We present a description of a new instrument designed to detect formaldehyde (HCHO) in situ on airborne platforms. The instrument combines state-of-the art laser technology with single-photon counting detection to provide unmatched performance in a small autonomous package. The development of this In Situ Airbornes Formaldehyde (ISAF) instrument provides a significant new capability for NASA’s high altitude aircraft that requires little space and provides ultra-sensitive detection.

A new cloud detection algorithm using the downwelling IR radiation has been developed by utilizing the spectral and temporal characteristics of clouds which significantly increase the measured radiance and temporal variability. Algorithm performance is evaluated by collocated ceilometer data showing the proportion of correct and probability of detection values of 88.3% and 90.8%, respectively. The algorithm is found to be insensitive to the presence of the inversion layer.

In this paper the representativeness of ground-based cloud observatories and their comparability to satellite data and weather prediction models is examined. It is performed by analysing correlation of time series of SEVIRI pixels. The representativeness strongly depends on the used channels and ranges between 1km and over 20km.

This paper presents a quantitative analysis of the impact of a wind farm on measurements from a nearby Doppler weather radar, based on 6 years of operational radar data. We show that radar measurements from a large area at and downrange from the wind farm as well as up to 3 km above the wind turbines were impacted. We also show that, when weather echoes give rise to higher reflectivity values than those of the wind farm, the negative impact of the wind turbines is greatly reduced.

The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance. The Clouds and Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene-type-dependent angular distribution models (ADMs). This paper describes the next-generation CERES ADMs that are developed for TOA radiative flux inversion.

The paper summarizes the scientific objectives and the observational/modeling strategy of the atmospheric electricity PEACH project of the HyMeX program focusing on the lightning activity and the electrical state of Mediterranean thunderstorms. Examples of concurrent observations from radio frequency to acoustic for regular and atypical lightning flashes and for storms are discussed, showing the unique and comprehensive description of lightning flashes recorded during a dedicated field campaign.

In this paper, we have assessed the sensitivity of the operational Ozone Monitoring Instrument ozone profile retrieval algorithm to a number of a priori and radiative transfer assumptions. We then modified the algorithm to improve the retrieval of tropospheric ozone. We found that the modified retrieval unmasks systematic problems in the radiative transfer/instrument model and is more sensitive to tropospheric ozone variation: it is able to capture the tropospheric ozone morphology better.

A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax suspensions. Using different cooling rates, a small time dependence of ice nucleation induced by two different classes of ice nucleators was detected and the corresponding heterogeneous ice nucleation rate coefficient was quantified.

A so-called six-beam method is proposed to measure atmospheric turbulence using a ground-based wind lidar. This method is presented as an alternative to the so-called velocity azimuth display (VAD) method that is routinely used in commercial wind lidars, and which usually results in significant averaging effects of measured turbulence.

We characterize the wavelengths and slit functions of Airborne Compact Atmospheric Mapper (ACAM) measurements in ~304--500 nm through the cross-correlation technique. It is necessary to account for atmospheric gas absorption and the ring effect. The derived broadened Gaussian slit functions agree very well with laboratory measurements. Trace gas retrieval comparisons demonstrate that the cross-correlation technique can be reliably used to characterize slit functions.

This paper presents ground-based direct-sun and airborne multi-axis DOAS measurements of O2O2 absorption optical depths under atmospheric conditions in two wavelength regions (335-–390nm and 435--490nm). Our results show that laboratory-measured σ(O2O2) is applicable for observations over a wide range of atmospheric conditions. Temperature dependence of σ(O2O2) is about 9±2.5% from 231K to 275K.

Our analytical system is a promising tool for investigating the triple oxygen isotope composition of CO2 from stratospheric air samples of volumes 100ml and smaller. The method is designed for measuring air samples with CO2 mole fractions between 360 and 400ppm, and it is the first fully automated analytical system that uses CeO2 as the isotope exchange medium.

Wind-profiling lidars are now regularly used in boundary-layer meteorology and in applications like wind energy, but their use often relies on assuming homogeneity in the wind. Using numerical simulations of stable flow past a wind turbine, we quantify the error expected because of the inhomogeneity of the flow. Large errors (30%) in winds are found near the wind turbine, but by three rotor diameters downwind, errors in the horizontal components have decreased to 15% of the inflow.

Only few measurements focused on vertical profiles of aerosol hygroscopic and optical properties in airborne studies. For this purpose the white-light optical particle spectrometer (WHOPS) was developed. It allows a relatively fast measurement of the particles hygroscopicity, mixing state and index of refraction of particles in the optically relevant size range. This paper presents a detailed technical description and characterization of the WHOPS and first results from the field.

Two methods are compared to retrieve aerosols, formaldehyde and nitrogen dioxide in the lower troposphere from ground-based remote sensing observations of scattered sunlight in multiple viewing directions. Observations were done in the Beijing area (2008–2011). The two methods show good agreement with respect to the total amount (vertical column) and reasonable agreement with respect to concentrations near the surface and first-order estimates of the vertical profile shape.

We report the first atmospheric measurement of methyl peroxy nitrate (CH3O2NO2) and describe an experimental strategy to obtain NO2 observations free of methyl peroxy nitrate (CH3O2NO2). The accuracy of the CH3O2NO2 measurements are (+/- 40%) with a LOD of 15 pptv/min. We observe that CH3O2NO2 is ubiquitous in the upper troposphere with median mixing ratios of 100 to 200 pptv, and its composition to the total NOy budget is comparable to HNO3.