[i] An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO 2 , 26.8 Tg NO x , 9870 Tg CO 2 , 279 Tg CO, 107 Tg CH 4 , 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH 3 . In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE-P and ACE-Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO 2 , 11.4 Tg NO x , 3820 Tg CO 2 , 116 Tg CO, 38.4 Tg CH 4 , 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH 3 . Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s x 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE-P and ACE-Asia data interpretation. During the observation period of March/ April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO 2 to a high of ±450% for OC.

An inventory of gaseous and primary aerosol emissions in Asia in the year 2000 : NASA global tropospheric experiment transport and chemical evolution over the pacific (TRACE-P): Measurements and analysis (TRACEP1)

Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast laser-induced spin dynamics, exchange bias, and microstructural effects. Here we present the key methods used in atomistic spin models which are then applied to a range of magnetic problems. We detail the parallelization strategies used which enable the routine simulation of extended systems with full atomistic resolution.

/pdf/atomistic-spin-model-simulations-of-magnetic-nanomaterials-31j7wcva63.pdf

Atomistic spin model simulations of magnetic nanomaterials.

Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth’s radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable and arguable lines of evidence, including modelling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of −1.60 to −0.65 W m−2, or −2.0 to −0.4 W m−2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted towards more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.

https://hal.archives-ouvertes.fr/hal-02322106/document

Bounding global aerosol radiative forcing of climate change

Highly chemically ordered L10 FePtX–Y nano-granular films with high perpendicular magnetic anisotropy are key media approaches for future heat-assisted magnetic recording (HAMR). They are sputtered at elevated temperature on glass disks coated with adhesion, heat sink, and texturing layers. Adding X = Ag reduces the required deposition temperature and X = Cu lowers the Curie temperature. Current seed layers are NiTa for adhesion and heat sink and well-oriented MgO (002) layers for highly textured FePtX(002) grains surrounded by Y = carbon and/or other segregants. Magnetic anisotropies larger than 4.5 × 107 erg cm−3 and coercivities beyond 5 Tesla have been achieved. The combination of thermal conductivity and Curie temperature determines the required laser power during recording. Key goals are to optimize media, heads, head-disk-spacing, and read-back channels to extend the areal density to 1.5–5 Tb in−2. 



Head and media in heat-assisted magnetic recording1. LD, laser diode; TFC, thermal fluctuation control; NFT, near field transducer. 1Lidu Huang et al., “HAMR Thermal Modeling Including Media Hot Spot”, APMRC 2012.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pssa.201329106

L10 FePtX–Y media for heat-assisted magnetic recording

This paper discusses heat-assisted magnetic recording (HAMR) media requirements and challenges for areal densities (AD) beyond 1 Tb/in2. Based on recent roadmap discussions the focus is primarily on granular chemically ordered L10 FePtX-Y-perpendicular media with reduced average grain size down to 〈D〉 = 3-5 nm relative to current CoCrPt based perpendicular magnetic recording (PMR) media with average grain size 〈D〉 = 7-9 nm. In HAMR media the combination of thermal conductivity and Curie temperature TC determines the required laser power during recording. Key challenges are sigma variations of D and TC which need to be reduced to σD/D ~ 10-15% and σTC/TC ~ 2%. In addition AD is limited by switching field distribution (SFD) and thermal spot size. The key goal going forward is to optimize heads, media, head-media-spacing (HMS) and read-back channel technologies to extend AD to 4 Tb/in2 and beyond.

A HAMR Media Technology Roadmap to an Areal Density of 4 Tb/in $^2$

We present atomistic calculations of the magnetic phase transition behavior in an L10 FePt system to study the effect of grain size distribution on the Curie temperature (Tc) dispersion with relevance to heat assisted magnetic recording. Identifying the relation between the size and Tc of a grain by means of finite size scaling analysis of the differentiated magnetization versus T data allows to show that a lognormal size distribution transforms into a lognormal Tc distribution with moments dependent on the critical exponents. We also address the question of the universality class of FePt.

/pdf/the-curie-temperature-distribution-of-fept-granular-magnetic-1wsabjgt1d.pdf

The Curie temperature distribution of FePt granular magnetic recording media

The rate of warming in the Arctic depends upon the response of low-level microphysical and radiative cloud properties to aerosols advected from distant anthropogenic and biomass-burning sources. Cloud droplet cross-section density increases with higher concentrations of cloud condensation nuclei, leading to an increase of cloud droplet absorption and scattering radiative cross-sections. The challenge of assessing the magnitude of the effect has been decoupling the aerosol impacts on clouds from how clouds change solely due to natural meteorological variability. Here we address this issue with large, multi-year satellite, meteorological, and tracer transport model datasets to show that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between two and eight times higher than has been observed elsewhere. However, a previously described response of arctic clouds to biomass-burning plumes appears to be overstated because the interactions are rare and modification of cloud radiative properties appears better explained by coincident changes in temperature, humidity, and atmospheric stability.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017GL075795

High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport

. The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol–cloud interaction (ACInet) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACInet is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACInet averages 0.12 ± 0.02 for cloud-droplet effective radius and 0.16 ± 0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds.

/pdf/effects-of-long-range-aerosol-transport-on-the-microphysical-10st351p9c.pdf

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL079873

Evidence for Changes in Arctic Cloud Phase Due to Long-Range Pollution Transport

/pdf/space-based-analysis-of-the-cloud-thermodynamic-phase-f1v1m022kd.pdf

Q. Coopman

Papers

The Curie temperature distribution of FePt granular magnetic recording media

High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

Evidence for Changes in Arctic Cloud Phase Due to Long-Range Pollution Transport

Space‐Based Analysis of the Cloud Thermodynamic Phase Transition for Varying Microphysical and Meteorological Regimes