COASTAL CCN MEASUREMENTS AT MACE HEAD WITH ENHANCED CONCENTRATIONS INSTRONG WINDS

Surface measurements of cloud condensation nuclei (CCN) number concent ration (cm(-3)) are presented for unmodified marine air and for pollut ed air at Mace Head, for the years 1994 and 1995. The CCN number conce ntration active at 0.5% supersaturation is found to be approximately l og-normal for marine and polluted air at the site. Values of geometric mean, median and arithmetic mean of CCN number concentration (cm(-3)) for marine air are in the range 124-135, 140-150 and 130-157 for the two years of data. Analysis of CCN number concentration for high wind speed, U, up to 20 m s(-1) show enhanced CCN production for U in exces s of about 10-12 m s(-1). Approximately 7% increase in CCN per 1 m s(- 1) increase in wind speed is found, up to 17 m s(-1). A relationship o f the form log(10)CCN = a + bU is obtained for the periods March 1994 and January, February 1995 for marine air yielding values a of 1.70; 1 .90 and b of 0.035 for both periods. (C) 1998 Elsevier Science B.V.