[1] A three-dimensional (3-D) cloud-scale chemical transport model that includes a parameterized source of lightning NO x on the basis of observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (P IC ) and cloud-to-ground (P CG ) flash is estimated by assuming various values of P IC and P CG for each storm and determining which production scenario yields NO x mixing ratios that compare most favorably with in-cloud aircraft observations. We obtain a mean P CG value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, P IC may be nearly equal to P CG , which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud-to-ground flashes. This study also presents vertical profiles of the mass of lightning NO x after convection based on 3-D cloud-scale model simulations. The results suggest that following convection, a large percentage of lightning NO x remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2-D cloud-scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a ''C-shaped'' profile). The new model results (a backward C-shaped profile) suggest that chemical transport models that assume a C-shaped vertical profile of lightning NO x mass may place too much mass near the surface and too little in the middle troposphere.

[1] A three-dimensional cloud-scale chemical transport model has been used to simulate trace gas transport, lightning NO production, and photochemical ozone production in the 12 July 1996 storm observed during the Stratosphere-Troposphere Experiment: Radiation, Aerosols and Ozone (STERAO-A) field experiment. The model is driven by meteorological fields from a nonhydrostatic cloud-resolving model (see Stenchikov et al., 2005). An assumption that both cloud-to-ground and intracloud flashes produce 460 moles NO/flash on average yielded the best comparison with the profile of NO observed in the storm anvil. Scenarios in which the NO production of an intracloud flash was 75 to 100% of the production of a cloud-to-ground flash best matched the column NO x mass computed from observations. Additional ozone production attributable to lightning NO within the storm cloud during the lifetime of the storm was very small ($2 ppbv). However, simulations of the photochemistry over the 24 hours following the storm show that an additional 10 ppbv of ozone production can be attributed to lightning NO production in the upper troposphere. Convective transport of HO x precursors led to the generation of a HO x plume, which substantially aided the downstream ozone production. Soluble species mixing ratios in the simulated cloud were all within a factor of two of observations. Citation: DeCaria, A. J., K. E. Pickering, G. L. Stenchikov, and L. E. Ott (2005), Lightning-generated NO X and its impact on tropospheric ozone production: A three-dimensional modeling study of a Stratosphere-Troposphere Experiment: Radiation, Aerosols and Ozone (STERAO-A) thunderstorm,

Abstract. Recent in situ and satellite measurements suggest a contribution of ∼5 pptv to stratospheric inorganic bromine from short-lived bromocarbons. We conduct a modeling study of the two most important short-lived bromocarbons, bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ), with the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to account for this missing stratospheric bromine. We derive a "top-down" emission estimate of CHBr 3 and CH 2 Br 2 using airborne measurements in the Pacific and North American troposphere and lower stratosphere obtained during previous NASA aircraft campaigns. Our emission estimate suggests that to reproduce the observed concentrations in the free troposphere, a global oceanic emission of 425 Gg Br yr −1 for CHBr 3 and 57 Gg Br yr −1 for CH 2 Br 2 is needed, with 60% of emissions from open ocean and 40% from coastal regions. Although our simple emission scheme assumes no seasonal variations, the model reproduces the observed seasonal variations of the short-lived bromocarbons with high concentrations in winter and low concentrations in summer. This indicates that the seasonality of short-lived bromocarbons is largely due to seasonality in their chemical loss and transport. The inclusion Correspondence to: Q. Liang (qing.liang@nasa.gov) of CHBr 3 and CH 2 Br 2 contributes ∼5 pptv bromine throughout the stratosphere. Both the source gases and inorganic bromine produced from source gas degradation (Br VSLS y ) in the troposphere are transported into the stratosphere, and are equally important. Inorganic bromine accounts for half (2.5 pptv) of the bromine from the inclusion of CHBr 3 and CH 2 Br 2 near the tropical tropopause and its contribution rapidly increases to ∼100% as altitude increases. More than 85% of the wet scavenging of Br VSLS y occurs in large-scale precipitation below 500 hPa. Our sensitivity study with wet scavenging in convective updrafts switched off suggests that Br VSLS y in the stratosphere is not sensitive to convection. Convective scavenging only accounts for ∼0.2 pptv (4%) difference in inorganic bromine delivered to the stratosphere.

A B S T R A C TUsing an Observing System Simulation Experiment (OSSE), we investigate the impact of JAXA Greenhouse gases Observing SATellite 'IBUKI' (GOSAT) sampling on the estimation of terrestrial biospheric flux with the NASA Carbon Monitoring System Flux (CMS-Flux) estimation and attribution strategy. The simulated observations in the OSSE use the actual column carbon dioxide (X CO 2 ) b2.9 retrieval sensitivity and quality control for the year 2010 processed through the Atmospheric CO 2 Observations from Space algorithm. CMSFlux is a variational inversion system that uses the GEOS-Chem forward and adjoint model forced by a suite of observationally constrained fluxes from ocean, land and anthropogenic models. We investigate the impact of GOSAT sampling on flux estimation in two aspects: 1) random error uncertainty reduction and 2) the global and regional bias in posterior flux resulted from the spatiotemporally biased GOSAT sampling. Based on Monte Carlo calculations, we find that global average flux uncertainty reduction ranges from 25% in September to 60% in July. When aggregated to the 11 land regions designated by the phase 3 of the Atmospheric Tracer Transport Model Intercomparison Project, the annual mean uncertainty reduction ranges from 10% over North American boreal to 38% over South American temperate, which is driven by observational coverage and the magnitude of prior flux uncertainty. The uncertainty reduction over the South American tropical region is 30%, even with sparse observation coverage. We show that this reduction results from the large prior flux uncertainty and the impact of non-local observations. Given the assumed prior error statistics, the degree of freedom for signal is Â1132 for 1-yr of the 74 055 GOSAT X CO 2 observations, which indicates that GOSAT provides Â1132 independent pieces of information about surface fluxes. We quantify the impact of GOSAT's spatiotemporally sampling on the posterior flux, and find that a 0.7 gigatons of carbon bias in the global annual posterior flux resulted from the seasonally and diurnally biased sampling when using a diagonal prior flux error covariance.