Troposphere

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Daniel J Jacob - One of the best experts on this subject based on the ideXlab platform.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 3 origin of tropospheric ozone and effects of nonmethane hydrocarbons
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Daniel J Jacob, Jennifer A Logan
    Abstract:

    A global three-dimensional model of tropospheric O3-NOx-hydrocarbon chemistry is used to investigate the factors controlling ozone concentrations in the Troposphere. Model results indicate a close balance between chemical production and chemical loss of ozone in the tropospheric column at all latitudes (except high latitudes in winter). Using separate tracers for ozone produced in the stratosphere and in different regions of the Troposphere, we find that the contribution of transport from the stratosphere to ozone concentrations in the Troposphere is about 30% at midlatitudes in winter, 10% in summer, and 5% in the tropics. Production of ozone in the upper, middle, and continental lower Troposphere all make significant contributions (10–50%) to ozone concentrations throughout the Troposphere. The middle Troposphere is a major global source region for ozone even though it is not a region of net production. The springtime maximum of ozone observed at remote sites in the northern extratropics is explained by a phase overlap between ozone transported from the stratosphere which peaks in late winter and ozone produced in the Troposphere which peaks in late spring. Our model results do not support previous explanations of the springtime maximum based on wintertime accumulation of ozone or its precursors in the Arctic. The particularly strong springtime maximum at Mauna Loa Observatory (Hawaii) is attributed to long-range transport of Asian pollution over the North Pacific in spring. A sensitivity simulation without nonmethane hydrocarbons (NMHCs) indicates small decreases of ozone concentrations (<15%) in the remote Troposphere and a 20% increase in the global mean OH concentration. Without NMHCs as a source of peroxyacetylnitrate, concentrations of NOx decrease by 30% in the remote lower Troposphere but increase by 70% in the continental lower Troposphere and by 40% in the upper Troposphere. Biogenic isoprene accounts for about half of the NMHC effects in the model.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 2 model evaluation and global ozone budget
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Jennifer A Logan, Daniel J Jacob
    Abstract:

    Results from a global three-dimensional model for tropospheric O3-NOx-hydrocarbon chemistry are presented and evaluated with surface, ozonesonde, and aircraft measurements. Seasonal variations and regional distributions of ozone, NO, peroxyacetylnitrate (PAN), CO, ethane, acetone, and H2O2 are examined. The model reproduces observed NO and PAN concentrations to within a factor of 2 for a wide range of tropospheric regions including the upper Troposphere but tends to overestimate HNO3 concentrations in the remote Troposphere (sometimes several fold). This discrepancy implies a missing sink for HNO3 that does not lead to rapid recycling of NOx; only in the upper Troposphere over the tropical South Atlantic would a fast conversion of HNO3 to NOx improve the model simulation for NOx. Observed concentrations of acetone are reproduced in the model by including a large biogenic source (15 Tg C yr−1), which accounts for 40% of the estimated global source of acetone (37 Tg C yr−1). Concentrations of H2O2 in various regions of the Troposphere are simulated usually to within a factor of 2, providing a test for HOx chemistry in the model. The model reproduces well the observed concentrations and seasonal variations of ozone in the Troposphere, with some exceptions including an underestimate of the vertical gradient across the tropical trade wind inversion. A global budget analysis in the model indicates that the supply and loss of tropospheric ozone are dominated by photochemistry within the Troposphere and that NOx. emitted in the southern hemisphere is twice as efficient at producing ozone as NOx emitted in the northern hemisphere.

  • a persistent imbalance in ho x and no x photochemistry of the upper Troposphere driven by deep tropical convection
    Geophysical Research Letters, 1997
    Co-Authors: Michael J Prather, Daniel J Jacob
    Abstract:

    Convection in the tropics turns over the upper Troposphere at rates (0.08 d−1) comparable to photochemical processes controlling the absolute abundance of HOx (OH + HO2) and the abundance of NOx (NO + NO2) relative to HNO3. Here we identify convection of boundary-layer CH3OOH as a primary source of HOx to the upper Troposphere. Turnover of NOx leads to NO/HNO3 ratios much higher than predicted for local photochemical steady-state. Through convective transport the upper Troposphere is more photochemically active in producing O3, an important greenhouse gas.

Jennifer A Logan - One of the best experts on this subject based on the ideXlab platform.

  • Ozone in the Pacific Troposphere from Ozonesonde Observations
    2020
    Co-Authors: Samuel J. Oltmans, Anne M Thompson, Jennifer A Logan, Bryan J. Johnson, Joyce M. Harris, H. Voemel, K. Koshy, P. Simon, R. J. Bendura, Fumio Hasebe
    Abstract:

    Ozone vertical profile measurements obtained from ozonesondes flown at Fiji, Samoa, Tahiti and the Galapagos are used to characterize ozone in the Troposphere over the tropical Pacific. There is a significant seasonal variation at each of these sites. At sites in both the eastern and western Pacific, ozone is highest at almost all levels in the Troposphere during the September-November season and lowest during, March-May. There is a relative maximum at all of the sites in the mid-Troposphere during all seasons of the year (the largest amounts are usually found near the tropopause). This maximum is particularly pronounced during, the September-November season. On average, throughout the Troposphere at all seasons, the Galapagos has larger ozone amounts than the western Pacific sites. A trajectory climatology is used to identify the major flow regimes that are associated with the characteristic ozone behavior at various altitudes and seasons. The enhanced ozone seen in the mid-Troposphere during September-November is associated with flow from the continents. In the western Pacific this flow is usually from southern Africa (although 10-day trajectories do not always reach the continent), but also may come from Australia and Indonesia. In the Galapagos the ozone peak in the mid-Troposphere is seen in flow from the South American continent and particularly from northern Brazil. The time of year and flow characteristics associated with the ozone mixing ratio peaks seen in both the western and eastern Pacific suggest that these enhanced ozone values result from biomass burning. In the upper Troposphere low ozone amounts are seen with flow that originates in the convective western Pacific.

  • origins of tropospheric ozone interannual variation over reunion a model investigation
    Journal of Geophysical Research, 2016
    Co-Authors: Jose M Rodriguez, Anne M Thompson, Jennifer A Logan, Anne R. Douglass, Mark A Olsen, Stephen D Steenrod, Francoise Posny
    Abstract:

    Observations from long-term ozone sonde measurements show robust variations and trends in the evolution of ozone in the middle and upper Troposphere over Reunion Island (21.1°S, 55.5°E) in June–August. Here we examine possible causes of the observed ozone variation at Reunion Island using hindcast simulations by the stratosphere-Troposphere Global Modeling Initiative chemical transport model for 1992–2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications meteorological fields. Reunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Reunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper Troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper Troposphere over Reunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited to the lower Troposphere near the surface in August–September.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 3 origin of tropospheric ozone and effects of nonmethane hydrocarbons
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Daniel J Jacob, Jennifer A Logan
    Abstract:

    A global three-dimensional model of tropospheric O3-NOx-hydrocarbon chemistry is used to investigate the factors controlling ozone concentrations in the Troposphere. Model results indicate a close balance between chemical production and chemical loss of ozone in the tropospheric column at all latitudes (except high latitudes in winter). Using separate tracers for ozone produced in the stratosphere and in different regions of the Troposphere, we find that the contribution of transport from the stratosphere to ozone concentrations in the Troposphere is about 30% at midlatitudes in winter, 10% in summer, and 5% in the tropics. Production of ozone in the upper, middle, and continental lower Troposphere all make significant contributions (10–50%) to ozone concentrations throughout the Troposphere. The middle Troposphere is a major global source region for ozone even though it is not a region of net production. The springtime maximum of ozone observed at remote sites in the northern extratropics is explained by a phase overlap between ozone transported from the stratosphere which peaks in late winter and ozone produced in the Troposphere which peaks in late spring. Our model results do not support previous explanations of the springtime maximum based on wintertime accumulation of ozone or its precursors in the Arctic. The particularly strong springtime maximum at Mauna Loa Observatory (Hawaii) is attributed to long-range transport of Asian pollution over the North Pacific in spring. A sensitivity simulation without nonmethane hydrocarbons (NMHCs) indicates small decreases of ozone concentrations (<15%) in the remote Troposphere and a 20% increase in the global mean OH concentration. Without NMHCs as a source of peroxyacetylnitrate, concentrations of NOx decrease by 30% in the remote lower Troposphere but increase by 70% in the continental lower Troposphere and by 40% in the upper Troposphere. Biogenic isoprene accounts for about half of the NMHC effects in the model.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 2 model evaluation and global ozone budget
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Jennifer A Logan, Daniel J Jacob
    Abstract:

    Results from a global three-dimensional model for tropospheric O3-NOx-hydrocarbon chemistry are presented and evaluated with surface, ozonesonde, and aircraft measurements. Seasonal variations and regional distributions of ozone, NO, peroxyacetylnitrate (PAN), CO, ethane, acetone, and H2O2 are examined. The model reproduces observed NO and PAN concentrations to within a factor of 2 for a wide range of tropospheric regions including the upper Troposphere but tends to overestimate HNO3 concentrations in the remote Troposphere (sometimes several fold). This discrepancy implies a missing sink for HNO3 that does not lead to rapid recycling of NOx; only in the upper Troposphere over the tropical South Atlantic would a fast conversion of HNO3 to NOx improve the model simulation for NOx. Observed concentrations of acetone are reproduced in the model by including a large biogenic source (15 Tg C yr−1), which accounts for 40% of the estimated global source of acetone (37 Tg C yr−1). Concentrations of H2O2 in various regions of the Troposphere are simulated usually to within a factor of 2, providing a test for HOx chemistry in the model. The model reproduces well the observed concentrations and seasonal variations of ozone in the Troposphere, with some exceptions including an underestimate of the vertical gradient across the tropical trade wind inversion. A global budget analysis in the model indicates that the supply and loss of tropospheric ozone are dominated by photochemistry within the Troposphere and that NOx. emitted in the southern hemisphere is twice as efficient at producing ozone as NOx emitted in the northern hemisphere.

David W J Thompson - One of the best experts on this subject based on the ideXlab platform.

  • a critical comparison of stratosphere Troposphere coupling indices
    Quarterly Journal of the Royal Meteorological Society, 2009
    Co-Authors: Mark P Baldwin, David W J Thompson
    Abstract:

    Assessing stratosphere-Troposphere coupling in observational data or model output requires a multi-level index with high time resolution. Ideally, such an index would (1) represent spatial patterns in the Troposphere that are most strongly coupled with stratospheric variability and (2) be robust and computationally feasible in both observations and standard model output. Several of the indices used to diagnose extratropical stratosphere-Troposphere coupling are based on the Northern and Southern Hemisphere annular modes. The annular mode indices are commonly defined as the leading empirical orthogonal functions (EOFs) of monthly-mean, hemispheric geopotential height. In the lowermost Troposphere, the structure of the annular modes is defined as the leading EOF of the near-surface geopotential height field, and these patterns correspond well to the patterns of variability induced by stratospheric circulation changes. At pressure levels above the surface, the structure of the annular modes is typically found by either calculating the local EOF or regressing geopotential height data onto the leading principal component time series of near-surface geopotential height. Here we make a critical comparison of the existing methodologies used to diagnose stratosphere-Troposphere coupling, including EOF-based indices as well as measures based on zonal-mean wind at a fixed latitude and geopotential height over the polar cap. We argue in favour of an alternative methodology based on EOFs of daily zonally-averaged geopotential. We find that (1) the daily evolution of stratosphere-Troposphere coupling events is seen most clearly with this methodology, and (2) the methodology is robust and requires few subjective choices, making it readily applicable to climate model output available only in zonal-mean form. Copyright c ! 2009 Royal Meteorological Society

  • A critical comparison of stratosphere–Troposphere coupling indices
    Quarterly Journal of the Royal Meteorological Society, 2009
    Co-Authors: Mark P Baldwin, David W J Thompson
    Abstract:

    Assessing stratosphere-Troposphere coupling in observational data or model output requires a multi-level index with high time resolution. Ideally, such an index would (1) represent spatial patterns in the Troposphere that are most strongly coupled with stratospheric variability and (2) be robust and computationally feasible in both observations and standard model output. Several of the indices used to diagnose extratropical stratosphere-Troposphere coupling are based on the Northern and Southern Hemisphere annular modes. The annular mode indices are commonly defined as the leading empirical orthogonal functions (EOFs) of monthly-mean, hemispheric geopotential height. In the lowermost Troposphere, the structure of the annular modes is defined as the leading EOF of the near-surface geopotential height field, and these patterns correspond well to the patterns of variability induced by stratospheric circulation changes. At pressure levels above the surface, the structure of the annular modes is typically found by either calculating the local EOF or regressing geopotential height data onto the leading principal component time series of near-surface geopotential height. Here we make a critical comparison of the existing methodologies used to diagnose stratosphere-Troposphere coupling, including EOF-based indices as well as measures based on zonal-mean wind at a fixed latitude and geopotential height over the polar cap. We argue in favour of an alternative methodology based on EOFs of daily zonally-averaged geopotential. We find that (1) the daily evolution of stratosphere-Troposphere coupling events is seen most clearly with this methodology, and (2) the methodology is robust and requires few subjective choices, making it readily applicable to climate model output available only in zonal-mean form. Copyright c ! 2009 Royal Meteorological Society

Yuhang Wang - One of the best experts on this subject based on the ideXlab platform.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 3 origin of tropospheric ozone and effects of nonmethane hydrocarbons
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Daniel J Jacob, Jennifer A Logan
    Abstract:

    A global three-dimensional model of tropospheric O3-NOx-hydrocarbon chemistry is used to investigate the factors controlling ozone concentrations in the Troposphere. Model results indicate a close balance between chemical production and chemical loss of ozone in the tropospheric column at all latitudes (except high latitudes in winter). Using separate tracers for ozone produced in the stratosphere and in different regions of the Troposphere, we find that the contribution of transport from the stratosphere to ozone concentrations in the Troposphere is about 30% at midlatitudes in winter, 10% in summer, and 5% in the tropics. Production of ozone in the upper, middle, and continental lower Troposphere all make significant contributions (10–50%) to ozone concentrations throughout the Troposphere. The middle Troposphere is a major global source region for ozone even though it is not a region of net production. The springtime maximum of ozone observed at remote sites in the northern extratropics is explained by a phase overlap between ozone transported from the stratosphere which peaks in late winter and ozone produced in the Troposphere which peaks in late spring. Our model results do not support previous explanations of the springtime maximum based on wintertime accumulation of ozone or its precursors in the Arctic. The particularly strong springtime maximum at Mauna Loa Observatory (Hawaii) is attributed to long-range transport of Asian pollution over the North Pacific in spring. A sensitivity simulation without nonmethane hydrocarbons (NMHCs) indicates small decreases of ozone concentrations (<15%) in the remote Troposphere and a 20% increase in the global mean OH concentration. Without NMHCs as a source of peroxyacetylnitrate, concentrations of NOx decrease by 30% in the remote lower Troposphere but increase by 70% in the continental lower Troposphere and by 40% in the upper Troposphere. Biogenic isoprene accounts for about half of the NMHC effects in the model.

  • global simulation of tropospheric o3 nox hydrocarbon chemistry 2 model evaluation and global ozone budget
    Journal of Geophysical Research, 1998
    Co-Authors: Yuhang Wang, Jennifer A Logan, Daniel J Jacob
    Abstract:

    Results from a global three-dimensional model for tropospheric O3-NOx-hydrocarbon chemistry are presented and evaluated with surface, ozonesonde, and aircraft measurements. Seasonal variations and regional distributions of ozone, NO, peroxyacetylnitrate (PAN), CO, ethane, acetone, and H2O2 are examined. The model reproduces observed NO and PAN concentrations to within a factor of 2 for a wide range of tropospheric regions including the upper Troposphere but tends to overestimate HNO3 concentrations in the remote Troposphere (sometimes several fold). This discrepancy implies a missing sink for HNO3 that does not lead to rapid recycling of NOx; only in the upper Troposphere over the tropical South Atlantic would a fast conversion of HNO3 to NOx improve the model simulation for NOx. Observed concentrations of acetone are reproduced in the model by including a large biogenic source (15 Tg C yr−1), which accounts for 40% of the estimated global source of acetone (37 Tg C yr−1). Concentrations of H2O2 in various regions of the Troposphere are simulated usually to within a factor of 2, providing a test for HOx chemistry in the model. The model reproduces well the observed concentrations and seasonal variations of ozone in the Troposphere, with some exceptions including an underestimate of the vertical gradient across the tropical trade wind inversion. A global budget analysis in the model indicates that the supply and loss of tropospheric ozone are dominated by photochemistry within the Troposphere and that NOx. emitted in the southern hemisphere is twice as efficient at producing ozone as NOx emitted in the northern hemisphere.

David M Straus - One of the best experts on this subject based on the ideXlab platform.

  • stratospheric predictability and sudden stratospheric warming events
    Journal of Geophysical Research, 2009
    Co-Authors: Cristiana Stan, David M Straus
    Abstract:

    [1] A comparative study of the limit of predictability in the stratosphere and Troposphere in a coupled general circulation model is carried out using the National Center for Environmental Prediction (NCEP) Climate Forecast System Interactive Ensemble (CFSIE). In “identical twin experiments”, we compare the forecast errors of zonal wind and potential temperature in the Troposphere and stratosphere for various wave groups. The results show smaller intrinsic error growth in the lower stratosphere compared with Troposphere. The limit of predictability of sudden stratospheric warming events, measured by the errors in the divergence of the Eliassen-Palm flux, is dominated by the amplification of small errors in the individual fields due to differences between the phase of the waves.