Dear Jonathan,
I really appreciate your thoroughness. Yes - there can also be the need to record the "daily maximum 1-hour value".
Just to wet your appetite: it can get worse than that if you look at the US EPA ozone standard: "0.075 ppm over 8 hour period: To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations measured at each monitor within an area over each year must not exceed 0.075 ppm." Or (even better) from a new standard proposal
http://www.epa.gov/air/ozonepollution/fr/20100119.pdf : "cumulative, seasonal standard expressed as an annual index of the sum of weighted hourly concentrations, cumulated over 12 hours per day (8 am to 8 pm) during the consecutive 3-month period within the O3 season with the maximum index value, set at a level within the range of 7 to 15 ppm-hours"
These kind of "interval" definitions may not be imminent right now, but as we are trying to engage the air quality community in "semantic interoperability", I am quite sure this will come up eventually. Is there any other community out there that has similar issues?
Cheers,
Martin
> -----Original Message-----
> From: Jonathan Gregory [mailto:j.m.gregory at reading.ac.uk]
> Sent: Thursday, October 20, 2011 11:40 AM
> To: Schultz, Martin
> Cc: cf-metadata at cgd.ucar.edu
> Subject: Re: daily maximum of running 8-hour means
>
> Dear Martin
>
> Yes, I agree, "interval" is an ambiguous word, unfortunately.
>
> > YES - there will be a need for this. Current air quality data bases -
> > the largest are probably the American AQS and the European AirBase
> > systems - do store hourly data and "daily max 8-hour mean" values, and
> > you want to be able to differentiate between those automatically
>
> OK. The distinction between those two can already be made like this:
>
> - hourly data have coordinates spaced hourly, and cell_methods with "mean"
> or "point" (depending on wheher they were hourly time-means or
> instantaneous values at hourly intervals).
>
> - daily max of running means have coordinates spaced daily, and
> cell_methods with "maximum".
>
> What we *can't* record in a standardised way is the extra information that
> the maximum was calculated from running means. We need to do this if
> there are also daily maxima calculated from other kinds of subdaily data.
>
> I apologise if this is frustrating. I am trying only to clarify what is needed in
> practice!
>
> Best wishes
>
> Jonathan
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Received on Thu Oct 20 2011 - 12:03:47 BST
