Stratospheric Injection of Brominated Very Short‐Lived Substances: Aircraft Observations in the Western Pacific and Representation in Global Models

We quantify the stratospheric injection of brominated very short‐lived substances (VSLS) based on aircraft observations acquired in winter 2014 above the Tropical Western Pacific during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and the Airborne Tropical TRopopause EXperiment (ATTREX) campaigns. The overall contribution of VSLS to stratospheric bromine was determined to be 5.0 ± 2.1 ppt, in agreement with the 5 ± 3 ppt estimate provided in the 2014 World Meteorological Organization (WMO) Ozone Assessment report (WMO 2014), but with lower uncertainty. Measurements of organic bromine compounds, including VSLS, were analyzed using CFC‐11 as a reference stratospheric tracer. From this analysis, 2.9 ± 0.6 ppt of bromine enters the stratosphere via organic source gas injection of VSLS. This value is two times the mean bromine content of VSLS measured at the tropical tropopause, for regions outside of the Tropical Western Pacific, summarized in WMO 2014. A photochemical box model, constrained to CONTRAST observations, was used to estimate inorganic bromine from measurements of BrO collected by two instruments. The analysis indicates that 2.1 ± 2.1 ppt of bromine enters the stratosphere via inorganic product gas injection. We also examine the representation of brominated VSLS within 14 global models that participated in the Chemistry‐Climate Model Initiative. The representation of stratospheric bromine in these models generally lies within the range of our empirical estimate. Models that include explicit representations of VSLS compare better with bromine observations in the lower stratosphere than models that utilize longer‐lived chemicals as a surrogate for VSLS

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Tropospheric Chemical Impact of Considering a Surrogate vs. an Explicit VSLBr Mechanism on the O3 and HOx Distributions within the CAM-Chem model

EGU General Assembly 2019,Vienna, Austria, 7–12 April 2019. -- https://www.geophysical-research-abstracts.net/egu2019.html. -- Conferencia invitadaThe contribution of very short-lived bromine (VSLBr) represent 5 ± 2 ppt ( ~ 25%) of total stratospheric bromine (WMO, 2018), which is still nowadays dominated by long-lived bromocarbons that do not impact on tropospheric chemistry. Due to their shorter lifetimes, the overall injection to the stratosphere of VSLBr compounds possesses two distinct pathways: i) Source Gas Injection (SGI), where the brominated species are injected as they were emit- ted at the surface; and ii) Product Gas Injection (PGI), where the photochemical processing of reactive species aris- ing from SG degradation must be considered. Depending on the partitioning and distribution of SGI and PGI, the chemical impact of VSLBr on tropospheric and lowermost stratospheric ozone, HO x and other oxidizing species can be very different. Many Chemistry Climate Models (CCMs) include a simplified treatment of tropospheric VSLBr sources by as- suming a long-lived halocarbon (usually CH3Br) as a Surrogate for VSLBr. Even though these surrogate models possess a consistent evolution of the stratospheric bromine loading, CCMs including an explicit VSLBr represen- tation compare better with organic and inorganic bromine observations in the lowermost stratosphere (Wales et al., 2018). Here we used the halogenated version of the CAM-Chem model (Fernandez et al., 2014) to evaluate the chemical impact of considering an explicit treatment of VSLBr versus considering a simplified tropospheric treatment of long-lived CH3Br as surrogate of VSLBr. The explicit mechanism considers a full gas- and aerosol- phase chem- ical scheme (including sea-salt dehalogenation) as well as time-dependent and geographically-distributed VSLBr emissions inventory (Ordoñez et al., 2012), which replaces the typical lower-boundary surface conditions for long- lived compounds usually considered in CCMs. An additional baseline simulation neglecting the contribution of VSLBr is also considered. First we show the differences in the overall inorganic bromine (Bry) burden as a func- tion of altitude, latitude and time of the year, and compare the model changes on SGI and PGI for each model configuration. Based on the vertical and latitudinal Bry distributions, we focus the analysis on determining the surrogate vs. explicit VSLBr impact on the tropospheric ozone burden, as well as the changes in HO x and NO x mixing ratios within different regions. In particular, seasonal variations in the Odd-Oxygen chemical loss channels during within the marine boundary layer (MBL), tropical tropopause layer (TTL) and mid-latitudes upper tropo- sphere (UT) are evaluated. Our results indicate that the impact of VSLBr species is strongly underestimated when a simplified treatment of tropospheric VSLBr chemistry is considered, which might have strong climatic impacts

Intercomparison between surrogate, explicit, and full treatments of VSL bromine chemistry within the CAM-Chem chemistry-climate model

Many Chemistry-Climate Models (CCMs) include a simplified treatment of brominated very short-lived (VSLBr) species by assuming CH3Br as a surrogate for VSLBr. However, neglecting a comprehensive treatment of VSLBr in CCMs may yield an unrealistic representation of the associated impacts. Here, we use the Community Atmospheric Model with Chemistry (CAM-Chem) CCM to quantify the tropospheric and stratospheric changes between various VSLBr chemical approaches with increasing degrees of complexity (i.e., surrogate, explicit, and full). Our CAM-Chem results highlight the improved accuracy achieved by considering a detailed treatment of VSLBr photochemistry, including sea-salt aerosol dehalogenation and heterogeneous recycling on ice-crystals. Differences between the full and surrogate schemes maximize in the lowermost stratosphere and midlatitude free troposphere, resulting in a latitudinally dependent reduction of ∼1–7 DU in total ozone column and a ∼5%–15% decrease of the OH/HO2 ratio. We encourage all CCMs to include a complete chemical treatment of VSLBr in the troposphere and stratosphere.Fil: Fernandez, Rafael Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Interdisciplinario de Ciencias Básicas. - Universidad Nacional de Cuyo. Instituto Interdisciplinario de Ciencias Básicas; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; España. Universidad Tecnológica Nacional. Facultad Regional de Mendoza; ArgentinaFil: Barrera, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Interdisciplinario de Ciencias Básicas. - Universidad Nacional de Cuyo. Instituto Interdisciplinario de Ciencias Básicas; ArgentinaFil: Lopez Noreña, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Tecnológica Nacional. Facultad Regional de Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Kinnison, Douglas E.. National Center for Atmospheric Research; Estados UnidosFil: Nicely, Julie M.. University of Maryland; Estados Unidos. Nasa Goddard Space Flight Center; Estados UnidosFil: Salawitch, Ross J.. University of Maryland; Estados UnidosFil: Wales, Pamela A.. Nasa Goddard Space Flight Center; Estados Unidos. Universities Space Research Association; Estados UnidosFil: Toselli, Beatriz Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Tilmes, Simone. National Center for Atmospheric Research; Estados UnidosFil: Lamarque, Jean François. National Center for Atmospheric Research; Estados UnidosFil: Cuevas, Carlos Alberto. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Saiz López, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; Españ

BrO and inferred Bry profiles over the western Pacific : Relevance of inorganic bromine sources and a Bry minimum in the aged tropical tropopause layer

We report measurements of bromine monoxide (BrO) and use an observationally constrained chemical box model to infer total gas-phase inorganic bromine (Bry) over the tropical western Pacific Ocean (tWPO) during the CONTRAST field campaign (January-February 2014). The observed BrO and inferred Bry profiles peak in the marine boundary layer (MBL), suggesting the need for a bromine source from sea-salt aerosol (SSA), in addition to organic bromine (CBry). Both profiles are found to be C-shaped with local maxima in the upper free troposphere (FT). The median tropospheric BrO vertical column density (VCD) was measured as 1.6×1013 molec cm-2, compared to model predictions of 0.9×1013 molec cm-2 in GEOS-Chem (CBry but no SSA source), 0.4×1013 molec cm-2 in CAM-Chem (CBry and SSA), and 2.1×1013 molec cm-2 in GEOS-Chem (CBry and SSA). Neither global model fully captures the C-shape of the Bry profile. A local Bry maximum of 3.6 ppt (2.9-4.4 ppt; 95 % confidence interval, CI) is inferred between 9.5 and 13.5 km in air masses influenced by recent convective outflow. Unlike BrO, which increases from the convective tropical tropopause layer (TTL) to the aged TTL, gas-phase Bry decreases from the convective TTL to the aged TTL. Analysis of gas-phase Bry against multiple tracers (CFC-11, H2O-O3 ratio, and potential temperature) reveals a Bry minimum of 2.7 ppt (2.3-3.1 ppt; 95 % CI) in the aged TTL, which agrees closely with a stratospheric injection of 2.6 ± 0.6 ppt of inorganic Bry (estimated from CFC-11 correlations), and is remarkably insensitive to assumptions about heterogeneous chemistry. Bry increases to 6.3 ppt (5.6-7.0 ppt; 95 % CI) in the stratospheric "middleworld" and 6.9 ppt (6.5-7.3 ppt; 95 % CI) in the stratospheric "overworld". The local Bry minimum in the aged TTL is qualitatively (but not quantitatively) captured by CAM-Chem, and suggests a more complex partitioning of gas-phase and aerosol Bry species than previously recognized. Our data provide corroborating evidence that inorganic bromine sources (e.g., SSA-derived gas-phase Bry) are needed to explain the gas-phase Bry budget in the upper free troposphere and TTL. They are also consistent with observations of significant bromide in Upper Troposphere-Lower Stratosphere aerosols. The total Bry budget in the TTL is currently not closed, because of the lack of concurrent quantitative measurements of gas-phase Bry species (i.e., BrO, HOBr, HBr, etc.) and aerosol bromide. Such simultaneous measurements are needed to (1) quantify SSA-derived Bry in the upper FT, (2) test Bry partitioning, and possibly explain the gas-phase Bry minimum in the aged TTL, (3) constrain heterogeneous reaction rates of bromine, and (4) account for all of the sources of Bry to the lower stratosphere

Clinical Clearance of the Cervical Spine in Blunt Trauma Patients Younger than 3 Years: a Multi-Center Study of the American Association for the Surgery of Trauma.

BACKGROUND: Cervical spine clearance in the very young child is challenging. Radiographic imaging to diagnose cervical spine injuries (CSI) even in the absence of clinical findings is common, raising concerns about radiation exposure and imaging-related complications. We examined whether simple clinical criteria can be used to safely rule out CSI in patients younger than 3 years. METHODS: The trauma registries from 22 level I or II trauma centers were reviewed for the 10-year period (January 1995 to January 2005). Blunt trauma patients younger than 3 years were identified. The measured outcome was CSI. Independent predictors of CSI were identified by univariate and multivariate analysis. A weighted score was calculated by assigning 1, 2, or 3 points to each independent predictor according to its magnitude of effect. The score was established on two thirds of the population and validated using the remaining one third. RESULTS: Of 12,537 patients younger than 3 years, CSI was identified in 83 patients (0.66%), eight had spinal cord injury. Four independent predictors of CSI were identified: Glasgow Coma Score CONCLUSIONS: CSI in patients younger than 3 years is uncommon. Four simple clinical predictors can be used in conjunction to the physical examination to substantially reduce the use of radiographic imaging in this patient population