The optical properties of randomly oriented ice hydrometeors are reviewed from a perspective of microwave mass retrievals. The soft particle approximation is found to be highly problematic, and the alternative approach presented by Geer and Baordo (2014) should instead be used. We present a simplified version of this approach, and point out several critical limitations of existing DDA data.

Water and ice clouds affect detection and retrieval of volcanic ash clouds by satellite instruments. Synthetic infrared satellite images were generated for the Eyjafjallajokull 2010 and Grimsvotn 2011 eruptions by combining weather forecast, ash transport and radiative transfer modelling. Clouds decreased the number of pixels identified as ash and generally increased the retrieved ash-mass loading compared to the cloudless case; however, large differences were seen between scenes.

We present a new real-time algorithm for compensation of the filter-loading effect in filter photometers, based on a two parallel spot measurement of optical absorption. This algorithm has been incorporated into the new Aethalometer AE33. Intercomparison studies show excellent reproducibility of the AE33 measurements and very good agreement with post-processed data obtained using earlier aethalometer models and other filter-based absorption photometers.

Polar mesospheric clouds are clouds that form in the summer polar mesopause, 80km above the surface. In this study we present new measurements by the Odin satellite, which are able to determine water vapour, temperature and cloud coverage with a high resolution and a large geographical coverage. Using these data we can see structures in the clouds and background atmosphere that have not been detectable by previous measurements.

This report presents an overview and detailed description of the measurement methods, analysis approach, and example data from a 10-week EDF-sponsored field campaign measuring methane emissions from natural gas gathering and processing facilities across the US. The dual-tracer ratio method was employed to quantify methane release rates and identify emission sources at a wide variety of facilities, using downwind measurements of CH4, C2H6, CO2, and CO with N2O and C2H2 as tracers.

Temperature inversion layers originate based on the combined forcing of local- and large-scale synoptic meteorology. A numerical procedure based on a linear interpolation function of variable length that minimizes an error function set a priori is proposed to extract thermodynamic information of the multilayered thermal structure. The method is demonstrated to detect surface-based inversion and multilayered elevated inversions present often in high-latitude atmospheres.

We have developed a fast, spatially direct scanning tunable diode laser absorption spectrometer (dTDLAS) that combines four polygon-mirror based scanning units with low-cost retro-reflective foils. The spectrometer is a robust and easy to set up instrument for tomographic reconstructions of 2-D-concentration fields that can be considered as a good basis for future field measurements in environmental research.

We attempt to understand why volcanic ash grains found 100s of km from their source volcanoes (cryptotephra), which are typically 20–125 microns in length, are much larger than the size distributions measured by satellite remote sensing, which are centred at less than 10 microns. Our observations and models show that cryptotephra-sized grains are to be expected in distal plumes. Retrievals of effective radius made on simulated satellite images are shown to be biased toward smaller values.

This work thoroughly discusses a methodology, as summarized in a flowchart, for the round-robin evaluation and geophysical validation of nadir ozone profile retrievals and applies the proposed best practice to a pair of optimal-estimation algorithms run on exactly the same level-1 radiance measurements. The quality assessment combines data set content studies, information content studies, and comparisons with ground-based reference measurements.

Tropospheric halogens and small oxygenated VOC (OVOC) modify tropospheric HOx and NOx, O3 and aerosols. We have measured bromine monoxide (BrO), iodine monoxide (IO), glyoxal (CHOCHO) profiles from research aircraft in the tropical troposphere and compare with ship- and aircraft-based in situ sensors. Our measurements point to the need to improve the representation of halogens and organic carbon sources in atmospheric models.

Submerged oceanic bubbles, which could have a much longer life span than whitecaps or bubble rafts, have been hypothesized to increase the water-leaving radiance and thus affect satellite-based estimates of water-leaving radiance to non-trivial levels. This study explores this effect further to determine if such bubbles are of sufficient magnitude to impact satellite aerosol optical depth retrievals through perturbation of the lower boundary conditions.

Weather radar data are processed to obtain various 2D products. In this research, an algorithm of interpolation of polar reflectivity data with respect to quality index (QI) data is applied to find the Cartesian reflectivity as PPI products and generate a corresponding QI field. On this basis, quality-based algorithms for the generation of the standard products have been developed: ETOP, MAX, and VIL. Moreover a detection of convection has been defined as a specific combination of the products.

The World Meteorological Organization has expressed concern over the increasing number of impact cases of wind turbine farms on weather radars. This paper proposes a wind turbine clutter reflectivity model, which aims at being of great help in the evaluation of the potential impact of a certain wind farm on the weather radar operation. First the radar cross section (RCS) of wind turbines is characterized by means of computer simulations and then a simplified RCS model is proposed.

This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of 6 months. The comparison of the attenuated backscatter profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the SNR, but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term.

A dynamic system for the calibration of acyl peroxynitrate compounds has been developed to reduce the difficulty, required time, and stability of laboratory standards. We present a photochemical source for the generation of acetyl peroxynitrate (PAN), propionyl peroxynitrate (PPN), acryloyl peroxynitrate (APAN), methacryloyl peroxynitrate (MPAN), and crotonyl peroxynitrate (CPAN). Validation of the APN products was performed using iodide ion chemical ionization mass spectroscopy (I- CIMS).