Summary: 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.
Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data
M. J. Alvarado, V. H. Payne, K. E. Cady-Pereira, J. D. Hegarty, S. S. Kulawik, K. J. Wecht, J. R. Worden, J. V. Pittman, and S. C. Wofsy Atmos. Meas. Tech., 8, 965-985, 2015 AbstractFinal Revised Paper (PDF, 4214 KB)Discussion Paper (AMTD)
27 Feb 2015
MAX-DOAS observations of aerosols, formaldehyde and nitrogen dioxide in the Beijing area: comparison of two profile retrieval approaches
Summary: 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.
T. Vlemmix, F. Hendrick, G. Pinardi, I. De Smedt, C. Fayt, C. Hermans, A. Piters, P. Wang, P. Levelt, and M. Van Roozendael Atmos. Meas. Tech., 8, 941-963, 2015 AbstractFinal Revised Paper (PDF, 2047 KB)Discussion Paper (AMTD)
25 Feb 2015
The white-light humidified optical particle spectrometer (WHOPS) – a novel airborne system to characterize aerosol hygroscopicity
Summary: 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.
Quantifying error of lidar and sodar Doppler beam swinging measurements of wind turbine wakes using computational fluid dynamics
Summary: 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.
Continuous-flow IRMS technique for determining the 17O excess of CO2 using complete oxygen isotope exchange with cerium oxide
Summary: 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.
Ground-based direct-sun DOAS and airborne MAX-DOAS measurements of the collision-induced oxygen complex, O2O2, absorption with significant pressure and temperature differences
Summary: 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.
ECOC comparison exercise with identical thermal protocols after temperature offset correction – instrument diagnostics by in-depth evaluation of operational parameters
P. Panteliadis, T. Hafkenscheid, B. Cary, E. Diapouli, A. Fischer, O. Favez, P. Quincey, M. Viana, R. Hitzenberger, R. Vecchi, D. Saraga, J. Sciare, J. L. Jaffrezo, A. John, J. Schwarz, M. Giannoni, J. Novak, A. Karanasiou, P. Fermo, and W. Maenhaut Atmos. Meas. Tech., 8, 779-792, 2015 AbstractFinal Revised Paper (PDF, 2896 KB)Supplement (2047 KB)Discussion Paper (AMTD)
17 Feb 2015
Assessment of the performance of the inter-arrival time algorithm to identify ice shattering artifacts in cloud particle probe measurements
Characterization and verification of ACAM slit functions for trace-gas retrievals during the 2011 DISCOVER-AQ flight campaign
Summary: 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.
A six-beam method to measure turbulence statistics using ground-based wind lidars
Summary: 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.
BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation
Summary: 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.