Aerosol observations were carried out at Ny-Alesund, Svalbard. Arctic from December 15, 1997 to March 11, 1998. Variation of aerosol particle number in the period measured by the optical particle counter is reported in this paper. Three observational flights around Svalbard were carried out between March 8 and 10,1998. The flights were part of the Arctic Airborne Measurement
Program 1998 (AAMP 98). Detailed data in the above period are also reported for supporting discussions with flight observation data.