Air Mass Exchange between Principal Atmospheric Domains

5 Air Mass Exchange between Principal Atmospheric Domains 

A simple yet very useful concept in treating material transport in geochemistry and in atmospheric chemistry as well is to consider a small number of reservoirs that communicate with each other across common boundaries. Ideally, the contents of each reservoir should be well mixed that is, the rate of internal mixing should exceed the rate of material exchange between adjoining reservoirs. In these so-called box models, the exchange is treated kinetically as a first-order process. 

After subtracting the second equation from the first and dividing through 

From Fig. 1-2 one estimates that Am = 0.66ppmv during the period considered. The value for P.d is given by the slope of the rise curve, or more precisely by the average slope (AmN + Ams)/2At = 0.64. The exchange coefficient thus is ktt = 0.64/0.66 = 0.97 yr-1. The corresponding exchange time is Ttt = l/x-n- — 1 yr. 

The solution to these equations is derived most conveniently from two new equations obtained from the above by addition and subtraction, respectively  

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