THE JUNGFRAUJOCH HIGH-ALPINE RESEARCH STATION (3454M) AS A BACKGROUNDCLEAN CONTINENTAL SITE FOR THE MEASUREMENT OF AEROSOL PARAMETERS

The first annual data set of climatically important aerosol parameters , measured at the Jungfraujoch (JFJ) high-alpine research station (345 4 m, Switzerland) from an ongoing field campaign since July 1995, is p resented. Analysis of diurnal variations in continuous measurements of the total and backward hemispheric scattering coefficients (sigma(SP) , sigma(BSP)), the absorption coefficient (sigma(AP), from aethalomete r data), condensation nuclei (CN) concentration, and epiphaniometer si gnal (related to surface area (S) concentration) established the diurn al period 0300-0900 as being representative of the free tropospheric b ackground aerosol. The annual data set was then edited to omit (1) the period 0900-0300 (i.e., 18 hours), taken to represent possible planet ary boundary layer influenced conditions and (2) in-cloud conditions u sing a cloud liquid-water monitor. The seasonal aerosol cycle exhibite d a July maximum and a December minimum in most aerosol parameters. Ty pical monthly median values for the free troposphere exhibit the follo wing seasonal maxima and minima, respectively: sigma(SP) (550 nm) simi lar to 16.1 and 0.43 x 10(-6) m(-1), sigma(BSP) (550 nm) similar to 2. 10 and 0.09 x 10(-6) m(-1), sigma(AP) (550 nm) similar to 10.4 and 0.7 6 x 10(-7) m(-1) (approximate to 104 and 7.6 ng m(-3) black carbon), C N concentration similar to 670 and 280 cm(-3), and epiphaniometer sign al similar to 9.26 and 0.67 counts s(-1) (S concentration approximate to 24.1 and 1.7 mu m(2) cm(-3)). Aerosol parameters were found to be c omparable in magnitude to other NOAA baseline and regional stations an d suggest that a clean continental designation for the JFJ site is app licable, when removing the planetary boundary layer influenced period.