Cloud top height (CTH) affects the radiative properties of clouds. Improved CTH observations will allow for improved parameterizations in large-scale models and accurate information on CTH is also ...important when studying variations in freezing point and cloud microphysics. NASAs airborne Research Scanning Polarimeter (RSP) is able to measure cloud top height using a novel multi-angular contrast approach. For the determination of CTH, a set of consecutive nadir reflectances is selected and the cross-correlations between this set and co-located sets at other viewing angles are calculated for a range of assumed cloud top heights, yielding a correlation profile. Under the assumption that cloud reflectances are isotropic, local peaks in the correlation profile indicate cloud layers. This technique can be applied to every RSP footprint and we demonstrate that detection of multiple peaks in the correlation profile allow retrieval of heights of multiple cloud layers within single RSP footprints. This paper provides an in-depth description of the architecture and performance of the RSPs CTH retrieval technique using data obtained during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC(exp. 4)RS) campaign. RSP retrieved cloud heights are evaluated using collocated data from the Cloud Physics Lidar (CPL). The method's accuracy associated with the magnitude of correlation, optical thickness, cloud thickness and cloud height are explored. The technique is applied to measurements at a wavelength of 670 nm and 1880 nm and their combination. The 1880-nm band is virtually insensitive to the lower troposphere due to strong water vapor absorption.
The Twomey effect describes the radiative forcing associated with a change in cloud albedo due to an increase in anthropogenic aerosol emissions. It is driven by the perturbation in cloud droplet ...number concentration (ΔNd, ant) in liquid-water clouds and is currently understood to exert a cooling effect on climate. The Twomey effect is the key driver in the effective radiative forcing due to aerosol–cloud interactions, but rapid adjustments also contribute. These adjustments are essentially the responses of cloud fraction and liquid water path to ΔNd, ant and thus scale approximately with it. While the fundamental physics of the influence of added aerosol particles on the droplet concentration (Nd) is well described by established theory at the particle scale (micrometres), how this relationship is expressed at the large-scale (hundreds of kilometres) perturbation, ΔNd, ant, remains uncertain. The discrepancy between process understanding at particle scale and insufficient quantification at the climate-relevant large scale is caused by co-variability of aerosol particles and updraught velocity and by droplet sink processes. These operate at scales on the order of tens of metres at which only localised observations are available and at which no approach yet exists to quantify the anthropogenic perturbation. Different atmospheric models suggest diverse magnitudes of the Twomey effect even when applying the same anthropogenic aerosol emission perturbation. Thus, observational data are needed to quantify and constrain the Twomey effect. At the global scale, this means satellite data. There are four key uncertainties in determining ΔNd, ant, namely the quantification of (i) the cloud-active aerosol – the cloud condensation nuclei (CCN) concentrations at or above cloud base, (ii) Nd, (iii) the statistical approach for inferring the sensitivity of Nd to aerosol particles from the satellite data and (iv) uncertainty in the anthropogenic perturbation to CCN concentrations, which is not easily accessible from observational data. This review discusses deficiencies of current approaches for the different aspects of the problem and proposes several ways forward: in terms of CCN, retrievals of optical quantities such as aerosol optical depth suffer from a lack of vertical resolution, size and hygroscopicity information, non-direct relation to the concentration of aerosols, difficulty to quantify it within or below clouds, and the problem of insufficient sensitivity at low concentrations, in addition to retrieval errors. A future path forward can include utilising co-located polarimeter and lidar instruments, ideally including high-spectral-resolution lidar capability at two wavelengths to maximise vertically resolved size distribution information content. In terms of Nd, a key problem is the lack of operational retrievals of this quantity and the inaccuracy of the retrieval especially in broken-cloud regimes. As for the Nd-to-CCN sensitivity, key issues are the updraught distributions and the role of Nd sink processes, for which empirical assessments for specific cloud regimes are currently the best solutions. These considerations point to the conclusion that past studies using existing approaches have likely underestimated the true sensitivity and, thus, the radiative forcing due to the Twomey effect.
A longstanding source of uncertainty within the climate system is our understanding of clouds and their response to aerosols. The resulting cloud optical property changes constitute the largest ...uncertainty in our understanding of 20th century climate change. Central to being able to monitor and better understand the effects aerosols composition, size and concentration have on cloud reflectivity are accurate observations of the cloud droplet number concentration. Cloud droplet number concentrations couple aerosol properties to changes in cloud brightness. In the first portion of this dissertation, I present the development and evaluation of two techniques for observing cloud properties. The first is a new method of observing cloud droplet number concentration that uses polarimetric measurements and requires relatively few assumptions. The theoretical derivation is first presented followed by a method of implementation using NASA’s airborne Research Scanning Polarimeter (RSP). I use data obtained during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). Comparing cloud droplet number concentration retrievals with in situ measurements made by a cloud droplet probe during NAAMES shows strong agreement between measurements over a range of meteorological conditions and cloud types. Multilayered clouds are ubiquitous within Earth’s atmosphere, yet detecting their presence and height has been a longstanding challenge for passive remote sensing instruments. Retrieving the cloud top height is also an important part of the droplet concentration retrieval, and detecting the presence of multilayered clouds supports interpreting results. For this second technique, I present an assessment of RSP cloud top height retrievals, which are based on the concept of parallax. By comparing RSP cloud top height retrievals to the Cloud Physics Lidar (CPL), the technique is found to be capable of determining the presence and heights of up to three cloud layers, which is innovative for a passive remote sensing instrument. A second element essential to addressing the uncertainty in cloud’s response to aerosols is to better understand processes and drivers of cloud properties. Air-campaign studies offer opportunities to study high temporal and spatial resolution measurements that are needed to better understand the complex processes between aerosols, clouds and meteorological properties. My final investigation uses the two developed cloud property retrievals, in conjunction with other in situ and remotely sensed data, to undertake a broad investigation quantifying connections observed between aerosols, clouds and meteorology. I find a well- defined link between cloud microphysical property changes and marine biogenic aerosol concentrations. Changes in cloud properties are consistent with the Twomey effect, whereby an increase in cloud condensation nuclei is associated with increases in droplet concentrations and decreased droplet sizes. I also observe complex, non-linear secondary effects of aerosols on clouds such as cloud thinning and decreased droplet distribution width. I conclude this study by integrating my findings and discussing plausible linkages between aerosol, cloud and meteorological properties within the context of existing concepts.
The NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) produced a unique dataset for research into aerosol–cloud–meteorology interactions, with applications ...extending from process-based studies to multi-scale model intercomparison and improvement as well as to remote-sensing algorithm assessments and advancements. ACTIVATE used two NASA Langley Research Center aircraft, a HU-25 Falcon and King Air, to conduct systematic and spatially coordinated flights over the northwest Atlantic Ocean, resulting in 162 joint flights and 17 other single-aircraft flights between 2020 and 2022 across all seasons. Data cover 574 and 592 cumulative flights hours for the HU-25 Falcon and King Air, respectively. The HU-25 Falcon conducted profiling at different level legs below, in, and just above boundary layer clouds (< 3 km) and obtained in situ measurements of trace gases, aerosol particles, clouds, and atmospheric state parameters. Under cloud-free conditions, the HU-25 Falcon similarly conducted profiling at different level legs within and immediately above the boundary layer. The King Air (the high-flying aircraft) flew at approximately ∼ 9 km and conducted remote sensing with a lidar and polarimeter while also launching dropsondes (785 in total). Collectively, simultaneous data from both aircraft help to characterize the same vertical column of the atmosphere. In addition to individual instrument files, data from the HU-25 Falcon aircraft are combined into “merge files” on the publicly available data archive that are created at different time resolutions of interest (e.g., 1, 5, 10, 15, 30, 60 s, or matching an individual data product's start and stop times). This paper describes the ACTIVATE flight strategy, instrument and complementary dataset products, data access and usage details, and data application notes. The data are publicly accessible through https://doi.org/10.5067/SUBORBITAL/ACTIVATE/DATA001 (ACTIVATE Science Team, 2020).
Purpose. The aim of the current investigation was to examine the effects of different footwear on the kinetics and kinematics of performing a 180° cutting manoeuvre.
Methods. Nine male participants ...performed maximal 180° cut movements in court shoes, minimalist footwear, energy return, and conventional running shoes. Lower limb kinematic data were collected with the use of an 8 camera motion capture system, ground reaction forces were quantified with an embedded force platform, and tibial accelerations were obtained by means of an accelerometer. Differences in kinetics and kinematics between footwear were examined by one-way repeated measures ANOVA.
Results. The results showed that both instantaneous loading rate and peak tibial acceleration were significantly larger in the minimalist (282.91 BW/s and 6.38 g) and court (326.67 BW/s and 6.35 g) footwear compared with the conventional (143.19 BW/s and 5.46 g) and energy return (106.14 BW/s and 4.98 g) footwear. In addition, peak inversion was revealed to be significantly larger in the minimalist (16.36°) than in conventional (11.86°), court (12.61°), and energy return (10.12°) footwear.
Conclusions. These findings indicate that minimalist and court footwear may place athletes at increased risk from injury when performing 180° cut movements.
Path analysis was used to test a model designed to encapsulate the flow of influences theorized to exist between five types of musical performance and four factors derived from a ...researcher-administered questionnaire. Results, using a sample of 101 high school wind instrumentalists, reveal major differences in the pattern of influences leading to the re-creative skill of performing a repertoire of rehearsed music for a formal music examination, compared to the creative ability of improvising. Performing a repertoire of rehearsed music was found to be influenced most by an ability to sight-read, together with a factor consisting of variables concerned with the length of time a subject had been studying his or her instrument and taking lessons. In sharp contrast, an ability to improvise was most markedly influenced by an ability to play by ear. Results for this sample of instrumentalists exposed to a "traditional" style of teaching also suggest that instrumentalists' ability to sight-read may be influenced by how well they are able to play by ear.
We describe the development of a waveguide Fourier-transform spectrometer for space-borne high-resolution sensing. A prototype device is designed to monitor the water vapor absorption band near ...1,364 nm with a resolution of 0.05 nm. It has no moving parts and is based on a unique concept of arrayed interferometers implemented in silicon-on-insulator planar waveguide chip. The optical input is formed by many independent waveguides, providing a significantly increased light gathering capability (étendue) compared to single-waveguide input configurations. Enhancements of the spectrometer capabilities are achieved by stacking planar waveguide layers and by using surface gratings to couple light into the waveguides.
To estimate the effectiveness of a new high-performance Australian medical sheepskin (meeting Australian Standard 4480.1-1998) in preventing pressure ulcers in a general hospital population at low to ...moderate risk of these ulcers.
Open-label randomised controlled clinical trial.
A large metropolitan teaching hospital in Melbourne, Victoria, in 2000.
441 patients aged over 18 years admitted between 12 June and 30 November 2000, with expected length of stay over 2 days and assessed as at low to moderate risk of developing pressure ulcers.
Patients were randomly allocated to receive a sheepskin mattress overlay for the duration of their hospital stay (218 patients) or usual treatment, as determined by ward staff (referent group, 223 patients).
Incidence rate and cumulative incidence of pressure ulcers, assessed daily throughout hospital stay.
58 patients developed pressure ulcers (sheepskin group, 21; referent group, 37). Cumulative incidence risk was 9.6% in the sheepskin group (95% CI, 6.1%-14.3%) versus 16.6% in the referent group (95% CI, 12.0%-22.1%). Patients in the sheepskin group developed new pressure ulcers at a rate less than half that of referent patients (rate ratio, 0.42; 95% CI, 0.26-0.67).
The Australian Medical Sheepskin is effective in reducing the incidence of pressure ulcers in general hospital inpatients at low to moderate risk of these ulcers.
Over the past decade, the depth and breadth of catalyst technologies for addition polymerization have expanded tremendously, both for Ziegler‐Natta catalysts as well as for single‐site catalysts. It ...seems that every day someone adds a new element to this understanding, opening up new or improved ways to make specific polymers with targeted characteristics and performance.
Combinatorial techniques are accelerating this process of discovery even further, perhaps by one order of magnitude. Synergistic interactions between catalyst technologies and production process technologies are resulting in step‐change increases in manufacturing efficiency and in product range capabilities. The net result is that the industry and its scientists seem to have perfected the process of creating potential value at a tremendous rate.
The critical challenge now facing the industry is how to realize this potential value: how to connect the technology to the market. In this, speed is of the essence. Until the connection is made, the commercial value of the technology is nothing more than intangible “potential”. Meanwhile, the patents are aging and competitors lurk around the corner to steal the potential before the developer has the chance to reap his just rewards. Fortunately, technology‐leading companies are developing new efficient and fast business processes to speed products to market, and the full value of new technologies is being realized.
Fifteen families of SSC‐based polymers have been developed over the past decade; 12 of these are already commercial, and 3 are approaching commercialization. Of these fifteen, 11 are totally new to the industry, and 4 are new versions of established families (HDPE, LLDPE,PP, EPDM). The industry required 25 years to commercialize the first 4 families, and an additional 20 to fully develop markets for them. How will it deal with the introduction of three times as many new families in one third of the time, while concurrently developing the new SSC‐based versions of traditional polymers? How soon will the potential created by technological innovation be translated into tangible value? Some projections are given.
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