The implementation of the CLaMS Lagrangian transport core into the chemistry climate model EMAC 2.40.1: application on age of air and transport of long-lived trace species

Hoppe, Charlotte; Hoffmann, Lars; Konopka, Paul; Grooß, Jens‐Uwe; Ploeger, Felix; Günther, G.; Jöckel, Patrick; Müller, Rolf

doi:10.5194/gmd-7-2639-2014

Cited by 39 publications

(67 citation statements)

References 48 publications

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“…In contrast EMAC-RC1SD uses the flux-form semi-Lagrangian transport scheme, where (numerical) diffusion is more pronounced in regions of strong barriers (e.g., at the arctic and antarctic polar vortex), so unresolved diffusion is higher than in CLaMS there. This is consistent with Hoppe et al (2014), who found in free-running simulations with the coupled model system EMAC-CLaMS, that transport barriers (polar vortex and tropical pipe) are stronger, if using the CLaMS tracer transport scheme compared to FFSL transport scheme. The stronger transport barrier in CLaMS can be also seen in Fig.…”

Section: Calculation Of Aging By Mixing On Resolved and Unresolved Scsupporting

confidence: 80%

“…A particular advantage of CLaMS Lagrangian transport is that the trajectory calculation is non-diffusive per se, and that the strength of diffusion induced by parametrized small-scale mixing may be controlled. For that reason, a critical Lyapunov exponent λ c has to be specified, which controls the relative distance between model grid points to be affected by mixing (for details see e.g., Hoppe et al, 2014). Table 1 gives an overview over all model simulations used for the present study.…”

Section: Model Description Of the Chemical Lagrangian Model Of The Stmentioning

confidence: 99%

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Effects of mixing on resolved and unresolved scales on stratospheric age of air

et al. 2017

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Abstract. Mean age of air (AoA) is a widely used metric to describe the transport along the Brewer-Dobson circulation. We seek to untangle the effects of different processes on the simulation of AoA, using the chemistry-climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) and the Chemical Lagrangian Model of the Stratosphere (CLaMS). Here, the effects of residual transport and two-way mixing on AoA are calculated. To do so, we calculate the residual circulation transit time (RCTT). The difference of AoA and RCTT is defined as aging by mixing. However, as diffusion is also included in this difference, we further use a method to directly calculate aging by mixing on resolved scales. Comparing these two methods of calculating aging by mixing allows for separating the effect of unresolved aging by mixing (which we term "aging by diffusion" in the following) in EMAC and CLaMS. We find that diffusion impacts AoA by making air older, but its contribution plays a minor role (order of 10 %) in all simulations. However, due to the different advection schemes of the two models, aging by diffusion has a larger effect on AoA and mixing efficiency in EMAC, compared to CLaMS. Regarding the trends in AoA, in CLaMS the AoA trend is negative throughout the stratosphere except in the Northern Hemisphere middle stratosphere, consistent with observations. This slight positive trend is neither reproduced in a free-running nor in a nudged simulation with EMAC -in both simulations the AoA trend is negative throughout the stratosphere. Trends in AoA are mainly driven by the contributions of RCTT and aging by mixing, whereas the contribution of aging by diffusion plays a minor role.

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Section: Calculation Of Aging By Mixing On Resolved and Unresolved Scsupporting

confidence: 80%

Section: Model Description Of the Chemical Lagrangian Model Of The Stmentioning

confidence: 99%

Effects of mixing on resolved and unresolved scales on stratospheric age of air

et al. 2017

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“…This indicates a need for further improvements of the model dynamics, particularly the forcing by gravity waves (Brühl et al, 2007). Furthermore, in a more recent study by Hoppe et al (2014) it was shown that the standard flux-form semiLagrangian scheme used in EMAC may be too diffusive near the transport barriers and that the simulation results can be improved when a Lagrangian transport scheme is used instead.…”

Section: Discussionmentioning

confidence: 99%

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

et al. 2018

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Abstract. We present model simulations with the atmospheric chemistry-climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) nudged toward European Centre for Medium-Range Weather Forecasts (ECMWF) ERAInterim reanalyses for the Arctic winters 2009/2010 and 2010/2011. This study is the first to perform an extensive assessment of the performance of the EMAC model for Arctic winters as previous studies have only made limited evaluations of EMAC simulations which also were mainly focused on the Antarctic winter stratosphere. We have chosen the two extreme Arctic winters 2009/2010 and 2010/2011 to evaluate the formation of polar stratospheric clouds (PSCs) and the representation of the chemistry and dynamics of the polar winter stratosphere in EMAC. The EMAC simulations are compared to observations by the Michelson Interferometer for Passive Atmospheric Soundings (Envisat/MIPAS) and the observations from the Aura Microwave Limb Sounder (Aura/MLS). The Arctic winter 2010/2011 was one of the coldest stratospheric winters on record, leading to the strongest depletion of ozone measured in the Arctic. The Arctic winter 2009/2010 was, from the climatological perspective, one of the warmest stratospheric winters on record. However, it was distinguished by an exceptionally cold stratosphere (colder than the climatological mean) from mid-December 2009 to mid-January 2010, leading to prolonged PSC formation and existence. Significant denitrification, the removal of HNO 3 from the stratosphere by sedimentation of HNO 3 -containing polar stratospheric cloud particles, occurred in that winter. In our comparison, we focus on PSC formation and denitrification. The comparisons between EMAC simulations and satellite observations show that model and measurements compare well for these two Arctic winters (differences for HNO 3 generally within ±20 %) and thus that EMAC nudged toward ECMWF ERA-Interim reanalyses is capable of giving a realistic representation of the evolution of PSCs and associated sequestration of gas-phase HNO 3 in the polar winter stratosphere. However, simulated PSC volume densities are smaller than the ones derived from Envisat/MIPAS observations by a factor of 3-7. Further, PSCs in EMAC are not simulated as high up (in altitude) as they are observed. This underestimation of PSC volume density and vertical extension of the PSCs results in an underestimation of the vertical redistribution of HNO 3 due to denitrification/re-nitrification. The differences found here between model simulations and observations stipulate further improvements in the EMAC set-up for simulating PSCs.

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“…We conducted box-model simulations for which the impact of mixing is neglected; however mixing across the Antarctic vortex edge is frequently overestimated substantially in current chemistry climate models (Hoppe et al, 2014). For the box model, the development of temperature, potential temperature and solar zenith angle along a typical air parcel trajectory in Antarctic spring is shown in Fig.…”

Section: Maintenance Of Chlorine Activationmentioning

confidence: 99%

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

Müller¹,

Grooß²,

Zafar

et al. 2018

Atmos. Chem. Phys.

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Abstract. The Antarctic ozone hole arises from ozone destruction driven by elevated levels of ozone destroying ("active") chlorine in Antarctic spring. These elevated levels of active chlorine have to be formed first and then maintained throughout the period of ozone destruction. It is a matter of debate how this maintenance of active chlorine is brought about in Antarctic spring, when the rate of formation of HCl (considered to be the main chlorine deactivation mechanism in Antarctica) is extremely high. Here we show that in the heart of the ozone hole (16-18 km or 85-55 hPa, in the core of the vortex), high levels of active chlorine are maintained by effective chemical cycles (referred to as HCl null cycles hereafter). In these cycles, the formation of HCl is balanced by immediate reactivation, i.e. by immediate reformation of active chlorine. Under these conditions, polar stratospheric clouds sequester HNO 3 and thereby cause NO 2 concentrations to be low. These HCl null cycles allow active chlorine levels to be maintained in the Antarctic lower stratosphere and thus rapid ozone destruction to occur. For the observed almost complete activation of stratospheric chlorine in the lower stratosphere, the heterogeneous reaction HCl + HOCl is essential; the production of HOCl occurs via HO 2 + ClO, with the HO 2 resulting from CH 2 O photolysis. These results are important for assessing the impact of changes of the future stratospheric composition on the recovery of the ozone hole. Our simulations indicate that, in the lower stratosphere, future increased methane concentrations will not lead to enhanced chlorine deactivation (through the reaction CH 4 + Cl −→ HCl+CH 3 ) and that extreme ozone destruction to levels below ≈ 0.1 ppm will occur until mid-century.

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The implementation of the CLaMS Lagrangian transport core into the chemistry climate model EMAC 2.40.1: application on age of air and transport of long-lived trace species

Cited by 39 publications

References 48 publications

Effects of mixing on resolved and unresolved scales on stratospheric age of air

Effects of mixing on resolved and unresolved scales on stratospheric age of air

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

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