AIRS Instrument Research Articles

Anomalies of Thermal Fields Revealed by Satellite Data during Preparatio n and Occurrence of Strong Earthquakes in the Region of the Baikal Rift Zone in 2008–2022

Long-term changes in thermal fields were studied before and during strong earthquakes with magnitudes from 5.1 to 5.6 that occurred in the region of the Baikal rift zone in 2008–2022. Satellite data were used for these studies. For the analysis we used the values of land surface temperature, temperature of the near-surface layer of the atmosphere, outgoing long-wave radiation, and relative humidity recorded using the AIRS instrument mounted on the Aqua satellite. During the periods of preparation and occurrence of these seismic events, anomalous variations in the parameters of thermal fields registered with satellite were revealed. They exceeded the average long-term values: for land surface temperature and temperature of the near-surface layer of the atmosphere by 5–10%, for outgoing long-wave radiation by 11–15%, and for relative humidity by 6–10%. A strong negative correlation was found between changes in the temperature of the near-surface layer of the atmosphere and relative humidity (correlation coefficient of –0.75), as well as antiphase oscillations between the values of the outgoing long-wave radiation and relative humidity. The obtained results can be used for studies of the precursor variability of thermal fields during monitoring of seismic hazard zones.

Research Progress of Atmospheric CO2 Monitoring by Satellite Remote Sensing

Carbon peaking and carbon neutrality are gaining popularity in the international community. As a result, there is a growing demand for high-accuracy quantification of carbon sources and sinks. Global carbon dioxide (CO2) concentrations measured by satellite are essential evidence for accurate CO2 emissions estimation. And advances in infrared hyper-spectral technologies have enhanced satellite-derived CO2 estimation. This paper reviews the development of space-borne instruments, such as the infrared hypersoectral sounder and lidar, from the 1950s. The two types of infrared hyperspectral sounders, including sounders for observing atmospheric profiles, such as AIRS, IASI, CrIS, and HIRAS, and special instruments for observing atmospheric composition, such as GOSAT, OCO, GAS, and ACGS/TanSAT. The precision of total volume CO2 concentration products has improved. It therefore encourages satellite observation based researches into carbon sources and sinks, as well as emissions inventories. And rising of related publication is well corresponding to the launch of new instruments. And in the future, the rapid development of lidar observation will further improve accuracy of CO2 monitoring.

Baseline Air Monitoring of Fine Particulate Matter and Trace Elements in Ontario’s Far North, Canada

Large mineral deposits have been discovered in Ontario’s Far North and are being considered for further development. Particulate matter and trace elements can be emitted from potential mining activities and these air pollutants are associated with health risks and harmful to the sensitive ecosystem. An air monitoring station, powered by solar panels and a wind turbine, was established in this near-pristine area to monitor baseline levels of fine particulate matter (PM2.5) and trace elements downwind of a proposed mine site. Levels of PM2.5 and trace elements observed from 2015 to 2018 were much lower than measurements observed in southern Ontario, suggesting minimal influence of primary emissions in the study area. One episodic PM2.5 event in July 2015 was attributable to wildfire emissions in northern Ontario. Only 8 out of the 31 target elements were detected in 25% or more of the samples. Good correlations among As, Se, Pb, and Sb, between Mn and Fe, as well as between Ce and La indicated they originated from long-range atmospheric transport from the south. Ontario’s Ambient Air Quality Criteria were not exceeded for any target air pollutants. Four years of air measurements filled the data gap of baseline information in this near-pristine study area and can be used to assess impacts of potential mining activities in the future. Field operations during this study period indicated that the battery-powered air instruments and meteorological sensors worked well in the harsh environment of Ontario’s Far North even in cold winter months. The field experiences gained in this study can be applied to future air monitoring activities in harsh environments where no direct power supply is available and site access is limited.

Multisensor and Multimodel Monitoring and Investigation of a Wintertime Air Pollution Event Ahead of a Cold Front Over Eastern China

AbstractGiven the limitations in pollutant measurements (e.g., coverage, observation errors) and air quality model uncertainties (e.g., with parameterizations and emissions), a multisensor and multimodel approach offers additional benefits compared to a single‐instrument and deterministic approach for monitoring, investigating, and predicting air pollution events. In this study, we use multisensors (including the spaceborne MODIS, OCO‐2, AIRS, and OMPS instruments as well as surface instruments) and multimodels (including WRF‐Chem and WRF‐CO2) to investigate a severe air pollution event on December 9, 2016 over eastern China. During this episode, a strong cold front moved southward. At the leading edge of the front, WRF‐CO2 simulates an enhanced XCO2 belt while WRF‐Chem simulates a belt of high PM2.5 concentration. The XCO2 and PM2.5 belts are generally colocated, due to coemission of CO2 and pollutants (or their precursors). Satellite observations including MODIS AOD, OCO‐2 XCO2, OMPS NO2, AIRS CO, and surface data confirm the simulated pollution and XCO2 belts. Later on, the front became distorted due to terrain blocking and mountain channel flows. Both observations and simulations show that the channel winds between Mountains Dabie and Huang transport the haze plume into Jiangxi province, enhancing pollution in the region. It is concluded that the multisensor (including space‐based and ground‐based instruments) and multimodel (e.g., WRF‐CO2, WRF‐Chem) approach can be used to collectively monitor and investigate air pollution events, given that emissions of the involved species have generally similar spatial distributions.

Retrieval of total columnar precipitable water vapour using radio occultation technique over the Indian region

Total column precipitable water vapour (PWV) is retrieved using radio occultation retrievals of water vapour from COSMIC satellites over four regions of India. This analysis is carried out to assess the accuracy of the radio occultation technique for estimating PWV and to observe the PWV variation over these regions. The impact points of radio occultation are investigated for one year to select those points which are very near to the surface for the four regions. Total column PWV is estimated using these points data and further compared to the PWV values obtained from AIRS instrument and reanalysis data from MERRA2. The findings obtained using the radio occultation technique show that the vertical profile of PWV from COSMIC provides almost similar results at different pressure levels with AIRS and MERRA2 PWVs. The PWV values obtained from COSMIC are 16 mm, 17 mm, 27 mm, and 52 mm approximately for region1, region2, region3, and region4 respectively having differences in the range of 0.2 mm–7 mm with respect to PWV values estimated from AIRS and MERRA2. On the surface level, the average difference is estimated to be less than 1 mm. It is inferred that a good estimation of total column PWV is obtained using the radio occultation technique which can be further used for rainfall prediction, its impact on climate change and to study hydrological cycle more efficiently.

Satellite Monitoring of Anomalous Wildfires in Australia

Here we present the results of satellite monitoring of wildfires in Australia for the period of 2001–2020. Annual and monthly dynamics of wildfire areas and CO and CO2 carbon-bearing trace gas emissions from wildfires have been analyzed for the whole territory of Australia based on satellite data. It was found that anomalous fires occurred in the territory of New South Wales during the 2019–2020 fire season. Values of burned-out areas exceeded the values of previous years 3.5–25.8-fold. Annual mean volumes of carbon-bearing gas emissions in this region exceeded the values of previous years 4–59-fold for carbon monoxide CO and 4.6–50-fold for carbon dioxide CO2. The spatial distribution of the excess concentrations of CO from wildfires in New South Wales was recorded according to the monthly mean data of the AIRS instrument (Aqua satellite). At the same time, the excess of CO2 concentration in the atmosphere was estimated using the TANSO-FTS (GOSAT satellite) data. It was demonstrated that an anomalously high number of fires in this state of Australia was caused by extreme drought associated with abnormally high surface temperatures, low rainfall and humidity which created conditions for intense fires and emissions of carbon-bearing gases associated with the combustion of eucalyptus and tropical rain forests prevailing in this region.

Challenges characterizing N deposition to high elevation protected areas: A case study integrating instrument, simulated, and lichen inventory datasets for the Devils Postpile National Monument and surrounding region, USA

Excess N deposition is a common stressor of ecological health. Sensitive biota, including many lichens, respond to small differences in atmospheric N deposition. For lands with a conservation mandate, obtaining sufficient N data to evaluate risks is a challenge, especially in Mediterranean or arid landscapes. Managers in the Western U.S. commonly use epiphytic (“tree-dwelling”) lichens to supplement N assessments, although options for higher elevations lacking epiphytes are poorly developed. Managers instead rely on broad-scale air quality simulations like the Total Deposition Model (TDEP). The Sierra Nevada Range is an example where anthropogenic N reaches mid-to-high elevation protected areas but managers lack tools for monitoring at ecologically relevant spatial-scales. Our main goals were to demonstrate how well-studied epiphytic bioindicators can supplement N assessments and recommend saxicolous (“rock-dwelling”) candidates for similar development to improve coverage in higher elevations. As a case study, we characterized N deposition at a small (323 ha) protected area, Devils Postpile National Monument (DEPO), by integrating data from TDEP, air instruments, and assays of %N in the epiphyte Letharia vulpina. We used the regional N threshold associated with detrimental effects to epiphytic lichen communities, 2.9 kg N ha−1 yr−1 in throughfall (i.e. under a tree canopy), as a provisional critical load (CL) for indicating areas at risk of ecological impacts. Results clearly showed the need for empirical, diverse, and finer-scaled information, even for an area as small as DEPO. Importantly, simulations from TDEP overestimated dry deposition of oxidized N, making total N estimates nearly twice measured values (6.0 vs 3.03 – 3.66 kg N ha−1 yr−1, respectively). While small, our L. vulpina dataset (n = 5) from the Monument indicated highly variable N in throughfall (1.7 – 4.44 kg N ha−1 yr−1), with small-scale drivers, like proximity to the river canyon and the Central Valley, tipping the scale towards CL exceedance. Regional L. vulpina assays (n = 355) showed a distinct north-to-south gradient in California where N deposition at DEPO was highly similar to the nearby protected area, Yosemite National Park, where ecological impacts of excess N are well-documented. To expand N bio-monitoring into higher elevation areas, we recommend vetting five widespread saxicolous species, Rhizoplaca melanophthalma, Umbilicaria phaea, U. polaris, Xanthoparmelia coloradoënsis, and X. cumberlandia.

Joint Analysis of Anomalies of Different Geophysical Fields, Recorded from Space before Strong Earthquakes in California

Results are presented from using satellite data to study anomalies of different geophysical fields due to the interaction of the lithosphere, atmosphere, and ionosphere. The anomalies are mid- and short-term precursors of strong earthquakes in California that occurred on July 4 and 5, 2019 (M = 6.4 and M = 7.1). Precursory changes in the lithosphere are analyzed using lineament system characteristics obtained by processing satellite imagery (Terra/Aqua satellites and MODIS instrument), along with variations in the Earth’s surface temperature (the Aqua satellite and the AIRS instrument). Fluctuations in the temperature of the near-surface atmospheric layer are studied to detect atmospheric anomalies during preparation of seismic events, as are fluctuations in the air temperature now at an altitude of 1000 hPa and changes in outgoing longwave radiation recorded by the AIRS instrument on the Aqua satellite. Variations in the ionospheric electron density in the F2-layer maximum are studied with GPS data to reveal ionospheric anomalies during the precursors and occurrence of earthquakes. Joint analysis of anomalies in different geophysical fields, identified via satellite monitoring, allow precursory changes in the lithosphere to be detected a month before strong earthquakes. Precursory changes in the atmosphere and ionosphere can be detected 3–6 days and 3–5 or 10 days before earthquakes, respectively.

Spectrally Resolved Fluxes from IASI Data: Retrieval Algorithm for Clear-Sky Measurements

AbstractSpace-based measurements of the outgoing longwave radiation (OLR) are essential for the study of Earth’s climate system. While the CERES instrument provides accurate measurements of this quantity, its measurements are not spectrally resolved. Here we present a high-resolution OLR product (sampled at 0.25 cm−1), derived from measurements of the IASI satellite sounder. The applied methodology relies on precalculated angular distribution models (ADMs). These are usually calculated for tens to hundreds of different scene types (characterized by surface and atmosphere parameters). To guarantee accurate results in the range 645–2300 cm−1 covered by IASI, we constructed ADMs for over 140 000 scenes. These were selected from one year of CAMS reanalysis data. A dissimilarity-based selection algorithm was applied to choose scenes as different from each other as possible, thereby maximizing the performance on real data, while keeping the number of scenes manageable. A comparison of the IASI OLR integrated over the 645–2300 cm−1 range was performed with the longwave broadband OLR products from CERES and the AIRS instrument. The latter are systematically higher due to the contribution of the far infrared to the total IR spectral range, but as expected exhibit generally high spatial correlations with the IASI OLR, except for some areas in the tropical region. We also compared the IASI OLR against the spectrally resolved OLR derived from AIRS. A good agreement was found above 1200 cm−1 while AIRS OLR appeared to be systematically higher in the atmospheric window region, likely related to differences in overpass time or to the use of a different cloud detection algorithm.

Validation of estimated cloud fraction from MERRA-2 and AIRS data using ground based observation over IAO, Hanle

We report for validation of cloud fraction estimated from high-resolution (hourly) data from MERRA-2 and AIRS instrument aboard NASA’s Aqua satellite during its ascending and descending orbits with hourly ground-based visual observation taken at Indian Astronomical Observatory (IAO), Hanle during 1997–2018. The study reveals 70% useful nights, equivalent to 254 spectroscopic nights in a year. A comparative study of cloud fraction was performed using homogeneous and continuous data spanning six years (2013–2018) from MERRA-2 and AIRS over IAO, Hanle and Merak sites in the Himalayan region, and several astronomical observatories located in Atacama desert in Chile, Canary islands in Spain, National Astronomical Observatory (NAO), Mexico, and Mauna Loa in Hawaii. The study reveals cloud fractions of 0.07–0.11 at 25% (1st Quartile) and 0.32–0.40 at 50% (median) at the Himalayan sites. On the other hand, the median cloud fractions are 0.06–0.13 at the Chilean sites, 0.16 at NAO, and 0.29 at Canary islands. The observed 25% of the cloud fraction at the Himalayan sites during the lowest three cloud-fractional months (October-December) are comparable with other sites located in Chile and Canary islands. The median cloud fraction at Hanle is slightly lower than Mauna Loa. The study further concluded that the percentage of useful nights obtained from the visual observation (70%) at IAO-Hanle is very close to the percentage of clear sky (68%) estimated from the MERRA-2 data.

A new way of monitoring mechanical ventilation by measurement of particle flow from the airways using Pexa method in vivo and during ex vivo lung perfusion in DCD lung transplantation

BackgroundDifferent mechanical ventilation settings are known to affect lung preservation for lung transplantation. Measurement of particle flow in exhaled air may allow online assessment of the impact of ventilation before changes in the tissue can be observed. We hypothesized that by analyzing the particle flow, we could understand the impact of different ventilation parameters.MethodsParticle flow was monitored in vivo, post mortem, and in ex vivo lung perfusion (EVLP) in six porcines with the Pexa (particles in exhaled air) instrument. Volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) were used to compare small versus large tidal volumes. The surfactant lipids dipalmitoylphosphatidylcholine (DPPC) and phosphatidylcholine (PC) were quantified by mass spectrometry.ResultsIn vivo the particle mass in VCV1 was significantly lower than in VCV2 (p = 0.0186), and the particle mass was significantly higher in PCV1 than in VCV1 (p = 0.0322). In EVLP, the particle mass in VCV1 was significantly higher than in PCV1 (p = 0.0371), and the particle mass was significantly higher in PCV2 than in PCV1 (p = 0.0127). DPPC was significantly higher in EVLP than in vivo.ConclusionsHere, we introduce a new method for measuring particle flow during mechanical ventilation and confirm that these particles can be collected and analyzed. VCV resulted in a lower particle flow in vivo but not in EVLP. In all settings, large tidal volumes resulted in increased particle flow. We found that DPPC was significantly increased comparing in vivo with EVLP. This technology may be useful for developing strategies to preserve the lung and has a high potential to detect biomarkers.

Study of the exceptional meteorological conditions, trace gases and particulate matter measured during the 2017 forest fire in Doñana Natural Park, Spain

In late June 2017, a forest fire occurred in Doñana Natural Park, which is located in southwestern Europe. Many animal and plant species, some of which are threatened, suffered from the impact of this fire, and important ecosystems in the European Union were seriously affected. This forest fire occurred under exceptional weather conditions. The meteorological situation was studied at both the synoptic scale and the local scale using meteorological fields in the ERA-Interim global model from ECMWF (European Centre for Medium Range Weather Forecasts), the WRF (Weather Research and Forecasting) mesoscale model and ground observations collected at El Arenosillo observatory. Anomalies were obtained using records (observations and simulations) over the last two decades (1996–2016). An anticyclonic system dominated the synoptic meteorological conditions, but a strong pressure gradient was present; positive high pressure anomalies and negative low pressure anomalies resulted in intense NW flows. At the surface, wind gusts of 80 km h−1, temperatures up to 35 °C and relative humidity values <20% were observed. In terms of anomalies, these observations corresponded to positive temperature anomalies (differences of 12 °C), positive wind speed anomalies (>29 km h−1) and negative relative humidity anomalies (differences of 40%). The forest fire reached El Arenosillo observatory approximately 8 h after it began. When the fire started, record-setting maximum values were measured for all gases monitored at this site (specifically, peaks of 99,995 μg m−3 for CO, 951 μg m−3 for O3, 478 μg m−3 for NO2, 116 μg m−3 for SO2 and 1000 μg m−3 for PM10). According to the temporal evolution patterns of these species, the atmosphere over a burnt area can recover to initial atmospheric levels between 48 and 96 h after an event. The impact of the Doñana plume was studied using hourly forward trajectories computed with the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to analyse the emission source for the burnt area. The Doñana fire plume affected large metropolitan areas near the Mediterranean coast. Air quality stations located in the cities of Seville and Cadiz registered the arrival of the plume based on increases in CO and PM10. Using CO as a tracer, measurements from the AIRS and MOPITT instruments allowed us to observe the transport of the Doñana plume from the Strait of Gibraltar to the Mediterranean. Finally, after two days, the Doñana forest fire plume reached the western Mediterranean basin.

Near-complete optic nerve transection by high-pressure air.

The use of high-pressure air instruments has become more common. Consequently, there have been a number of cases of orbital emphysema caused by contact with high-pressure air. In this case, a 62-year-old male patient visited an emergency medical center after his left eye was shot by an air compressor gun that was used to wash cars. Lacerations were observed in the upper and lower eyelids of his left eye. Radiological examinations revealed orbital emphysema, optic nerve transection, pneumocephalus, and subcutaneous emphysema in the face, neck, shoulder, and mediastinum. Canalicular injury repair was performed, and the emphysema resolved. However, there was near-complete vision loss in the patient’s left eye. Because most optic nerve transections occur after a severe disruption in bone structure, pure optic nerve transections without any injury of the bone structure, as in the present case, is extremely rare.

A comparison of spatial predictors when datasets could be very large

In this article, we review and compare a number of methods of spatial prediction, where each method is viewed as an algorithm that processes spatial data. To demonstrate the breadth of available choices, we consider both traditional and more-recently-introduced spatial predictors. Specifically, in our exposition we review: traditional stationary kriging, smoothing splines, negative-exponential distance-weighting, fixed rank kriging, modified predictive processes, a stochastic partial differential equation approach, and lattice kriging. This comparison is meant to provide a service to practitioners wishing to decide between spatial predictors. Hence, we provide technical material for the unfamiliar, which includes the definition and motivation for each (deterministic and stochastic) spatial predictor. We use a benchmark dataset of $\mathrm{CO}_{2}$ data from NASA’s AIRS instrument to address computational efficiencies that include CPU time and memory usage. Furthermore, the predictive performance of each spatial predictor is assessed empirically using a hold-out subset of the AIRS data.

Studying the Timing of Discrete Musical Air Gestures

Motion-sensing technologies enable musical interfaces where a performer controls sound by moving his or her body “in the air,” without touching a physical object. These interfaces work well when the movement and resulting sound are smooth and continuous, but it has proven difficult to design air instruments that trigger discrete sounds with precision that feels natural to performers and allows them to play rhythmically complex music. This article presents a study of “air drumming” gestures. Participants performed drumming-like gestures in time to simple recorded rhythms. These movements were recorded and examined to look for aspects of the movement that correspond to the timing of the sounds. The goal is to understand what we do with our bodies when we gesture in the air to trigger a sound. Two movement features of the hand are studied: Hits are the moment where the hand changes direction at the end of the striking gesture, and acceleration peaks are sharp peaks in magnitude acceleration as the hand decelerates. Hits and acceleration peaks are also detected for the movement of the wrist. It is found that the acceleration peaks are more useful than the hits because they occur earlier and with less variability, and their timing changes less with note speed. It is also shown that timing differences between hand and wrist features can be used to group performers into different movement styles.

Using Remote Sensing and Geospatial Technology for Climate Change Education

ABSTRACT This curriculum and instruction paper describes initial implementation and evaluation of remote-sensing exercises designed to promote post-secondary climate literacy in the geosciences. Tutorials developed by the first author engaged students in the analysis of climate change data obtained from NASA satellite missions, including the LANDSAT, MODIS, ASTER, SSMIS, AIRS and GRACE instruments. The tutorials incorporated image processing technology through software such as ESRI's ArcGIS and ERDAS Imagine. The relative emphasis on the technological tools versus the application to improving knowledge about climate change was adjusted across implementation in three geography courses. The adjustment of the relative emphasis placed on four primary teaching and learning objectives provides a framework for considering adaptation of the exercises across the educational spectrum. For example, activities are already being designed to expand to secondary school and general elective undergraduate geography courses. Online material provides full details for implementation of each exercise and associated student-generated products. Pre- and post-course surveys provided student perspectives about the courses and their learning. Student performance on completion of the tutorials was monitored by the instructor and performance on independent course projects evaluated students' ability to learn and apply their knowledge and skills to problems of their choice. Survey and performance data illustrated that the tutorials were successful in meeting their intended learning objectives. Discussion highlights the unique opportunities these tutorials provided to engage introductory and advanced students in authentic and relevant analysis of satellite data to explore climate change.

Ultra-high voltage capillary electrophoresis >300 kV: Recent advances in instrumentation and analyte detection

Instrumentation has been developed for the implementation of ultra-high voltage capillary electrophoresis (UHVCE) with potentials up to and exceeding 300kV. Several separations have been used to demonstrate the utility of higher applied voltages for improving the resolution of peptide, protein, and nucleic acid separations. Previously reported instrumentation was limited to 120kV and required submersion in a bath of transformer oil to prevent corona and high voltage arcing between the components of the instrument [Hutterer, 1999, 2000, 2005] [1–3]. A modular design that uses plastic dielectric materials to overcome these obstacles enabling simplified operation of the instrument in air is described here in detail. A forced air system developed to control the temperature of the instrument to within a few degrees over a range of 25–60°C for use with ultra-high voltage capillary gel electrophoresis is also described. UHVCE instrumentation and its applications with UV absorption and laser induced fluorescence detection are further developed, and the first demonstration of UHVCE coupled to electrospray ionization-mass spectrometry is shown.

A Comparison of the Performance of Samplers for Respirable Dust in Workplaces and Laboratory Analysis for Respirable Quartz

The divergent sampling techniques for respirable dust and the analyses for crystalline silica are an important area of interest and discussion among industrial occupational hygienists in Europe. The variety of equipment for air sampling, methods and instrumentation can cause differences between results for the analysis of respirable crystalline silica (RCS). In this study, a Workplace Atmosphere Multi-sampler (WAM), developed by Adhesia, was used to compare respirable dust samplers in the workplace. This rotating device enables the comparison of 12 samplers in a workplace in each run. Seven laboratories participated in the comparison, using six different respirable dust samplers [British Cast Iron Research Association (BCIRA) to the Higgins Dewell (HD) design, Dorr Oliver, Casella SIMPEDS, SKC HD with a polycarbonate filter and polyvinylchloride filter, and the CIP10-R). Each laboratory analysed samples supplied by the samplers and reported the total respirable dust concentration and the RCS concentration. The techniques used were X-ray diffraction direct-on-filter, X-ray diffraction with deposition, infrared direct-on-filter, and infrared with potassium bromide (KBr) discs. The experiments were carried out in four different industries (enamel, sand extraction, foundry and brickworks). Generally, the SKC conductive black plastic sampler is oversampled (y = 1.52x + 0.008) and the CIP10 is undersampled (y = 0.74x + 0.068) when compared with the median air concentration. A pair-wise comparison of the different industries using t-tests indicated significant differences (P < 0.05) between the SKC conductive plastic samplers and the other samplers. The same series of statistical calculations were performed for the results obtained for RCS (quartz) and showed significant differences for the CIP10 techniques and the SKC conductive plastic cyclone analyses when using a polyvinylchloride filter.

Microtribological performance of Au–MoS2 nanocomposite and Au/MoS2 bilayer coatings

Scratch tests, reciprocating microwear, and scanning wear tests were performed on pure Au, bilayer Au/MoS2, and co-sputtered Au–MoS2 using a nanoindentation instrument in dry air. These different lubrication strategies (i.e. nanocomposite and bilayer coatings) were compared in terms of mechanical properties, friction coefficient, and wear behavior. The results were correlated to the tribofilm formation, which was analyzed using ex situ characterization of the wear track with a Scanning Electron Microscope (SEM), micro-Raman spectrometer, and an atomic force microscope (AFM). It was observed that the nanocomposite Au–MoS2 coatings increased the wear resistance compared to pure Au films, which was explained by the increase in hardness values and the decrease in surface adhesion forces. Similarly for bilayer Au/MoS2 samples, the wear resistance of the Au film was enhanced by the MoS2 top layer, which behaved as a sacrificial layer protecting the Au.

The use of variable CO2 in the data assimilation of AIRS and IASI radiances

AbstractAn important component of the assimilation of radiance observations from the AIRS and IASI satellite instruments is the radiative transfer modelling. Currently, the RTTOV model used in the ECMWF IFS system uses a fixed value for CO2. Neglecting the spatio‐temporal variability of CO2 introduces an error in the simulation of the satellite radiances, which could affect the quality of the analyses and forecasts. The current assumption is that variational bias correction corrects most of this error and therefore minimizes the impact on the forecast scores. This paper investigates the possibility of modelling CO2 within the IFS to improve the radiative transfer modelling. Results show that the required bias correction is significantly reduced when using more realistic CO2 values. The impact on the analysis quality and forecast scores is mostly neutral with some indication of improvement in the Tropics and the stratosphere.