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A new description of probability density distributions of polar mesospheric clouds

In this paper we present a new description of statistical probability density functions (pdfs) of polar mesospheric clouds (PMC). We derive a new class of pdfs that describes successfully the probability statistic of ALOMAR lidar observations of different ice parameters. As a main advantage the new method allows us to connect different observational PMC distributions of lidar and satellite data, and also to compare with distributions from ice model studies.

Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method

As frozen soil, called permafrost, increasingly thaws over the years, scientists have put much effort into understanding how this may increase carbon emissions, which would exacerbate climate change. Our work supports the emerging view that these efforts should also include nitrous oxide (N₂O), a more potent greenhouse gas. Using a low-flying aircraft to study thousands of acres of Alaskan permafrost, we observed average N₂O emissions higher than typically assumed for regions such as this.

Trends in global tropospheric ozone inferred from a composite record of TOMS/OMI/MLS/OMPS satellite measurements and the MERRA-2 GMI simulation

Both a 38-year merged satellite record of tropospheric ozone from TOMS/OMI/MLS/OMPS and a MERRA-2 GMI model simulation show large increases of 6–7 Dobson units from the Near East to India–East Asia and eastward over the Pacific. These increases in tropospheric ozone are attributed to increases in pollution over the region over the last several decades. Secondary 38-year increases of 4–5 Dobson units with both GMI model and satellite measurements occur over central African–tropical Atlantic.

TOMS/OMI/MLS/OMPS satellite measurements and the MERRA-2 GMI simulation">Read more

Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes

Chloromethane is the most important natural carrier of chlorine to the stratosphere. From a newly determined carbon isotope effect of −11.2 ‰ for the tropospheric loss of CH₃Cl we derive a tropical rainforest CH₃Cl source of 670 ± 200 Gg a⁻¹, 60 % smaller than previous estimates. A revision of previous bottom-up estimates using above-ground biomass instead of rainforest area strongly supports this lower estimate. Our results suggest a large unknown tropical value of 1530 ± 200 Gg a⁻¹.

Positive matrix factorization of organic aerosol: insights from a chemical transport model

The ability of positive matrix factorization (PMF) factor analysis to identify and quantify the organic aerosol (OA) sources accurately is tested in this modeling study. The estimated uncertainty of the contribution of fresh biomass burning is less than 30 % and of the other primary sources is less than 40 %, when these sources contribute more than 20 % to the OA. Τhe first oxygenated OA factor includes mainly highly aged OA, while the second oxygenated OA factor contains fresher secondary OA.

Volatile organic compounds and ozone in Rocky Mountain National Park during FRAPPÉ

Rocky Mountain National Park experiences high ozone concentrations that can exceed the National Ambient Air Quality Standard. As part of the FRAPPÉ field campaign, a suite of volatile organic compounds were measured to characterize the sources of ozone precursors that contribute to high ozone in the park. These measurements indicate emissions from the Front Range in Colorado tied to oil and gas operations, urban areas, and the stratosphere contribute to episodes of elevated ozone.

FRAPPÉ">Read more

Structural changes in the shallow and transition branch of the Brewer–Dobson circulation induced by El Niño

This paper assesses the structural changes in the shallow and transition branches of the BDC induced by El Nino using the Lagrangian model simulations driven by ERAi and JRA-55 combined with MLS observations. We found a clear evidence of a weakening of the transition branch due to an upward shift in the dissipation height of the planetary and gravity waves and a strengthening of the shallow branch due to enhanced GW breaking in the tropics–subtropics and PW breaking at high latitudes.

Photochemical box modelling of volcanic SO2 oxidation: isotopic constraints

Volcanic sulfur can have climatic impacts for the planet via sulfate aerosol formation, leading also to pollution events. We provide model constraints on tropospheric volcanic sulfate formation, with implications for its lifetime and impacts on regional air quality. Oxygen isotope investigations from our model suggest that in the poor tropospheric plumes of halogens, the O2/TMI sulfur oxidation pathway might significantly control sulfate production. The produced sulfate has no isotopic anomaly.

The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe

The impact of desert dust on cloud formation is investigated for a major Saharan dust event over Europe by interactive regional dust modeling. Dust particles are very efficient ice-nucleating particles promoting the formation of ice crystals in clouds. The simulations show that the observed extensive cirrus development was likely related to the above-average dust load. The interactive dust–cloud feedback in the model significantly improves the agreement with aircraft and satellite observations.

Mesospheric bores at southern midlatitudes observed by ISS-IMAP/VISI: a first report of an undulating wave front

Spatial structures of wave disturbances in the upper atmosphere were investigated with space-borne imaging from the International Space Station. The wave disturbance occurred around an altitude of 100 km, and is called a mesospheric bore. The large-scale structure of mesospheric bores has not been fully captured by previous ground-based imagers, but the space-borne imaging captured a bore with a wide field of view, and showed that bores can have a large undulating wave front as long as 2000 km.

ISS-IMAP/VISI: a first report of an undulating wave front">Read more

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