Days 181.0 to 187.0, 30-June to 06-July

Significant events at the ship during this period.
Meteorological Summary: A low pressure system moved over the ship on day 182 (1 July). This is seen in the radiosonde data showing no boundary layer on day 182 (convective to over 5km), in the winds at all levels under 5km becoming less southwesterly and more northwesterly, in the surface solar radiation measurements (one of the most cloudy days), and in the satellite pictures showing a clearly defined low. During most of this period back trajectories arrived at the ship from the north for altitudes of 750mb and lower. By the last day of this period (day 186, 5July) a high pressure system west of the Iberian Peninsula had moved sufficiently north to draw trajectories from the east, drawing polluted air over the ship. This feature is also seen in the radiosonde wind plot, with winds at altitudes of 500 to 2000m shifting from westerly to easterly during day 185. Boundary layer heights were near 2000m until day 185, except for an undefined BL during the frontal passage on day 182 and also on day 184. On day 186 BL heights dropped to 300m.

Met data available for Period 3