R/V Ronald H. Brown Daily Summaries

Daily Summary July 21, 2002, DOY = 202

As forecast, the winds in the western part of the Gulf of Maine veered to the SW after midnight. Surface winds were from the west for a short period around dawn. The winds were light and generally from the SW through the morning and early afternoon backing to the southeast and increasing substantially as a sea breeze set up along the coast.

The ship spent the predawn hours on a track from about 6 nm off the tip of Cape Ann to a point about 2 miles south of White Island. At approximately 8:30 AM local time the ship began to execute a box pattern around the Isles of Shoals with one 10 nm leg 2nm off of, and parallel to the NH coast. This pattern was continued throughout the day with one break for an easterly leg to a point approximately 20 nm off the coast to map the wind and pollutant fields off shore.

Pollution levels in the Gulf rose soon after the wind shifted to the SW. NOy levels were around 10 ppb throughout most of the area sampled with levels above 20 ppb in the SW sector. This sector also contained elevated levels of sulfur dioxide and particles. Ozone levels rose slowly throughout the day reaching a maximum around 50 ppb, which was sustained throughout most of the afternoon. Concentrations of both gaseous and particulate pollutants dropped dramatically as the ship moved more than 10 nm from the NH coast. Numerous plumes associated with commercial and recreational boat traffic were seen throughout the day.

Nighttime levels of NO3 and N2O5 were quite low due to low levels of the precursor compounds, NO2 and ozone. However there was 'a little less of nothing than the night before'. Clearly, some of us have been at sea too long. The aerosols being sampled in the New England area continue to contain more acidity than those collected in the clean marine air that was encountered early in the cruise. The VOC samples collected during the day showed the presence of anthropogenic VOCs (aromatics) and well-processed biogenics (i.e., isoprene).

For all plots, time is indicated in GMT. Eastern time is -5 hours.

Temperature, Pressure
Sea Surface Temperature, Relative Humidity
True Wind Speed, Direction
Ship Speed, Direction
Relative Wind Speed, Direction

Textual information and data plots are for quicklook and overview purposes only.