Spectral analysis of variations of the concentrations of near-ground submicron aerosol and soot

摘要

Continuous round-the-clock measurements of the aerosol scattering coefficient of the dry matter of aerosol particles at the wavelength of 0.52 μm (nephelometer) and the mass concentration of Black Carbon (aethalometer) were carried out at the aerosol monitoring station IAO in 1998-2003. Seasonal, annual and total data arrays are formed, and the power density spectra of variations of the aerosol characteristics in the ranges of diurnal, synoptic and seasonal oscillations are calculated. Analysis of the 6-year series of observations allowed us to reveal the significant mean frequencies of oscillations of aerosol, BC and relative content of BC in particles in the short-period (up to 1 month) and long-period (from 1 to 6 months) ranges: 0.5, 1, 2, 3.5, 5, 7, 10-11, 15, 20 days and 1, 1.5, 2.3, 3, 4.3 and 6 months. The amplitude spectra of aerosol and soot variations are close to each other and have the interannual stability. Summer is characterized by the most stable shape of spectra containing the majority of frequencies. The amplitudes of oscillations with the periods less than 3.5 days decrease when passing to cold season, and many spectral lines are shifted and split. On the contrary to aerosol, the 0.5-day period of oscillations of black carbon (soot) is usually observed. It is evidence of the fact that the idea of existence of the absorbing substance as a passive admixture in the composition of particles is only an approximation. Contributions of diurnal, synoptic and seasonal oscillations into the total variance of the aerosol and BC concentrations are estimated.