complished 
cainers at 
but it does 
o 
7) 
(D 
E^) 
> 
wo 
   
- 1297 - 
Hence substituting equations 5a, 3b into equetion 1: 
1 2 2,1 ao 
Ta” le T sal m Ta sol 
Ta 5 ----------- Vu +0 --------------- (4) 
8 M. sel Mor ir 
sal sal sal sal 
one obtains a linear equation (e equation 4) relatino tomperature 
as measured by the Barnes rediometer, and digitized output in 
terms of known constents (Tg pul 
In our case equation 4 takes the form 
= 17 - / (o 
Tg = 11.426 Va. - 14.25 ( C) (5) 
To obtain temperatures capables 9 comparison to a blacktody 
(T b?* various authors (8), (9), :( 14), 01 5),(16) propose the 
first order correction: 
Ton * Ig * A corr ac - L6) 
where À -ort is the instrument's correction. 
8) Correction for ambient temperaturs 
The ambient tempereture affects the exactitude of the mea- 
sured temperztures since the cavity temperature is slightly in- 
fluenced by amb£ie-t temperatures on the sther hand, a fraction 
of the energy reaching the detactor is due to the thernai emis- 
sion generated in the vicinity of tha sensor, introducing.sn 
error 4 The magnitude o? this error nay be estimated by 
calibratiËn (17): The reference temperature is in first orcer 
the product of the emission coefficient of the chuoner (€ 
by its temperature added to the product of its reiílection 
coefficient (r=1 -€ Dy the cavity temserature AG ). Thus: 
T eof = Ech Te *a(i. s ecu? Tc (7) 
since T_ is constant the increment between two temperatures 
wiil be! 
A ref 5 fen 81 = f oh (T ral 1) 
am ca 
where 
Tan = ambient temperature when measure takes place 
Cal? ambient temperature when calibration takes place. 
From this it results that the radiation temperature measur- 
ed at an altitude z, T,(z), is given by 
TS = Tho * Fe Ell, “iT oy) (9) 
m cal 
which results in 
_ - \ 
7.(z) = Ta *Acorr + 0.1 (T n T al) (10)