Formaldehyde is toxic to humans and is formed in the atmosphere in the presence of air pollution, but the measurements are sparse. Pandonia Global Network instruments measure total formaldehyde column from the surface to the top of troposphere and will be widely available. This study compared formaldehyde Pandora columns with the surface and aircraft-integrated columns near Seoul, South Korea. Relatively good agreement was observed between the three datasets with some overestimation by Pandora.

This study presents three signal-processing methods to improve estimates derived from a vertically pointing 35 GHz cloud radar deployed at Oliktok Point, Alaska. The first method removes ground clutter from the Doppler velocity spectra. The second method estimates multiple peaks and high-order moments from the improved spectra. The third method removes high-frequency variability in high-order moments by shifting original 2 s spectra to a common reference before averaging over a 15 s interval.

In this paper MUSICA IASI tropospheric water vapour profile retrievals are evaluated by performing theoretical error assessments and comparisons to GRUAN radiosonde measurements. We show that the vertical water vapour distribution is well captured from 1 km above the ground up to the tropopause. Largest error sources are unrecognized clouds and uncertainties in atmospheric temperature, which can reach about 25 %.

A new aircraft-mounted probe for collecting samples of cloud water has been designed, fabricated, and extensively tested. Cloud drop composition provides valuable insight into atmospheric processes, but separating liquid samples from the airstream in a controlled way at flight speeds has proven difficult. The features of the design have been analysed with detailed numerical flow simulations and the new probe has demonstrated improved efficiency and performance through extensive flight testing.

A few ground-based stations have provided time series of HCHO columns until now, which was not optimal for providing good diagnostics for satellite or model validation. In this work, HCHO time series have been determined in a harmonized way at 21 stations ensuring, in addition to a better spatial and level of abundances coverage, that internal biases within the network have been minimized. This data set shows consistent good agreement with model data and is ready for future satellite validation.

The sources and atmospheric chemistry of gas-phase organic acids are currently poorly understood, due in part to the limited range of measurement techniques available. We evaluated the use of SF₆⁻ as a sensitive and selective chemical ionization reagent ion for real-time measurements of gas-phase organic acids at a rural site in Yorkville, Georgia. We found that ambient concentrations of organic acids ranged from a few ppt to several ppb, and are dependent on ambient temperature.

Total ozone columns (TOCs) measured by Brewer spectrophotometers located at Rome and Aosta (Italy) were calculated using different processing software packages, and the differences in the TOC retrievals are investigated. Large differences in TOC retrievals can be experienced when the instrumental sensitivity exhibits a long-term drift. The variability in TOC retrievals depends on the algorithm for calculating the standard lamp correction.

In this paper, we perform a comprehensive validation of the IASI/Metop ozone data using independent observations (satellite, ground-based and ozonesonde). The quality of the IASI total and tropospheric ozone columns in terms of bias and long-term stability is generally good. Compared with ozonesonde data, IASI overestimates (underestimates) the ozone abundance in the stratosphere (troposphere). A negative drift in tropospheric ozone is observed, which is not well understood at this point.

The lack of collocated meteorological data at GNSS stations makes it difficult to take full advantage of GNSS observations for weather studies. This research demonstrates the potentials of retrieving accurate PWV from GNSS using adjacent synoptic data and generating high-quality PWV maps from the GNSS network for weather prediction in near-real time. Results also demonstrate that it's possible to reveal the moisture advection, transportation and convergence during heavy rainfalls using PWV maps.

The performance of the cosine error correction method for correcting spectral UV measurements of the Brewer spectroradiometer was studied. The correction depends on the sky radiation distribution, which can change during one spectral scan. The results showed that the correction varied between 4 and 14 %, and that the relative differences between the reference and the Brewer diminished by 10 %. The method is applicable to other instruments as long as the required input parameters are available.

The paper aims at characterising and quantifying the spatio-temporal variability of the melting layer (ML; transition zone from solid to liquid precipitation). A method based on the Fourier transform is found to accurately describe different ML signatures. Hence, it is applied to characterise the ML variability in a relatively flat area and in an inner Alpine valley in Switzerland, where the variability at smaller spatial scales is found to be relatively more important.

We present an overview of the GreenHouse gas Observations of the Stratosphere and Troposphere (GHOST) instrument, a novel shortwave infrared grating spectrometer designed for remote sensing of total column greenhouse gas concentrations from an aircraft. Using laboratory measurements we show that the GHOST design is able to achieve its science objectives. We conclude by describing GHOST's maiden flights on board the NASA Global Hawk UAV during CAST/ATTREX and show some of the initial results.

The calibration of ground-based weather radar (GR) can be improved a posteriori by comparing observed GR reflectivity to well-established spaceborne radar platforms (SR), such as TRMM or GPM. Our study shows that the consistency between GR and SR reflectivity measurements can be enhanced by considering the quality of GR data from areas where signals may have been blocked due to the surrounding terrain, and provides an open-source toolset to carry out corresponding analyses.

We present a detailed analysis of the long-term performance of the Global Ozone Monitoring Experiment (GOME) on-board ERS-2, which provided measurements of atmospheric constituents for the 16-year period from 1995 to 2011. By means of various in-flight calibration parameters, we monitor the behavior and stability during the entire mission. Furthermore, we introduce the new homogenized level 1 product generated using the recently developed GOME Data Processor Version 5.1.

Near-UV AAI is a qualitative parameter detecting the elevated absorbing aerosol layer. A long-term AAI record of satellite observations has the potential to quantify aerosol absorption on a global scale. Our study presents the possibility of retrieving single-scattering albedo with OMI-measured AAI. The comparison with AERONET is satisfactory and further research will be on how the aerosol wavelength-dependent refractive index and aerosol profile affect the quantification of aerosol absorption.

Energetic photons, such as ultraviolet light, are able to eject electrons from a material surface, thus creating an electrical current, also called a photocurrent. A proper estimation of this photocurrent can be crucial for space- or rocket-borne particle detectors, as it can dominate over the currents that are of scientific interest (induced by charged particles, for example). This article outlines the design for photocurrent modelling and for experimental confirmation in a laboratory.

Ice nucleation commonly studied using droplet freezing measurements suffers from artifacts caused by water impurities or substrate effects. We evaluate a series of substrates and water sources to find methods that reduce the background freezing temperature limit. The best performance was obtained from our new microfluidic device and hydrophobic glass surfaces, using filtered HPLC bottled water. We conclude with recommendations for best practices in droplet freezing experiments and data analysis.

The exchange rate of carbon dioxide (CO₂) between the atmosphere and the sea is typically small compared to the fluxes observed in the terrestrial ecosystems, causing technical challenges for the measurements of the CO₂ sea–air fluxes. In this paper, we examine CO₂ sea–air flux measurements carried out on a fixed station on an island. The problems generated by water vapor interference and unmet theoretical assumptions of the eddy covariance method are addressed.

In this paper, a novel cloud classification method is proposed to group images into five cloud types based on manifold and texture features. The proposed method is comprised of three stages: data pre-processing, feature extraction and classification. Compared to the recent cloud type recognition methods, the experimental results illustrate that the proposed method acquires a higher recognition rate with an increase of 2%–10% on the ground-based infrared datasets.

Atmospheric aerosols are an important constituent of the atmosphere. Measurement networks using radiometers such as SKYNET have been developed. There are two constants that we must determine to make accurate measurements. One of them is the calibration constant. The accuracy of the current method to determine this was investigated and the new method for water vapor and near-infrared channels was developed. Utilizing the results of this paper, SKYNET measurement data will become more reliable.

Atmospheric aerosols are an important constituent of the atmosphere. Measurement networks using radiometers such as SKYNET have been developed. There are two constants that we must determine. One of them is the solid view angle (SVA) of the radiometer. The problems related to SVA were investigated. It was shown that the conventional method can cause a systematic underestimation, and an improved method was proposed. Utilizing the results of this paper, SKYNET data will become more reliable.

EMI is a nadir-viewing wide-field imaging spectrometer aiming to quantify the global distribution of tropospheric and stratospheric trace gases. The spectral range is 240–710 nm, with the spectral resolution 0.3–0.5 nm. The preflight accuracy of wavelength calibration is less than 0.05 nm; the accuracy of radiance calibration is less than 5 %. The obtained calibration key data are used for the L1b processor. In-orbit wavelength/radiometric calibration is used to monitor performance changes.