Test of Wet Scavenging Parameterization Schemes by Simulation of Monthly Depositions of ⁷Be using Normally Available Data on Environmental Monitoring and Local Meteorology

Abstract

Two wet scavenging parameterization schemes, those of Kasibhatla et al. (K scheme) and Giorgi and Chameides (GC scheme), were examined by the simulation of beryllium-7 (⁷Be) monthly depositions using normally available data on environmental monitoring and local meteorology. The washout scheme of ApSimon et al. and the dry deposition scheme of Wesely et al. were used for the calculation of the total ⁷Be depositions. By simulation over a 5-year period, from 1986 to 1990, the following conclusions were drawn: (1) Annual mean monthly depositions of ⁷Be simulated by the K and GC schemes agreed with the annual mean observed ones within about a factor of 2. The ratio of the monthly depositions simulated by the GC scheme to the observed ones was much closer to 1 than that of the K scheme; (2) the ⁷Be monthly depositions simulated with the K scheme showed a tendency to exceed the observed ones, when heavy rain was measured. The overestimation was reduced by taking the decrease of ⁷Be in clouds from rainout into consideration. It was suggested that aerosols containing ⁷Be were removed at a relatively high rate in comparison to the supply of aerosols containing ⁷Be, based on an atmospheric diffusion and concentration gradient.

KEYWORDS:

• aerosol
• rainout
• washout coefficient
• dry deposition velocity
• natural radionuclides
• beryllium 7
• deposition
• meteorology
• environmental monitoring