= Solution
The observed value is about 4 ppb higher than the local chemical–<dry deposition> balance predicts. <Entrainment> from the ozone-richer <free troposphere> adds a term $(w_e/H)(\chi_{\rm FT}-\chi_{\rm BL})$; horizontal <Advection> can likewise import <ozone> or longer-lived precursors from other regions. Time dependence, including the day–night cycle of <photodissociation> and changes in mixing depth, is also omitted. The approximately four-day model adjustment time means that air arriving at the measurement location need not have attained the assumed local <steady state (chemistry)>. These transport and history terms can raise <ozone> without changing the given local chemical constants.
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