Using beryllium-7 to assess cross-tropopause transport in global models

Abstract

Abstract. We use the Global Modeling Initiative (GMI) modeling framework to assess the utility of cosmogenic beryllium-7 ( 7 Be), a natural aerosol tracer, for evaluating cross-tropopause transport in global models. The GMI chemical transport model (CTM) was used to simulate atmospheric 7 Be distributions using four different meteorological data sets (GEOS1-STRAT DAS, GISS II GCM, fvGCM, and GEOS4-DAS), featuring significantly different stratosphere-troposphere exchange (STE) characteristics. The simulations were compared with the upper troposphere and/or lower stratosphere (UT/LS) 7 Be climatology constructed from ∼ 25 years of aircraft and balloon data, as well as climatological records of surface concentrations and deposition fluxes. Comparison of the fraction of surface air of stratospheric origin estimated from the 7 Be simulations with observationally derived estimates indicates excessive cross-tropopause transport at mid-latitudes in simulations using GEOS1-STRAT and at high latitudes using GISS II meteorological data. These simulations also overestimate 7 Be deposition fluxes at mid-latitudes (GEOS1-STRAT) and at high latitudes (GISS II ), respectively. We show that excessive cross-tropopause transport of 7 Be corresponds to overestimated stratospheric contribution to tropospheric ozone. Our perspectives on STE in these meteorological fields based on 7 Be simulations are consistent with previous modeling studies of tropospheric ozone using the same meteorological fields. We conclude that the observational constraints for 7 Be and observed 7 Be total deposition fluxes can be used routinely as a first-order assessment of cross-tropopause transport in global models.

Global O<sub>3</sub>–CO correlations in a chemistry and transport model during July–August: evaluation with TES satellite observations and sensitivity to input meteorological data and emissions

“…Because 210 Pb and 7 Be attach to submicron aerosols after production and are therefore scavenged by precipitation or deposited to the surface, they have been used as a pair to test wet-deposition schemes in global models (e.g., Liu et al, 2001). 7 Be is also used as a tracer for STE (Dibb et al, 1994;Liu et al, 2001Liu et al, , 2016. The ratio 7 Be / 210 Pb is useful as an indicator of vertical transport because the ratio is insensitive to precipitation scavenging (Koch et al, 1996).…”

“…The number of soundings at each station is adequate for defining monthly means used to evaluate the accuracy of the model results Liu et al, 2016). Three TOC products are used in this study: Total Ozone Mapping Spectrometer (TOMS)-Solar Backscatter Ultraviolet (SBUV), OMI/MLS, and directly retrieved TOC from TES.…”

“…The model can incorporate different inputs and components (e.g., meteorological fields, emission inventories, and chemical mechanisms), allowing us to test the sensitivity of model simulations to input meteorological data sets (e.g., Douglass et al, 1999;Considine et al, 2005;Liu et al, 2016). Model simulations are evaluated using ozonesonde and satellite observations.…”

Meteorological Notes for Understanding the Transport of Beryllium-7 in the Troposphere

“…3 in LIU et al. 18) According to their results, in mid-and high latitudes where concentrations are large, the latitudinal difference in concentrations is small. Thus, the gradient is recognized solely in the vertical direction.…”

Regional background O<sub>3</sub> and NO<sub><i>x</i></sub> in the Houston–Galveston–Brazoria (TX) region: a decadal-scale perspective

“…Two intensive air quality campaigns investigated peak O 3 in the HGB region during 2000 and 2006 (Daum et al, 2003;Ryerson et al, 2003;Daum et al, 2004;Banta et al, 2005;Rappenglück et al, 2008;Neuman et al, 2009;Pierce et al, 2009;Langford et al, 2010a). The O 3 pollution in this region was likely a result of abundant precursors emitted locally from urban and industrial sources (particularly, the highly reactive VOCs (HRVOCs) from the petroleum refineries) and the local chemistry sustained by the high summer temperature and land-sea breeze effects.…”