Assessing numerical impacts on stratospheric dynamics and transport using the age of air and the leaky pipe theoretical model

2020 ◽  
Author(s):  
Aman Gupta ◽  
Edwin Gerber ◽  
Peter Lauritzen
Keyword(s):  
Finite Volume ◽  
Climate Models ◽  
Trace Gases ◽  
Atmospheric Modeling ◽  
Numerical Representation ◽  
Vertical Resolution ◽  
Tracer Transport ◽  
Stratospheric Dynamics ◽  
High Vertical Resolution ◽  
Diabatic Forcing

<p>Accurate representation of tracer transport --- the movement of trace constituents by the atmospheric flow --- continues to be a challenge for climate models. Differences in the resolved circulation, biases due to physical parameterizations, and differences in the numerical representation of trace gases result in large variations in transport, even among state-of-the-art climate models. These differences result in disagreement among model projections of the evolution of stratospheric ozone throughout the 21st century particularly in the recovery of the Antarctic ozone hole. In addition to transport, the delicate momentum balance in the upper-troposphere and lower-stratosphere (UTLS) also presents a stiff challenge for model numerics, exposing the impacts of numerical dissipation, the resolution of waves, and the consequences of imperfect momentum conservation. Biases in this region impact the global circulation, e.g., influencing the extratropics jets and stratospheric polar vortices, and alter the transport and exchange of trace gases between and through the troposphere and stratosphere.</p><p> </p><p>In this study, we compare 2 modern dynamical cores (dycores) that employ very different numerics: the cubed sphere finite volume (CSFV) core from GFDL and the spectral element (SE) core from NCAR-CAM5. We force these dycores using identical Held-Suarez diabatic forcing in the troposphere and Polvani-Kushner diabatic forcing in the stratosphere, varying the horizontal and vertical resolution. We observe significant differences in circulation, between the two models at high vertical resolution in the lower and middle tropical stratosphere. While the finite volume core is relatively insensitive to any changes in vertical resolution, the PS and SE dycores resolve considerably different tropical stratospheric dynamics at high vertical resolution (80 levels). These models develop QBO-like westerly winds in the tropics and induce a secondary meridional circulation in the tropical stratosphere, which sets of transport between the models. Using the theoretical leaky pipe transport model we analyze and separate out the transport differences due to differences is diabatic circulation and isentropic mixing and infer that this secondary circulation strikingly modulates stratospheric tracer transport (age of air) by altering the tropical-extratropical mixing, and impacts the extratropical circulation through the subtropical jets. Implications for comprehensive atmospheric modeling are discussed.</p>

scholarly journals Atmospheric transport and chemistry of trace gases in LMDz5B: evaluation and implications for inverse modelling

2015 ◽  
Vol 8 (2) ◽  
pp. 129-150 ◽  
Author(s):  
R. Locatelli ◽  
P. Bousquet ◽  
F. Hourdin ◽  
M. Saunois ◽  
A. Cozic ◽  
...  
Keyword(s):  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Atmospheric Transport ◽  
Trace Gases ◽  
Inverse Modelling ◽  
Trace Gas ◽  
Vertical Resolution ◽  
Tracer Transport ◽  
Gas Emissions ◽  
The Impact

Abstract. Representation of atmospheric transport is a major source of error in the estimation of greenhouse gas sources and sinks by inverse modelling. Here we assess the impact on trace gas mole fractions of the new physical parameterizations recently implemented in the atmospheric global climate model LMDz to improve vertical diffusion, mesoscale mixing by thermal plumes in the planetary boundary layer (PBL), and deep convection in the troposphere. At the same time, the horizontal and vertical resolution of the model used in the inverse system has been increased. The aim of this paper is to evaluate the impact of these developments on the representation of trace gas transport and chemistry, and to anticipate the implications for inversions of greenhouse gas emissions using such an updated model. Comparison of a one-dimensional version of LMDz with large eddy simulations shows that the thermal scheme simulates shallow convective tracer transport in the PBL over land very efficiently, and much better than previous versions of the model. This result is confirmed in three-dimensional simulations, by a much improved reproduction of the radon-222 diurnal cycle. However, the enhanced dynamics of tracer concentrations induces a stronger sensitivity of the new LMDz configuration to external meteorological forcings. At larger scales, the inter-hemispheric exchange is slightly slower when using the new version of the model, bringing them closer to observations. The increase in the vertical resolution (from 19 to 39 layers) significantly improves the representation of stratosphere/troposphere exchange. Furthermore, changes in atmospheric thermodynamic variables, such as temperature, due to changes in the PBL mixing modify chemical reaction rates, which perturb chemical equilibriums of reactive trace gases. One implication of LMDz model developments for future inversions of greenhouse gas emissions is the ability of the updated system to assimilate a larger amount of high-frequency data sampled at high-variability stations. Others implications are discussed at the end of the paper.

scholarly journals Technical Note: A new global database of trace gases and aerosols from multiple sources of high vertical resolution measurements

2008 ◽  
Vol 8 (17) ◽  
pp. 5403-5421 ◽  
Author(s):  
B. Hassler ◽  
G. E. Bodeker ◽  
M. Dameris
Keyword(s):  
Binary Data ◽  
Trace Gases ◽  
Potential Temperature ◽  
Technical Note ◽  
Percentage Error ◽  
Vertical Resolution ◽  
Geographic Latitude ◽  
Multiple Sources ◽  
Global Database ◽  
High Vertical Resolution

Abstract. A new database of trace gases and aerosols with global coverage, derived from high vertical resolution profile measurements, has been assembled as a collection of binary data files; hereafter referred to as the "Binary DataBase of Profiles" (BDBP). Version 1.0 of the BDBP, described here, includes measurements from different satellite- (HALOE, POAM II and III, SAGE I and II) and ground-based measurement systems (ozonesondes). In addition to the primary product of ozone, secondary measurements of other trace gases, aerosol extinction, and temperature are included. All data are subjected to very strict quality control and for every measurement a percentage error on the measurement is included. To facilitate analyses, each measurement is added to 3 different instances (3 different grids) of the database where measurements are indexed by: (1) geographic latitude, longitude, altitude (in 1 km steps) and time, (2) geographic latitude, longitude, pressure (at levels ~1 km apart) and time, (3) equivalent latitude, potential temperature (8 levels from 300 K to 650 K) and time. In contrast to existing zonal mean databases, by including a wider range of measurement sources (both satellite and ozonesondes), the BDBP is sufficiently dense to permit calculation of changes in ozone by latitude, longitude and altitude. In addition, by including other trace gases such as water vapour, this database can be used for comprehensive radiative transfer calculations. By providing the original measurements rather than derived monthly means, the BDBP is applicable to a wider range of applications than databases containing only monthly mean data. Monthly mean zonal mean ozone concentrations calculated from the BDBP are compared with the database of Randel and Wu, which has been used in many earlier analyses. As opposed to that database which is generated from regression model fits, the BDBP uses the original (quality controlled) measurements with no smoothing applied in any way and as a result displays higher natural variability.

Assessing Tracer Transport Algorithms and the Impact of Vertical Resolution in a Finite-Volume Dynamical Core

2012 ◽  
Vol 140 (5) ◽  
pp. 1620-1638 ◽  
Author(s):  
James Kent ◽  
Christiane Jablonowski ◽  
Jared P. Whitehead ◽  
Richard B. Rood
Keyword(s):  
Finite Volume ◽  
Vertical Component ◽  
Vertical Motion ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Vertical Resolution ◽  
Tracer Transport ◽  
Dynamical Core ◽  
Lagrangian Coordinate ◽  
The Impact

Abstract Modeling the transport of trace gases is an essential part of any atmospheric model. The tracer transport scheme in the Community Atmosphere Model finite-volume dynamical core (CAM-FV), which is part of the National Center for Atmospheric Research’s (NCAR’s) Community Earth System Model (CESM1), is investigated using multidimensional idealized advection tests. CAM-FV’s tracer transport algorithm makes use of one-dimensional monotonic limiters. The Colella–Sekora limiter, which is applied to increase accuracy where the data are smooth, is implemented into the CAM-FV framework, and compared with the more traditional monotonic limiter of the piecewise parabolic method (the default limiter). For 2D flow, CAM-FV splits dimensions, allowing overshoots and undershoots, with the Colella–Sekora limiter producing larger overshoots than the default limiter. The impact of vertical resolution is also explored. A vertical Lagrangian coordinate is used in CAM-FV, and is periodically remapped back to a fixed Eulerian grid. For purely vertical motion, it is found that less-frequent remapping of the Lagrangian coordinate in CAM-FV improves results. For full 3D tests, the vertical component of the tracer transport dominates the error and limits the overall accuracy. If the vertical resolution is inadequate, increasing the horizontal resolution has almost no effect on accuracy. This is because the vertical resolution currently used in CAM version 5 may not be sufficiently fine enough to resolve some atmospheric tracers and provide accurate vertical advection. Idealized tests using tracers in a gravity wave agree with these results.

scholarly journals Technical Note: A new global database of trace gases and aerosols from multiple sources of high vertical resolution measurements

2008 ◽  
Vol 8 (2) ◽  
pp. 7657-7702
Author(s):  
B. Hassler ◽  
G. E. Bodeker ◽  
M. Dameris
Keyword(s):  
Binary Data ◽  
Trace Gases ◽  
Potential Temperature ◽  
Technical Note ◽  
Percentage Error ◽  
Vertical Resolution ◽  
Geographic Latitude ◽  
Multiple Sources ◽  
Global Database ◽  
High Vertical Resolution

Abstract. A new database of trace gases and aerosols with global coverage, derived from high vertical resolution profile measurements, has been assembled as a collection of binary data files; hereafter referred to as the "Binary DataBase of Profiles" (BDBP). Version 1.0 of the BDBP, described here, includes measurements from different satellite- (HALOE, POAM II and III, SAGE I and II) and ground-based measurement systems (ozonesondes). In addition to the primary product of ozone, secondary measurements of other trace gases, aerosol extinction, and temperature are included. All data are subjected to very strict quality control and for every measurement a percentage error on the measurement is included. To facilitate analyses, each measurement is added to 3 different instances (3 different grids) of the database where measurements are indexed by: (1) geographic latitude, longitude, altitude (in 1 km steps) and time, (2) geographic latitude, longitude, pressure (at levels ~1 km apart) and time, (3) equivalent latitude, potential temperature (8 levels from 300 K to 650 K) and time. In contrast to existing zonal mean databases, by including a wider range of measurement sources (both satellite and ozonesondes), the BDBP is sufficiently dense to permit calculation of changes in ozone by latitude, longitude and altitude. In addition, by including other trace gases such as water vapour, this database can be used for comprehensive radiative transfer calculations. By providing the original measurements rather than derived monthly means, the BDBP is applicable to a wider range of applications than databases containing only monthly mean data. Monthly mean zonal mean ozone concentrations calculated from the BDBP are compared with the database of Randel and Wu, which has been used in many earlier analyses. As opposed to that database which is generated from regression model fits, the BDBP uses the original (quality controlled) measurements with no smoothing applied in any way and as a result displays higher natural variability.

scholarly journals Atmospheric transport and chemistry of trace gases in LMDz5B: evaluation and implications for inverse modelling

2014 ◽  
Vol 7 (4) ◽  
pp. 4993-5048 ◽  
Author(s):  
R. Locatelli ◽  
P. Bousquet ◽  
F. Hourdin ◽  
M. Saunois ◽  
A. Cozic ◽  
...  
Keyword(s):  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Atmospheric Transport ◽  
Trace Gases ◽  
Inverse Modelling ◽  
Trace Gas ◽  
Vertical Resolution ◽  
Tracer Transport ◽  
Gas Emissions ◽  
The Impact

Abstract. Representation of atmospheric transport is a major source of error in the estimation of greenhouse gas sources and sinks by inverse modelling. Here we assess the impact on trace gas mole fractions of the new physical parameterisations recently implemented in the Atmospheric Global Climate Model LMDz to improve vertical diffusion, mesoscale mixing by thermal plumes in the planetary boundary layer (PBL), and deep convection in the troposphere. At the same time, the horizontal and vertical resolution of the model used in the inverse system has been increased. The aim of this paper is to evaluate the impact of these developments on the representation of trace gas transport and chemistry, and to anticipate the implications for inversions of greenhouse gas emissions using such an updated model. Comparison of a one-dimensional version of LMDz with large eddy simulations shows that the thermal scheme simulates shallow convective tracer transport in the PBL over land very efficiently, and much better than previous versions of the model. This result is confirmed in three dimensional simulations, by a much improved reproduction of the Radon-222 diurnal cycle. However, the enhanced dynamics of tracer concentrations induces a stronger sensitivity of the new LMDz configuration to external meteorological forcings. At larger scales, the inter-hemispheric exchange is slightly slower when using the new version of the model, bringing them closer to observations. The increase in the vertical resolution (from 19 to 39 layers) significantly improves the representation of stratosphere/troposphere exchange. Furthermore, changes in atmospheric thermodynamic variables, such as temperature, due to changes in the PBL mixing, significantly modify chemical reaction rates and the equilibrium value of reactive trace gases. One implication of LMDz model developments for future inversions of greenhouse gas emissions is the ability of the updated system to assimilate a larger amount of high-frequency data sampled at high-variability stations. Others implications are discussed at the end of the paper.

scholarly journals Methodology to obtain highly resolved SO<sub>2</sub> vertical profiles for representation of volcanic emissions in climate models

2021 ◽  
Author(s):  
Oscar S. Sandvik ◽  
Johan Friberg ◽  
Moa K. Sporre ◽  
Bengt G. Martinsson
Keyword(s):  
Climate Models ◽  
Dispersion Model ◽  
Meteorological Data ◽  
Potential Temperature ◽  
Orthogonal Polarization ◽  
Height Distribution ◽  
Vertical Profiles ◽  
Vertical Resolution ◽  
Volcanic Emissions ◽  
High Vertical Resolution

Abstract. In this study we describe a methodology to create high vertical resolution SO2 profiles from volcanic emissions. We demonstrate the method’s performance for the volcanic clouds following the eruption of Sarychev in June 2009. The resulting profiles are based on a combination of satellite SO2 and aerosol retrievals together with trajectory modelling. We use satellite-based measurements, namely lidar back-scattering profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument to create vertical profiles for SO2 swaths from the Atmospheric Infrared Sounder (AIRS) aboard the Aqua satellite. Vertical profiles are created by transporting the air containing volcanic aerosol seen in CALIOP observations using the dispersion model FLEXPART, while preserving the high vertical resolution by using the potential temperatures from the MERRA-2 meteorological data for the original CALIOP swaths. For the Sarychev eruption, air tracers from 75 CALIOP swaths within 9 days after the eruption are transported forwards and backwards, and then combined at a point in time when AIRS swaths cover the complete volcanic SO2 cloud. Our method creates vertical distributions for column density observations of SO2 for individual AIRS swaths. The resulting dataset gives insight to the height distribution in the different sub-clouds of SO2 within the stratosphere. We have compiled a gridded high vertical resolution SO2 inventory that can be used in Earth system models, with vertical resolution of 1 K in potential temperature or 61 ± 56 m and 1.8 ± 2.9 mbar.

scholarly journals A Note on the Numerical Representation of Surface Dynamics in Quasigeostrophic Turbulence: Application to the Nonlinear Eady Model

2009 ◽  
Vol 66 (4) ◽  
pp. 1063-1068 ◽  
Author(s):  
Ross Tulloch ◽  
K. Shafer Smith
Keyword(s):  
Numerical Models ◽  
Buoyancy Frequency ◽  
Complete Suppression ◽  
Numerical Representation ◽  
Vertical Resolution ◽  
Surface Dynamics ◽  
Coriolis Parameter ◽  
Theoretical Predictions ◽  
Vertical Grid ◽  
Similar Restriction

Abstract The quasigeostrophic equations consist of the advection of linearized potential vorticity coupled with advection of temperature at the bounding upper and lower surfaces. Numerical models of quasigeostrophic flow often employ greater (scaled) resolution in the horizontal than in the vertical (the two-layer model is an extreme example). In the interior, this has the effect of suppressing interactions between layers at horizontal scales that are small compared to Nδz/f (where δz is the vertical resolution, N the buoyancy frequency, and f the Coriolis parameter). The nature of the turbulent cascade in the interior is, however, not fundamentally altered because the downscale cascade of potential enstrophy in quasigeostrophic turbulence and the downscale cascade of enstrophy in two-dimensional turbulence (occurring layerwise) both yield energy spectra with slopes of −3. It is shown here that a similar restriction on the vertical resolution applies to the representation of horizontal motions at the surfaces, but the penalty for underresolving in the vertical is complete suppression of the surface temperature cascade at small scales and a corresponding artificial steepening of the surface energy spectrum. This effect is demonstrated in the nonlinear Eady model, using a finite-difference representation in comparison with a model that explicitly advects temperature at the upper and lower surfaces. Theoretical predictions for the spectrum of turbulence in the nonlinear Eady model are reviewed and compared to the simulated flows, showing that the latter model yields an accurate representation of the cascade dynamics. To accurately represent dynamics at horizontal wavenumber K in the vertically finite-differenced model, it is found that the vertical grid spacing must satisfy δz ≲ 0.3f/(NK); at wavenumbers K &gt; 0.3f/(Nδz), the spectrum of temperature variance rolls off rapidly.

On the role of vertical and horizontal model resolution for the simulation of stratospheric transport

2021 ◽  
Author(s):  
Hella Garny ◽  
Simone Dietmüller ◽  
Roland Eichinger ◽  
Aman Gupta ◽  
Marianna Linz
Keyword(s):  
Climate Models ◽  
Horizontal Resolution ◽  
Climate Forcing ◽  
Numerical Dispersion ◽  
Mixing Efficiency ◽  
Vertical Resolution ◽  
Model Resolution ◽  
Residual Circulation ◽  
Year 2000

&lt;p&gt;The stratospheric transport circulation, or Brewer-Dobson Circulation (BDC), is often conceptually seperated into advection along the residual circulation and two-way mixing. In particular the latter part has recently been found to exert a strong influence on inter-model differences of mean age of Air (AoA), a common measure of the BDC. However, the precise reason for model differences in two-way mixing remains unknown, as many model&lt;br&gt;components in multi-model projects differ. One component that likely plays an important role is model resolution, both vertically and horizontally. To analyse this aspect, we carried out a set of simulations with identical and constant year 2000 climate forcing varying the spectral horizontal&lt;br&gt;resolution (T31,T42,T63,T85) and the number of vertical levels (L31,L47,L90). We find that increasing the vertical resolution leads to an increase in mean AoA. Most of this change can be attributed to aging by mixing. The mixing efficiency, defined as the ratio of isentropic mixing strength and the diabatic circulation, shows the same dependency on vertical resolution. While horizontal resolution changes do not systematically change mean AoA, we do&lt;br&gt;find a systematic decrease in the mixing efficiency with increasing horizontal resolution. Non-systematic changes in the residual circulation partly compensate the mixing efficiency changes, leading to the non-systematic mean AoA changes. The mixing efficiency changes with vertical and horizontal resolution are consistent with expectations on the effects of numerical dispersion on mean AoA. To further investigate the most relevant regions of mixing differences, we analyse height-resolved mixing efficiency differences. Overall, this work will help to shed light on the underlying reasons for the large biases of climate models in simulating stratospheric transport.&lt;/p&gt;

scholarly journals First results of the PML monitor of atmospheric turbulence profile with high vertical resolution

2013 ◽  
Vol 559 ◽  
pp. L6 ◽  
Author(s):  
A. Ziad ◽  
F. Blary ◽  
J. Borgnino ◽  
Y. Fanteï-Caujolle ◽  
E. Aristidi ◽  
...  
Keyword(s):  
Atmospheric Turbulence ◽  
Vertical Resolution ◽  
First Results ◽  
High Vertical Resolution
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