We have described an approach to estimating the background concentration level of a species, such as methane, in the atmosphere from an analysis of the measured data provided by the National Physical Laboratory's differential absorption lidar (DIAL) system. The estimation of the background level supports the mapping of pollutant concentrations and the determination of emission fluxes. Results for data provided by a field measurement are presented, and ideas for future work are discussed.

A new portable, online instrument was designed, built and characterised to quantify reactive oxygen species (ROS) in atmospheric aerosols for laboratory and field deployment. ROS are potentially major contributors to the toxicity of particles. Our new instrument allows automated quantification of ROS over days with a detection limit of about 4 nmol [H₂O₂] equivalents per cubic metre of air, allowing for continuous atmospheric measurements of this important aerosol toxicity parameter.

The micro-RPAS SUMO (Small Unmanned Meteorological Observer) equipped with a five-hole-probe (5HP) system for turbulent flow measurements was operated in 49 flight missions during the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign in 2011. Based on data sets from these flights, we investigate the potential and limitations of airborne velocity variance and TKE (turbulent kinetic energy) estimations by an RPAS with a take-off weight below 1 kg.

In this study we have performed an inter-comparison between EddyUH and EddyPro, two public and commonly used software packages for eddy covariance data processing and calculation. The aims are to estimate the flux uncertainty due to the use of different software packages, and to assess the most critical processing steps, determining the largest deviations in the calculated fluxes. We focus not only on water vapour and carbon dioxide fluxes, but also on the methane flux.

This work analyses the lidar polarizing sensitivity by means of the Stokes–Müller formalism and provides a new tool to quantify the systematic error of the volume linear depolarization ration (δ) using the Monte Carlo technique. Results evidence the importance of the lidar polarizing effects which can lead to systematic errors larger than 100 %. Additionally, we demonstrate that a proper lidar characterization helps to reduce the uncertainty.

In 2016, the Sentinel 5 Precursor mission will be launched, with the TROPOMI instrument as its single payload. It will deliver daily global measurements of carbon monoxide for air quality monitoring as part of the Copernicus atmospheric services. In this paper, we focus on the operational data processing of the CO product from TROPOMI measurements of the shortwave infrared spectral range, and we discuss the algorithm's maturity.

The vertical distribution of cloud cover has a significant impact on a large number of meteorological and climatic processes. Cloud top altitude (CTOP) and cloud geometrical thickness (CGT) are essential for understanding these processes. Previous studies established the possibility of retrieving those parameters from multi-angular oxygen A-band measurements. Here we perform a study and comparison of the performance of future instruments.

Here we describe the determination of C-14 concentration in stratospheric CO₂ samples collected using the AirCore sampling method. Two stratospheric AirCore profiles, collected in Sodankylä, were used for this study. The stratospheric profile was divided into six sections. CO₂ from each section was extracted and converted to graphite for the determination of C-14 using AMS. Through this study, we show that the AirCore is a viable and valuable sampling method for stratospheric C-14 measurements.

We present a comparison study of two data inversion algorithms that are used to derive microphysical properties of atmospheric particle pollution. The algorithms have been developed for the analysis of data collected with advanced light detection and ranging (lidar) instruments from the European EARLINET network. The result of this study shows that two key parameters needed for climate change studies, i.e. particle size and light absorption capacity, can be derived with reasonable accuracy.

The tropical tropospheric column ozone (TCO) from 5 GOME-type satellite instruments were harmonised to get a consistent time series of tropospheric ozone for 20 years. The time series showed a global ozone trend below 10 km of 0.7 DU per decade. Also the regional trends were analysed and trends up to 1.8 DU per decade or decreases as low as 0.8 DU per decade were observed. The TCO will be part of the operation product for Tropomi/S5P and thereby extended for at least 7 years.

Validation of the above-cloud aerosol optical depth retrieved using the "color ratio" method applied to MODIS cloudy-sky measurements against airborne direct measurements made by NASA’s AATS and 4STAR sun photometers during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS 2013 reveals a good level of agreement (difference < 0.1), in which most matchups are found be constrained within the estimated uncertainties associated with the MODIS retrievals (-10 % to +50 %).

Although high-spatial-resolution weather radar observations are of primary relevance for urban hydrology, weather radar siting and characterization are challenging in an urban environment. Buildings, masts and trees cause partial beam blockages and clutter that seriously affect the observations. For the first time, this paper investigates the benefits of using airborne laser scanner (ALS) data for quantitative estimations of partial beam blockages in an urban environment.

Global Positioning System (GPS) radio occultation (RO) signals can be inverted to provide profiles of temperature. Earlier inversion method that used geometric optics were observed to have large errors in the few kilometers of the atmosphere. Different theoretical methods were developed to address the deficiencies of the GO methods. In this study, we implement the full-spectrum inversion (FSI) method for inversion of GPSRO signal received by a receiver placed on an aircraft.

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were performed in the urban environment of Madrid, Spain, where Sahara dust intrusion sometimes occurs. The study shows a high performances in the retrieval of aerosol optical depth, the surface extinction coefficient and an elevated layer during dust episodes, validated by AERONET in situ and modeling data. It is essential to capture the extinction properties of both local aerosol and Saharan dust.

We report the characteristics and performances of a cavity ring-down spectrometer (CRDS) designed for field measurements that uses light absorption at 662 and 405 nm to detect different reactive nitrogen species or group of species in the gas phase, either directly or after thermal decomposition. We report improvements compared to currently existing instruments, and describe the corrections applied to the raw data to account for chemical and optical interferences.

The database contains the complete (polarimetric) scattering information for different types of ice particles at different incident and scattered radiation directions at four microwave wavelengths. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident and scattered radiation. It is also useful in ice-property retrievals, radar forward simulation.

The subject of our study concerns measurements with optical array probes (OAPs) on fast-flying aircraft such as the G550 (HALO or HIAPER). At up to Mach 0.7 the effect of air compression upstream of underwing-mounted instruments and particles' inertia need consideration for determining ambient particle concentrations. Compared to conventional practices the introduced correction procedure eliminates ambiguities and exhibits consistency over flight speeds between 50 and 250 m s⁻.

We review available methods for the random error estimation of turbulent fluxes that are widely used by the flux community. Flux errors are evaluated theoretically as well as via numerical calculations by using measured and simulated records. We recommend two flux random errors with clear physical meaning: the total error resulting from stochastic nature of turbulence, well approximated by the method of Finkelstein and Sims (2001), and the error of the flux due to the instrumental noise.

In cloud condensation nuclei (CCN) measurements, the supersaturation scan is often time-consuming and limits the temporal resolution of CCN measurements. Here we present a new concept, termed the broad supersaturation scanning (BS2) method, in which a range of supersaturation is simultaneously scanned, resulting in fast measurements of CCN activity.

We show in this study that the non-linearity of NO_x chemistry implies that the local derivative (of a first-order Taylor expansion) is better suited in the inverse modelling of NO_x emissions over eastern China. We used single-grid-cell-based perturbation sensitivity calculation. The method leads to smaller NO_x emission over highly polluted regions and higher NO_x emission over rural regions. There are also more consistent results from using two different satellite instruments.

We present the comparison between satellite- and ground-based atmospheric NO₂ observations in Helsinki (Finland). The results show that, despite some limitations due to cloud contamination and low solar angles, satellite data are able to describe urban air quality features such as the weekly and seasonal cycles. The results support air quality satellite data exploitation at high latitudes and prepare for similar applications for future missions.

We present a comparison of aircraft measurements of important trace gases from a co-ordinated campaign in Jan–Feb 2014 in the tropical west Pacific involving the NASA Global Hawk, NCAR GV and FAAM BAe-146 aircraft. The paper studies the comparability of separate measurements across platforms and demonstrates that aircraft measurements are relevant for characterising the vertical uplift of important gases, such as those with ozone-depleting potential, to the upper troposphere–lower stratosphere.

We present an analysis of uncertainties in global measurements of the column-averaged dry-air mole fraction of CO₂ (XCO₂) by the satellite OCO-2. The analysis is based on our best estimates for uncertainties in the OCO-2 operational algorithm and its inputs. From these results we estimate the "variable error", which differs between soundings, to infer the error in the difference of XCO₂ between any two soundings. Variable errors are usually < 1 ppm over ocean and ~ 0.5–2 ppm over land.

A multi-source water vapor tomography model is developed using GPS (Global Positioning System), radiosonde, WVR (water vapor radiometer), NWP (numerical weather prediction), AERONET (AErosol RObotic NETwork) sunphotometer and synoptic stations' data. Results show that the assimilation of multi-source data can increase the quality of the tomographic solution. Evaluation shows that the tomography model is robust during heavy rain conditions, and it can contribute to severe weather forecasting.