Transcript Ozone time series and trends Various groups compute trends in different ways. One goal of the workshop is to be able to.

Ozone time series and trends
Various groups compute trends in different ways.
One goal of the workshop is to be able to compare time
series and trends from different groups.
Therefore we are requesting that participants compute
trends for common time periods in a common manner, to
facilitate intercomparison of results. This is not
mandatory, but is highly desirable.
This does not preclude participants presenting trends
computed in other ways for other time periods (e.g., their
entire record).
Recommendations for trend intercomparison.
•
The template is a guide, to be followed as much as
possible for the trend intercomparison.
•
Comparing trends is only one aspect of the
« Tropospheric O3 Changes » issue.
•
Key points are:
•
to show the entire time-series in ppb, as there is
often non-linear behavior
•
to analyse trends
•
to check the regional consistency within different
datasets.
General recommendations:
Please calculate all trends as the slope of the linear
regression line and give the corresponding 95%
confidence interval for the trend (2σ) and r2 for the fit.
Also give the intercept (with a confidence limit) for a selected
reference year (e.g. 2000) or give the average mixing ratio
for the record.
ALL trends (including seasonal trends) should be calculated
based on monthly mean anomalies (i.e. deseasonalized
trends) and reported in ppb/year +/- 2σ.
Specific recommendations for surface stations :
Monthly means are calculated using original data resolution
(e.g. hourly means).
Monthly mean is considered valid if less than 33% of points
are missing.
Specific recommendations for vertical profiles :
1. Monthly means should be reported for the following
vertical layers:
• A: surface layer (ground-1 km)
• B: lower free troposphere (1-3 km)
• C: mid free troposphere (3-8 km)
• D: upper troposphere (8 km - tropopause) :
• E: UTLS
2. Or use vertical resolution of ~1 km from ground to the
tropopause
3. Or if you use some other vertical grid, it would be
helpful to report trends on the recommended altitude
ranges.
Recommended time intervals
•
Three time periods should be investigated if
your data covers these periods:
1990-2009, 1990-1999 and 2000-2009.
1980-2009
•
If these are not available, just use the data
range you have e.g, 1995-2008 for MOZAIC
•
Compute trends for 1995-2008 if you wish to
compare to MOZAIC trends.
Data presentations talks (no more
than 10 slides)
• Description of station/data set : 1 slide as suggested below
(#7 or #9 for either surface or vertical profile station)
• Display of entire time series (in ppb) and highlight of special
features. 1 slide
• Display of time series anomalies (in ppb) over 1990-2009
and/or 1990-1999 and/or 2000-2009 if possible and include
a linear fit with indications on slope/2σ/r2 and intercept or
average concentration over the record. (max 3 slides)
• Display of summary tables : 1 slide as suggested below (#8
or #10 for either surface or vertical profile station)
• Discussion points (1 slide).
• Comparison with neighboring sites and/or alternative
statistical approaches. (max. 2 slides)
• Summary and open issues. 1 slide
General information about surface station:
1) The station :
Name, Latitude, Longitude, Altitude,
Surrounding (possible sources of precursors/
anthropogenic impact), Systematic changes in
environment
2) Instrument (general performance/calibration)
3) Data set:
Period:
% of missing points:
Particularities (e.g. years of the general tendency
change)
Annual trends
From monthly mean
anomalies based on
all available data
From night data only From day data only
(11 p.m. – 4 a.m.
(11 a.m.- 4p.m. local
local time)
time)
1990-2009
1990-1999
2000-2009
« Night / Day » can be replaced by « Baseline / Non-Baseline » or « Regional / Local » influence
Seasonal trends (for day and night values)
DJF
1990-2009
1990-1999
2000-2009
MAM
JJA
SON
General information about the vertical profile
station:
1) The station:
Name, Latitude, Longitude, launch altitude,
Launch time and frequency
surrounding (possible sources of precursors/
anthropogenic impact), systematic changes in
environment
2) Instrument (general performance/calibration)
3) Data set:
Period
Big data gaps
Particularities (e.g. years of the general tendency
change)
Annual trends for the five altitude layers
(or whatever is convenient with your dataset)
From monthly mean anomalies (in ppb) based on all available data
A
B
C
D
1990-2009
1990-1999
2000-2009
A, B, C, D, E altitude levels can be replaced by plots of profile trends
Seasonal trends
DJF
1990-2009
1990-1999
2000-2009
MAM
JJA
SON
E
Model evaluation talks
(no more than 12 slides – focus on reanalysis simulations)
• Description of model and simulation set-up : 1 slide
• General characterization of simulation results (e.g. maps or
“Stevenson-plot” (multi-panel regional averages): 1 slide
• Up to 4 slides with time series comparisons for surface sites. Use
monthly mean anomalies as the data people; individual stations or
regional averages: all graphs should have time axes 1990-2009
and/or 1990-1999 and/or 2000-2009 and include a linear fit with
indications on slope/2σ/r2 and intercept or average concentration
over the record.
• Up to 4 slides to analyze modeled vertical profiles versus MOZAIC
and/or sondes. For MOZAIC use 1995-1999 and 2000-2008, for
sondes 1990-1999 and 2000-2008. Show time series at standard
pressure levels (850, 500, 250 hPa) plus summary slide for trend
(ppbv/year) versus altitude.
• Discussion points (1 slide)
• Summary and open issues: 1slide