Yes, I believe that our trajectory model is the best way to show wind
current origins for rain falling on a given day. Keep in mind, however,
that you are running the model in the backward mode -- which means that
you need to be careful to run the model at a height that is reasonably
representative of where the material measured in rain samples originated.
You also need to make some good guesses about the location of the
important emission sources. We typically run our trajectories in the
lower part of the cloud layer -- about 2000 m above the ground. For a
given day, if you run at several heights ranging between cloud base and
say 3000 m, you will get some notion of wind sheer. I tend to believe
trajectories when sheer is minimal. Otherwise, trajectories may come from
all over the place. You will still need to guess about the real sources
of the materials found in the rain. We do have some sophisticated
techniques involving trajectories run in a forward mode that, when coupled
with a good emission inventory, gives a good estimate of individual source
contributions to actual sample concentrations measured.
You may also want to check out the web site for the National Atmospheric
Deposition Program --
http://nadp.sws.uiuc.edu. NADP is a rich source
for annual deposition and concentration maps on a national basis, as
well as of recent publications. The publication section can be
cumbersome, but if you are persistent, there are some good things to be
found. Pay attention to recent articles by James Lynch and Van
Bowersox.
Rick Artz
NOAA/ARL