cc: Phil Jones
date: Wed, 15 Apr 2009 16:08:54 +0100
from: Ian Harris
subject: Re: CRU Radiation data.
to: "Juckes, MN (Martin)"
Hi Martin,
I've tracked down a file of the same name here, it looks to have been
generated by Mark New in January 1999. Mark is of course at Oxford now.
Mark's 1999 paper suggests that the conventional Doorenbos-Pruit
calculations were used to convert between sun hours and cloud cover.
More helpfully, I've found an IDL program in Mark New's space, not a
million miles from the data file. It looks like this:
pro netrad,jday,rlat,albedo,t,sun,ed,rn
;
; calculates net radiation using equations in Shuttleworth (1993)
;
; rlat - latitude
; jday - Julian day
; t - temperature
; sun - sunshine hours (per day)
; ed - vapour pressure (mb)
; albedo
; ac,bc - parameters of cloudiness equation
; rn - net radiation (mm/day)
;
; local variable declarations
as=0.25 & bs=0.5 & ae=0.34 & be=-0.14 & bolz=0.000000004903
ac=1.0 & bc=0.0
;
; first get extraterrestrial solar radiation
;
hlat=2.501-0.002361*t
solar,jday,rlat,s0,smax
s0mj=s0*hlat
;
; now calculate incoming short-wave radiation
;
IF smax gt 0.0 THEN begin
st=(as+bs*sun/smax)*s0mj
ELSE
st=0.0
ENDIF
;
; net short-wave radiation
;
sn=st*(1.0-albedo)
;
; long-wave radiation
;
IF(ed>-5.0)THEN
edkpa=ed*0.1
emm=ae+be*sqrt(edkpa)
ELSE
emm=-0.02+0.261*(exp(-0.000777*t*t))
ENDIF
sto=(as+bs)*s0mj
IF(abs(sto)>0.0)THEN begin
f=ac*(st/sto)+bc
endif ELSE begin
f=0.0
ENDelse
rln=-1.0*f*emm*bolz*(t+273.2)^4
;
; calculate net radiation
;
rnmj=sn+rln
IF(rnmj eq 0.0)THEN begin
rn=0.0
endif ELSE begin
rn=rnmj/hlat ; mm/day
ENDelse
END ; PRO netrad
Hope that helps!
Cheers
Harry
On 8 Apr 2009, at 12:28, P.Jones@uea.ac.uk wrote:
> Hi Martin,
> I'm in the US and get back on Good Friday. Harry is
> off this week. We'll have a look the week after Easter.
>
> I'd suspect this file might be normals for 61-90
> which are calculated from cloudiness with a formula.
>
> If this is the case the formula should be in one of
> the New et al papers in J. Climate in 1999 ro 2000.
>
> Cheers
> Phil
>
>> Hello Ian, Phil,
>>
>>
>>
>> I have got a user query about some radiation data we have on the IPCC
>> DDC. It is the file crad6190.zip available from this page:
>> http://www.ipcc-data.org/obs/get_30yr_means.html.
>>
>>
>>
>> There is no reference to "rad" data on your high resolution page
>> http://www.cru.uea.ac.uk/cru/data/hrg.htm -- do you know where
>> crad6190.zip comes from?
>>
>>
>>
>> Sincerely,
>>
>> Martin Juckes
>>
>>
>> --
>>
>> Scanned by iCritical.
>>
>
>
Ian "Harry" Harris
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich NR4 7TJ
United Kingdom