My son, a 7th grader, is working on a science fair project that will hopefully show varying levels of acid rain in our county. Is the HYSPLIT trajectory model the best way to show wind current origins for rain falling on a given day, or is there another way to show this? Also, can you recommend any other sites/sources for middle school level research on acid rain effects, sources, detection, etc.?


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.eduthis link opens in a new window. 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