Robust RF estimates of this potential contribution to AIC RF are missing due to lack of observational evidence and uncertainties in underlying mechanisms and their parameterisation. Mechanisms include modification of ultrafine aqueous plume aerosols during transport from cruise altitudes to lower cloud levels and pre-activation of emitted soot particles in contrails. Given the small size and the substantial fraction of organic matter in aqueous plume particles and the largely insoluble nature of exhaust soot (Box 1), particles processed in ageing aircraft plumes 114 are neither expected to be efficient liquid cloud-nucleating particles nor potent heterogeneous ice nuclei. This casts doubt on their capability to facilitate cloud water droplet or ice crystal formation in atmospheric conditions. Pre-activation refers to an increase in an aerosol particle’s freezing temperature after ice nucleation occurred. While pre-activation has been observed in laboratory settings, it is not known whether it occurs on aircraft-emitted, small (<100 nm) soot particles in the atmosphere or in contrails.
Liquid aerosol particles produced from gaseous aircraft engine emissions are influenced by fuel composition (Box 1) but are not well represented in emission inventories used to initialise global models. They must be specified to estimate the formation and evolution of ultrafine aqueous plume particles. The sulphur dioxide (SO 2) emission index in kerosene varies widely around a mean value ≈1 g (kg-fuel) −1 depending on the origin of the crude oil 4; most jet fuel has lower emissions. The fraction of SO 2 converted to condensable sulphuric acid at emission (few %) and the mass and chemical nature of emissions of condensable organic vapours are not well known. With regard to aircraft-emitted soot particles, emission inventories only provide mass-based soot emissions 115– 117—often as a single, fleet-averaged surface-level value—from which particle numbers at cruise are inferred using empirical correlations. This seriously underestimates variability in soot particle numbers in contrails at formation.
To parameterise aqueous plume particle formation and contrail ice nucleation properly in climate models, it is necessary to inform global aircraft emission inventories with additional sulphate/organics mass and soot particle number emissions. Such improved inventories better represent aviation activity and allow for more realistic simulations of the formation stage, AIC RF and effects on natural clouds by way of parameterisation.
Radiative transfer parameterisations commonly used in climate models are designed to represent effects of natural cirrus that are composed of ice crystals, whose mean maximum dimensions hardly fall below 10 µm. In dense flight corridors, AIC might on average be composed of such small ice crystals 17, 118. As neither geometric optics nor Mie theory accurately describe such cases, other optical models might be employed to provide more realistic parameterisations of ice crystal scattering properties in contrails and contrail cirrus. Shapes of small ice crystals are largely unconstrained by direct observations (Box 2), constituting a significant drawback in applying advanced optical parameterisations. Before being implemented in global models, such parameterisations might be tested in regional models providing more detailed information on ice crystal size and habit distributions. This better constrains SW radiative transfer calculations and helps improve estimates of AIC RF and climate sensitivity.
Solar radiation fluxes declined from the 1950s to 1980s and partially recovered since mid-1980s 119. A statistically significant increase in broadband (wavelength-integrated) SW radiation at the Earth’s surface in cloudless scenes has been observed at several locations across the continental U.S.A. in the period 1996–2007 (ref. 120). The observed trend was almost entirely due to an increase in the diffuse irradiance, while the direct component remained virtually unchanged, ruling out a concomitant decrease in atmospheric aerosol OD as the sole cause of the increase. Recent analyses using diffuse SW spectral measurements 121 confirmed this trend coined as ‘clear-sky whitening’. Ref. 121 hypothesised that while a decreased aerosol load did increase the total SW irradiance, an increase in subvisible contrail-generated ice crystal ‘haze’ repartitioned this increase from the direct into the diffuse component. Formation and spreading stage processes including radiative effects of small ice crystals must be understood well to explore this plausible hypothesis.
On the one hand, instrumental challenges pose significant limitations in measurements of microphysical and optical properties of contrail cirrus. This heightens the role of models (Table 2) in providing RF estimates. On the other hand, improved scientific understanding is required before embarking on parameterisation.
Challenges in modelling radiative forcing due to aircraft-induced clouds
| Model scale | Spatial resolution | Contrail stages | Major challenges | Approach/solution | |
|---|---|---|---|---|---|
| Horizontal | Vertical | ||||
| Local | <10 m | <10 m | Formation stage | Ice crystal number and size distribution | Turbulence–microphysics coupling |
| Regional | <1000 m | <100 m | Spreading stage | Radiative flux changes and interaction with natural clouds | Contrail to contrail cirrus transition |
| Global | <100 km | <1 km | Full life cycle | Ice crystal formation and ice supersaturation | Parameterisation and high resolution |
Improvements in a hierarchy of local- to global-scale models to be realised in conjunction with observations providing data for cloud and radiation parameterisation development and overall model validation
Local scale process and fluid-dynamical models systematically explore how plume turbulence and wake dynamics affects nucleation and properties of contrail ice crystals (Fig. 2) and how predictions of nucleated ice numbers (Fig. 3) and sublimation losses (Fig. 4) relate to aircraft measurements. Cloud-resolving and regional models—driven with appropriate meteorological boundary conditions and combined with optical parameterisations capturing the SW response of µm-sized ice crystals—analyse large atmospheric regions based on collocated aircraft and satellite measurements to better judge AIC RF and the radiative significance of natural cirrus perturbed by contrails. These models capture variability in ice supersaturation and are employed to drive LES to gain more detailed understanding of the contrail-to-contrail cirrus transition. Global models use information regarding properties of thin ice supersaturated layers (Fig. 5) derived from high-resolution simulations or radiosonde data 122 to improve their representation of AIC supporting areas 50. They also use parameterisations of formation stage processes to initialise AIC properties and rely on progress in simulating the formation of natural cirrus more realistically 61.
Global models represent much of the system complexity, but account for processes and their variability affecting RF only to a degree, depending on the model’s representation of clouds. They track atmospheric motion and clouds with ≈10 min time steps and represent them with coarse spatial resolution. This means that formation and effects of clouds must be parameterised. Cloud microphysical and optical variables evolve on unresolved temporal and spatial scales. The connection of unresolved processes to resolved (large-scale) model variables is not always obvious. With higher resolution, fewer parameterisations are required. The prospect to perform in the near-term global studies that resolve explicitly the regional scales crucial for AIC development 123 is very promising. More aircraft travelling in the same regions may not necessarily lead to more AIC coverage due to overlap effects and merging with natural cirrus, thus limiting increases in RF for higher air traffic volume. Moreover, AIC and natural cirrus do not evolve independently 6, 49. A new generation of high-resolution global models explores such effects in the spreading stage with increased confidence.
Improving and validating AIC in global models requires an integrative analysis framework that unravels crucial cloud-controlling factors and conditions. Propitious weather conditions leading to large radiative impact of contrail outbreaks are tied to synoptic-scale, enhanced moisture transport and uplift (cooling), in which moderately high ice supersaturation at the same time minimises sedimentation losses and maximises OD by generating ice crystals within an optimal size range 31, reminiscent of the ‘Goldilocks principle’. A suitable framework combines aircraft and active remote sensing observations and local and regional models to study characteristics of and linkages between individual processes (bottom-up) with passive remote sensing observations, and global models to explore large-scale constraints arising from the coupled dynamics-aerosol-cloud-radiation system (top–down).
Methodologies combining estimates of contrail coverage from meteorological reanalysis data and mean contrail OD in off-line radiative transfer models and used to diagnose global contrail RF in climate models have been replaced by simulations of AIC within global models 62. Adding or elaborating on processes may be required to improve on specific problems. However, this would expand the space of underlying model parameters, possibly compromising the robustness of the models’ predictive capability and the goal of reducing overall model uncertainty 124. Parameterisation schemes used in such models should therefore be informed by theory, whereby it is important to capture the most influential processes governing a specific application, and document the physical soundness and plausibility of the scheme. Understanding how well global climate models work for a specific purpose (evaluation) is important, but in itself is not a straightforward task. At times the disagreement of a model with observations motivates model improvements.
Another important task in support of model improvement is ascertaining its “truth” (validation), e.g., by comparison with suitable measurements. In models with many compensating uncertainties, several pathways of process representation conforming to the same set of underlying physical laws may lead to similar plausible agreement with observations. Just because models agree with some measurements does not imply reduced uncertainty in their RF predictions. In view of the case study nature of many measurements, observationalists and modellers should aspire to clarify if and exactly how measurements can be used to validate models and constrain uncertainty. Introducing microphysical mechanisms in cloud parameterisations without critical analysis, theoretical underpinning or support by empirical evidence increases the likelihood of model fallacies. Unexamined process representation carries the danger of proliferating unsubstantiated conclusions. The resulting enhanced uncertainty levels are difficult to judge and may be irreducible.
Lack of rigorous model evaluation and validation has serious repercussions for the interpretation of model results. A way out could be to devise models based on a minimal set of processes with only a few open physical parameters and expounding meaningful ways of how model behaviour could be confirmed or falsified. Complexity would be added only when needed, fulfilling a methodological principle known as ‘Ockham’s razor’. To minimise AIC model uncertainty, ice cloud parameterisations should conform to a number of tenets: full inclusion of AIC into the model’s hydrological cycle, as cloud-induced changes in the moisture and heat budget cause feedbacks on natural cloudiness; consideration of vertical overlap between AIC and natural clouds, as cloud overlap statistic has a profound impact on overall fractional cloud coverage within a model grid box and on net RF; realistic representation of AIC within the model’s radiation scheme, as optical properties differ from those of natural cirrus; and abandonment of instantaneous conversion of water vapour above ice saturation into cloud ice (and the reverse process below ice saturation), as ice crystal growth and sublimation can be kinetically hindered in thin or aged contrail cirrus; moreover, the kinetic treatment of water vapour uptake involving size-dispersed populations of disparate ice nuclei is a perquisite for the proper treatment of ice nucleation in models. Implementing these improvements will also lead to better simulations of natural cirrus.
Commercial aircraft are in service for 20–30 years meaning that adoption of new technologies from research to integration takes many decades. Therefore, in addition to scientific challenges, the implementation of AIC mitigation options also faces engineering and economical hurdles and will only be realised when disruptive change in the air transportation system can be avoided. Accomodating the expected growth in air travel while reducing the impact of AIC RF may require a combination of options.
The International Civil Aviation Organization (ICAO) agreed upon a carbon offsetting and reduction scheme for global aviation 125, but does not explicitly address AIC in their environmental protection activities. Integrating AIC in these activities would constitute an important stepping stone in support of widespread implementation of AIC mitigation options. The use of biofuels has already been initiated by the aviation industry in the necessary transition away from fossil-based fuels. Besides implementing a standard for carbon neutral growth, ICAO has also developed certified testing procedures applying from 2020 for particulate emissions from aircraft engines based on particle mass and number 125. This action facilitates the realisation of mitigation solutions addressing formation stage (emission-related) processes and holds promise to reduce AIC effects on climate on short time scales 96. With regard to the spreading stage, while an interim strategy has been conceived 126, ATM is considered to offer a potential long-term solution as meteorological forecast skills mature and if ATM proves to be flexible enough to allocate climate-compatible flight routes quickly and safely.
Compelling evidence has been presented as to the urgency to prevent human activities from causing unacceptable environmental change 127. Studying climate change in response to AIC involves basic scientific challenges and is important to address in the larger context of how anthropogenic activities affect natural cirrus clouds and climate 61. Better understanding the radiative response of contrail cirrus as it emerges from coupled meteorological and microphysical controls requires an integrative approach aiming at understanding on the process level at small scales and at the same time be cognisant of interactions that operate on large scales.


Web Audio MOS 6581 SID simulation
This is a Web Audio simulation of my software for the HardSID card. Every button or slider on this interface (except the Start / Stop button) corresponds to a button or knob on the Behringer BCR2000 MIDI control surface which is used to control the SID sounds. In the HardSID version, the pitch and duration of the note can be controlled using a MIDI keyboard or sequencer.
Some differences exist between the capabilities of the Web Audio software synthesizer and the MOS 6581 digital/analogue hardware synthesizer. Rather than emulate SID exactly, this simulation allows some Web Audio characteristics to be explored, and also reveals differences between browser implementations (Chrome and Firefox).
Filter cutoff may be varied between 20 Hz - 20 kHz. Resonance may be varied up to 1000, which is an enormous value for any hardware resonant filter. This will distort the output of the Web Audio simulation, so to reduce the final output gain a Volume slider is provided (equivalent to register $18 in the SID). Filter modes are low pass, band pass, high pass, notch and all pass in the Web Audio simulation and the oscillator waveforms available are sine, triangle, sawtooth, square and pulse.
Here is some text
Cutoff Resonance Filter mode Volume
Oscillator one Coarse tune Fine tune Waveform Pulse width Attack Decay Sustain Release
Oscillator two Coarse tune Fine tune Waveform Pulse width Attack Decay Sustain Release
Oscillator three Coarse tune Fine tune Waveform Pulse width Attack Decay Sustain Release


npm
JavaScript and Node.js package manager.
Manage Node.js projects and their module dependencies.
More information: home page
- Interactively create a `package.json` file:
npm init
- Download all the packages listed as dependencies in package.json:
npm install
- Download a specific version of a package and add it to the list of dependencies in `package.json`:
npm install module_name@version
- Download a package and add it to the list of dev dependencies in `package.json`:
npm install module_name --save-dev
- Download a package and install it globally:
npm install --global module_name
- Uninstall a package and remove it from the list of dependencies in `package.json`:
npm uninstall module_name
- Print a tree of locally installed dependencies:
npm list
- List top-level globally installed modules:
npm list --global --depth=0


Arkham LCG: Betrayal at the Mountains of Madness
Arkham LCG: Call of the Plaguebearer
Arkham LCG: Cyclopean Foundations
Drafonfire
Folklore
Middara
Starwars : Imperial Assault
Sword & Sorcery : Darkness Falls


Jonathan Reeve
Literary Modeling and Visualization Lab
Group for Experimental Methods in the Humanities
Columbia University
Consider these near-synonyms:
life, light, world, woman, new, great, consciousness, live, eye, knowledge, long
life, Paris, old, live, time, sit, key, soul, prayer, consciousness, belief, marriage
Novels set in Paris, or London?
morning, early, breakfast, afternoon, summer, autumn, winter, sunday, weather, october, arrival, june, september, saturday, awoke, situated, november, july, season, december
replied, retorted, inquired, doesn’t, haven’t, mustn’t, shouldn’t, wid, fer, wi, em, yer, protested, nothin
kissed, farewell, bye, muttered, parted, disappeared, sank, page, asleep, strode, chapter, kiss, withdrew, homeward, sobbing, thanked, wept, murmured, prayed


Single-cell RNA-seq can be used to infer copy number variations. Below, four brain cancer samples show large deletions in chr1p and chr19q, among other cytogenetic abnormalities.
This prototype reproduces a study in Single Cell Portal using inferCNV workflow output as run on Terra. Visualizations use Ideogram.js.


Select File from MenuBar or
Press / from any GIN Mode.
This displays the File Menu:
New
Open Open the file for Read-Write
Save Saves without closing.
SaveAs Copy and continue on copy.
Close Save and close.
Drawing Setup Sheet display setup: Pen color, Layer status, Tracing status
Maintenance
Import
Export
Print Output hardcopy
Plot
Recent
Recover
Run Execute an external program
Exit Quit


---
layout: page
title: "About"
description: "Hey, this is Shengwen."
header-img: "img/about-bg.jpg"
---
A good programmer always looks both ways before crossing a one-way street.
About me
- I'm a software developer
- Master's degree in Computer Engineering from Drexel University
- 3 years of professional experience, actively involved in all stages of SDLC including requirement analysis, design, development, implementation, maintenance and testing
- Extensive experience in developing web applications using .NET Framework, ASP.NET, ASP.NET MVC, ADO.NET and Java EE technologies
- Hands on experience in front-end design using HTML 4.0/5, CSS 3, XML, jQuery and AJAX
- Proficient on database design and developing SQL, Stored Procedures, Functions and Triggers on relational databases, and implementing persistent layer with ORM frameworks like EF and NHibernate
- Solid knowledge in Object-Oriented Programming, Data structures, Algorithms, Computer Networking Protocols and Design Patterns like MVC, Factory and DAO
- A self starter with a result-driven attitude
Skills
- .NET Technologies: ASP.NET 4, ASP.NET MVC 4/5, ADO.NET, Entity Framework, Web API
- Languages: C#, Java, C/C++, JavaScript, Perl, Shell Scripting
- Web: HTML5, CSS3, Bootstrap, jQuery, XML, JASON
- Databases: SQL Server, MySQL, Oracle, MS Access
Hobbies
Your work is going to fill a large part of your life, and the only way to be truly satisfied is to do what you believe is great work. And the only way to do great work is to love what you do. If you haven’t found it yet, keep looking. Don’t settle. As with all matters of the heart, you’ll know when you find it.
If you want to live your life in a creative way, as an artist, you have to not look back too much. You have to be willing to take whatever you’ve done and whoever you were and throw them away.
-- Steve Jobs
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