Precipitation scavenging of beryllium-7 (7Be): Observation results and parameterization

Abstract

This study aims to develop a 1D model that makes it possible to calculate the daily total 7Be wet deposition flux. For this purpose, long-term (2015–2021), high-frequency (daily) and time-synchronized series of observations of 7Be wet deposition flux and its atmospheric activity concentration are analyzed in this paper. Daily mean 7Be activity concentration in the atmosphere, daily total 7Be wet deposition flux and mean 7Be activity concentration, washout ratio, deposition velocity and scavenging coefficient with individual precipitation events lie in the range of 0.1–17 mBq m−3, 0.8–117.2 Bq m−2 d−1, 0.4–11.3 Bq L−1, 331–3799, 0.2–24.7 cm s−1 and (0.8–35.6) × 10−5 s−1, respectively. Quantitative estimates of the influence of precipitation parameters (amount, intensity and duration) on the daily total 7Be wet deposition flux, mean 7Be activity concentration in precipitation, washout ratio, deposition velocity and scavenging coefficient with individual precipitation events have been obtained using correlation analysis. It has been found that precipitation amount has the greatest influence on 7Be deposition flux and deposition velocity, precipitation intensity has the greatest influence on washout ratio and scavenging coefficient, and precipitation duration has the greatest influence on 7Be activity concentration in precipitation. The relationships between these parameters have been parameterized. Based on these parameterizations, five 1D models that calculate the daily total 7Be wet deposition flux have been introduced and validated against the observation data. It has been revealed that the model, which is based on deposition velocity parameterization and uses the data on 7Be activity concentration in the atmosphere and the daily amount of precipitation as predictors, reproduces the highest fraction of the observational data (88%) with the lowest average calculation error (32%) compared to the other four models.