cc: Phil Jones <P.JonesatXYZxyz.ac.uk>

date: Wed, 15 Apr 2009 16:08:54 +0100

from: Ian Harris <i.harrisatXYZxyz.ac.uk>

subject: Re: CRU Radiation data.

to: "Juckes, MN (Martin)" <martin.juckesatXYZxyzc.ac.uk>

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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.JonesatXYZxyz.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

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