Publications Archive – TPChange

New publication on aerosol transport

Aurelia Müller — Tue, 08 Sep 2026 12:17:46 +0000

Downward transport of tropical upper-tropospheric aerosols: multi-year insights from idealized simulations.
Hernández Pardo, L., J. Curtius, P. Jöckel, J. M. Menken, C. Pöhlker, M. Pöhlker, and A. Possner (2026)
Atmospheric Chemistry and Physics 26 (17), 12275–12293. doi: 10.5194/acp-26-12275-2026.

Abstract

Recent studies suggest that significant aerosol formation occurs in the tropical upper troposphere (UT). However, the impact of these particles at lower levels remains poorly understood. We present results from multi-year global EMAC simulations investigating the downward transport of UT tracers and their resulting spatial distribution. Nineteen idealized tracers were released in the tropical UT and subjected to resolved-scale advection, parameterized convection, turbulent mixing, and wet/dry deposition. Transport diagnostics are highly sensitive to source extent: the age of air at 500 hPa is ≈ 45 d for tropical-wide tracers, compared to over 250 d for regional continental sources, reflecting the importance of mixing, dilution, and source-receptor geometry. A complementary time-to-threshold diagnostic reveals faster transport pathways, with all source regions exhibiting descent times shorter than 7 d to reach 10 % of the source average. Advection dominates vertical transport, with convective and vertical diffusion parameterizations contributing marginally. Injection height exerts a stronger influence on descent time than parameterized transport or particle size in the 20–100 nm range. Tracer maxima are typically advected east of their source centers, resulting in significant concentrations (≈ 10 %–15 % of source values) in the mid-troposphere. Offline calculations show that, for initial particle numbers below ≈ 6×10⁷ kg⁻¹, the mid-troposphere values predicted by the model are reduced by less than 10 % when coagulation is considered, but substantial deviations occur at higher concentrations. These results provide quantitative constraints on particle transport efficiency and inform expectations for aerosol distributions following UT nucleation events.

Related TPChange projects:

C06 The importance of upper troposphere aerosol transport and processing for low- and mid-troposphere aerosol concentrations

Der Beitrag New publication on aerosol transport erschien zuerst auf TPChange.

New publication on gravity waves and mixing

Aurelia Müller — Tue, 25 Aug 2026 12:06:44 +0000

Evidence of gravity wave contribution to vertical shear and mixing in the lower stratosphere.
Umbarkar, M., D. Kunkel, A. Miltenberger, H.-C. Lachnitt, T. Kaluza, C. Schwenk, and P. Hoor (2026)
Atmospheric Chemistry and Physics 26 (16), 12067–12096. doi: 10.5194/acp-26-12067-2026

Abstract

Small-scale dynamics, particularly gravity waves (GWs), modify vertical wind shear and can trigger turbulence in the lowermost stratosphere (LMS), thereby influencing the transport of trace species across the tropopause. Although idealized modeling and observational case studies have demonstrated this link, the contribution of small-scale dynamics to turbulence generation remains poorly understood, particularly under real atmospheric conditions. Here, we investigate the relationship between GWs, vertical wind shear, and clear-air turbulence (CAT) in the LMS over the North Atlantic during a baroclinic life cycle. We combine airborne observations with ERA5 reanalysis and high-resolution forecasts from the IFS and ICON models. To isolate the contribution of small-scale dynamics to turbulence generation, we extract the small-scale divergent component of the modeled wind field. From this, we derive momentum flux, perturbation vertical wind shear, and the turbulence indices TI1 and TI2, and compare these quantities with those calculated from the full wind fields. Trace-species mixing is observed within a region of enhanced GW activity over Iceland that is characterized by increased vertical wind shear and turbulence. ERA5 reproduces the spatial and temporal distribution of enhanced shear and turbulence but underestimates shear magnitudes relative to the forecasts while yielding comparable values of TI1 and TI2. These findings extend previous idealized studies from Umbarkar and Kunkel (2025) to real atmospheric conditions and provide further evidence that GW-induced small-scale dynamics contribute to turbulence generation in the LMS. They also demonstrate the potential of ERA5 for long-term investigations of the role of small-scale dynamics in transport and mixing near the tropopause.

Related TPChange projects:

B06 Impact of small-scale dynamics on UTLS transport and mixing

Der Beitrag New publication on gravity waves and mixing erschien zuerst auf TPChange.

New publication on gravity waves and tracer transport

Aurelia Müller — Fri, 21 Aug 2026 19:52:35 +0000

Impact of small-scale gravity waves on tracer transport
Knop, I., S. Dolaptchiev, and U. Achatz (2026):
Quarterly Journal of the Royal Meteorological Society 152 (776), e70091. doi: https://doi.org/10.1002/qj.70091.

Abstract

Small-scale gravity waves, with horizontal wavelengths of up to a few hundred kilometers and vertical wavelengths of up to a few kilometers, play a crucial role in atmospheric tracer transport. However, their effects remain unresolved in climate models and must be parametrized. This study investigates how gravity waves influence large-scale tracer distributions, utilizing a multiple-scale analysis to systematically identify the governing terms of gravity wave-induced tracer fluxes. The analysis reveals both leading-order and next-order impacts: the former being the inertia–gravity-wave-induced tracer Stokes drift, which acts perpendicular to both the large-scale tracer gradient and the wave number, whereas the latter becomes significant at lower latitudes where Coriolis effects diminish. A numerical framework is developed to incorporate these fluxes into a gravity wave parametrization model, potentially enhancing climate model accuracy without requiring explicit resolution of small-scale wave dynamics. Model validation against high-resolution wave-resolving simulations confirms the effectiveness of this approach. By improving the representation of gravity-wave-induced tracer transport, this research advances the accuracy of climate simulations, particularly in their depiction of microphysics and radiative processes.

Related TPChange projects:

B06 Impact of small-scale dynamics on UTLS transport and mixing

B07 Impact of cirrus clouds on tropopause structure

Z03 Joint model development and modelling synthesis

Der Beitrag New publication on gravity waves and tracer transport erschien zuerst auf TPChange.

New publication on chemistry in volcanic plumes

Aurelia Müller — Wed, 19 Aug 2026 12:31:03 +0000

On-filter derivatisation and alkaline trap sampling for UAV-based gas-phase halogen speciation in volcanic plumes
Geil, B., N. Bobrowski, and T. Hoffmann (2026)
Analytical and Bioanalytical Chemistry. doi: 10.1007/s00216-026-06403-7

Related TPChange projects:

A05 Chemical characterisation of organic aerosol in the UTLS

Der Beitrag New publication on chemistry in volcanic plumes erschien zuerst auf TPChange.

New publication on particle formation

Aurelia Müller — Mon, 17 Aug 2026 13:22:57 +0000

CERN CLOUD chamber measurements investigate the synergistic new particle formation rates and mechanisms involving methanesulfonic acid, sulfuric acid and two different amines under marine boundary layer conditions.

Rapid new particle formation driven by methanesulfonic acid and amines

Klebach, H., L. Caudillo-Plath, M. Heinritzi, D. M. Russell, B. Rörup, R. Baalbaki, J. Shen, E. Sommer, A. Kürten, D. Alfaouri, J. Almeida, A. Amorim, L. J. Beck, H. Beckmann, M. Berntheusel, T. Christoudias, L. Dada, J. DeVivo, N. Donahue, J. Duplissy, I. El Haddad, A. Hansel, H. Harder, X.-C. He, M. Kulmala, F. Kunkler, K. Lehtipalo, L. Liu, B. Mentler, T. Petäjä, P. Rato, S. Richter, S. Schobesberger, W. Scholz, M. Simon, R. C. Thakur, A. Tomé, Y. Tong, J. Top, R. Volkamer, P. M. Winkler, B. Yang, M. Zauner-Wieczorek, J. Zhang, J. Kirkby, and J. Curtius

Environmental Science: Atmospheres (2026), doi: 10.1039/d5ea00081e

Related TPChange projects:

A03 Aerosol nucleation in the upper troposphere

Der Beitrag New publication on particle formation erschien zuerst auf TPChange.

New publication on ISSRs

Vera Bense — Mon, 17 Aug 2026 08:51:04 +0000

We studied ice-supersaturated regions in the upper troposphere and lower stratosphere where high humidity can lead to cloud and contrail formation. Using data from 2010 to 2020, we found these regions to have fractal characteristics by applying an area-perimeter method. The fractal dimension follows a seasonal cycle. Our results can help evaluate climate models and have possible implications on contrail mitigation.

Schuh, H. Z., P. Reutter, S. Niebler, and P. Spichtinger (2026): Fractal characteristics of ice-supersaturated regions in the tropopause region of the northern midlatitudes. Atmospheric Chemistry and Physics 26 (15), 11235–11253. doi: 10.5194/acp-26-11235-2026

Related TPChange projects:

C01 Life Cycle of Ice Supersaturated Regions in the UTLS

B07 Impact of cirrus clouds on tropopause structure

Der Beitrag New publication on ISSRs erschien zuerst auf TPChange.

New publication on aerosol transport

Aurelia Müller — Wed, 29 Jul 2026 15:20:29 +0000

This study shows that aerosol transported from the Asian summer monsoon region can substantially alter the background composition of the extratropical lower stratosphere. Aircraft-based measurements and model simulations reveal a strong increase of ammonium nitrate aerosol from summer to autumn 2023 caused by transport of young air masses from South and East Asia. These particles can persist for months and undergo chemical aging.

Enhancement of ammonium nitrate aerosol in the Northern Hemisphere lower stratosphere linked to Asian summer monsoon outflow
Ekinci, F., O. Eppers, O. Appel, F. Ploeger, A. Dragoneas, S. Molleker, P. Brauner, H.-C. Lachnitt, F. Weyland, L. Ort, N. Emig, H.-C. Clemen, L. Tomsche, M. Ebert, P. Hoor, B. Vogel, Y. Cheng, J. Schneider, S. Borrmann, and F. Köllner (2026).
Atmospheric Chemistry and Physics 26 (14), 10399–10421. doi: 10.5194/acp-26-10399-2026.

Related TPChange projects:

A04 Sources and processes controlling aerosol composition in the UTLS – From tropical mosoon to extratropical regions (Phase I)

A04 Composition and transport of aerosol particles in the upper troposphere and lower stratosphere (UTLS) and their interactions with cirrus clouds (Phase II)

C03 Improving process understanding and model representation of stratospheric water vapour and related climate feedbacks

B01 Exchange of humidity and aerosol particles at the tropopause: Dynamics versus moist diabatics and radiation

A01 Impact of aircraft emissions and convection on the composition of the UTLS

A06 Composition and variability of UTLS refractory aerosol and ice-nucleating particles

Der Beitrag New publication on aerosol transport erschien zuerst auf TPChange.

New publication on gravity wave spectra

Aurelia Müller — Thu, 09 Jul 2026 11:45:21 +0000

The study analyzes gravity waves in a high-resolution simulation. A unique methodology is applied to compute three-dimensional gravity wave spectra while keeping the data on the original triangular model grid and using linear wave theory. The results show the structure of gravity waves that would remain unresolved by a model with lower horizontal resolution. It is shown that the spectra can be highly simplified, which can help constructing precise but efficient gravity wave parametrisation.

Variability of local gravity wave spectra from data of a high-resolution icosahedral-grid global model
Procházková, Z., E. Mahmoudi, R. Chew, S. Dolaptchiev, C. C. Stephan, G. S. Völker, and U. Achatz (2026)
Atmospheric Chemistry and Physics 26 (13), 9541–9558. doi: 10.5194/acp-26-9541-2026.

Related TPChange projects:

B06 Impact of small-scale dynamics on UTLS transport and mixing

B07 Impact of cirrus clouds on tropopause structure

Z03 Joint model development and modelling synthesis

Der Beitrag New publication on gravity wave spectra erschien zuerst auf TPChange.

New publication on the impact of gravity waves on transport and mixing

Aurelia Müller — Tue, 24 Mar 2026 10:26:12 +0000

The Impact of Non-Orographic Gravity Waves on Transport and Mixing: Effects of Oblique Propagation and Coupling to Turbulence.

Banerjee, T., Y. H. Kim, G. S. Voelker, S. Borchert, A. Kosareva, D. Kunkel, G. T. Masur, Z. Prochazkova, J. Schmidli, and U. Achatz (2026)
Journal of Geophysical Research: Atmospheres 131(6), e2025JD045270. doi: https://doi.org/10.1029/2025JD045270

Plain Language Summary

In the middle and upper atmosphere, small-scale waves called gravity waves (GW) caused by events like thunderstorms or jet streams strongly influence winds, temperature, and circulation. This paper explores how non-orographic GWs, especially those traveling at an angle to the vertical (obliquely), alter transport and mixing of air. Unlike vertically propagating GWs, oblique GWs can deposit their momentum and energy across a wider region and altitudes. Using a state-of-the-art GW parameterization and atmospheric model alongside a novel theoretical framework, we simulate these oblique GWs and their interaction with turbulence—the chaotic motions of the atmosphere. Results show that neglecting these processes may lead models to underestimate transport, mixing, and circulation, particularly in the tropical stratosphere and mesosphere where GW activity is strongest. Oblique propagation is found to cool and lower the summer mesopause (the coldest region of the atmosphere), while reducing vertical shear and intensifying turbulence. In contrast, when GWs are coupled to turbulence, the mesopause warms and rises, but shear is still reduced and turbulence intensified. This coupling also enhances mixing, influencing heat and chemical redistribution. Overall, the findings point to the need for GW parameterizations that account for oblique propagation and turbulence coupling.

Related TPChange projects:

B06 Impact of small-scale dynamics on UTLS transport and mixing

B07 Impact of cirrus clouds on tropopause structure

Z03 Joint model development and modelling synthesis

Der Beitrag New publication on the impact of gravity waves on transport and mixing erschien zuerst auf TPChange.