We discuss a high-quality data set of simultaneous observations of 25 OH bands with an astronomical echelle spectrograph. These data allowed us to analyse band-dependent OH populations and temperatures. In particular, we could find different non-LTE contributions to OH rotational temperatures depending on band, line set, and observing time. This is critical for mesopause studies that use these temperatures as a proxy of the true temperatures.

This study highlights that there are no effective ways to remove the black carbon exclusively without influencing the other co-emitted components, our results therefore indicate that a reduction in BC emission can lead to an unexpected warming on the Earth’s climate system in the future.

Submicron particle mass concentration in the Amazon during the wet season of 2008 was dominated by organic material. The PMF analysis finds a comparable importance of gas-phase (gas-to-particle condensation) and particle-phase (reactive uptake of isoprene oxidation products, especially of epoxydiols to acidic haze, fog, or cloud droplets) production of secondary organic material during the study period, together accounting for >70% of the organic-particle mass concentration.

Ice nucleation in clouds has a significant influence on the global radiative budget and the hydrological cycle. Several studies have investigated the ice formation in droplets and parameterizations have been developed in order to include immersion freezing in climate models. In contrast, there are fewer studies regarding the conversion of water vapor into ice (so-called deposition nucleation) which is the topic of this paper which investigates deposition nucleation by Arizona Test dust in detail

Measurements of cloud microphysics are reported from the Aerosol-Cloud Coupling And Climate Interactions (ACCACIA) campaign. Concentrations of ice particles from two spring and two summer cases are compared with particular attention to the role of secondary ice in these clouds. In addition aerosol measurements were used as input to a primary ice nucleation parameterisation which was compared with observed values of primary ice in these clouds. We found higher concentrations of ice during summer.

Time series of the satellite-observed stratospheric tracer, CH4, are analyzed to see whether they indicate a significant trend for the hemispheric Brewer--Dobson circulation (BDC) for 1992-2005. Trends in CH4 for the lower stratosphere are generally positive and equivalent to those of the troposphere. However, the Northern Hemisphere BDC is clearly accelerated in the mid-stratosphere (20 to 7hPa). Corresponding trends for the Southern Hemisphere are smaller and less significant.

Southeast Asia stands out globally, as it hosts one of the most complex meteorological and environmental conditions, making remote sensing difficult both for AERONET and satellites. Cloud-cleared data leave gaps in our remote sensing data record, and conversely, residual cloud contamination of remotely sensed data causes challenging tasks for scientists studying aerosols. With the main motivation of overcoming this problem, an AOD-predicting model is proposed.

This work explores the impact of acidic sulfate aerosol on the formation of SOA from isoprene and 1,3-butadiene. This study expands on previous work by extending the analysis over a broader range of humidities and aerosol liquid water contents. Extending the experiments to a wider range of hydrocarbons and across a more realistic range of humidities provides data of greater atmospheric relevance and contributes to development of acidity-influenced SOA chemistry mechanisms in air quality models.

Interest in numerical wind models continues to increase, especially for models that can simulate winds at relatively high spatial resolution (~100m). However, limited observational data exist for evaluation of model predictive performance. This study presents high-resolution surface wind data sets collected from an isolated mountain and a steep river canyon. The data are available to the public at http://www.firemodels.org/index.php/windninja-introduction/windninja-publications.

A new parametrization for cloud droplet nucleation is described. This revised approach makes use of a simple look-up table which is very efficient and computationally very cheap. Adopting this approach further allows for a more accurate treatment of the necessary approximations of supersaturation evolution and ultimately leads to a more accurate calculation of peak supersaturation and hence droplet nucleation.

To study the growth/shrinking of a hygroscopic nanoparticle during hydration/dehydration in an atmosphere of water vapour we employed a thermodynamic approach. For application to a nanometric sodium chloride particle we extended the original approach and demonstrated how the solution/solute interface energy and the correlation length of a thin solution film can be determined from a combination of experimentally determinable efflorescence and deliquescence humidities with the present calculus.

We use a comprehensive set of diagnostics to investigate how two widely used modern reanalysis data sets might affect studies of lower stratospheric polar processing and ozone loss. Our results show that the agreement in temperature diagnostics between the two reanalyses improves over time in both hemispheres with increasing assimilation model inputs. This suggests that both data sets are appropriate choices for studies of polar processing in recent winters.

This study demonstrated the potential use of MOPITT CO measurements to better understand the CO sources over Alberta. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons: summer and spring. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values, while the poor dispersion in central and southern Alberta exacerbates the surface CO pollution.

Dimensions of ice crystals increased with an increase in temperature and the L-W relationships of crystals with a given L depended heavily on temperature, whereas the aspect ratio depended only weakly on temperature. The relative frequency of occurrence of plates was much larger in anvil clouds compared to that of columnar crystals (i.e., columns and bullet rosettes), whereas the relative occurrence frequency of columnar crystals was much larger in non-anvil clouds.

This study examines quantitatively the impact of methodological choices, in particular of averaging of multi-model ensembles, on climate metrics for ozone precursors. Estimates of the standard deviation of radiative forcing (RF), global warming and temperature potential (GWP, GTP) from ensemble-mean input fields generally overestimate the true value. The multi-model average fields are appropriate for calculating mean metrics, but are not a reliable method for calculating the uncertainty.