Test of Wet Scavenging Parameterization Schemes by Simulation of Monthly Depositions of7Be using Normally Available Data on Environmental Monitoring and Local Meteorology

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

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.

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation

This study uses airborne cloud water composition measurements to characterize the vertical structure of air-equivalent mass concentrations of water-soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water-soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in-cloud altitude for particulate species directly emitted from sources below cloud without in-cloud sources (e.g., Cl^- and Na⁺), (ii) an increase of concentration with in-cloud altitude (e.g., NO₂ ^- and formate), and (iii) species exhibiting a peak in concentration in the middle of cloud (e.g., non-sea-salt SO₄ ^2-, NO₃ ^-, and organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.