Data management office notes on supplementary fields - aerosols data

lat, lon

A nominal ship location is given in lat/lon.  The location is the noon
position most near the middle of the sampling period, e.g. for a sample
which was pumped intermittently from Jan. 3 - 5, the location is given for
noon, Jan. 4.  Intended as an aid to understanding, not a discrete location.

date_begin, date_end

We have included the start and stop day for each sample which we
believe constrains the sample time about as well as is useful for these
data.  We also have pump volume and thus a mean concentration of dust
per cubic meter of air for that time frame.  The actual number of hours
sampled during a time block (number of days) is complicated to
present.  Pumps were turned on and off repetitively depending upon ship
maneuvers and relative wind direction (to prevent ship exhaust
contamination).  Also, the total number of hours the pumps were on is a
less useful measure than pump volume, because of the variability in
pump efficiency due to changing barometric pressures. An hours worth of
pumping does not always yield the same volume of air.