This paper covers the problems related to the derivation of aerosol extinction coefficients and Ångström exponents from space-borne instruments working in limb and occultation viewing geometries. Aerosol extinction coefficients and Ångström exponents were calculated from the SCIAMACHY aerosol particle size data set. The results were compared with the data from SAGE II and OSIRIS. The Ångström exponent in the tropical regions and its dependency on particle size parameters are discussed.

In thermal–optical measurement techniques – widely used techniques to separate organic and elemental carbon – a filter sample is heated stepwise first in He and then in He+O₂. Pyrolysis of organic material occurring during heating in He influences the results but is not fully understood. In this study, structural changes of carbonaceous material during a thermal–optical heating procedure are analyzed with Raman spectroscopy, TEM, UV–VIS and the integrating-sphere method.

An innovative and flexible methodology for cloud identification and classification, CIC, is tested on a synthetic dataset of high spectral resolution radiances in the far- and mid-infrared part of the spectrum, simulating measurements from the FORUM (Far Infrared Outgoing Radiation Understanding and Monitoring) mission. Results show that classification scores are greatly increased when far-infrared channels are accounted for and the identification of thin cirrus clouds is improved.

A new method is proposed to retrieve the size-resolved real part of the refractive index (RRI). The main principle of deriving the RRI is measuring the scattering intensity by a single-particle soot photometer of a size-selected aerosol. This method is validated by a series of calibration experiments using the components of the known RI. The retrieved size-resolved RRI covers a wide range, from 200 nm to 450 nm, with uncertainty of less than 0.02.

The Geostationary Environment Monitoring Spectrometer (GEMS) will be launched by South Korea in 2019, and it will measure radiances ranging from 300 to 500 nm every hour with a fine spatial resolution of 7 km x 8 km over Seoul in South Korea to monitor column concentrations of air pollutants including O₃, NO₂, SO₂, and HCHO, as well as aerosol optical properties. This paper describes a GEMS formaldehyde retrieval algorithm including a number of sensitivity tests for algorithm evaluation.

This paper presents a generic simulation rotating-beam scatterometer scheme, which includes pencil-beam and fan-beam instruments. SCAT (CFOSAT), WindRAD, and SeaWinds are chosen to represent the current or near-future rotating-beam scatterometers. Their capacity for wind retrieval and figures of merit are analyzed and compared with each other. Increasing the number of views is able to improve the wind retrieval, but the improvement also can reach saturation with even more views.

Aerosols are small particles in the atmosphere such as dust or smoke. They are routinely monitored by satellites due to their importance for climate and air quality. However aerosols above clouds are more difficult to monitor. This study describes an improvement to a technique to monitor light-absorbing aerosols above clouds from four Earth-orbiting satellite instruments. The improved method is evaluated using data from the ORACLES field campaign, which measured these aerosols from aircraft.

Using more satellite data in cloudy areas helps improve weather forecasts, but all-sky assimilation is still tricky, particularly for infrared data. To allow the use of hyperspectral infrared sounder radiances in all-sky conditions, an error model is developed that, in the presence of cloud, broadens the correlations between channels and increases error variances. After fixing problems of gravity wave and bias amplification, the results of all-sky assimilation trials were promising.

In this paper we show that sodium chloride particles with a mobility diameter below 10 nm indicate different activation regimes. The results of our studies reveal that with increasing humidity the activation of NaCl particles with a standard butanol-based CPC can be enhanced. For Ag this humidity dependence could not be observed – an indicator for the importance of molecular interactions between seed and vapor molecules.

This article presents the updated MAPIR algorithm, which uses infrared satellite data to obtain the global 3-D distribution of mineral aerosols. A description of the method together with its technical improvements is given. Additionally, a 10-year data set was generated and used to evaluate this new algorithm against AERONET, CALIOP, CATS and two ground-based lidar stations. We have shown that the new MAPIR algorithm provides reliable aerosol optical depth and dust layer mean altitude profiles.

Water vapour trend calculations with lidars require rigorous calibrations. Here, we improve water vapour lidar calibrations using GCOS Reference Upper Air Network (GRUAN) radiosondes and a new trajectory method. The trajectory method improved the lidar calibration and more consistently agreed with the radiosonde measurement compared to the traditional method. Using GRUAN radiosondes enabled the calculation, for the first time, of a complete uncertainty budget of the calibration constant.

A closed-path infrared absorption spectrometer was outfitted with the option for active continuous passivation for measuring large, rapid gradients in atmospheric NH₃ from a research aircraft. In-flight and ground observations show utility in passivant addition for recovering instrument time response when sampling surfaces are contaminated and cannot be cleaned in a timely manner and for maintaining rapid time response in an NH₃-rich and humid environment over a several-week-long field campaign.

Liquid water path (LWP) is a combination of rain liquid water path (RLWP) and cloud liquid water path (CLWP) in stratiform precipitation systems. LWP partitioning is important but poorly understood. Here we estimate the RLWP and CLWP below the melting base simultaneously and separately using ceilometer and radar measurements. Results show that the occurrence of cloud particles below the melting base is low; however, when cloud particles exist, the CLWP value is much larger than the RLWP.

Recent advancements in atmospheric mass spectrometry provide large amounts of new information but at the same time present considerable challenges for the data analysis, for example, in high-resolution peak identification and separation. To address these problems, this study presents a simple and novel method, which succeeds in analyzing both synthetic and ambient datasets. We believe it will become a powerful approach in the data analysis of mass spectra.

This work improves OMI ozone profile retrievals by accounting for spectral fit residuals caused by slit function errors as a pseudo absorber in the optimal-estimation-based spectral fitting process.

This study proposes an aerosol-type classification based on parameters from the AErosol RObotic NETwork (AERONET) version 3 level 2.0 inversion product that describe light depolarization and absorption properties of atmospheric particles. We compare our classification with an earlier method and find that the new approach allows for a refined classification of mineral dust that occurs as a mixture with other absorbing aerosols.

Within the EU COST Action ES1206 we have studied the horizontal variability of the atmosphere using signals from GPS satellites, distant quasars, and a microwave radiometer. We find a consistent picture: horizontal variability over timescales of months are mainly due to atmospheric pressure, whereas water vapour is the main cause of variations over times from minutes to hours. An understanding of these variations helps to improve the accuracy of GPS applications in both geodesy and meteorology.

A new method to retrieve CCN number concentrations using multiwavelength Raman lidars is proposed. The method implements hygroscopic enhancements of backscatter and extinction with relative humidity to represent particle hygroscopicity. The retrieved CCN number concentrations are in good agreement with theoretical calculated values. Sensitivity tests indicate that retrieval error in CCN arises mostly from uncertainties in extinction coefficients and RH profiles.

The identification and quantification of compounds within an atmospheric particle can be difficult to achieve. We present a supercritical fluid chromatography method to separate these compounds prior to mass spectrometry analysis. The aqueous methylglyoxal–ammonium sulfate system was used as a proxy for atmospheric aerosol; polar columns combined with a carbon dioxide and methanol mobile phase provided the most efficient separation. This method can be extended to other atmospheric systems.

Volcanic ash is a hazard associated with volcanoes. Knowing an ash cloud’s location is essential for minimising the hazard. This includes knowing the height. This study adapted a well-known technique for obtaining the height of meteorological clouds, known as CO₂ slicing, for volcanic ash. Modelled data were used to refine the method and then demonstrate that the technique could work for volcanic ash. It was then successfully applied to data from the Eyjafjallajökull and Grímsvötn eruptions.

Recent atmospheric observations have indicated emissions of iron-oxide-containing aerosols from anthropogenic sources could be 8x higher than previous estimates, leading models to underestimate their climate impact. Previous studies have shown the single particle soot photometer (SP2) can quantify the atmospheric abundance of these aerosols. Here, I explore a machine learning approach to improve SP2 detection, significantly reducing misclassifications of other aerosols as iron oxide aerosols.

An air-to-air ultrafine particle concentrator (Aerosol Dynamics Inc. concentrator; ADIc) has been tailored for the low (~ 0.08 L min⁻¹) inlet flow of aerosol mass spectrometers, and it provides a factor of 8–21 enrichment in the concentration of particles. The ADIc was evaluated in laboratory and field measurements. The results showed that the concentration factor depends primarily on the ratio between the sample flow and the output flow and is independent of particle size above about 10 nm.

This paper builds upon the work in von Clarmann and Grabowski (2007) concerning the a priori profile influence in the optimal estimation method applied to active remote sensing measurements, with examples given for lidar retrievals of temperature and water vapor mixing ratio. The optimal estimation method is a new technique for many active remote sensing researchers. This study gives insight into understanding the effect on retrievals of the a priori information.

We examine the differences between assimilating ozone profiles retrieved from IASI or the corresponding infrared spectra in a chemical transport model. This allows the impact of the retrieval's prior information on ozone reanalyses to be quantified. We found that significant differences can arise between the two approaches, depending on the latitude. An improved O₃ variability is obtained assimilating IASI radiances directly. The implications for coupled Earth system models are discussed.

The JAXA is surveying the feasibility of a potential satellite mission equipped with a precipitation radar on a geostationary orbit, as a successor of the GPM Core Observatory. We investigate what kind of observation data will be available from the radar using simulation techniques. Although the quality of the observation depends on the radar specifications and the position of precipitation systems, the results demonstrate that it would be possible to obtain three-dimensional precipitation data.

Satellite observations depend on Sun and view angles due to anisotropy of the Earth's atmosphere and surface reflection. But most of the ultraviolet and visible cloud, aerosol, and trace-gas algorithms utilize surface reflectivity databases that do not account for surface anisotropy. We create a surface database using the GLER concept which adequately accounts for surface anisotropy, validate it with independent satellite data, and provide a simple implementation to the current algorithms.

In this study, we introduce the new tethered balloon system BELUGA, which includes different modular instrument packages for measuring turbulence and radiation in the atmospheric boundary layer. BELUGA was deployed in an Arctic field campaign in 2017, providing details of boundary layer processes in combination with low-level clouds. Those processes are still not fully understood and in situ measurements in the Arctic improve our understanding of the Arctic response in terms of global warming.

This work assesses water vapour profiles acquired by Atmospheric Chemistry Experiment (ACE) satellite instruments in the upper troposphere and lower stratosphere (UTLS) using comparisons to radiosondes and ground-based Fourier transform infrared spectrometer measurements acquired at a Canadian high Arctic measurement site in Eureka, Nunavut. Additional comparisons are made between these Eureka measurements and other water vapour satellite datasets for context, including AIRS, MLS, and others.

Stratospheric aerosol backscatter ratios in the Arctic using Rayleigh, Mie and Raman backscattered signals were calculated. A backscatter ratio calculation during daytime was performed for the first time. Sharp aerosol layers thinner than 1 km over several days were observed. The seasonal cycle of stratospheric background aerosol in high latitudes including the summer months was calculated for the first time. Top altitude of the aerosol layer was found to reach up to 34 km, especially in summer.

We present a new ground-based instrument (CORAM) that measures atmospheric carbon monoxide (CO) concentrations within approximately 47–87 km in altitude with a 1 h time resolution. The measurements are made at Ny-Ålesund (79° N), Svalbard, and add much-needed coverage to the high Arctic. The first measured CO profiles from winter 2017/2018 are compared to co-located measurements from the Aura MLS satellite instrument and show agreement on daily and monthly timescales.

The use of AOD data retrieved from ATSR-2, AATSR and AVHRR to produce a very long time series is investigated. The study is made over a small area in northern China with a large variation of AOD values. Sun photometer data from AERONET and CARSNET and radiance-derived AOD are used as reference. The results show that all data sets compare well. However, AVHRR underestimates high AOD (mainly occurring in summer) but performs better than (A)ATSR in winter.

Inference of the tropopause from temperature profiles of finite vertical resolution entails an uncertainty of the tropopause altitude. We assess this effect by degrading the resolution of the sonde data. The tropopause altitude inferred from coarse grid profiles was found to be lower than that inferred from the original profiles for tropical and midlatitudinal radiosonde profiles. The mean displacement of the lapse rate tropopause inferred from a 3 km resolution profile is −400 m for Hilo.

Ceilometers are laser cloud base recorders which retrieve information about atmospheric aerosol and differing cloud types. In order to ensure the information retrieved from the ceilometer is correct and comparable with other ceilometers in an observation network, a calibration is needed. Presented here is a novel automated calibration method, which includes a correction for the effects of water vapour in the atmosphere and shows its application on the UK Met Office's ceilometer network.