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The Brewer ozone spectrophotometer (the Brewer) was designed at Environment and Climate Change Canada (ECCC) in the 1970s to make accurate automated total ozone column measurements. Since the 1980s, the Brewer instrument has become a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) standard ozone monitoring instrument. Now, more than 230 Brewers have been produced. To assure the quality of the Brewer measurements, a calibration chain is maintained, i.e., first, the reference instruments are independently absolutely calibrated, and then the calibration is transferred from the reference instrument to the travelling standard, and subsequently from the travelling standard to field instruments. ECCC has maintained the world Brewer reference instruments since the 1980s to provide transferable calibration to field instruments at monitoring sites. Three single-monochromator (Mark II) type instruments (serial numbers 008, 014, and 015) formed this world Brewer reference triad (BrT) and started their service in Toronto, Canada, in 1984. In the 1990s, the Mark III type Brewer (known as the double Brewer) was developed, which has two monochromators to reduce the internal instrumental stray light. The double-Brewer world reference triad (BrT-D) was formed in 2013 (serial numbers 145, 187 and 191), co-located with the BrT. The first assessment of the BrT's performance was made in 2005, covering the period between 1984 and 2004 (Fioletov et al., 2005). The current work provides an updated assessment of the BrT's performance (from 1999 to 2019) and the first comprehensive assessment of the BrT-D. The random uncertainties of individual reference instruments are within the WMO/GAW requirement of 1 % (WMO, 2001): 0.49 % and 0.42 % for BrT and BrT-D, respectively, as estimated in this study. The long-term stability of the reference instruments is also evaluated in terms of uncertainties of the key instrument characteristics: the extraterrestrial calibration constant (ETC) and effective ozone absorption coefficients (both having an effect of less than 2 % on total column ozone). Measurements from a ground-based instrument (Pandora spectrometer), satellites (11 datasets, including the most recent high-resolution satellite, TROPOspheric Monitoring Instrument), and reanalysis model (the second Modern-Era Retrospective analysis for Research and Applications, MERRA-2) are used to further assess the performance of world Brewer reference instruments and to provide a context for the requirements of stratospheric ozone observations during the last two decades.

A LiDAR Statistical Barnes Objective Analysis (LiSBOA) for the optimal design of lidar scans and retrieval of the velocity statistical moments is proposed. LiSBOA represents an adaptation of the classical Barnes scheme for the statistical analysis of unstructured experimental data in N-dimensional space, and it is a suitable technique for the evaluation over a structured Cartesian grid of the statistics of scalar fields sampled through scanning lidars. LiSBOA is validated and characterized via a Monte Carlo approach applied to a synthetic velocity field. This revisited theoretical framework for the Barnes objective analysis enables the formulation of guidelines for the optimal design of lidar experiments and efficient application of LiSBOA for the postprocessing of lidar measurements. The optimal design of lidar scans is formulated as a two-cost-function optimization problem, including the minimization of the percentage of the measurement volume not sampled with adequate spatial resolution and the minimization of the error on the mean of the velocity field. The optimal design of the lidar scans also guides the selection of the smoothing parameter and the total number of iterations to use for the Barnes scheme. LiSBOA is assessed against a numerical data set generated using the virtual lidar technique applied to the data obtained from a large eddy simulation (LES). The optimal sampling parameters for a scanning Doppler pulsed wind lidar are retrieved through LiSBOA, and then the estimated statistics are compared with those of the original LES data set, showing a maximum error of about 4 % for both mean velocity and turbulence intensity.

This work describes key improvements made to the in situ laser-induced fluorescence instrument for measuring sulfur dioxide (SO2) that was originally described by Rollins et al. (2016). Here, we report measurements of the SO2 fluorescence emission spectrum. These measurements allow for the determination of the most appropriate bandpass filters to optimize the fluorescence signal, while reducing the instrumental background. Because many aromatic species fluoresce in the same spectral region as SO2, fluorescence spectra were also measured for naphthalene and anisole to determine if ambient SO2 measurements could be biased in the presence of such species. Improvement in the laser system resulted in better tunability, and a significant reduction in the 216.9 nm laser linewidth. This increases the online/offline signal ratio which, in turn, improves the precision and specificity of the measurement. The effects of these improvements on the instrumental sensitivity were determined by analyzing the signal and background of the instrument, using varying optical bandpass filter ranges and cell pressures and calculating the resulting limit of detection. As a result, we report an improvement to the instrumental sensitivity by as much as 50 %.

We introduce a new method to detect and monitor sudden stratospheric warming (SSW) events using Global Navigation Satellite System (GNSS) radio occultation (RO) data at high northern latitudes and demonstrate it for the well-known January–February 2009 event. We first construct RO temperature, density, and bending angle anomaly profiles and estimate vertical-mean anomalies in selected altitude layers. These mean anomalies are then averaged into a daily updated 5∘ latitude × 20∘ longitude grid over 50–90∘ N. Based on the gridded mean anomalies, we employ the concept of threshold exceedance areas (TEAs), the geographic areas wherein the anomalies exceed predefined threshold values such as 40 K or 40 %. We estimate five basic TEAs for selected altitude layers and thresholds and use them to derive primary-, secondary-, and trailing-phase TEA metrics to detect SSWs and to monitor in particular their main-phase (primary- plus secondary-phase) evolution on a daily basis. As an initial setting, the main phase requires daily TEAs to exceed 3×106 km2, based on which main-phase duration, area, and overall event strength are recorded. Using the January–February 2009 SSW event for demonstration, and employing RO data plus cross-evaluation data from analysis fields of the European Centre for Medium-Range Weather Forecasts (ECMWF), we find the new approach has strong potential for detecting and monitoring SSW events. The primary-phase metric shows a strong SSW emerging on 20 January, reaching a maximum on 23 January and fading by 30 January. On 22–23 January, temperature anomalies over the middle stratosphere exceeding 40 K cover an area of more than 10×106 km2. The geographic tracking of the SSW showed that it was centered over east Greenland, covering Greenland entirely and extending from western Iceland to eastern Canada. The secondary- and trailing-phase metrics track the further SSW development, where the thermodynamic anomaly propagated downward and was fading with a transient upper stratospheric cooling, spanning until the end of February and beyond. Given the encouraging demonstration results, we expect the method to be very suitable for long-term monitoring of how SSW characteristics evolve under climate change and polar vortex variability, using both RO and reanalysis data.

All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10∘, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

On 16–17 February 2020, dust within a Saharan Air Layer (SAL) from western Africa moved over the eastern Atlantic Ocean. Satellite imagery and products from ABI on GOES-16, VIIRS on NOAA-20, and CALIOP on CALIPSO along with retrieved values of layer and total precipitable water (TPW) from MiRS and NUCAPS, respectively, were used to identify dust within the SAL over the eastern Atlantic Ocean. Use of various satellite imagery and products were also used to characterize the distribution of water vapor within the SAL. There was a distinct pattern between dust detection and dust masking and values of precipitable water. Specifically, dust was detected when values of layer or TPW were approximately 14 mm; in addition, dust was masked when values of layer or TPW were approximately 28 mm. In other words, water vapor masked infrared dust detection if sufficient amounts of water vapor existed in a column. Results herein provide observational support to two recent numerical studies that concluded water vapor can mask infrared detection of airborne dust.

Sea ice is difficult, expensive, and potentially dangerous to observe in nature. The remoteness of the Arctic Ocean and Southern Ocean complicates sampling logistics, while the heterogeneous nature of sea ice and rapidly changing environmental conditions present challenges for conducting process studies. Here, we describe the Roland von Glasow Air-Sea-Ice Chamber (RvG-ASIC), a laboratory facility designed to reproduce polar processes and overcome some of these challenges. The RvG-ASIC is an open-topped 3.5 m3 glass tank housed in a cold room (temperature range: −55 to +30 ∘C). The RvG-ASIC is equipped with a wide suite of instruments for ocean, sea ice, and atmospheric measurements, as well as visible and UV lighting. The infrastructure, available instruments, and typical experimental protocols are described. To characterise some of the technical capabilities of our facility, we have quantified the timescale over which our chamber exchanges gas with the outside, τl=(0.66±0.07) d, and the mixing rate of our experimental ocean, τm=(4.2±0.1) min. Characterising our light field, we show that the light intensity across the tank varies by less than 10 % near the centre of the tank but drops to as low as 60 % of the maximum intensity in one corner. The temperature sensitivity of our light sources over the 400 to 700 nm range (PAR) is (0.028±0.003) W m−2 ∘C−1, with a maximum irradiance of 26.4 W m−2 at 0 ∘C; over the 320 to 380 nm range, it is (0.16±0.1) W m−2 ∘C−1, with a maximum irradiance of 5.6 W m−2 at 0 ∘C. We also present results characterising our experimental sea ice. The extinction coefficient for PAR varies from 3.7 to 6.1 m−1 when calculated from irradiance measurements exterior to the sea ice and from 4.4 to 6.2 m−1 when calculated from irradiance measurements within the sea ice. The bulk salinity of our experimental sea ice is measured using three techniques, modelled using a halo-dynamic one-dimensional (1D) gravity drainage model, and calculated from a salt and mass budget. The growth rate of our sea ice is between 2 and 4 cm d−1 for air temperatures of (-9.2±0.9) ∘C and (-26.6±0.9) ∘C. The PAR extinction coefficients, vertically integrated bulk salinities, and growth rates all lie within the range of previously reported comparable values for first-year sea ice. The vertically integrated bulk salinity and growth rates can be reproduced well by a 1D model. Taken together, the similarities between our laboratory sea ice and observations in nature, as well as our ability to reproduce our results with a model, give us confidence that sea ice grown in the RvG-ASIC is a good representation of natural sea ice.

Este trabalho apresenta um estudo teórico e experimental sobre o instrumento de medição de vazão calha Parshall da empresa Armfield, o qual apresentava resultados experimentais diferentes da literatura ao realizar as medições de vazão no canal hidráulico de fundo reclinável presente na Universidade Presbiteriana Mackenzie. Contudo, foram realizados procedimentos para adequar o funcionamento do equipamento, tais como: conferência das dimensões da calha, verificação do medidor eletromagnético do canal, teste de declividade de fundo do canal e sua interferência no equipamento, ensaios para determinação da vazão e afogamento da calha. Em síntese, foi elaborada uma nova equação, que se adequou melhor ao funcionamento do aparelho e demonstrou ser efetiva para a utilização deste equipamento. Palavras-chave: Calha Parshall. Medição de Vazão. Canal Hidráulico. Armfield.

Esta revisão descreve o comportamento do mercúrio (Hg) no ambiente, desde sua origem até as implicações no ecossistema e na saúde humana. O Hg constitui um dos poluentes de maior risco para o equilíbrio ecológico e saúde humana, justificado pela elevada toxicidade e potencial de bioacumulação e biomagnificação através da cadeia alimentar. Nos solos a mobilidade do Hg é controlada pelas espécies do elemento e pelos atributos do solo, como pH, matéria orgânica e mineral de argila. Em plantas, o Hg afeta a fotossíntese, a absorção de nutrientes e a transpiração, porém algumas plantas desenvolveram mecanismos para tolerar esse metal, como acumular altas concentrações nas raízes sem translocá-lo para as partes aéreas. Foram abordadas as principais fontes de Hg, os métodos de determinação usados para quantificar esse metal e a ocorrência em ecossistemas e seus desdobramentos, bem como foram identificadas áreas com elevadas contaminações por diferentes fontes, com destaque para contaminação industrial e mineração. Dessa forma, mais estudos devem ser replicados, no intuito de garantir saltos para promover a redução da emissão e incorporação ao sistema, assim como recuperar as áreas já contaminadas. Palavras-chave: Mercúrio. Saúde Humana. Meio Ambiente.

Important uncertainties remain in our understanding of the spatial and temporal variability of atmospheric hydroxyl radical concentration ([OH]). Carbon-14-containing carbon monoxide (14CO) is a useful tracer that can help in the characterization of [OH] variability. Prior measurements of atmospheric 14CO concentration ([14CO] are limited in both their spatial and temporal extent, partly due to the very large air sample volumes that have been required for measurements (500–1000 L at standard temperature and pressure, L STP) and the difficulty and expense associated with the collection, shipment, and processing of such samples. Here we present a new method that reduces the air sample volume requirement to ≈90 L STP while allowing for [14CO] measurement uncertainties that are on par with or better than prior work (≈3 % or better, 1σ). The method also for the first time includes accurate characterization of the overall procedural [14CO] blank associated with individual samples, which is a key improvement over prior atmospheric 14CO work. The method was used to make measurements of [14CO] at the NOAA Mauna Loa Observatory, Hawaii, USA, between November 2017 and November 2018. The measurements show the expected [14CO] seasonal cycle (lowest in summer) and are in good agreement with prior [14CO] results from another low-latitude site in the Northern Hemisphere. The lowest overall [14CO] uncertainties (2.1 %, 1σ) are achieved for samples that are directly accompanied by procedural blanks and whose mass is increased to ≈50 µgC (micrograms of carbon) prior to the 14C measurement via dilution with a high-CO 14C-depleted gas.

The Compact Rayleigh Autonomous Lidar (CORAL) is the first fully autonomous middle atmosphere lidar system to provide density and temperature profiles from 15 to approximately 90 km altitude. From October 2019 to October 2020, CORAL acquired temperature profiles on 243 out of the 365 nights (66 %) above Río Grande, southern Argentina, a cadence which is 3–8 times larger as compared to conventional human-operated lidars. The result is an unprecedented data set with measurements on 2 out of 3 nights on average and high temporal (20 min) and vertical (900 m) resolution. The first studies using CORAL data have shown, for example, the evolution of a strong atmospheric gravity wave event and its impact on the stratospheric circulation. We describe the instrument and its novel software which enables automatic and unattended observations over periods of more than a year. A frequency-doubled diode-pumped pulsed Nd:YAG laser is used as the light source, and backscattered photons are detected using three elastic channels (532 nm wavelength) and one Raman channel (608 nm wavelength). Automatic tracking of the laser beam is realized by the implementation of the conical scan (conscan) method. The CORAL software detects blue sky conditions and makes the decision to start the instrument based on local meteorological measurements, detection of stars in all-sky images, and analysis of European Center for Medium-range Weather Forecasts Integrated Forecasting System data. After the instrument is up and running, the strength of the lidar return signal is used as additional information to assess sky conditions. Safety features in the software allow for the operation of the lidar even in marginal weather, which is a prerequisite to achieving the very high observation cadence.

Polar stratospheric clouds (PSCs) play an important role in the spatial and temporal evolution of trace gases inside the polar vortex due to different processes, such as chlorine activation and NOy redistribution. As there are still uncertainties in the representation of PSCs in model simulations, detailed observations of PSCs and information on their type – nitric acid trihydrate (NAT), supercooled ternary solution (STS), and ice – are desirable. The measurements inside PSCs made by the CRISTA-NF (CRyogenic Infrared Spectrometers and Telescope for the Atmosphere – New Frontiers) airborne infrared limb sounder during the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) aircraft campaign showed a spectral peak at about 816 cm−1. This peak is shifted compared with the known peak at about 820 cm−1, which is recognised as being caused by the emission of radiation by small NAT particles. To investigate the reason for this spectral difference, we performed a large set of radiative transfer simulations of infrared limb emission spectra in the presence of various PSCs (NAT, STS, ice, and mixtures) for the airborne viewing geometry of CRISTA-NF. NAT particles can cause different spectral features in the 810–820 cm−1 region. The simulation results show that the appearance of the feature changes with an increasing median radius of the NAT particle size distribution, from a peak at 820 cm−1 to a shifted peak and, finally, to a step-like feature in the spectrum, caused by the increasing contribution of scattering to the total extinction. Based on the appearance of the spectral feature, we defined different colour indices to detect PSCs containing NAT particles and to subgroup them into three size regimes under the assumption of spherical particles: small NAT (≤ 1.0 µm), medium NAT (1.5–4.0 µm), and large NAT (≥ 3.5 µm). Furthermore, we developed a method to detect the bottom altitude of a cloud by using the cloud index (CI), a colour ratio indicating the optical thickness, and the vertical gradient of the CI. Finally, we applied the methods to observations of the CRISTA-NF instrument during one local flight of the RECONCILE aircraft campaign and found STS and medium-sized NAT.

Nitrogen oxides (NOx≡NO+NO2) in the NOx-limited upper troposphere (UT) are long-lived and so have a large influence on the oxidizing capacity of the troposphere and formation of the greenhouse gas ozone. Models misrepresent NOx in the UT, and observations to address deficiencies in models are sparse. Here we obtain a year of near-global seasonal mean mixing ratios of NO2 in the UT (450–180 hPa) at 1∘×1∘ by applying cloud-slicing to partial columns of NO2 from TROPOMI. This follows refinement of the cloud-slicing algorithm with synthetic partial columns from the GEOS-Chem chemical transport model. TROPOMI, prior to cloud-slicing, is corrected for a 13 % underestimate in stratospheric NO2 variance and a 50 % overestimate in free-tropospheric NO2 determined by comparison to Pandora total columns at high-altitude free-tropospheric sites at Mauna Loa, Izaña, and Altzomoni and MAX-DOAS and Pandora tropospheric columns at Izaña. Two cloud-sliced seasonal mean UT NO2 products for June 2019 to May 2020 are retrieved from corrected TROPOMI total columns using distinct TROPOMI cloud products that assume clouds are reflective boundaries (FRESCO-S) or water droplet layers (ROCINN-CAL). TROPOMI UT NO2 typically ranges from 20–30 pptv over remote oceans to >80 pptv over locations with intense seasonal lightning. Spatial coverage is mostly in the tropics and subtropics with FRESCO-S and extends to the midlatitudes and polar regions with ROCINN-CAL, due to its greater abundance of optically thick clouds and wider cloud-top altitude range. TROPOMI UT NO2 seasonal means are spatially consistent (R=0.6–0.8) with an existing coarser spatial resolution (5∘ latitude × 8∘ longitude) UT NO2 product from the Ozone Monitoring Instrument (OMI). UT NO2 from TROPOMI is 12–26 pptv more than that from OMI due to increase in NO2 with altitude from the OMI pressure ceiling (280 hPa) to that for TROPOMI (180 hPa), but possibly also due to altitude differences in TROPOMI and OMI cloud products and NO2 retrieval algorithms. The TROPOMI UT NO2 product offers potential to evaluate and improve representation of UT NOx in models and supplement aircraft observations that are sporadic and susceptible to large biases in the UT.

Objectives : Determination of reaction order (n) and rate constants (k) of the CaCO3 scale formation reaction that was accelerated by the HVI (high voltage impulse) induction.Methods : HVI was inducted to the synthetic solution containing 2.5 mM of Ca2+ ion at different temperatures of 25, 40, 60℃. The concentration of Ca2+ ion has been monitored as voltages of the HVI increased from 0 to 5, 10, 15 kV. Reaction order and the rate constants of the CaCO3 formation reaction were determined with the experimental dataset of Ca2+ concentration vs. time plots.Results and Discussion : The CaCO3 formation was determined to follow two-molecules 2nd order reaction. The reaction rate constant, k increased as temperature and the applied voltages of HVI increased. The rate constant, k at 25℃ and 15 kV of HVI was 8.2×10-3 L/(mmol･hr), which was 2.7 times greater than the k of the control at 25℃, 3.0×10-3 L/(mmol･hr).Conclusions : The reaction of CaCO3 formation was accelerated by HVI as the applied voltages of HVI increased, indicating that the HVI could be used as an alternative desalting technology for scale control.

Wide-field spectrometers for Earth observation missions require in-flight radiometric calibration for which the Sun can be used as a known reference. Therefore, a diffuser is placed in front of the spectrometer in order to scatter the incoming light into the entrance slit and provide homogeneous illumination. The diffuser, however, introduces interference patterns known as speckles into the system, yielding potentially significant intensity variations at the detector plane, called spectral features. There have been several approaches implemented to characterize the spectral features of a spectrometer, e.g., end-to-end measurements with representative instruments. Additionally, in previous publications a measurement technique was proposed, which is based on the acquisition of monochromatic speckles in the entrance slit following a numerical propagation through the disperser to the detection plane. Based on this measurement technique, we present a stand-alone prediction model for the magnitude of spectral features in imaging spectrometers, requiring only few input parameters and, therefore, mitigating the need for expensive measurement campaigns.

The presence of 3D cloud radiative effects in OCO-2 retrievals is demonstrated from an analysis of 2014–2019 OCO-2 XCO2 raw retrievals, bias-corrected XCO2bc data, ground-based Total Carbon Column Observation Network (TCCON) XCO2, and Moderate Resolution Imaging Spectroradiometer (MODIS) cloud and radiance fields. In approximate terms, 40 % (quality flag – QF = 0, land or ocean) and 73 % (QF = 1, land or ocean) of the observations are within 4 km of clouds. 3D radiative transfer calculations indicate that 3D cloud radiative perturbations at this cloud distance, for an isolated low-altitude cloud, are larger in absolute value than those due to a 1 ppm increase in CO2. OCO-2 measurements are therefore susceptible to 3D cloud effects. Four 3D cloud metrics, based upon MODIS radiance and cloud fields as well as stand-alone OCO-2 measurements, relate XCO2bc–TCCON averages to 3D cloud effects. This analysis indicates that the operational bias correction has a nonzero residual 3D cloud bias for both QF = 0 and QF = 1 data. XCO2bc–TCCON averages at small cloud distances differ from those at large cloud distances by −0.4 and −2.2 ppm for the QF = 0 and QF = 1 data over the ocean. Mitigation of 3D cloud biases with a table lookup technique, which utilizes the nearest cloud distance (Distkm) and spatial radiance heterogeneity (CSNoiseRatio) 3D metrics, reduces QF = 1 ocean and land XCO2bc–TCCON averages from −1 ppm to near ±0.2 ppm. The ocean QF = 1 XCO2bc–TCCON averages can be reduced to the 0.5 ppm level if 60 % (70 %) of the QF = 1 data points are utilized by applying Distkm (CSNoiseRatio) metrics in a data screening process. Over land the QF = 1 XCO2bc–TCCON averages are reduced to the 0.5 (0.8) ppm level if 65 % (63 %) of the data points are utilized by applying Diastkm (CSNoiseRatio) data screening. The addition of more terms to the linear regression equations used in the current bias correction processing without data screening, however, did not introduce an appreciable improvement in the standard deviations of the XCO2bc–TCCON statistics.

Continuous advancements in pulsed wind lidar technology have enabled compelling wind turbulence measurements within the atmospheric boundary layer with probe lengths shorter than 20 m and sampling frequency on the order of 10 Hz. However, estimates of the radial velocity from the back-scattered lidar signal are inevitably affected by an averaging process within each probe volume, generally modeled as a convolution between the true velocity projected along the lidar line-of-sight and an unknown weighting function representing the energy distribution of the laser pulse along the probe length. As a result, the spectral energy of the turbulent velocity fluctuations is damped within the inertial subrange, thus not allowing one to take advantage of the achieved spatio-temporal resolution of the lidar technology. We propose to correct the turbulent energy damping on the lidar measurements by reversing the effect of a low-pass filter, which can be estimated directly from the power spectral density of the along-beam velocity component. Lidar data acquired from three different field campaigns are analyzed to describe the proposed technique, investigate the variability of the filter parameters and, for one dataset, assess the corrected velocity variance against sonic anemometer data. It is found that the order of the low-pass filter used for modeling the energy damping on the lidar velocity measurements has negligible effects on the correction of the second-order statistics of the wind velocity. In contrast, the cutoff wavenumber plays a significant role in spectral correction encompassing the smoothing effects connected with the lidar probe length. Furthermore, the variability of the spatial averaging on wind lidar measurements is investigated for different wind speed, turbulence intensity, and sampling height. The results confirm that the effects of spatial averaging are enhanced with decreasing wind speed, smaller integral length scale and, thus, for smaller sampling height. The method proposed for the correction of the second-order turbulent statistics of wind-velocity lidar data is a compelling alternative to existing methods because it does not require any input related to the technical specifications of the used lidar system, such as the energy distribution over the laser pulse and lidar probe length. On the other hand, the proposed method assumes that surface-layer similarity holds.

The retrieval of aerosol parameters from passive satellite instruments in cloudy scenes is challenging, partly because clouds and cloud-related processes may significantly modify aerosol optical depth (AOD) and particle size, a problem that is further compounded by 3D radiative processes. Recent advances in retrieval algorithms such as the “color ratio” method, which utilizes the measurements at a shorter (470 nm) and a longer (860 nm) wavelength, have demonstrated the simultaneous derivation of AOD and cloud optical depth (COD) for scenes in which absorbing aerosols are found to overlay low-level cloud decks. This study shows simultaneous retrievals of above-cloud aerosol optical depth (ACAOD) and aerosol-corrected cloud optical depth (COD) from airborne measurements of cloud-reflected and sky radiances using the color ratio method. These airborne measurements were taken over marine stratocumulus clouds with NASA's Cloud Absorption Radiometer (CAR) during the SAFARI 2000 field campaign offshore of Namibia. The ACAOD is partitioned between the AOD below-aircraft (AOD_cloudtop) and above-aircraft AOD (AOD_sky). The results show good agreement between AOD_sky and sun-photometer measurements of the above-aircraft AOD. The results also show that the use of aircraft-based sun-photometer measurements to validate satellite retrievals of the ACAOD is complicated by the lack of information on AOD below aircraft. Specifically, the CAR-retrieved AOD_cloudtop captures this “missing” aerosol layer caught between the aircraft and cloud top, which is required to quantify above-cloud aerosol loading and effectively validate satellite retrievals. In addition, the study finds a strong anticorrelation between the AOD_cloudtop and COD for cases in which COD < 10 and a weaker anticorrelation for COD > 10, which may be associated with the uncertainties in the color ratio method at lower AODs and CODs. The influence of 3D radiative effects on the retrievals is examined, and the results show that at cloud troughs, 3D effects increase retrieved ACAOD by about 3 %–11 % and retrieved COD by about 25 %. The results show that the color ratio method has little sensitivity to 3D effects at overcast stratocumulus cloud decks. These results demonstrate a novel airborne measurement approach for assessing satellite retrievals of aerosols above clouds, thereby filling a major gap in global aerosol observations.

Proton-transfer-reaction mass spectrometry (PTR-MS) is widely used in atmospheric sciences for measuring volatile organic compounds in real time. In the most widely used type of PTR-MS instruments, air is directly introduced into a chemical ionization reactor via an inlet capillary system. The reactor has a volumetric exchange time of ∼0.1 s, enabling PTR-MS analyzers to measure at a frequency of 10 Hz. The time response does, however, deteriorate if low-volatility analytes interact with surfaces in the inlet or in the instrument. Herein, we present the extended volatility range (EVR) PTR-MS instrument which mitigates this issue. In the EVR configuration, inlet capillaries are made of passivated stainless steel, and all wetted metal parts in the chemical ionization reactor are surface-passivated with a functionalized hydrogenated amorphous silicon coating. Heating the entire setup (up to 120 ∘C) further improves the time-response performance. We carried out time-response performance tests on a set of 29 analytes having saturation mass concentrations C0 in the range between 10−3 and 105 µg m−3. The 1/e-signal decay times after instant removal of the analyte from the sampling flow were between 0.2 and 90 s for gaseous analytes. We also tested the EVR PTR-MS instrument in combination with the chemical analysis of aerosols online (CHARON) particle inlet, and 1/e-signal decay times were in the range between 5 and 35 s for particulate analytes. We show on a set of example compounds that the time-response performance of the EVR PTR-MS instrument is comparable to that of the fastest flow tube chemical ionization mass spectrometers that are currently in use. The fast time response can be used for rapid (∼1 min equilibration time) switching between gas and particle measurements. The CHARON EVR PTR-MS instrument can thus be used for real-time monitoring of both gaseous and particulate organics in the atmosphere. Finally, we show that the CHARON EVR PTR-MS instrument also rapidly detects highly oxygenated species (with up to eight oxygen atoms) in particles formed by limonene ozonolysis.

Atmospheric black carbon (BC) is the strongest solar radiative absorber in the atmosphere, exerting significant influences on the earth's radiation budget. The mass absorption cross section (MAC) is a crucial parameter for converting the light absorption coefficient (σab) to the equivalent BC mass concentration (EBC). Traditional filter-based instruments, such as the AE33, use a constant MAC of 7.77 m2/g at 880 nm to derive the EBC, which may lead to uncertainty in the EBC. In this paper, a new method of converting σab to the EBC is proposed by incorporating the variations of the MAC attributed to the influences of the aerosol coating state. A Mie simulation showed that the MAC varied dramatically with different core sizes and shell thicknesses. We compared our new method with the traditional method during a field measurement at a site on the North China Plain. The results showed that the MAC at 880 nm was smaller (larger) than 7.77 m2/g for particles smaller (larger) than 280 nm, resulting in an EBC mass size distribution derived from the new method that was higher (lower) than the traditional method for particles smaller (larger) than 280 nm. The size-integrated EBC derived from the new method was 16 % higher than that derived from the traditional method. Sensitivity analysis indicated that the uncertainty in the EBC caused by the refractive index (RI) was within 35 %, and the imaginary part of the RI had dominant influence on the derived EBC. This study emphasizes the necessity to take variations of the MAC into account when deriving the EBC from σab and can help constrain the uncertainty in EBC measurements.

Billions of litres of wastewater are produced daily from domestic and industrial areas, and whilst wastewater is often perceived as a problem, it has the potential to be viewed as a rich source for resources and energy. Wastewater contains between four and five times more energy than is required to treat it, and is a potential source of bio-hydrogen—a clean energy vector, a feedstock chemical and a fuel, widely recognised to have a role in the decarbonisation of the future energy system. This paper investigates sustainable, low-energy intensive routes for hydrogen production from wastewater, critically analysing five technologies, namely photo-fermentation, dark fermentation, photocatalysis, microbial photo electrochemical processes and microbial electrolysis cells (MECs). The paper compares key parameters influencing H2 production yield, such as pH, temperature and reactor design, summarises the state of the art in each area, and highlights the scale-up technical challenges. In addition to H2 production, these processes can be used for partial wastewater remediation, providing at least 45% reduction in chemical oxygen demand (COD), and are suitable for integration into existing wastewater treatment plants. Key advancements in lab-based research are included, highlighting the potential for each technology to contribute to the development of clean energy. Whilst there have been efforts to scale dark fermentation, electro and photo chemical technologies are still at the early stages of development (Technology Readiness Levels below 4); therefore, pilot plants and demonstrators sited at wastewater treatment facilities are needed to assess commercial viability. As such, a multidisciplinary approach is needed to overcome the current barriers to implementation, integrating expertise in engineering, chemistry and microbiology with the commercial experience of both water and energy sectors. The review concludes by highlighting MECs as a promising technology, due to excellent system modularity, good hydrogen yield (3.6–7.9 L/L/d from synthetic wastewater) and the potential to remove up to 80% COD from influent streams.

This study reviews the available and most commonly used methods of gas deodorization. Comparing various methods of odor removal, undoubtedly biological methods of pollution degradation have an advantage over others—chemical and physical. This advantage is manifestedmainly in ecological and economic terms. The possibility of using biological methods to remove H2S and NH3, as the most common emitted by the municipal sector companies, was analyzed in terms of their removal efficiency. The method of bio-purification of air in biotrickling filters is more advantageous than the others, due to the high effectiveness of VOCs and odors degradation, lack of secondary pollutants, and economic aspects—it is a method competitive to the commonly used air purification method in biofilters.

A new facility has been developed which allows for a stable and reproducible production of ambient-like model aerosols (PALMA) in the laboratory. The set-up consists of multiple aerosol generators, a custom-made flow tube homogeniser, isokinetic sampling probes, and a system to control aerosol temperature and humidity. Model aerosols containing elemental carbon, secondary organic matter from the ozonolysis of α-pinene, inorganic salts such as ammonium sulfate and ammonium nitrate, mineral dust particles, and water were generated under different environmental conditions and at different number and mass concentrations. The aerosol physical and chemical properties were characterised with an array of experimental methods, including scanning mobility particle sizing, ion chromatography, total reflection X-ray fluorescence spectroscopy and thermo-optical analysis. The facility is very versatile and can find applications in the calibration and performance characterisation of aerosol instruments monitoring ambient air. In this study, we performed, as proof of concept, an intercomparison of three different commercial PM (particulate matter) monitors (TEOM 1405, DustTrak DRX 8533 and Fidas Frog) with the gravimetric reference method under three simulated environmental scenarios. The results are presented and compared to previous field studies. We believe that the laboratory-based method for simulating ambient aerosols presented here could provide in the future a useful alternative to time-consuming and expensive field campaigns, which are often required for instrument certification and calibration.

Nos artigos anteriores desta série, mostrou-se que sistemas de lagoas de estabilização (LE) apresentam desvantagens que podem ser reduzidas ou mesmo eliminadas quando se substitui a configuração convencional (lagoa anaeróbia/lagoa facultativa/lagoas de maturação) por um sistema composto de um reator UASB seguido por Lagoas de polimento (LP). Essa substituição possibilita o aumento da capacidade de tratamento, melhora a qualidade do efluente, reduz o tamanho e consequentemente os custos de construção, além de permitir a captura do biogás e o aproveitamento do lodo como biofertilizante. Como exemplo, analisaram-se as vantagens de aplicar o reator UASB seguido de LP em substituição ao sistema convencional de LE que se encontra em operação na cidade de Campina Grande, Paraíba. A atual ETE de Campina Grande é constituída por duas lagoas anaeróbias, duas lagoas facultativas e quatro lagoas de maturação, com capacidade para tratar 13.000 m3/d. A análise mostrou que todas as vantagens do novo sistema podem ser materializadas no caso de Campina Grande. Quando se substitui o sistema convencional pela nova alternativa, a capacidade de tratamento da ETE, com a infraestrutura existente, aumentaria para 40.000 m3/d se o efluente fosse utilizado para fertirrigação ou 20.000 m3/d se o efluente fosse utilizado para fins industriais; nesse caso, a remoção de nutrientes é necessária. Assim, todo o efluente seria utilizado de maneira produtiva e não haveria mais descarga nas águas de superfície. Palavras-chave: Lagoas de polimento. Reúso agrícola. Reúso industrial. Custo construção.

Neste artigo, apresenta-se um modelo para a remoção de fósforo em um robusto sistema de tratamento de esgoto que alia o tratamento anaeróbio em um reator UASB ao pós-tratamento em lagoas de polimento, operadas em regime de batelada sequencial (LPBS). Os processos que ocorrem nas LPBS favorecem um aumento no valor do pH, o que leva à remoção de fósforo pela precipitação de fosfato na presença de íons de cálcio. Foi possível obter uma reduzida concentração de fósforo (

Este estudo objetivou desenvolver expressões para determinar o valor da constante de decaimento em lagoas de polimento tratando efluente de reator UASB em função da profundidade da lagoa e da temperatura, bem como avaliou a influência do regime hidráulico sobre a eficiência da remoção bacteriana, visando estimar o tempo de permanência necessário para obter um efluente com qualidade higiênica para uso na irrigação irrestrita. A remoção bacteriana foi avaliada, em termos de E.coli, em 06 lagoas com profundidades variando entre 0,2 a 2,8 m. Pôde-se verificar que a constante de decaimento variou de modo inversamente proporcional à profundidade das lagoas. Além disso, o decaimento bacteriano se desenvolveu, em boa aproximação, conforme um processo de primeira ordem, tendo, portanto, uma vantagem considerável nas unidades operadas em regime de bateladas sequenciais (onde o decaimento é inversamente exponencial) sobre as lagoas de fluxo contínuo (onde o decaimento é inversamente hiperbólico). Palavras-chave: Tratamento de esgoto. Qualidade higiênica. Coliformes Termotolerantes. Cinética de decaimento.

Em lagoas que tratam águas residuárias, há componentes voláteis em intercâmbio com gases na atmosfera. Os principais componentes são dióxido de carbono, oxigênio dissolvido e amônia. O intercâmbio desses compostos com o ar é importante porque afeta o pH e a disponibilidade de oxigênio dissolvido em lagoas de polimento. Uma investigação experimental demonstrou que a cinética de transferência dos compostos é regida pela lei de Fick; esta afirma que a taxa de transferência é proporcional ao déficit, ou seja, há diferença entre a concentração do composto volátil dissolvido e sua concentração de saturação. A constante de transferência foi determinada experimentalmente e a influência da temperatura e da profundidade foi estabelecida. Em soluções supersaturadas, os componentes tendem a se desprender como bolhas de gás, mas esse desprendimento não se verifica para concentrações normalmente encontradas para O2, CO2 e NH3 em lagoas de tratamento de esgoto. Palavras-chave: Lagoas de polimento. Cinética de transferência. Compostos voláteis.

An operational data product available for both the Suomi National Polar-orbiting Partnership (S-NPP) and National Oceanic and Atmospheric Administration-20 (NOAA-20) platforms provides high-spatial-resolution infrared (IR) absorption band radiances for Visible Infrared Imaging Radiometer Suite (VIIRS) based on a VIIRS and Crosstrack Infrared Sounder (CrIS) data fusion method. This study investigates the use of these IR radiances, centered at 4.5, 6.7, 7.3, 9.7, 13.3, 13.6, 13.9, and 14.2 µm, to construct atmospheric moisture products (e.g., total precipitable water and upper tropospheric humidity) and to evaluate their accuracy. Total precipitable water (TPW) and upper tropospheric humidity (UTH) retrieved from hyperspectral sounder CrIS measurements are provided at the associated VIIRS sensor's high spatial resolution (750 m) and are compared subsequently to collocated operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and S-NPP VIIRS moisture products. This study suggests that the use of VIIRS IR absorption band radiances will provide continuity with Aqua MODIS moisture products.

O reator UASB produz um lodo concentrado que já sai do reator estabilizado, contudo precisa passar por um processo de secagem para seu uso posterior. Neste trabalho, descreve-se uma investigação experimental em escala piloto que visa estabelecer o desempenho de leitos de secagem de lodo anaeróbio. Três tipos de leito foram pesquisados: (1) leitos ao ar livre; (2) leitos cobertos (coberturas opaca e transparente); e (3) leitos com revolvimento de lodo ao ar livre. Desenvolveu-se um método experimental para determinar a produtividade de leitos de secagem. A produtividade é a massa de lodo seco que pode ser produzida em um leito por unidade de área e por unidade de tempo. Estabeleceu-se que a produtividade depende, além do tipo de leito, de três fatores: (1) a taxa de evaporação de água; (2) a carga de sólidos aplicada; e (3) a umidade final desejada. Foi desenvolvida uma expressão que permite calcular a produtividade de leitos em função dessas três variáveis. Os resultados mostraram que a produtividade de leitos cobertos com material transparente é muito parecida com a de leitos sem a cobertura, mas a produtividade de leitos com cobertura opaca é muito menor. Em contraste, o revolvimento do lodo resulta num aumento significativo da produtividade de leitos. Também foi analisada a influência da água de chuva sobre a produtividade de leitos de secagem. Estabeleceu-se que a água fica incorporada quantitativamente no lodo enquanto a umidade do lodo é maior que 65%. Para umidades menores, a água de chuva em grande parte percola e tem relativamente pouca influência sobre a produtividade dos leitos. Palavras-chave: Secagem de lodo. Tipos de leitos. Produtividade. Carga de sólidos.

The OMPS Limb Profiler (LP) instrument is designed to provide high-vertical-resolution ozone and aerosol profiles from measurements of the scattered solar radiation in the 290–1000 nm spectral range. It collected its first Earth limb measurement on 10 January 2012 and continues to provide daily global measurements of ozone and aerosol profiles from the cloud top up to 60 and 40 km, respectively. The relatively high vertical and spatial sampling allow detection and tracking of sporadic events when aerosol particles are injected into the stratosphere, such as volcanic eruptions or pyrocumulonimbus (PyroCb) events. In this paper we discuss the newly released Version 2.0 OMPS multi-wavelength aerosol extinction coefficient retrieval algorithm. The algorithm now produces aerosol extinction profiles at 510, 600, 674, 745, 869 and 997 nm wavelengths. The OMPS LP Version 2.0 data products are compared to the SAGE III/ISS, OSIRIS and CALIPSO missions and shown to be of good quality and suitable for scientific studies. The comparison shows significant improvements in the OMPS LP retrieval performance in the Southern Hemisphere (SH) and at lower altitudes. These improvements arise from use of the longer wavelengths, in contrast with the V1.0 and V1.5 OMPS aerosol retrieval algorithms, which used radiances only at 675 nm and therefore had limited sensitivity in those regions. In particular, the extinction coefficients at 745, 869 and 997 nm are shown to be the most accurate, with relative accuracies and precisions close to 10 % and 15 %, respectively, while the 675 nm relative accuracy and precision are on the order of 20 %. The 510 nm extinction coefficient is shown to have limited accuracy in the SH and is only recommended for use between 20–24 km and only in the Northern Hemisphere. The V2.0 retrieval algorithm has been applied to the complete set of OMPS LP measurements, and the new dataset is publicly available.

Correct, timely and meaningful interpretation of polarimetric weather radar observations requires an accurate understanding of hydrometeors and their associated microphysical processes along with well-developed techniques that automatize their recognition in both the spatial and temporal dimensions of the data. This study presents a novel technique for identifying different types of hydrometeors from quasi-vertical profiles (QVPs). In this new technique, the hydrometeor types are identified as clusters belonging to a hierarchical structure. The number of different hydrometeor types in the data is not predefined, and the method obtains the optimal number of clusters through a recursive process. The optimal clustering is then used to label the original data. Initial results using observations from the National Centre for Atmospheric Science (NCAS) X-band dual-polarization Doppler weather radar (NXPol) show that the technique provides stable and consistent results. Comparison with available airborne in situ measurements also indicates the value of this novel method for providing a physical delineation of radar observations. Although this demonstration uses NXPol data, the technique is generally applicable to similar multivariate data from other radar observations.

Oxidative stress can be used to evaluate not only adverse health effects but also adverse ecological effects, but limited research uses eco-toxicological assay to assess the risks posed by particle matters to non-human biomes. One important reason might be that the concentration of toxic components of atmospheric particles is far below the high detection limit of eco-toxic measurement. To solve the rapid detection problem, we extended a versatile aerosol concentration enrichment system (VACES) for ecotoxicity aerosol measurement and firstly used VACES to provide a comparison of ecotoxicity between non-concentrated and concentrated aerosols in ambient air. In this study, the total concentration (number or mass), the concentration of chemical components and the ecotoxicity were all increased by approximately 7 to 10 times in VACES, making the detection of ecotoxicity above the baseline. The comparison of ecotoxicity data and PM2.5 concentration showed that low concentration was not matched with ecotoxicity, although high concentration corresponded to higher ecotoxicity. In addition, the higher saturation temperature in VACES caused a loss of particulate matter, of which nitrate accounted for about 18 %.

The ability of single-frequency, millimeter-wavelength radar reflectivity observations to provide useful constraints for retrieval of snow particle size distribution (PSD) parameters, snowfall rates, and snowfall accumulations is examined. An optimal estimation snowfall retrieval that allows analyses of retrieval uncertainties and information content is applied to observations of near-surface W-band reflectivities from multiple snowfall events during the 2006–2007 winter season in southern Ontario. Retrieved instantaneous snowfall rates generally have uncertainties greater than 100 %, but single-event and seasonal snow accumulations from the retrieval results match well with collocated measurements of accumulations. Absolute fractional differences are mainly below 30 % for individual events that have more substantial accumulations and, for the season, 12.6 %. Uncertainties in retrieved snowfall rates are driven mainly by uncertainties in the retrieved PSD parameters, followed by uncertainties in particle model parameters and, to a lesser extent, the uncertainties in the fall-speed model. Uncertainties attributable to assuming an exponential distribution are negligible. The results indicate that improvements to PSD and particle model a priori constraints provide the most impactful path forward for reducing uncertainties in retrieved snowfall rates. Information content analyses reveal that PSD slope is well-constrained by the retrieval. Given the sensitivity of PSD slope to microphysical transformations, the results show that such retrievals, when applied to radar reflectivity profiles, could provide information about microphysical transformations in the snowing column. The PSD intercept is less well-constrained by the retrieval. While applied to near-surface radar observations in this study, the retrieval is applicable as well to radar observations aloft, such as those provided by profiling ground-based, airborne, and satellite-borne radars under lighter snowfall conditions when attenuation and multiple scattering can be neglected.

By now, a series of advanced wave optical approaches to the processing of radio occultation (RO) observations are widely used. In particular, the canonical transform (CT) method and its further developments need to be mentioned. The latter include the full spectrum inversion (FSI) method, the geometric optical phase matching (PM) method, and the general approach based on the Fourier integral operators (FIOs), also referred to as the CT type 2 (CT2) method. The general idea of these methods is the application of a canonical transform that changes the coordinates in the phase space from time and Doppler frequency to impact parameter and bending angle. For the spherically symmetric atmosphere, the impact parameter, being invariant for each ray, is a unique coordinate of the ray manifold. Therefore, the derivative of the phase of the wave field in the transformed space is directly linked to the bending angle as a single-valued function of the impact parameter. However, in the presence of horizontal gradients, this approach may not work. Here we introduce a further generalization of the CT methods in order to reduce the errors due to horizontal gradients. We describe, in particular, the modified CT2 method, denoted CT2A, which complements the former with one more affine transform: a new coordinate that is a linear combination of the impact parameter and bending angle. The linear combination coefficient is a tunable parameter. We derive the explicit formulas for the CT2A and develop the updated numerical algorithm. For testing the method, we performed statistical analyses based on RO retrievals from data acquired by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) and collocated analysis profiles of the European Centre for Medium-Range Weather Forecasts (ECMWF). We demonstrate that it is possible to find a reasonably optimal value of the new tunable CT2A parameter that minimizes the root mean square difference between the RO retrieved and the ECMWF refractivity in the lower troposphere and allows the practical realization of the improved capability to cope with horizontal gradients and serve as the basis of a new quality control procedure.

The CAPS PMssa monitor is a recently commercialized instrument designed to measure aerosol single-scattering albedo (SSA) with high accuracy (Onasch et al., 2015). The underlying extinction and scattering coefficient measurements made by the instrument also allow calculation of aerosol absorption coefficients via the extinction-minus-scattering (EMS) method. Care must be taken with EMS measurements due to the occurrence of large subtractive error amplification, especially for the predominantly scattering aerosols that are typically found in the ambient atmosphere. Practically this means that although the CAPS PMssa can measure scattering and extinction coefficients with high accuracy (errors on the order of 1 %–10 %), the corresponding errors in EMS-derived absorption range from ∼10 % to greater than 100 %. Therefore, we examine the individual error sources in detail with the goal of constraining these as tightly as possible. Our main focus is on the correction of the scattered light truncation effect (i.e., accounting for the near-forward and near-backward scattered light that is undetectable by the instrument), which we show to be the main source of underlying error in atmospheric applications. We introduce a new, modular framework for performing the truncation correction calculation that enables the consideration of additional physical processes such as reflection from the instrument's glass sampling tube, which was neglected in an earlier truncation model. We validate the truncation calculations against comprehensive laboratory measurements. It is demonstrated that the process of glass tube reflection must be considered in the truncation calculation, but that uncertainty still remains regarding the effective length of the optical cavity. Another important source of uncertainty is the cross-calibration constant that quantitatively links the scattering coefficient measured by the instrument to its extinction coefficient. We present measurements of this constant over a period of ∼5 months that demonstrate that the uncertainty in this parameter is very well constrained for some instrument units (2 %–3 %) but higher for others. We then use two example field datasets to demonstrate and summarize the potential and the limitations of using the CAPS PMssa for measuring absorption. The first example uses mobile measurements on a highway road to highlight the excellent responsiveness and sensitivity of the instrument, which enables much higher time resolution measurements of relative absorption than is possible with filter-based instruments. The second example from a stationary field site (Cabauw, the Netherlands) demonstrates how truncation-related uncertainties can lead to large biases in EMS-derived absolute absorption coefficients. Nevertheless, we use a subset of fine-mode-dominated aerosols from the dataset to show that under certain conditions and despite the remaining truncation uncertainties, the CAPS PMssa can still provide consistent EMS-derived absorption measurements, even for atmospheric aerosols with high SSA. Finally, we present a detailed list of recommendations for future studies that use the CAPS PMssa to measure absorption with the EMS method. These recommendations could also be followed to obtain accurate measurements (i.e., errors less than 5 %–10 %) of SSA and scattering and extinction coefficients with the instrument.

Smartphones are increasingly being equipped with atmospheric measurement sensors, providing huge auxiliary resources for global observations. Although China has the highest number of cellphone users, there is little research on whether these measurements provide useful information for atmospheric research. Here, for the first time, we present the global spatial and temporal variation of smartphone pressure measurements collected in 2016 from the Moji Weather app. The data have an irregular spatiotemporal distribution, with a high density in urban areas, a maximum in summer and two daily peaks corresponding to rush hours. With the dense dataset, we have developed a new bias correction method based on a machine learning approach without requiring users' personal information, which is shown to reduce the bias of pressure observation substantially. The potential application of the high-density smartphone data in cities is illustrated by a case study of a hailstorm occurred in Beijing in which high-resolution gridded pressure analysis is produced. It is shown that the dense smartphone pressure analysis during the storm can provide detailed information about fine-scale convective structure and decrease errors from an analysis based on surface meteorological-station measurements. This study demonstrates the potential value of smartphone data and suggests some future research need for its use in atmospheric science.

Low concentrations of 106Ru were detected across Europe at the turn of September and October 2017. The origin of 106Ru has still not been confirmed; however, current studies agree that the release occurred probably near Mayak in the southern Urals. The source reconstructions are mostly based on an analysis of concentration measurements coupled with an atmospheric transport model. Since reasonable temporal resolution of concentration measurements is crucial for proper source term reconstruction, the standard 1-week sampling interval could be limiting. In this paper, we present an investigation of the usability of the newly developed AMARA (Autonomous Monitor of Atmospheric Radioactive Aerosol) and CEGAM (carousel gamma spectrometry) real-time monitoring systems, which are based on the gamma-ray counting of aerosol filters and allow for determining the moment when 106Ru arrived at the monitoring site within approx. 1 h and detecting activity concentrations as low as several mBq m−3 in 4 h intervals. These high-resolution data were used for inverse modeling of the 106Ru release. We perform backward runs of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) atmospheric transport model driven with meteorological data from the Global Forecast System (GFS), and we construct a source–receptor sensitivity (SRS) matrix for each grid cell of our domain. Then, we use our least squares with adaptive prior covariance (LS-APC) method to estimate possible locations of the release and the source term of the release. With Czech monitoring data, the use of concentration measurements from the standard regime and from the real-time regime is compared, and a better source reconstruction for the real-time data is demonstrated in the sense of the location of the source and also the temporal resolution of the source. The estimated release location, Mayak, and the total estimated source term, 237±107 TBq, are in agreement with previous studies. Finally, the results based on the Czech monitoring data are validated with the IAEA-reported (International Atomic Energy Agency) dataset with a much better spatial resolution, and the agreement between the IAEA dataset and our reconstruction is demonstrated. In addition, we validated our findings also using the FLEXPART (FLEXible PARTicle dispersion) model coupled with meteorological analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF).

A região Nordeste do Brasil sofre com déficit crônico de recursos hídricos, especialmente para abastecer as indústrias em cidades grandes. Como consequência, seu desenvolvimento industrial é restrito quando comparado com outras regiões do Brasil. Uma possibilidade para minorar esse problema é transformar o esgoto de regiões urbanas em água com utilidade para a indústria. Todavia, as lagoas de estabilização que já estão em operação não podem produzir um efluente que seja aceitável para uso industrial. Contudo, é possível transformar lagoas de estabilização existentes em sistemas com pré-tratamento eficiente, por exemplo, em reatores UASB e tratamento complementar em lagoas de polimento em regime de bateladas sequenciais (LPBS), podendo haver uma lagoa de transbordo intermediária. Nessa transformação, pode-se aproveitar a infraestrutura do sistema já existente. No presente trabalho, analisa-se um caso hipotético de um sistema de lagoas de estabilização sendo transformado num sistema UASB-LPBS. No exemplo, o sistema recebe uma vazão afluente de 45.000 m3/d de água residuária mista, de origem doméstica e industrial. O sistema convencional de lagoas de estabilização opera com um tempo de permanência de 28 d e ocupa uma área de 73 ha. Deseja-se obter um efluente com baixas concentrações dos constituintes indesejáveis: sólidos em suspensão, material orgânico, patógenos, nitrogênio, fósforo e sulfato. Para tanto, propõem-se as seguintes transformações: (1) reatores UASB serão construídos na lagoa anaeróbia existente; (2) a lagoa facultativa existente passará a funcionar como uma lagoa de transbordo e (3) as lagoas de maturação serão transformadas em lagoas de polimento. Palavras-chave: Tratamento de esgoto. Reúso industrial. Remoção de nutrientes. Reator UASB. Lagoa de polimento.

The mass concentration of black carbon (BC) particles in the atmosphere has traditionally been quantified with two methods: as elemental carbon (EC) concentrations measured by thermal–optical analysis and as equivalent black carbon (eBC) concentrations when BC mass is derived from particle light absorption coefficient measurements. Over the last decade, ambient measurements of refractory black carbon (rBC) mass concentrations based on laser-induced incandescence (LII) have become more common, mostly due to the development of the Single Particle Soot Photometer (SP2) instrument. In this work, EC and rBC mass concentration measurements from field campaigns across several background European sites (Palaiseau, Bologna, Cabauw and Melpitz) have been collated and examined to identify the similarities and differences between BC mass concentrations measured by the two techniques. All EC concentration measurements in PM2.5 were performed with the EUSAAR-2 thermal–optical protocol. All rBC concentration measurements were performed with SP2 instruments calibrated with the same calibration material as recommended in the literature. The observed values of median rBC-to-EC mass concentration ratios on the single-campaign level were 0.53, 0.65, 0.97, 1.20 and 1.29, respectively, and the geometric standard deviation (GSD) was 1.5 when considering all data points from all five campaigns. This shows that substantial systematic bias between these two quantities occurred during some campaigns, which also contributes to the large overall GSD. Despite considerable variability in BC properties and sources across the whole dataset, it was not possible to clearly assign reasons for discrepancies to one or the other method, both known to have their own specific limitations and uncertainties. However, differences in the particle size range covered by these two methods were identified as one likely reason for discrepancies. Overall, the observed correlation between rBC and EC mass reveals a linear relationship with a constant ratio, thus providing clear evidence that both methods essentially quantify the same property of atmospheric aerosols, whereas systematic differences in measured absolute values by up to a factor of 2 can occur. This finding for the level of agreement between two current state-of-the-art techniques has important implications for studies based on BC mass concentration measurements, for example for the interpretation of uncertainties in inferred BC mass absorption coefficient values, which are required for modeling the radiative forcing of BC. Homogeneity between BC mass determination techniques is also very important for moving towards a routine BC mass measurement for air quality regulations.

O aumento do pH em lagoas de polimento agrega importantes benefícios ao tratamento, uma vez que viabiliza a remoção do nitrogênio, por meio da dessorção, e do fósforo, como resultado da precipitação de hidroxiapatita. O objetivo do trabalho é apresentar um modelo preditivo da variação do pH em lagoas de polimento, operadas em regime de bateladas sequenciais e usadas no pós-tratamento de efluentes de reatores UASB. No modelo, considera-se que a variação do pH em lagoas de polimento deve-se, principalmente, à remoção biológica de CO2, mas os processos de dessorção de dióxido de carbono e amônia também são importantes. Mostra-se ainda que as variações do pH em lagoas de polimento podem ser preditas quantitativamente com o auxílio da estequiometria, considerando-se a remoção física e biológica do dióxido de carbono e a dessorção de amônia. Os fatores que influenciam a variação do pH em função do tempo são as taxas de produção de oxigênio, de dessorção de dióxido de carbono e de amônia, além dos valores iniciais da alcalinidade e do pH. A influência da temperatura e da profundidade das lagoas foram incorporadas ao modelo. Foi possível demonstrar que o modelo simula com precisão o valor do pH, da alcalinidade e a concentração de nitrogênio em função do tempo, sob uma gama ampla de condições operacionais e características do efluente do UASB. Palavras-chave: Modelamento do pH. Bateladas sequenciais. Remoção de nutrientes.

Wind data collection in the atmospheric boundary layer benefits from short-term wind speed measurements using unmanned aerial vehicles. Fixed-wing and rotary-wing devices with diverse anemometer technology have been used in the past to provide such data, but the accuracy still has the potential to be increased. A lightweight drone for carrying an industry-standard precision sonic anemometer was developed. Accuracy tests have been performed with the isolated anemometer at high tilt angles in a calibration wind tunnel, with the drone flying in a large wind tunnel and with the full system flying at different heights next to a bistatic lidar reference. The propeller-induced flow deflects the air to some extent, but this effect is compensated effectively. The data fusion shows a substantial reduction of crosstalk (factor of 13) between ground speed and wind speed. When compared with the bistatic lidar in very turbulent conditions, with a 10 s averaging interval and with the unmanned aerial vehicle (UAV) constantly circling around the measurement volume of the lidar reference, wind speed measurements have a bias between −2.0 % and 4.2 % (root-mean-square error (RMSE) of 4.3 % to 15.5 %), vertical wind speed bias is between −0.05 and 0.07 m s−1 (RMSE of 0.15 to 0.4 m s−1), elevation bias is between −1 and 0.7∘ (RMSE of 1.2 to 6.3∘), and azimuth bias is between −2.6 and 7.2∘ (RMSE of 2.6 to 8.0∘). Key requirements for good accuracy under challenging and dynamic conditions are the use of a full-size sonic anemometer, a large distance between anemometer and propellers, and a suitable algorithm for reducing the effect of propeller-induced flow. The system was finally flown in the wake of a wind turbine, successfully measuring the spatial velocity deficit and downwash distribution during forward flight, yielding results that are in very close agreement to lidar measurements and the theoretical distribution. We believe that the results presented in this paper can provide important information for designing flying systems for precise air speed measurements either for short duration at multiple locations (battery powered) or for long duration at a single location (power supplied via cable). UAVs that are able to accurately measure three-dimensional wind might be used as a cost-effective and flexible addition to measurement masts and lidar scans.

Aerial emission sampling of four natural gas boiler stack plumes was conducted using an unmanned aerial system (UAS) equipped with a lightweight sensor–sampling system (the “Kolibri”) for measurement of nitrogen oxide (NO), and nitrogen dioxide (NO2), carbon dioxide (CO2), and carbon monoxide (CO). Flights (n = 22) ranged from 11 to 24 min in duration at two different sites. The UAS was maneuvered into the plumes with the aid of real-time CO2 telemetry to the ground operators and, at one location, a second UAS equipped with an infrared–visible camera. Concentrations were collected and recorded at 1 Hz. The maximum CO2, CO, NO, and NO2 concentrations in the plume measured were 10 000, 7, 27, and 1.5 ppm, respectively. Comparison of the NOx emissions between the stack continuous emission monitoring systems and the UAS–Kolibri for three boiler sets showed an average of 5.6 % and 3.5 % relative difference for the run-weighted and carbon-weighted average emissions, respectively. To our knowledge, this is the first evidence of the accuracy performance of UAS-based emission factors against a source of known strength.

Fugitive emissions from tailings ponds contribute significantly to facility emissions in the Alberta oil sands, but details on chemical emission profiles and the temporal and spatial variability of emissions to the atmosphere are sparse, since flux measurement techniques applied for compliance monitoring have their limitations. In this study, open-path Fourier transform infrared spectroscopy was evaluated as a potential alternative method for quantifying spatially representative fluxes for various pollutants (methane, ammonia, and alkanes) from a particular pond, using vertical-flux-gradient and inverse-dispersion methods. Gradient fluxes of methane averaged 4.3 g m−2 d−1 but were 44 % lower than nearby eddy covariance measurements, while inverse-dispersion fluxes agreed to within 30 %. With the gradient fluxes method, significant NH3 emission fluxes were observed (0.05 g m−2 d−1, 42 t yr−1), and total alkane fluxes were estimated to be 1.05 g m−2 d−1 (881 t yr−1), representing 9.6 % of the facility emissions.

O regime de bateladas sequenciais em lagoas de polimento apresenta duas vantagens importantes em relação às lagoas de fluxo contínuo: (1) reduz consideravelmente o tempo necessário para a remoção bacteriana e (2) possibilita a remoção eficiente dos nutrientes nitrogênio e fósforo. Entretanto, a aplicabilidade do regime de bateladas sequenciais é limitada pela concentração de material orgânico no afluente da lagoa: se essa concentração é alta, a demanda por oxigênio excede a capacidade de geração na lagoa e o ambiente fica anaeróbio, o que é indesejável, pois a digestão anaeróbia deixa um residual de material orgânico alto. Nesse contexto, este trabalho teve como objetivo avaliar a remoção do material orgânico residual do efluente pré-tratado anaerobiamente (reator UASB) em lagoas de polimento operadas em regime de bateladas sequenciais. Além disso, avaliou-se a influência da concentração inicial do material orgânico e da profundidade no desempenho das lagoas. A operação das lagoas de polimento permitiu a remoção eficiente da DBO (em média 70%), mas o tempo para alcançar a DBO mínima aumentou com a profundidade. Durante o tratamento, a DBO passou por um mínimo e depois aumentou presumivelmente devido à produção de algas. Em todos os casos, quando a DBO do afluente da lagoa aumentou, a concentração mínima do efluente também aumentou. Palavras-chave: Pré-tratamento anaeróbio. Remoção da DBO. Profundidade da lagoa.

Electric vehicle (EV) penetration has been increasing globally and is expected to continue its exponential growth over the coming decades. Several countries have already announced plans to achieve total or partial electrification of their vehicle fleets. Such rapid transportation electrification will have a significant impact on society and businesses that support the transportation industry. Additionally, new business opportunities will be available to support this technological evolution. In this paper, the business opportunities emerging from EVs and their supporting infrastructure are reviewed. It has been observed that several businesses, such as sustainable mining and manufacturing, will need to be developed before EV growth as they provide the initial platform required for EV adoption. Other businesses such as fleet optimization, battery management, and recycling can be developed at a later stage. All of these businesses will also have social and technological impacts, which will drive policy decisions. Regional governments play a critical role in ensuring the smooth execution of a transition to transportation electrification through social programs, such as training and education for equitable growth, and legislative decisions, such as technology standardization.

O objetivo do trabalho foi propor e avaliar um sistema de tratamento de esgoto e de reúso agrícola aplicado em área rural, que permitisse contribuir com a melhoria das condições de esgotamento sanitário e incrementar a disponibilidade de água para uso na irrigação. O sistema de tratamento foi operado em escala unifamiliar, sendo composto de caixa de gordura, tanque de equalização, reator UASB e lagoas de polimento. O efluente tratado era encaminhado ao sistema de reúso, constituído por reservatório, motobomba e sistema de irrigação localizada, fertirrigando uma cultura do caju. Os resultados demonstraram que o sistema de tratamento operou com uma eficiência média de remoção de DBO5,20 de 74% e obteve efetividade na remoção de patógenos, visto que o efluente produzido apresentou um valor médio de E. coli de 2,2 * 104 NMP/100 mL e ausência de ovos de helmintos, atendendo às recomendações sanitárias da Organização Mundial da Saúde (OMS) para o uso pretendido. Preservaram-se também as concentrações iniciais de nitrogênio e fósforo, fundamentais para a nutrição da cultura explorada. O sistema de reúso incrementou a disponibilidade de água na propriedade em 40 m3/ano, reduzindo os gastos com adubação mineral e com a compra de água. Palavras-chave: Semiárido. Propriedade rural. Reúso agrícola. Qualidade higiênica.

Atmospheric ice-nucleating particles (INPs) play an important role in determining the phase of clouds, which affects their albedo and lifetime. A lack of data on the spatial and temporal variation of INPs around the globe limits our predictive capacity and understanding of clouds containing ice. Automated instrumentation that can robustly measure INP concentrations across the full range of tropospheric temperatures is needed in order to address this knowledge gap. In this study, we demonstrate the functionality and capacity of the new Portable Ice Nucleation Experiment (PINE) to study ice nucleation processes and to measure INP concentrations under conditions pertinent for mixed-phase clouds, with temperatures from about −10 to about −40 ∘C. PINE is a cloud expansion chamber which avoids frost formation on the cold walls and thereby omits frost fragmentation and related background ice signals during the operation. The development, working principle and treatment of data for the PINE instrument is discussed in detail. We present laboratory-based tests where PINE measurements were compared with those from the established AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Within experimental uncertainties, PINE agreed with AIDA for homogeneous freezing of pure water droplets and the immersion freezing activity of mineral aerosols. Results from a first field campaign conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) observatory in Oklahoma, USA, from 1 October to 14 November 2019 with the latest PINE design (a commercially available PINE chamber) are also shown, demonstrating PINE's ability to make automated field measurements of INP concentrations at a time resolution of about 8 min with continuous temperature scans for INP measurements between −10 and −30 ∘C. During this field campaign, PINE was continuously operated for 45 d in a fully automated and semi-autonomous way, demonstrating the capability of this new instrument to also be used for longer-term field measurements and INP monitoring activities in observatories.

We describe the development, characterization, and first field deployments of a quantum cascade laser direct absorption spectrometer (QCLAS) for water vapor measurements in the upper troposphere and lower stratosphere (UTLS). The instrument is sufficiently small (30×23×11 cm3) and lightweight (3.9 kg) to be carried by meteorological balloons and used for frequent soundings in the UTLS. The spectrometer is a fully independent system, operating autonomously for the duration of a balloon flight. To achieve the required robustness, while satisfying stringent mass limitations, the concepts for optics and electronics have been fundamentally reconsidered compared to laboratory-based spectrometers. A significant enhancement of the mechanical and optical stability is achieved by integrating a newly designed segmented circular multipass cell which allows for 6 m optical path length in a very compact fashion. The H2O volume mixing ratio is retrieved by calibration-free evaluation of the spectral data, i.e., only relying on SI-traceable measurements and absorption line parameters. The open-path design reduces the risk of contamination and allows for fast response and thus high vertical resolution. Laboratory-based characterization experiments show an agreement within 2 % of reference measurements and a precision of 0.1 % under conditions comparable to the UTLS. The instrument successfully performed two balloon-borne test flights up to 28 km altitude. In the troposphere, the retrieved spectroscopic data show an excellent agreement with the accompanying measurements by a frost point hygrometer (CFH). At higher altitude, the quality of the spectral data remained unchanged, but outgassed water vapor within the instrument enclosure was hindering an accurate measurement of the atmospheric water vapor. Despite this limitation, these test flights demonstrated the operation of a compact laser spectrometer in the UTLS aboard a low-volume meteorological balloon, opening the perspective for future highly resolved, accurate, and cost-efficient soundings.

In order to mitigate climate change, it is crucial to understand urban greenhouse gas (GHG) emissions precisely, as more than two-thirds of the anthropogenic GHG emissions worldwide originate from cities. Nowadays, urban emission estimates are mainly based on bottom-up calculation approaches with high uncertainties. A reliable and long-term top-down measurement approach could reduce the uncertainty of these emission inventories significantly. We present the Munich Urban Carbon Column network (MUCCnet), the world's first urban sensor network, which has been permanently measuring GHGs, based on the principle of differential column measurements (DCMs), since summer 2019. These column measurements and column concentration differences are relatively insensitive to vertical redistribution of tracer masses and surface fluxes upwind of the city, making them a favorable input for an inversion framework and, therefore, a well-suited candidate for the quantification of GHG emissions. However, setting up such a stationary sensor network requires an automated measurement principle. We developed our own fully automated enclosure systems for measuring column-averaged CO2, CH4 and CO concentrations with a solar-tracking Fourier transform spectrometer (EM27/SUN) in a fully automated and long-term manner. This also includes software that starts and stops the measurements autonomously and can be used independently from the enclosure system. Furthermore, we demonstrate the novel applications of such a sensor network by presenting the measurement results of our five sensor systems that are deployed in and around Munich. These results include the seasonal cycle of CO2 since 2015, as well as concentration gradients between sites upwind and downwind of the city. Thanks to the automation, we were also able to continue taking measurements during the COVID-19 lockdown in spring 2020. By correlating the CO2 column concentration gradients to the traffic amount, we demonstrate that our network is capable of detecting variations in urban emissions. The measurements from our unique sensor network will be combined with an inverse modeling framework that we are currently developing in order to monitor urban GHG emissions over years, identify unknown emission sources and assess how effective the current mitigation strategies are. In summary, our achievements in automating column measurements of GHGs will allow researchers all over the world to establish this approach for long-term greenhouse gas monitoring in urban areas.

No presente trabalho comparam-se diferentes sistemas que são usados para tratar esgoto, visando ao reúso agrícola ou industrial ou ainda à descarga em água de superfície. O tipo de sistema de tratamento deve atender aos requisitos necessários ao uso que se prevê para o efluente. Distinguem-se assim quatro tipos de sistemas de tratamento: lodo ativado, reator UASB, lagoas de estabilização e a combinação UASB-Lagoa de polimento (LP). O reator UASB sozinho não produz uma qualidade de efluente que permita o reúso ou descarga em águas de superfície. Se o reúso agrícola é desejado, não há necessidade de remoção de nutrientes. Nesse caso, os sistemas de lagoas de estabilização e UASB-LP podem ser usados. Se o reúso industrial é previsto, a remoção de nutrientes é necessária e pode-se usar o sistema de lodo ativado ou UASB-LP. Na escolha racional do tipo de sistema de tratamento, os fatores mais importantes são: desempenho e a área necessária. Pelo desempenho do sistema, avalia-se a capacidade de produzir a qualidade do efluente desejado e a área necessária indica se é factível a implantação do sistema. Outros fatores, como custo, simplicidade e estabilidade operacional também são relevantes. Ao fazer a comparação foi observado que o sistema com a melhor qualidade do efluente é UASB-LP, mas a área necessária é relativamente grande. O lodo ativado produz um efluente com qualidade muito boa, contudo o custo é alto, a operação não é simples e instabilidades podem ocorrer. O sistema de lagoas de estabilização deve ser evitado, porque é inferior ao UASB-LP em vários aspectos. Palavras-chave: Sistemas de tratamento de esgoto. Reúso agrícola. Reúso industrial. Lodo ativado. UASB. Lagoa de estabilização. UASB + lagoas de polimento.