Planetary boundary layer defined

Velocity and temperature gradients are confined to the surface layer defined by z < I-. Above L the wind velocity and potential temperature are virtually uniform with height. Venkatram (1978) has presented a method to estimate the value of the convective velocity scale w,. On the basis of this method, he showed that convective conditions in the planetary boundary layer are a common occurrence (Venkatram, 1980). In particular, the planetary boundary layer is convective during the daytime hours for a substantial fraction of each year ( 7 months). For example, for a wind speed of 5 m sec , a kinematic heat flux Qo as small as O.PC sec can drive the planetary boundary layer into a convective state. 

The MCM is a near-explicit chemical mechanism that describes the detailed degradation of a series of emitted VOC, and the resultant generation of ozone and other secondary pollutants, under conditions appropriate to the planetary boundary layer. Version 3 of the Master Chemical Mechanism (MCM v3) considers the oxidation of 125 VOC. The complete mechanism comprises 12,691 reactions of 4,351 organic species and 46 associated inorganic reactions, which were defined on the basis of the MCM scheme writing protocols (Jenkin et al, 1997, Saunders et al, 2003 Jenkin et al, 2003). Although MCM v3 has recently been superseded by v 3.1, the chemistry for non-aromatic VOC remains unchanged. 

The initial step taken by modelers in the U.S. and Western Europe in moving away from the Gaussian Modeling procedure mentioned above has come in the attempt to more precisely define the planetary boundary layer. Then, the... 

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