z-logo
open-access-imgOpen Access
Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer
Author(s) -
Andronache Constantin
Publication year - 2004
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003jd004050
Subject(s) - aerosol , scavenging , precipitation , atmospheric sciences , ultrafine particle , environmental science , nucleation , mass concentration (chemistry) , particle size , meteorology , chemistry , materials science , physics , nanotechnology , thermodynamics , biochemistry , antioxidant
Ultrafine particles (UFP) formed in the boundary layer (BL) by nucleation processes need to grow up to a diameter d p ∼ 100 nm to become activated as cloud droplets (CD). The time required to reach d p = 100 nm is about 2–3 days for a typical growth rate of 5 nm h −1 . If precipitation occurs, most UFP are too small to become CD, and some particles are removed by scavenging processes. A model to estimate the UFP wet removal from the BL by rainfall and coagulation is presented. The scavenging coefficient that describes the decay of aerosol mass in various size bins is a function of aerosol size ( d p ), rainfall rate ( R ), and BL background aerosol. The model is applied to determine the UFP 0.5‐folding time ( t 05 ) during rain events and results show that t 05 ∼ 1 hour for R ∼ 1 mm h −1 for newly created particles ( d p < 10 nm) and t 05 ∼ 1 day for larger UFP ( d p ∼ 10–100 nm). To infer the likelihood of UFP removal at a given location, the average time interval (Δ t ) between rain events with rainfall rate R = 1 mm h −1 at stations with different precipitation regimes was determined. Results show that on average, UFP are very effectively removed from the BL by below‐cloud scavenging in tropical regions (Δ t ∼ 1 day), removed to a significant extent in eastern U.S. regions (Δ t ∼ 3 days), and are less likely to be removed in southwest U.S. regions (Δ t ∼ 6–8 days), where the frequency of dry periods is high and UFP have sufficient time to grow.

The content you want is available to Zendy users.

Already have an account? Click here to sign in.
Having issues? You can contact us here