Technical note: Water vapour climatologies in the extra-tropical upper troposphere and lower stratosphere derived from a synthesis of passenger and research aircraft measurements

This study introduces a new method to derive adjusted water vapor (H2O) climatologies for the upper tropopshere and lower statosphere (UT/LS) using data from 60 000 flights under the IAGOS program. Biases in the IAGOS water vapour dataset are adjusted, based on the more accurate IAGOS-CARIBIC data. The resulting highly resolved H2O climatologies will contribute to a better understanding of the H2O variability in the UT/LS and its connection to various transport and mixing processes.

Inequality in Hazardous Air Pollutant Emissions and Concentrations Measured Over Los Angeles

Megacity-scale analysis of spatially resolved emissions and concentrations of hazardous air pollutants reveals census tract-scale inequalities, underestimated regulatory emissions, and solvent-related sources impacting low-income and minority communities in urban Los Angeles.

Kinetics of the reactions of OH with CO, NO, and NO2 and of HO2 with NO2 in air at 1 atm pressure, room temperature, and tropospheric water vapour concentrations

Highly accurate rate coefficients of termolecular reactions between OH and HO2 radicals and reactive nitrogen oxides were measured for conditions in the lower troposphere, providing improved constraints on recommended values. No dependence on water vapour was found except for the HO2+NO2 reaction, which can be explained by an enhanced rate coefficient of the NO2 reaction with the water complex of the HO2 radical.

The impact of photochemical aging on secondary aerosol formation from a marine engine

The emissions from a research ship engine operated with either low sulfur heavy fuel oil (LS-HFO) (FSC = 0.5%) or marine gas oil (MGO) (FSC = 0.01%), were photochemically processed in the oxidation flow reactor “PEAR” to achieve an equivalent photochemical age between 0 and 9 days in the atmosphere.

Machine learning for improvement of upper-tropospheric relative humidity in ERA5 weather model data

Upper-tropospheric relative humidity bias in the ERA5 weather model is corrected by 10 % by an artificial neural network using aircraft in-service humidity data and thermodynamic and dynamical variables. The improved skills of the weather model will advance cirrus research, weather forecasts, and measures for contrail reduction.

Temperature-dependent rate coefficients for the reactions of OH radicals with selected alkanes, aromatic compounds, and monoterpenes

This study reports temperature-dependent rate coefficients of the reaction of atmospherically relevant hydrocarbons from biogenic sources (methyl vinyl ketones and monoterpenes) and anthropogenic sources (alkanes and aromatics). Measurements were done at atmospheric conditions (ambient pressure and temperature range) in air.

Advances in an OH reactivity instrument for airborne field measurements

Significant improvements have been made to the instruments used to measure OH reactivity, which is equivalent to the sum of air pollutant concentrations. Accurate and precise measurements with a high time resolution have been achieved, allowing use on aircraft, as demonstrated during flights in the USA.

The MESSy DWARF (based on MESSy v2.55.2)

Normally, the Modular Earth Submodel System (MESSy) is linked to complete dynamic models to create chemical climate models. However, the modular concept of MESSy and the newly developed DWARF component presented here make it possible to create simplified models that contain only one or a few process descriptions. This is very useful for technical optimisation, such as porting to GPUs, and can be used to create less complex models, such as a chemical box model.

Can atmospheric chemistry deposition schemes reliably simulate stomatal ozone flux across global land covers and climates?

Over the past few decades, ozone risk assessments for vegetation have been developed based on stomatal O3 flux since this metric is more biologically meaningful than the traditional concentration-based approaches. However, uncertainty remains in the ability to simulate stomatal O3 fluxes accurately. Here, we investigate stomatal O3 fluxes simulated by six common air pollution deposition models across various land cover types worldwide.

Correction of ERA5 temperature and relative humidity biases by bivariate quantile mapping for contrail formation analysis

Aviation contributes to global emissions of carbon dioxide, aerosol particles, water vapor (WV), and other compounds. WV promotes the formation of condensation trails (contrails), which are known for their net warming effect on the climate.

Optimized step size control within the Rosenbrock solvers for stiff chemical ODE systems in KPP version 2.2.3_rs4

Numerical integration of multiphase chemical kinetics in atmospheric models is challenging. The underlying system of ordinary differential equations (ODEs) is stiff and thus difficult to solve. Rosenbrock solvers are a popular choice for such tasks.

The potential of drone observations to improve air quality predictions by 4D-Var

This article presents the first study of assimilating air pollutant observations from drones to evaluate the impact on local air quality analysis. The study uses the high-resolution air quality model EURAD-IM (EURopean Air pollution Dispersion – Inverse Model), including the four-dimensional variational data assimilation system (4D-Var), to perform the assimilation of ozone (O3) and nitrogen oxide (NO) vertical profiles. 4D-Var is an inverse modelling technique that allows for simultaneous adjustments of initial values and emissions rates.

The improved Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST): update, validation and applications

A global-scale horizontally and vertically resolved ozone climatology provides detailed insights into ozone variability. Here, the seasonal, annual and decadal monthly Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST) ozone climatology is improved and updated over 1970–2021.

Perhemiacetal formation and Cl/NO3-initiated chemistry of hydroperoxymethylthioformate (HPMTF) in atmospheric DMS oxidation

The emission of dimethylsulfide (DMS) is an important source of sulfur in the atmosphere. Its oxidation leads to enhanced particle formation, where OCS is a critical reaction intermediate as it can reach the stratosphere and oxidize to low-volatility H2SO4 acting as a condensation nucleus.

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