Do you have any historical data or "rule of thumb" information
regarding the amount of salt (seasalt) contained in the moisture
in the air around coastal areas?
Droplets are "emitted" from the ocean through wave action, etc., and the coastal
atmosphere is "laden" with this sea-salt aerosol. If the humidity is high -- above
maybe 60-70%, the aerosol is in the form of droplets. When the humidity decreases,
the droplets dry out and the aerosol is in the form of dry particles. Since the
humidity is often pretty high in coastal areas, droplets are often present.
When it rains, particles -- dry or wet -- get incorporated into rain drops. So,
measurements of rain tell you something about the composition of the atmosphere.
Its not all you need to know, but its something....
There's an extensive measurement program that measures the composition of preciptation
in the U.S., called the National Acid Deposition Program (NADP). Their web site is
at: http://nadp.sws.uiuc.edu/
There are more than 200 sites in the U.S. There aren't a lot in coastal regions,
but there are some. Coastal regions are regarded as being somewhat under-represented
in the network. Nevertheless, there are some, as can be seen from the site map at:
http://nadp.sws.uiuc.edu/sites/ntnmap.asp?
You can download data for any of the sites, and there are data going back many years.
Data includes the concentration of sodium and chloride in the precipitation, as well
as other ions and the pH.
There is also the IMPROVE network -- website at: http://vista.cira.colostate.edu/IMPROVE/
This network samples aerosols around the country. There are only a few "coastal" sites.
At many of the IMPROVE sites, the composition of the atmospheric aerosol is measured,
including I think the concentrations of sodium and chloride.
Dr. Mark Cohen