Diurnal concentration predictions

Fig. 4. Calculated diurnally averaged OH concentrations as a function of the assumed NO mixing ratio, f (NO, ). The broken line is the OH concentration predicted from Eqn. (1) and the solid line is the concentration obtained from a complete photochemical model.

The performances of BOLCHEM on the ability to predict O3 concentration over Italy were evaluated (Mircea et al., 2008). The comparison between computed and measured concentrations for some periods of 1999 showed that the model is capable to predict the diurnal cycle of O3, in particular in summer. The agreement between modeled and measured quantities is good during daytime while at night there is some problem connected to O3 destruction. However, US-EPA s criteria are met ... 

Fig. 5. Model calculated, diurnally and seasonally averaged OH concentrations as a function of altitude and latitude. The globally averaged OH concentration is predicted to be TxlO molecular cm-. ...

Since most (over 99%) of the odd oxygen is in the form of O3, the Chapman mechanism predicts that local stratospheric ozone concentrations are proportional to the square root of the O2 photolysis rate. At night, reactions 4.1 and 4.3 cease, but reactions 4.2 and 4.4 persist. Atomic oxygen concentrations fall rapidly, with the net effect that reactions 4.2 and 4.4 more or less balance each other so that diurnal variations in stratospheric O3 are small. 

The general covariance of natural leaf water and leaf nitrogen concentration (Scriber and Feeny, 1979) and a variety of other leaf chemicals (such as tannins, fiber, lignins, oils) confounds interpretations of insect-plant interactions. Diurnal variations in plant chemistry sometimes may be comparable to seasonal changes (Scriber, 1977 Pate, 1980). Although artificial diets permit investigation of chemical mechanisms and dose-response relationships between herbivores and specific chemicals, such information cannot be readily used for prediction of larval growth on plant tissues. 

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