We present the development and characterization of the NCAR Atmospheric Simulation Chamber, which is operated in steady state continuous flow mode for simulating atmospheric daytime and nighttime chemistry over chemical regimes not accessible in traditional static chamber experiments. We focus on establishing an intermediate NO regime characterized by a constant steady-state NO level ranging from tens of ppt to a few ppb in the chamber.

Comparing observational systems when observations are not taken at the exact same time or location can introduce sampling errors that can be come significant during error analysis. In this study, we develop two methods to reduce sampling errors: using ellipse distance constraints rather than circles and subtracting model background. We found that both the ellipses and subtracting model background from the observations reduce sampling errors caused by spatial and temporal differences.

Remotely piloted aircraft systems (RPAS), commonly called UAVs, are used in atmospheric science for in situ measurements. The presented work shows wind measurements from a five-hole probe on an RPAS. Comparisons with other instruments (sonic anemometer and cloud radar) show good agreement, validating the RPAS measurements. In situ vertical wind measurements at cloud base are highlighted because they are a major parameter needed for simulating aerosol–cloud interactions, though rarely collected.

We process global navigation satellite system radio occultation (RO) observations in a new way with integrated uncertainty propagation; in this study we focus on retrieving atmospheric bending angles from RO excess phase profiles. We find that this new approach within our novel Reference Occultation Processing System (rOPS) exploits the strengths of RO such as its high accuracy and long-term stability in a reliable manner for global climate monitoring and other weather and climate uses.

The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 algorithm retrieves aerosol extinction profiles at 675 nm by iteration, based on comparisons between the measured and calculated radiance profiles (assuming an aerosol size distribution). The most significant error source is uncertainty about the aerosol phase function. Horizontal variations in aerosol extinction may also limit the quality of the retrieved aerosol extinction profiles.

A new protocol for merging in situ atmospheric chemistry measurements with 3-D models is developed. This technique can identify the most reactive air parcels in terms of tropospheric production/loss of O₃ & CH₄. This approach highlights differences in 6 global chemistry models even with composition specified. Thus in situ measurements from, e.g., NASA's ATom mission can be used to develop a chemical climatology of, not only the key species, but also the rates of key reactions in each air parcel.

NO₂ is a pollutant that regularly exceeds its limit values in European cities. We developed a compact, mobile laser spectrometer that measures NO₂ concentrations and installed it on a tram in Zurich. Mobile operation resulted in NO₂ concentration data with high spatio-temporal resolution. The data were validated against fixed air-quality monitoring sites and provided detailed insights into the spatio-temporal concentration distribution of NO₂ in an urban environment.

We developed and field-tested a UAV-based active AirCore for atmospheric measurements of CO₂, CH₄, and CO. AirCore is an innovative tool that passively samples air using the atmospheric pressure gradient during descent. Here we have taken further steps to change the “active” sampling process with a pump, miniaturize it, and deploy it on a UAV. The active AirCore system opens up a wide variety of opportunities, e.g., quantifying CH₄ emissions from wetlands, landfills, other CH₄ hot spots.

Since about three years after the launch the Ozone Monitoring Instrument (OMI) on the EOS-Aura satellite, the sensor’s viewing capability has been affected by what is believed to be an internal obstruction that has reduced OMI’s spatial coverage. It currently affects about half of the instrument’s 60 viewing positions. In this work we carry out an analysis to assess the effect of the reduced spatial coverage on the monthly average values of retrieved parameters.

Atmospheric Infrared Sounder (AIRS) satellite observations are used to quantify the scale-dependent variance of temperature and water vapor in the atmosphere. The scale dependence is much more variable than previously thought, using a new methodology based on individual satellite swaths. A break in the scale dependence is found to vary from less than 100 to greater than 1000 km. These new variance scaling results are of high importance for improving climate GCM subgrid parameterizations.

The presented calibration method grants access to quality approved automated atmospheric water vapor profiles from lidar measurements. This method uses the Raman lidar data from the water vapor and nitrogen channels and additional data from sun photometer and GDAS. The retrieved water vapor profiles agree well with respective profiles from radio soundings. The paper describes this method and shows results from the CyCARE (Cyprus Cloud Aerosol and Rain Experiment) campaign in 2015–2017.

This work investigates the total conversion of particle-bound nitrogen and organic carbon across platinum and molybdenum catalysts followed by NO–O₃ chemiluminescence and nondispersive infrared CO₂ detection. We show the instrument is an accurate particle mass measurement method and demonstrate its ability to calibrate particle mass measurement instrumentation through comparisons with a calibrated particle-into-liquid sampler coupled to an electrospray ionization source of a mass spectrometer.

We developed a novel NO₂ DOAS retrieval for the GOME-2A instrument in the UV spectral range, which is compared with a NO₂ retrieval in the visible and model values. Regions representative for both anthropogenic and biomass burning NO₂ pollution are investigated. Anthropogenic air pollution is mostly located in the boundary layer close to the surface. In contrast, biomass burning NO₂ is often uplifted into elevated layers.

Measurements of nitrogen dioxide, known to originate from industrial and automotive combustion sources, have been made from space for two decades. Successive generations of instrument bring improvements in ground-pixel resolution; however features in the atmosphere are known to be smaller than what the satellites can resolve. Measurements of urban and industrial areas using a high-resolution airborne instrument allow the impact of the satellite's relatively low resolution to be evaluated.

A modular long-path folded tubular photometer for making absorbance measurements of air pollutant concentrations is described. The present paper applies this photometer to direct measurements of nitrogen dioxide and, indirectly, to nitric oxide. Excellent agreement for both was observed for measurements along an urban roadside compared with existing standard techniques. Advantages and extension of this technique to other atmospheric pollutants, including particulates, are discussed.

The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) is a newly designed research sensor aiming to continue high vertical resolution ozone records from space-borne sensors. In summer 2017 all LP measurements were processed with the new version 2.5 algorithm. In this paper we provide a description of the key changes implemented in the new algorithm and evaluate the quality of ozone retrievals by comparing with independent satellite profile measurements (MLS, ACE-FTS and OSIRIS).

Preparations are continuing for the launch of the Greenhouse Gases Observing Satellite 2 (GOSAT-2) in the fiscal year 2018. To improve the accuracy of the estimates of greenhouse gases concentrations, we need to refine the existing cloud discrimination algorithm. In this paper we showed a new cloud discrimination algorithm of pre-launch version for GOSAT-2, and compared the existing algorithm with the new algorithm.

We simulated instrumental line shape (ILS) degradations with respect to typical types of misalignment, and compared their influence on each NDACC gas. The requirements to suppress the ILS-degradation-related biases within a specified accuracy for all NDACC gases were deduced.

The paper's scope is to evaluate the performance of in situ atmospheric aerosol instrumentation on board unmanned aerial vehicles (UAVs) and the performance of algorithms used to calculate the aerosol mass from remote sensing instruments by comparing the two independent techniques to each other. Our results indicate that UAV-based aerosol measurements (using specific in situ and remote sensing instrumentation) can provide reliable ways to determine the aerosol mass throughout the atmosphere.

The aerosol layer height is one of four aerosol parameters which is needed to enhance our understanding of aerosols' role in the climate system. Both active and passive measurement methods may be used to estimate the aerosol layer height. Aerosol height estimates made from passive infrared and solar satellite sensors measurements are compared with satellite-borne lidar estimates. There is considerable variation between the retrieved dust heights and how they compare with the lidar.

OH*-spectrometer measurements allow the analysis of gravity wave ground-based periods, but spatial information cannot necessarily be deduced. We combine the approach of Wachter at al. (2015) in order to derive horizontal wavelengths (but based on only one OH* spectrometer) with additional information about wind and temperature and compute vertical wavelengths. Knowledge of these parameters is a precondition for the calculation of further information such as the wave group velocity.

The current study provides intercomparisons of various water vapour measurements in the Arctic. It compares ground-based GPS observations with satellite measurements in the infrared (IR), near-infrared (NIR) and visible (VIS) through a specific method allowing us to quantify their uncertainties and limits. Unlike IR, satellite observations in NIR and VIS bands are mostly sensible to cloud cover during summer and to albedo variability over canopy or polluted snow-covered surfaces in winter.

Aerosol water has become an important topic recently because of its implications for multiphase secondary aerosol formation during severe haze events in Asia. This is a timely paper on this topic; a novel method is proposed to calculate ambient aerosol liquid water contents based only on measurements of a three-wavelength humidified nephelometer system. The advantage of this method is that this technique can provide continuous measurements of the changing ambient conditions.

To accurately infer air pollutant concentrations from satellite observations, we must first know the reflectivity of the Earth’s surface. Using a model, we show that satellite observations are better able to observe NO₂ near the surface if snow is present. However, knowing when snow is present is difficult due to its variability. We test seven existing snow cover data sets to assess their ability to inform future satellite observations and find that the IMS data set is best suited for this task.

The performance of two kinds of optical instruments for aerosol mass measurements was explained by a Mie scattering theory. At the same time, the response of optical instruments for ambient aerosol with different size, chemical composition, and refractive index were also studied. These would help evaluate the applicability and limitations of these optical scattering instruments.

Few techniques can measure the contribution of refractory black carbon (rBC) to ice-nucleating particle (INP) concentrations. One technique uses the single particle soot photometer (SP2) as a pre-filter to an online INP counter to selectively remove rBC particles from an aerosol stream. In this work, we expand upon this technique by determining the effect of the SP2 laser on INP proxies mixed with rBC. We also bounded the SP2 conditions under which rBC is fully vaporized in the SP2 exhaust.

We investigate the feasibility of quantifying the difference in biases of two instrument types (i.e. radiosondes) by flying the old and new instruments on alternating days, so-called interlacing, to statistically derive the systematic biases between the instruments. While it is in principle possible to estimate the difference between two instrument biases from interlaced measurements, the number of required interlaced flights is very large for reasonable autocorrelation coefficient values.

Vertical profiles of the aerosol physical and optical properties, with a focus on seasonal means and on transport events, were investigated by the synergistic method using lidar and sky radiometer. The retrieved vertical profiles were input to the one-dimensional atmospheric model, and the impacts of the transported aerosols on the evolution of the atmospheric boundary layer (ABL) were studied. The vertical profile of the aerosol direct heating has important effects on the ABL evolution.

Diesel fuel, lubricating oil and diesel exhaust emissions all contain a very complex mixture of chemical compounds with diverse molecular structures. The GC × GC-ToF-MS analytical method is a very powerful way of separating and identifying those compounds. This paper describes the allocation of compounds into groups with similar molecular structures and chemical properties, which facilitates the intercomparison of very complex mixtures such as are found in diesel fuel, oil and emissions.

Estimating snowfall intensity from satellite and ground-based radar missions requires accurate retrieval models. Reflectivity–snowfall relations are obtained at cm and mm wavelengths using data recorded during the Biogenic Aerosols Effects on Clouds and Climate (BAECC) campaign in Finland. Lightly, moderately and heavily rimed snow cases are identified. Numerical simulations are performed to relate snowflake microphysical (video disdrometer) and multifrequency backscattering properties (radars).

Water vapor is the most important tropospheric greenhouse gas and is also highly variable in space and time. We study the vertical structure and variability of tropospheric humidity using various observing techniques (GPS radio occultation, radiosondes, Atmospheric Infrared Sounder) and models. Time–height cross sections reveal seasonal biases for different pressure layers. We find that radio occultation humidity has high accuracy and can contribute valuable information in data assimilation.

Using high-resolution surface irradiance data with original temporal resolutions between 0.01 s and 1 s from six different locations in the Northern Hemisphere, we characterize the changes in representation of temporal variability resulting from time averaging. Our results indicate that a temporal averaging time scale of around 1 s marks a transition in representing single-point irradiance variability, such that longer averages result in substantial underestimates of variability.

In this study, we perform global validation of MODIS high-resolution (3 km) AOD over global land by comparing against AERONET measurements. The MODIS–AERONET collocated data sets consist of 161 410 high-confidence AOD pairs from 2000 to 2015 for Terra MODIS and 2003 to 2015 for Aqua MODIS. We find that 62.5 and 68.4 % of AODs retrieved from Terra MODIS and Aqua MODIS, respectively, fall within previously published expected error.

In this paper, we propose a new observation strategy, called sweep mode, for a real three-dimensional tomographic reconstruction of gravity waves in the mesosphere and lower thermosphere by modifying the observation geometry of conventional limb-sounding measurements. It enhances the horizontal resolution that typical limb sounders can achieve while at the same time retaining the good vertical resolution they have.

In this paper a new algorithm for cloud top height retrieval from imager instruments like MODIS is presented. It uses artificial neural networks and reduces the mean absolute error by 32 % compared to two other operational cloud height algorithms. This means that improved cloud height retrieval for nowcasting, as input to models and in cloud climatologies is possible.