Cloud-resolving simulations of mercury scavenging and deposition in thunderstorms
| Autor: | Yuling Wu, J. T. Walters, Christopher D. Holmes, U. S. Nair, A. Ter Schure, George Kallos |
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| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Atmospheric Science
Convective Storms chemistry.chemical_element Transport Atmospheric sciences Troposphere lcsh:Chemistry Microphysics Parameterization Physical Sciences and Mathematics Upper Troposphere Atmospheric Mercury Scavenging Aerosols Wet Deposition Precipitable water Lower Stratosphere Life Sciences lcsh:QC1-999 Mercury (element) North-America Deposition (aerosol physics) chemistry lcsh:QD1-999 Climatology Regional Atmospheric Modeling System Convective storm detection Thunderstorm Florida Environmental science lcsh:Physics |
| Zdroj: | Nair, U. S; Wu, Y.; Holmes, C. D; Ter Schure, A.; Kallos, G.; & Walters, J. T. (2013). Cloud-resolving simulations of mercury scavenging and deposition in thunderstorms. Atmospheric Chemistry and Physics, 13(19), 10143-10157. doi: 10.5194/acp-13-10143-2013. UC Irvine: Retrieved from: http://www.escholarship.org/uc/item/6rr975hg Atmospheric Chemistry and Physics, Vol 13, Iss 19, Pp 10143-10157 (2013) |
| Popis: | This study examines dynamical and microphysical features of convective clouds that affect mercury (Hg) wet scavenging and concentrations in rainfall. Using idealized numerical model simulations in the Regional Atmospheric Modeling System (RAMS), we diagnose vertical transport and scavenging of soluble Hg species in thunderstorms under typical environmental conditions found in the Northeast and Southeast United States (US). Three important environmental characteristics that impact thunderstorm morphology were studied: convective available potential energy (CAPE), vertical shear (0–6 km) of horizontal wind (SHEAR) and precipitable water (PW). We find that in a strong convective storm in the Southeast US that about 40% of mercury in the boundary layer (0–2 km) can be scavenged and deposited to the surface. Removal efficiencies are 35% or less in the free troposphere and decline with altitude. Nevertheless, if we assume that soluble Hg species are initially uniformly mixed vertically, then about 60% deposited mercury deposited by the thunderstorm originates in the free troposphere. For a given CAPE, storm morphology and Hg deposition respond to SHEAR and PW. Experiments show that the response of mercury concentration in rainfall to SHEAR depends on the amount of PW. For low PW, increasing SHEAR decreases mercury concentrations in high-rain amounts (>13 mm). However, at higher PW values, increasing SHEAR decreases mercury concentrations for all rainfall amounts. These experiments suggest that variations in environmental characteristics relevant to thunderstorm formation and evolution can also contribute to geographical difference in wet deposition of mercury. An ensemble of thunderstorm simulations was also conducted for different combinations of CAPE, SHEAR and PW values derived from radiosonde observations at five sites in the Northeast United States (US) and at three sites in the Southeast US. Using identical initial concentrations of gaseous oxidized mercury (GOM) and particle-bound mercury (HgP), from the GEOS-Chem model, the simulations predict higher mercury concentrations in rainfall from thunderstorms forming in the environmental conditions over the Southeast US compared to the Northeast US. Mercury concentrations in rainfall are also simulated for a typical stratiform rain event and found to be less than in thunderstorms forming in environments typical of the Southeast US. The stratiform cloud scavenges mercury from the lower ~4 km of the atmosphere, while thunderstorms scavenge up to ~10 km. |
| Databáze: | OpenAIRE |
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