There remains the problem of evaluatinir f(z). This may be 

 done in one of two ways. If the extinction coefficients for 

 the area are known, we may employ the relationship 



"^'=«" (6, 



Here k is defined as the extinction coefficient. For practical 

 use it has become the convention in oceanography to consider k 

 a constant over a meter's thickness; therefore, k is generally 

 given per meter. For purposes of computation it is also more 

 convenient to utilize equation (6) over succeeding intervals of 

 one meter or more; if one meter is used, z - 1, If two meters 

 are used, z ■ 2, etc. 



Now, if we start at the surface with (Qab~'^b^ ^■'■^'^ designate 

 this quantity as Q,., the amount of incoming heat left at the 

 bottom of the first meter is 



°'.=°'«"' (7) 



where k^ is the extinction coefficient in the first meter. 

 The amount of heat absorbed In the first meter Is 



AQr=Qr-Qr e"*"' 



' (8) 



