deletions | additions       diff --git a/Characterisation_of_STTs.tex b/Characterisation_of_STTs.tex  index 0d0f34a..2718260 100644  --- a/Characterisation_of_STTs.tex  +++ b/Characterisation_of_STTs.tex 
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Two definitions of the tropopause height are calculated: the standard lapse rate tropopause \cite{WMO1957}, and the ozone tropopause \cite{Bethan1996}. At Davis, the ozone tropopause defintion is modificted for polar sites, following \cite{Tomikawa2009,Alexander2013}. While the ozone tropopause can be less robust during stratosphere-troposphere exchange, it performs better than the lapse rate tropopause at polar latitudes in winter and near jet streams in the lower stratosphere \cite{Bethan1996}. The lower of these tropopause altitudes is referred to as the tropopause for this study, because of the mixing of minor constituents in the upper troposphere and lower stratosphere, particularly when there is an ill-defined lapse rate tropopause. The monthly mean tropopause altitudes at each location are shown in Figure~\ref{fig:seasonaltpheights}, along with the altitudes from profiles for which an STT event was determined. The seasonal cycle in tropopause altitude at Melbourne is clearly apparent, as is the decreasing tropopause altitude poleward. It is worth noting that tropopause altitudes at Davis may exceed 11~km altitude under certain synoptic conditions \cite{Alexander2013}: the relation of tropopause altitude with STT events will be investigated in detail below.  %STTs have a clear effect on the ozone parts per billion volume(ppbv) profile above a grid point(henceforth a profile).  %One important factor of STT characterisation was the height of the tropopause, which can be defined in several ways. 
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%In order to avoid spurious events caused by surface pollution or Fourier transform anomalies these perturbation profiles are trimmed to between 2km above the surface and 1km below the tropopause.  %Now using all the trimmed filtered profiles we extract those with points above the 99th percentile(locally) of all ozone levels.  In order to remove unclear 'near tropopause' anomalies we remove events where the gradient between the maximum ozone peak and the altitude at 1~km below the is greater than $-20$~ppbv~km$^{-1}$ and require that the perturbation profile does not drop below zero between the event peak and the tropopause. %as well as having the Fourrier filtered profile not drop below zero between the event peak and the tropopause. To provide a conservative estimate of ozone flux into the troposphere for each event, the ozone concentration is integrated vertically over the interval for which an STT event is identified. An example of an ozone profile is illustrated in Figure~\ref{fig:filterEG} and indicates how the algorithm detects an STT event.  %\subsection{Conservative estimate of ozone flux}  %An initial conservative estimate of ozone flux in each event is made by interpolating to find the ozone concentration above the baseline at the peak of each event, bound above and below by where the Fourrier filtered profile becomes negative.  %An example illustrating the Fourier filter and how the flux is determined is provided in figure \ref{fig:filterEG}.