Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes can be a tool for volcano monitoring. Here, we report on a field study that demonstrates the feasibility of remotely measuring the volcanic enhancements of carbon dioxide, hydrogen fluoride, hydrogen chloride, sulfur dioxide, and bromine monoxide in the plume of Mt. Etna using portable spectroscopic instrumentation sampling the plume several kilometers downwind of the source.

Ground-based observations of GPS satellites disappearing below the local horizon are analysed. Starting at +2 degree elevation angle the GPS signals are recorded in open-loop tracking mode down to −1.5 degrees. The open-loop Doppler model has negligible influence on the derived data products for strong signal-to-noise ratios; at lower signal levels, however, a notable bias is uncovered. These results may have implications for the design of future space-based GPS radio occultation missions.

HAI is a fully autonomous, airborne hygrometer for atmospheric investigations for simultaneous gas-phase/total H₂O detection on the HALO aircraft. HAI employs first-principle, direct, tunable diode laser absorption spectroscopy (dTDLAS) for calibration-free, absolute H₂O detection. HAI simultaneously measures at 1.4/2.6 µm and in closed-/open-path configuration, covers a H₂O range of 1–40 000ppmv at up to 1.4 ms time resolution and achieves precisions of 0.18/0.055 ppmv at 1.4/2.6 µm.

The Orbiting Carbon Observatory-2 carries and points a three-channel imaging grating spectrometer designed to collect high-resolution spectra of reflected sunlight within the molecular oxygen A-band at 0.765 microns and the carbon dioxide bands at 1.61 and 2.06 microns. Here, we describe the OCO-2 instrument, its data products, and its performance during its first 18 months in orbit.

The In situ/Remote sensing aerosol Retrieval Algorithm (IRRA) provides vertical profiles of aerosol optical, microphysical and hygroscopic properties from airborne in situ and remote sensing measurements. The algorithm is highly advantageous for aerosol characterization in humid conditions, employing the ISORROPIA II model for acquiring the particle hygroscopic growth. IRRA can find valuable applications in aerosol–cloud interaction schemes and in validation of active space-borne sensors.

Processes driving production and transport of CH₄ in wetlands are complex. We present an algorithm to separate open-water automatic chamber CH₄ fluxes into diffusion and ebullition. This helps to reveal dynamics, identify drivers and obtain reliable CH₄ emissions. The algorithm is based on sudden concentration changes during single measurements. A variable filter is applied using a multiple of the interquartile range. The algorithm was verified for data of a rewetted former fen grassland site.

This paper provides a thorough description of the algorithm to retrieve SO₂ columns from TROPOMI/Sentinel-5 Precursor measurements. The different algorithmic steps including error analysis are detailed. Scientific verification of the algorithm and validation needs are also discussed.

A comparison between a microwave radiometer and radiosonde is carried out, and performances of zenith and off-zenith observations during snowfall are shown. In off-zenith observations, the effect of snow is obviously mitigated, and the deviation between microwave radiometer and radiosonde is small. With the aid of off-zenith observation, reliable thermodynamic atmospheric profiles can be collected, and those will be useful for the analysis and forecasting of severe convective weather.

UV backscatter limb sounding sensors have difficulty determining altitude registration to the accuracy needed for long-term ozone monitoring. We describe two methods to achieve this by comparing radiance measurements to models. Wavelengths and altitudes chosen minimize errors from aerosol interference, calibration errors, and ozone assumptions. The techniques are inexpensive, more comprehensive than external sources of attitude information, and track drifts in our altitude to better than 100 m.

Aerosol properties were studied during a mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solar radiation at the AERONET site in Tomsk and satellite observations. The data were analysed using multi-year measurements under background conditions and yearly observed wildfires. It is shown that the aerosol radiation characteristics during individual severe fires differ significantly from the ensemble smoke hazes which are typical for the Siberian region.

A cloud detection method for all-sky images is proposed. Obtaining improved cloud detection results is helpful for cloud classification, tracking and solar irradiance prediction. The features are extracted from local image patches with different sizes to include local structure and multi-resolution information. The cloud models are learned through the training process. We have shown that taking advantages of multiple classifiers and various patch sizes is able to increase the detection accuracy.

We present the retrieval of NO number densities from 60 km to 85 km from measurements of SCIAMACHY/Envisat in its nominal limb mode (0–91 km). We derive the densities from the NO gamma bands (230–300 nm). Using prior input reduces the incorrect attribution of NO from the lower thermosphere. The SCIAMACHY nominal limb scans provide almost 10 years of daily NO data in this altitude range, a unique data record to constrain NO in the mesosphere for testing and validating chemistry climate models.

The cloud radar on board the NASA CloudSat mission provides information on the vertical structure of the cloud that, in the present study, is matched to ground-based measurements of lightning occurrences. The aim of this research was to study the relationship between the ice content of the cloud and its capability to produce lightning. Results show the importance of high ice content, especially close to the cloud top, for producing lightning.

This paper presents a new ozone profile inversion algorithm for GOMOS/Envisat satellite data. This algorithm is enhanced with a DOAS-type method at visible wavelengths in the upper troposphere and the lower stratosphere. The new GOMOS ozone profiles have a significantly improved data quality in the UTLS compared to the official IPF V6 ozone profiles. The paper describes the inversion algorithm and present inter-comparisons with ozonesonde and satellite measurements.

This paper discusses trade-offs among various wind measurement strategies using scanning Doppler lidars. It is found that the trade-off exists between being able to make highly precise point measurements versus covering large spatial extents. The highest measurement precision is achieved when multiple lidar systems make wind measurements at one point in space, while highest spatial coverage is achieved through using single lidar scanning measurements and using complex retrieval techniques.

We show that the long-standing discrepancy between observed and calculated spectra of the PFS/MEx in the cores and wings of 4.3-micron region is explained by the non-thermal rotational distribution of molecules in the upper vibrational states of second hot (SH) CO₂ bands above 90 km altitude. We discuss the implications that accounting for this effect has for developing operational algorithms aimed at massive processing of PFS and other instrument limb observations.

There is a lack of knowledge of volatile organic acids (VOAs), other than formic and acetic acids in gas phase, and this is at least partly due to the lack of sensitive enough measurement methods. In the present study we developed an in situ GC–MS measurement method for measuring C2–C7 monocarboxylic VOAs at ambient air concentration levels, which we used to measure ambient air concentrations in a boreal forest site. In addition, found mixing ratios were compared with PTR-TOFMS data.

Whole air sampling followed by analysis by gas chromatography is a common technique for characterization of trace volatile organic compounds in the atmosphere. We describe a new automated gas chromatograph–mass spectrograph which uses a Stirling cooler for sample preconcentration at −165 °C without the need for a cryogen such as liquid nitrogen. We also discuss potential sources of artifacts from our electropolished stainless steel sampling system and present results from two field campaigns.

We show how the surface reflection can vary day to day in the blue part of the sun's spectrum where we measure the pollutant gas nitrogen dioxide using a satellite instrument called OMI. We use information from an imaging spectrometer on another satellite, MODIS, to estimate the angular surface effects. We can then use models of how the sunlight travels through the atmosphere to predict how the angle-dependent surface reflection will impact the values of pollutant levels inferred by OMI.

Global coverage of remotely sensed skin temperature, along with cloud/surface radiation parameters, produced in near-real time and from historical satellite data, is beneficial for weather and climate purposes. One key drawback is the dependence on view angle. Therefore, this article serves to validate a global, satellite-based skin temperature product, while highlighting an empirically adjusted theoretical model of satellite LST angular anisotropy, and the benefits gained from its application.

This article describes a new instrument for measuring and quantifying emission fluxes. It introduces the instrument using the solar occultation flux method. Results are presented from the FRAPPE field campaign near Denver, Colorado, from 2014. Calculations of emissions of sources are presented from FRAPPE and compared to emission inventories. Finally, structure functions are calculated to facilitate the future comparison of high-resolution measurements with low resolution satellite measurements.