Meteorological influences on coastal new particle formation

Abstract

The meteorological situation at the midlatitude coastal station of Mace Head, Ireland, is described based on observations during the New Particle Formation and Fate in the Coastal Environment (PARFORCE) experiments in September 1998 and June 1999. Micrometeorological sensors were mounted near the shore line on a small mast with a height of 3 m and on a 22 m high tower at about 100 m away from the sea. Turbulent fields of wind speed, air temperature, and water vapor were measured. Parameters such as the friction velocity, drag coefficient, kinematic fluxes of heat and water vapor, and various variances were derived. The influence of meteorological parameters on coastal nucleation events is examined, and it is found that the occurrence of nucleation is, more or less, independent of air mass origin and is primarily driven by the occurrence of exposed shore areas during low tide and solar radiation. Micrometeorological influences were also examined in terms of promoting particle production events in this environment. A positive correlation was found between kinematic heat flux and particle production probability. In contrast, a strong negative correlation was found between production probability and both kinematic water vapor fluxes and relative humidity. These results indicate that the occurrence of new particle production events in the coastal zone are most probable during conditions when the shore area containing coastal biota has dried out and the biota are exposed directly to the solar radiation flux and increased shore, or surface, temperatures. These conditions correspond to drying and stressing of the biota, which is known to increase the emissions of biogenic vapors.