Calculated 96h trajectories, daily
sector values and trajectory crossings are
available from this site for all EMEP stations. The 2D trajectories
have been calculated for 1985-1996 with a horisontal resolution of
150x150 km2 in the old
For 1997-2006 and 2007-2014 the trajectories have been calculated with
a horisontal resolution of 50x50 km 2 in
the EMEP grid.
The calculations are made for the period from 1985 to 2014.
If a station was not operative for a certain year, then no trajectory
data has been calculated for that year.
The 2D trajectories calculations are based on meteorological data from
the NWP(Numerical Weather Predicition) models, LAM150 for 1985-1996 and
PARLAM-PS for 1997-2006, both developed at the Norwegian Meteorological
Institute, and IFS for 2007-2012 developed at the ECMWF.
Modelled wind fields at 925hPa have been used for the calculations as
well as precipitation fields. Assimilated precipitation fields based
on actual observations have been used in the calculations. An exception
was made for March to August 1986 where precipitation fields from the
NWP were used in lack of observed values.
Anton Eliassen, Jørgen Saltbones, Frode Stordal, Øystein Hov, Ivar S. A. Isaksen, and Frode Stordal, 1982:
A Lagrangian Long-Range Transport Model with Atmospheric Boundary Layer Chemistry. J. Appl. Meteor., 21, 1645-1661.
Petterssen, S., 1956: Weather Analysis and Forecasting. McGraw-Hill, 503 pp.
Please refer to EMEP/MSC-W and emep.int if trajectory data is used for
96 h trajectories
The 96 h backwards trajectories are calculated by tracking an air parcel
every 2 hour for 96 hours backwards in time, 4 terms per day. The terms
are 00GMT, 06GMT, 12GMT and 18GMT. For each single term, 2D trajectories
are defined by a total of 49 position points (including the arrival point)
given as coordinates in the EMEP 150x150 km2
grid and for 1997-2006 even in the EMEP 50x50
km2 grid. For 2007-2014 coordinates are
only given in the EMEP 50x50 km2 grid.
If a trajectory starts from outside the EMEP domain, then the coordinates
giving the air parcel position are set to (0,0).
The 96h backwards 2D trajectory data can be retrieved by selection from
the upper panel. Data are organised as:
1 ASCII file per station per year 1985-1996
1 ASCII file per station per year 1997-2006
1 ASCII file per station per year 2007-2012
The X50 and Y50 coordinates are defined different before 2007 and after
2006. The X50/Y50 coordinates in the dataset of 2007-2014 is equal to
X50-35/X50-11 coordinates in 1997-2006. The latter dataset of X50/Y50
coordinates is corresponding to the EMEP 50 km grid
Daily sector values
The daily sector values are based on 96 h backwards trajectories. The
area around the arrival point has been divided into 8 equal sectors.
If the origin of the circle points straight upwards, Sector 1 (North)
begins from -22.5 degrees to 22.5 degrees. The next sectors are counted
clockwise. The area around the arrival point extends from a radius of
150 km to a radius of 1500 km. The criteria for allocation
of trajectories to one sector is that at least 50% of its given positions
found within that sector. Otherwise, sector 9 (inattributable) is allocated.
The daily sector data can be retrieved by selection from the upper
panel. Data are organised as:
0 ASCII file per station for years 1985 to 1996
1 ASCII file per station for years 1997 to 2006
1 ASCII file per station for years 2007 to 2014
-999 indicates that the station was not operative that year
Trajectory crossings maps
The trajectory crossings maps are based on 96 h backwards trajectories
calculated 4 terms per day. Each gridcell a trajectory has crossed on
its path to the arrival point, is accounted and the total number of times
a gridcell is crossed by a trajectory is added for either one month or
one year. There are two types of trajectory crossings maps: those
providing the number of trajectory crossings for the whole period
independently of weather conditions and those providing the number
of trajectory crossings only for days with precipitation at arrival point.
The following maps (as PNG files) with trajectory crossing numbers can
be retrieved by selection from the upper panel:
PNG file with trajectory crossings per station per month
PNG file with trajectory crossings on precipitation days per station per month
PNG file with trajectory crossings per station per year
PNG file with trajectory crossings on precipitation days per station per year
In 1986, trajectory crossings for March-August have been calculated
with modelled precipitation instead of observed precipitation. This
should be considered when using the data.
The trajectory crossings of January 1985 begin at January 1 12GMT because
meteorological data is missing for the first two terms of this month.
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