The ability to estimate snowfall accurately is important for both weather and climate applications. In this work we have intercompared snowfall estimates from two observing systems: the space-based Cloud Profiling Radar on board NASA's CloudSat satellite and Swerad, the ground-based Swedish national weather radar network. The intercomparison shows encouraging agreement between these two observing systems despite their different sensitivities and user applications. Hide

Measurements of atmospheric carbon dioxide and methane total vertical column abundance from onboard the research vessel "RV Polarstern" in March / April 2014. Along the journey on the Atlantic from Cape Town (South Africa) to Bremerhaven (Germany) we could reproduce the interhemispheric gradient of the target gases, and we compared the measurements with satellite and model data. Future campaigns could use the new mobility to characterize sources and sinks of carbon-dioxide and methane. Hide

Comparisons between satellite and ground-based measurements of the atmosphere are inevitably affected by natural variability due to mismatches in spatial and temporal co-location. These additional terms in the comparison error budget are quantified here for total ozone column comparisons using an Observing System Simulation Experiment. Even when using tight co-location criteria, atmospheric variability is found to impact the comparisons significantly. Hide

A large intercomparison study of 13 Q-ACSM was conducted for a 3-week period in the region of Paris to evaluate the performance of this instrument and to monitor the major NR-PM1 chemical components. Reproducibility expanded uncertainties of Q-ACSM concentration measurements were found to be 9, 15, 19, 28, and 36% for NR-PM1, NO3, OM, SO4, and NH4, respectively. Some recommendations regarding best calibration practices, standardized data processing and data treatment are also provided. Hide

Volcanic ash poses a serious threat to aircraft traffic. A simple neural-network based technique was developed to detect volcanic ash from space using satellite infrared observations. A validation study shows promising results for several individual case studies. Issues remain near the edge of the satellite's field of view as well as in situations where ash is mixed with meteorological clouds. Hide

This study investigates whether the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic beam and circumsolar irradiances under cloud-free conditions in a desert environment. By comparing the modelled irradiances against reference ground measurements, the monochromatic beam and circumsolar irradiances may very well be modelled using a set of inputs extracted from the AERONET data. Hide

The study reports on the application of an aircraft-based instrument (AirMAP) measuring atmospheric nitrogen dioxide. Two-dimensional maps are produced at a spatial resolution of 28m x 30m and with wide spatial coverage. The instrument characteristics are explained and the detailed mapping of a power plant emission plume is demonstrated. Small-scale enhanced amounts of nitrogen dioxide from traffic are observed above a motorway. Hide

Smoothing filters applied on lidar profiles reduce the resolution to a value indicated as the effective resolution (ERes). Several approaches to ERes estimation are investigated. The key result is an operative ERes calculation by ready-to-use equations. The presented procedures to assess the ERes are of general validity. The ERes equations are deemed to be used in automatic tools like the Single Calculus Chain. Several filters already employed in the lidar community are also critically analyzed. Hide

This study provides direct validations of Tropospheric Emission Spectrometer (TES) satellite retrieved profiles against coincident aircraft profiles of carbon monoxide, ammonia, methanol, and formic acid, all of which are of interest for air quality. The comparisons are performed over the Canadian oil sands region during an intensive field campaign in support of the Joint Canada-Alberta Implementation Plan for the Oil Sands Monitoring (JOSM). Initial model evaluations are also provided. Hide

Volcanic eruption can be a serious security risk for airplanes. We develop a new aerosol sensor for the reliable detection of volcanic ash on airplanes. We introduce here the laboratory prototype of this instrument, which is able to distinguish between water droplets and volcanic ash particles by measuring the scattered light at two distinct wavelengths simultaneously. The different optical behaviour of volcanic ash and water at these wavelengths makes this differentiation possible. Hide

This article presents validation results for stratospheric aerosol extinction profiles retrieved from limb-scatter measurements with the SCIAMACHY instrument on the Envisat satellite. The SCIAMACHY retrievals are compared to co-located measurements with the SAGE II instrument. Very good agreement to within about 15% is found in a global average sense at altitudes above 15 km. The article also presents sample results on the global morphology of the stratospheric aerosol layer from 2003 to 2011. Hide

We derived time series of column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) at Saga, Japan, with a ground-based high-resolution Fourier transform spectrometer (g-b FTS). The g-b FTS XCO2 and XCH4 data were compared with those derived from a satellite-based instrument (TANSO-FTS onboard GOSAT). Using aerosol information measured simultaneously with a sky radiometer and a lidar at Saga, we evaluated the influence of aerosols on the satellite observations. Hide

MODIS is a satellite sensor widely used in Earth science. Its scanning geometry results in a distortion called the ‘bow-tie effect’, which means that, depending on the location of a pixel relative to the satellite ground track, the size and shape of the pixel may be distorted. This affects data such as aerosol optical depth (AOD) derived from the measurements. This paper illustrates the bow-tie disortion’s effect on AOD and presents techniques to restore AOD data products to a more uniform grid Hide

Adsorption/desorption effects of trace gases in gas cylinders were investigated. Our measurements indicate a rather strong effect on steel cylinders for CO2 that becomes easily visible through enhanced concentrations for low (<20 bars) gas pressure. Much smaller effects are observed for CO and CH4. Significantly smaller effects are measured for all gas species investigated on aluminium cylinders. Careful selection of gas cylinders for high-precision calibration purposes is recommended. Hide

The identification of atmospheric CO2 observation data which are minimally influenced by very local emissions/removals is essential for trend analysis and for the estimation of regional sources and sinks. We compared four data filtering regimes based on the observation records at Lin'an station in China, and found that the use of meteorological parameters was the most favorable. This conclusion will aid regional data selection at the Lin'an station. Hide

CO is established as an important indirect greenhouse gas, as it is the major sink for the OH∙. We have developed a fully automated system for the determination of δ13C and δ18O in atmospheric CO. The blank signal of the Schütze reagent is 1-3 % of the typical sample size. The repeatability is 0.1 ‰ for δ13C and 0.2 ‰ for δ18O. The analytical repeatability for the mole fraction is ~0.7 nmol mol-1 for 100 mL of ambient air (185.4 nmol mol-1 of CO). A single measurement is performed in 18 min. Hide