2-day)"
else if (ounit.eq.2) then
refevt = (/ refevt*28.4 /)
refevt@units = "W/m2"
end if
end if
refevt = where(refevt.lt.0, 0, refevt)
copy_VarCoords(Tmean, refevt)
return(refevt)
end
;++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("crop_water_need")
function crop_water_need(pet:numeric, act_evap:numeric, opt[1]:logical)
;
; This is not in FAO-56 but is bundled within the FAO-56 library for convenience.
;
; http://www.physicalgeography.net/fundamentals/8j.html
; http://www.fao.org/docrep/s2022e/s2022e00.htm
local cwn
begin
cwn = pet - act_evap
cwn@long_name = "crop water need: PET-ActualEvap"
if (isatt(pet,"units")) then
cwn@units = pet@units
copy_VarCoords(pet, cwn)
return(cwn)
else
if (isatt(act_evap,"units"))
cwn@units = act_evap@units
copy_VarCoords(act_evap, cwn)
return(cwn)
end if
end if
return(cwn)
end
;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
undef("refevt_turc")
function refevt_turc(tmean:numeric, radsol:numeric, iounit[3]:integer)
;
; This is not in FAO-56 but is bundled within the FAO-56 library for convenience.
;
; Use the simple Turc method to derive reference evapotranspiration (ETo; here, evt)
;
; **NOTE**: Different papers indicate different units for Rs and ET0
; ; The units cal/cm2/day are used in the equation.
;
; Reference:
;
; C.-Y. Xu, V. P. Singh
; Evaluation and generalization of radiation-based methods for calculating evaporation
; Hydrol. Process . 14 , 339±349 (2000)
; http://folk.uio.no/chongyux/papers_SCI/HYP_4.pdf
;
; Turc L. 1961
; Estimation of irrigation water requirements, potential evapotranspiration:
; a simple climatic formula evolved up to date.
; Annals of Agronomy 12: 13-49
;
; Each input array (tmean, radsol) must be the same size (conform).
;
; nomenclature:
; tmean - temperature at 2-meters (reference height)
; radsol - solar radiation
; iounit - option for input [iounit(0 and 1)] and returned units [iounit(2)]
; iounit(0) =0: degC ; <b>input</b> units: <em>tmin/tmax</em>
; =1: degK
; =2: deg farenheit
;
; iounit(1) =0: mm/day ; <b>input</b>: <em>radsol</em>
; =1: MJ/(M2-day)
; =2: W/m2
; =3: cal/(cm2-day)
;
; iounit(2) =0: mm/day ; <b>output</b> (returned) units
; =1: MJ/(M2-day)
; =2: W/m2
; =3: cal/(cm2-day)
; opt - optional
local units, tavg, conu, evt, tk0, tCrit
begin
if (any(iounit.lt.0) .or. any(iounit.gt.3)) then ; iounit error check
if (iounit(0).lt.0 .or. iounit(0).gt.3) then
print("refevt_turc: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
end if
if (iounit(1).lt.0 .or. iounit(1).gt.3) then
print("refevt_turc: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
end if
if (iounit(2).lt.0 .or. iounit(2).gt.3) then
print("refevt_turc: unrecognized iounit(2) argument: iounit(2)="+iounit(2))
end if
exit
end if
if (isatt(tmean,"_FillValue")) then
tFill = tmean@_FillValue
else
tFill = 1e20
end if
conu = 0.40 ; monthly
conu = conu/30 ; daily (0.013)
; radsol ===> cal/(cm2-day)
if (iounit(1).eq.0) then
conrad = 58.5 ; mm/day => cal/(cm2-day)
end if
if (iounit(1).eq.1) then
conrad = 23.9 ; MJ/(m2-day) => cal/(cm2-day)
end if
if (iounit(1).eq.2) then
conrad = 2.064 ; W/m2 => cal/(cm2-day)
end if
if (iounit(1).eq.3) then
conrad = 1.0 ; cal/(cm2-day)
end if
tk0 = 273.16 ; degK
tCrit = 0 ; degC
if (iounit(0).eq.0) then ; degC
evt = where(tmean.gt.tCrit \ ; standard formula
,conu*((tmean/(tmean+15))*((radsol*conrad)+50)), tFill)
else
if (iounit(0).eq.1) then ; degK
tavg = tmean-tk0 ; degC
else ; deg Farenheit
tavg = (tmean-32)*0.5555556 ; degC
end if
evt = where(tavg.ge.tCrit \
,conu*((tmean/(tmean+15))*((radsol*conrad)+50)), tFill)
end if
evt@long_name = "reference evapotranspiration: Turc Method "
evt@units = "mm/day"
evt@info = "no correction for low humidity"
evt@url = "L. Turc (1961): Water Requirements ...(Annales Agronomiques, 12, 13-49"
evt@reference_doi= "http://dx.doi.org/10.4236/as.2013.48A008"
; convert mm/day
if (iounit(2).eq.1) then ; 1 mm/day = 2.45 MJ/(m2-day)
evt = (/ evt*2.45098 /) ; mm/day => MJ/(m2-day)
evt@units = "MJ/(m2-day)"
end if
if (iounit(2).eq.2) then ; 1 mm/day = 28.4 W/m2
evt = (/ evt*28.4 /) ; mm/day => W/m2
evt@units = "W/m2"
end if
if (iounit(2).eq.3) then ; 1 mm/day = 58.5 cal/(cm2-day)
evt = (/ evt*58.5 /) ; mm/day => cal/(cm2-day)
evt@units = "cal/(cm2-day)"
end if
return(evt)
end
;-----
undef("refevt_turc_rh")
function refevt_turc_rh(tmean:numeric, radsol:numeric, rh:numeric, iounit[3]:integer)
;
; This is not in FAO-56 but is bundled within the FAO-56 library for convenience.
;
; Use the simple Turc method to derive reference evapotranspiration (ETo; here, evt)
; Exactly the same as refevt_turc'
; BUT
; it has a correction factor for low relative humidity ( RH<50% )
;
; Reference:
; C.-Y. Xu, V. P. Singh
; Evaluation and generalization of radiation-based methods for calculating evaporation
; Hydrol. Process . 14 , 339±349 (2000)
; http://folk.uio.no/chongyux/papers_SCI/HYP_4.pdf
;
; Turc L. 1961
; Estimation of irrigation water requirements, potential evapotranspiration:
; a simple climatic formula evolved up to date.
; Annals of Agronomy 12: 13-49
;
; Each input array (tmean, radsol, rh) must be the same size (conform).
; nomenclature:
; tmean - temperature at 2-meters (reference height)
; radsol - solar radiation
; rh - relative humidity (%)
; iounit - option for input [iounit(0 and 1)] and returned units [iounit(2)]
; iounit(0) =0: degC ; <b>input</b> units: <em>tmin/tmax</em>
; =1: degK
; =2: deg farenheit
;
; iounit(1) =0: mm/day ; <b>input</b>: <em>radsol</em>
; =1: MJ/(M2-day)
; =2: W/m2
; =3: cal/(cm2-day)
;
; iounit(2) =0: mm/day ; <b>output</b> (returned) units
; =1: MJ/(M2-day)
; =2: W/m2
; =3: cal/(cm2-day)
local units, tavg, conu, rhcor, evt, tk0, tCrit
begin
if (any(iounit.lt.0) .or. any(iounit.gt.2)) then ; iounit error check
if (iounit(0).lt.0 .or. iounit(0).gt.2) then
print("refevt_turc_rh: unrecognized iounit(0) argument: iounit(0)="+iounit(0))
end if
if (iounit(1).lt.0 .or. iounit(1).gt.2) then
print("refevt_turc_rh: unrecognized iounit(1) argument: iounit(1)="+iounit(1))
end if
if (iounit(2).lt.0 .or. iounit(2).gt.2) then
print("refevt_turc_rh: unrecognized iounit(2) argument: iounit(2)="+iounit(2))
end if
exit
end if
if (isatt(tmean,"_FillValue")) then
tFill = tmean@_FillValue
else
tFill = 1e20
end if
conu = 0.40 ; monthly
conu = conu/30 ; daily (0.013)
; radsol ===> cal/(cm2-day)
if (iounit(1).eq.0) then
conrad = 58.5 ; mm/day => cal/(cm2-day)
end if
if (iounit(1).eq.1) then
conrad = 23.9 ; MJ/(m2-day) => cal/(cm2-day)
end if
if (iounit(1).eq.2) then
conrad = 2.064 ; W/m2 => cal/(cm2-day)
end if
if (iounit(1).eq.3) then
conrad = 1.0 ; cal/(cm2-day)
end if
tk0 = 273.16 ; degK
tCrit = 0 ; degC
rhcor = where(rh.ge.50, 1.0, (1+(50-rh)/70.0)) ; rh correction factor
conu = conu*rhcor
if (iounit(0).eq.0) then ; degC
evt = where(tmean.gt.tCrit \ ; standard formula
,conu*((tmean/(tmean+15))*(radsol*conrad+50)), tFill)
else
if (iounit(0).eq.1) then ; degK
tavg = tmean-tk0 ; degC
else ; deg Farenheit
tavg = (tmean-32)*0.5555556 ; degC
end if
evt = where(tavg.ge.tCrit \
,conu*((tmean/(tmean+15))*(radsol*conrad+50)), tFill)
end if
evt@long_name = "reference evapotranspiration: Turc Method "
evt@units = "mm/day"
evt@info = "correction for relative humidity < 50%"
evt@reference_doi = "http://dx.doi.org/10.4236/as.2013.48A008"
if (iounit(2).eq.1) then ; 1 mm/day = 2.45 MJ/(m2-day)
evt = (/ evt*2.45098 /) ; mm/day => MJ/(m2-day)
evt@units = "MJ/(m2-day)"
end if
if (iounit(2).eq.2) then ; 1 mm/day = 28.4 W/m2
evt = (/ evt*28.4 /) ; mm/day => W/m2
evt@units = "W/m2"
end if
if (iounit(2).eq.3) then ; 1 mm/day = 58.5 cal/(cm2-day)
evt = (/ evt*58.5 /) ; mm/day => cal/(cm2-day)
evt@units = "cal/(cm2-day)"
end if
return(evt)
end
;-----
undef("areores_full_fao56")
function areores_full_fao56(zm:numeric, zom:numeric, zh:numeric, zoh:numeric \
,d:numeric, uz:numeric, uzopt[1]:integer)
;
; Aerodynamic Resistance: http://agsys.cra-cin.it/tools/EvapoTranspiration/help/
; . The transfer of heat and water vapour from the evaporating surface into the air
; . above the canopy is determined by the aerodynamic resistance.
; . The wind speed measurement is assumed over clipped grass, even though
; . the reference type is tall.
;
; FAO-56: Equation 4
; ra - aerodynamic resistance [s m-1],
; zm - height of wind measurements [m],
; zh - height of humidity measurements [m],
; d - zero plane displacement height [m],
; zom - roughness length governing momentum transfer [m],
; zoh - roughness length governing transfer of heat and vapour [m],
; k - von Karman's constant, 0.41 [-],
; uz - wind speed at height z [m s-1]. [ (a+b*u2) ]
;
; Eqn (4) is for neutral stability conditions, i.e., where temperature, atmospheric
; pressure, and wind velocity distributions follow nearly adiabatic conditions
; (no heat exchange).
;
local a, b, k2, uu, ra
begin
a = 0.0 ; open air (default)
b = 1.0
if (uzopt.eq.1) then ; greenhouse
a = 1.0
b = 0.54
end if
k2 = 0.41^2 ; von Karman constant aquared
uu = a+b*u2
if (.not.isatt(u2,"_FillValue")) then
uu@_FillValue = default_fillvalue(typeof(u2))
end if
uu = where(uu.lt.0.5, 0.5, uu) ; recommended
ra = (log((zm-d)/zom)*log((zh-d)/zoh))/(k2*uu)
ra@long_name = "aerodynamic resistance"
ra@units = "s/m"
ra@info = "FAO 56; EQN 4; aerores_full_fao56"
return(ra)
end
;-----
undef("areores_grass_fao56")
function areores_grass_fao56(ch:numeric, u2:numeric, aeopt[1]:integer)
;
; Technically: Aerodynamic resistance for a grass reference surface
; In practice: For a wide range of crops
; ---- constant crop height of 0.12 m was used --------
;
; FAO-56: Box 4
; ra - aerodynamic resistance [s m-1],
; ch - crop height [m],
; u2 - wind speed at 2m [m/s]. [uz =< (a+b*u2) ]
; http://agsys.cra-cin.it/tools/EvapoTranspiration/help/
; low wind constant c=665 is from here.
;
;
local dimu2, ranku2, a, b, c, uu, ra, dims_abc, rank_abc, info2
begin
;---check which attributes (optional arguments) are present (kinda a 'pain')
if (aeopt) then
if (isatt(aeopt,"abc")) then
dims_abc = dimsizes(aeopt@abc)
rank_abc = dimsizes(dims_abc)
if (rank_abc.eq.1 .and. dims_abc.eq.3) then
; http://agsys.cra-cin.it/tools/EvapoTranspiration/help/
a = aeopt@abc(0) ; 1.0 recommmended for low wind
b = aeopt@abc(1) ; 0.54
c = aeopt@abc(2) ; 665.0
info2 = "a="+a+" b="+b+" c="+c
else
print("aerores_grass_fao56: attribute abc not as expected")
print(" must be rank=1 and length=3 ")
print(" rank_abc="+rank_abc)
print(" dims_abc="+dims_abc)
exit
end if
else
dimu2 = dimsizes(u2)
ranku2 = dimsizes(dimu2)
if (isatt(aeopt,"a") .and. isatt(aeopt,"b") .and.isatt(aeopt,"c")) then
a = aeopt@a ; should match dimu2, ranku2
b = aeopt@b
c = aeopt@c
info2 = "multidimensional a, b, c have been used"
else
print("aerores_grass_fao56: one or more attributes a/b/c not present")
exit
end if
end if
else ; aeopt=False
a = 0.0 ; open air (default); aeopt=False
b = 1.0
c = 208.0 ; fao-56
info2 = "a="+a+" b="+b+" c="+c
end if
; Values used by FAO-56 to derive approximation
;k = 0.41 ; von Karman constant
;k2 = k^2
;zm = 2
;zh = 2
;d = 0.666667*ch ; (2.0*ch)/3.0
;zom = 0.123*ch
;zoh = 0.1*zom
;ra = areores_full_fao56(zm, zom, zh, zoh, d, u2, u2opt)
conu = 1.0 ; unit conversion
;if (iunit.eq.0) then
; conu = ;
;else if (iunit.eq.1) then
; conu =
; end if
;end if
uu = a+b*(u2*conu) ; uu must be m/s
;if (.not.isatt(u2,"_FillValue")) then
; uu@_FillValue = default_fillvalue(typeof(u2))
;end if
uu = where(uu.lt.0.5, 0.5, uu) ; low wind "agsys.cra-cin.it/tools/..."
ra = c/uu
ra@long_name = "aerodynamic resistance"
ra@units = "s/m"
ra@info = "FAO 56; BOX 4; aerores_grass_fao56"
if (isvar("info2")) then
ra@info2 = info2
end if
return(ra)
end
;++++++++++ PROCEDURE ++++++++++++++++++++++++++++++++++++++++
undef("radcon_p") ; radcon_p: NOT USED
procedure radcon_p(x:numeric, units_in_row[1]:integer, units_out_col[1]:integer)
;
; FAO 56: TABLE 3. Conversion factors for radiation
; multiplier to obtain energy received on a unit surface per unit time: equivalent evaporation
; MJ/(m2-day) J/(cm2-day) cal/(cm2-day) W/m2 mm/day
; 1 MJ/(m2-day) 1 100 23.9 11.6 0.408
; 1 cal/(cm2-day) 4.1868e-2 4.1868 1 0.485 0.0171
; 1 W/m2 0.0864 8.64 2.06 1 0.035
; 1 mm/day 2.45068 245 58.5 28.4 1
; ---
; radcon_p is a procedure; use to hange units of input variable
; radcon_p( x, 0, 4 ) ; MJ/(m2-day) ==> mm/day
; radcon_p( x, 3, 0 ) ; mm/day ==> MJ/(m2-day)
;
local conv, units_row, units_col
begin
conv = (/ (/ 1.0, 100, 23.9 , 11.6 , 0.408 /), \ ; row 0
(/4.1868e-2, 4.1868, 1.0 , 0.485, 0.0171/), \ ; 1
(/ 0.0864, 8.64, 2.06, 1.0 , 0.035 /), \ ; 2
(/ 2.45, 245, 58.5 , 28.4 , 1 /) /) ; 3
; col 0, 1, 2, 3 , 4
units_row = (/"MJ/(m2-day)","cal/(cm2-day)", "W/m2", "mm/day"/)
units_col = (/"MJ/(m2-day)","J/(cm2-day)" ,"cal/(cm2-day)", "W/m2", "mm/day"/)
x = x*conv(units_in_row, units_out_col)
x@units = units_col(units_out_col)
end
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