All O3 observational data and aggregates on this EMEP TFMM wiki was processed by NILU/EMEP-CCC
Data were extracted for three periods
1990-2001
1990-2012
2002-2012
For each period the monitoring sites were selected based on:
>75 % data capture each year in > 75 % of the years
The raw hourly data are given in the proxy "ug/m3" as used in EBAS.
The conversion factor to ppb is 2 at nearly all sites (1 ppb = 2 ug/m3)
Consult the EMEP ozone data report (www.emep.int) for details about this.
All AOT40 data are given in ppb hours. They are computed according to the
UNECE convention, i.e. for hours when the global radiation > 50 W/m2
based on zenith angle and climatological data for the relationship
between radiation and zenith angle.
All trends were calculated by a Mann Kendall method (Gilbert, 1987) programmed
in IDL by NILU.
The slopes refer to Sen's slope.
Relative slopes refer to the start year
i.e. if y = a + b(t-t0) then rel.slope = b/y(t=t0)
Details about the trend metrics:
annual means are calculated based on the mean of the daily means
SOMO35 is the sum over the year of the daily max 8h running means above 35 ppb
SOMO10 is the sum over the year of the daily max 8h running means above 10 ppb
The daily max 8h running mean is allocated to the day for which the last hour
of the 8h period ends