Development of a Multilayer MODIS IST-Albedo Product of Greenland

A new multilayer IST-albedo Moderate Resolution Imaging Spectroradiometer (MODIS) product of Greenland was developed to meet the needs of the ice sheet modeling community. The multiple layers of the product enable the relationship between IST and albedo to be evaluated easily. Surface temperature is a fundamental input for dynamical ice sheet models because it is a component of the ice sheet radiation budget and mass balance. Albedo influences absorption of incoming solar radiation. The daily product will combine the existing standard MODIS Collection-6 ice-surface temperature, derived melt maps, snow albedo and water vapor products. The new product is available in a polar stereographic projection in NetCDF format. The product will ultimately extend from March 2000 through the end of 2017

An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020)

The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface ice slabs in the firn. Understanding how firn properties respond to climate is important for constraining the GrIS's future contribution to sea level rise in a warming climate. Observations of firn density provide detailed information about firn properties, but they are spatially and temporally limited. Here we use two firn models, the physics-based SNOWPACK model and the Community Firn Model configured with a semi-empirical densification equation (CFM-GSFC), to quantify firn properties across the GrIS from 1980 through 2020. We use an identical forcing (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) atmospheric reanalysis) for SNOWPACK and the CFM-GSFC in order to isolate firn model differences. To evaluate the models, we compare simulated firn properties, including firn air content (FAC), to measurements from the Surface Mass Balance and Snow on Sea Ice Working Group (SUMup) dataset of snow and firn density. Both models perform well (mean absolute percentage errors of 14 % in SNOWPACK and 16 % in the CFM-GSFC), though their performance is hindered by the spatial resolution of the atmospheric forcing. In the ice-sheet-wide simulations, the 1980–1995 average spatially integrated FAC (i.e., air volume in the firn) for the upper 100 m is 34 645 km3 from SNOWPACK and 28 581 km3 from the CFM-GSFC. The discrepancy in the magnitude of the modeled FAC stems from differences in densification with depth and variations in the sensitivity of the models to atmospheric forcing. In more recent years (2005–2020), both models simulate substantial depletion of pore space. During this period, the spatially integrated FAC across the entire GrIS decreases by 3.2 % (−66.6 km3 yr−1) in SNOWPACK and 1.5 % (−17.4 km3 yr−1) in the CFM-GSFC. These differing magnitudes demonstrate how model differences propagate throughout the FAC record. Over the full modeled record (1980–2020), SNOWPACK simulates a loss of pore space equivalent to 3 mm of sea level rise buffering, while the CFM-GSFC simulates a loss of 1 mm. The greatest depletion in FAC is along the margins and especially along the western margin where observations and models show the formation of near-surface, low-permeability ice slabs that may inhibit meltwater storage.</p

Increased snowfall over the Antarctic Ice Sheet mitigated twentieth-century sea-level rise

Changes in accumulated snowfall over the Antarctic Ice Sheet have an immediate and time-delayed impact on global mean sea level. The immediate impact is due to the instantaneous change in freshwater storage over the ice sheet, whereas the time-delayed impact acts in opposition through enhanced ice-dynamic flux into the ocean1. Here, we reconstruct 200 years of Antarctic-wide snow accumulation by synthesizing a newly compiled database of ice core records2 using reanalysis-derived spatial coherence patterns. The results reveal that increased snow accumulation mitigated twentieth-century sea-level rise by ~10 mm since 1901, with rates increasing from 1.1 mm decade−1 between 1901 and 2000 to 2.5 mm decade−1 after 1979. Reconstructed accumulation trends are highly variable in both sign and magnitude at the regional scale, and linked to the trend towards a positive Southern Annular Mode since 19573. Because the observed Southern Annular Mode trend is accompanied by a decrease in Antarctic Ice Sheet accumulation, changes in the strength and location of the circumpolar westerlies cannot explain the reconstructed increase, which may instead be related to stratospheric ozone depletion4. However, our results indicate that a warming atmosphere cannot be excluded as a dominant force in the underlying increase

Cooling in strongly correlated optical lattices: prospects and challenges

Optical lattices have emerged as ideal simulators for Hubbard models of strongly correlated materials, such as the high-temperature superconducting cuprates. In optical lattice experiments, microscopic parameters such as the interaction strength between particles are well known and easily tunable. Unfortunately, this benefit of using optical lattices to study Hubbard models come with one clear disadvantage: the energy scales in atomic systems are typically nanoKelvin compared with Kelvin in solids, with a correspondingly miniscule temperature scale required to observe exotic phases such as d-wave superconductivity. The ultra-low temperatures necessary to reach the regime in which optical lattice simulation can have an impact-the domain in which our theoretical understanding fails-have been a barrier to progress in this field. To move forward, a concerted effort to develop new techniques for cooling and, by extension, techniques to measure even lower temperatures. This article will be devoted to discussing the concepts of cooling and thermometry, fundamental sources of heat in optical lattice experiments, and a review of proposed and implemented thermometry and cooling techniques.Comment: in review with Reports on Progress in Physic

Особливості урбаністичного хронотопу в поезіях літугруповання “Бу-Ба-Бу”

Стаття присвячена дослідженню особливостей урбаністичного хронотопу в поезіях Ю. Андруховича, О. Ірванця, В. Неборака. Встановлено, що характерними модифікаціями урбаністичного хронотопу у творчості Ю. Андруховича є топографічний хронотоп із домінантами Львова й Станіслава та карнавалізоване Місто; у поезіях В. Неборака варіації урбаністичного хронотопу створюються за допомогою використання традиційних атрибутів міста, а також власне міських прошарків населення; урбаністичний хронотоп у поезіях О. Ірванця є найменше матеріалізованим і тяжіє до психологічно-метафізичного. Ключові слова: часопростір, хронотоп, топос, урбанізм, карнавалізація.Статья посвящена изучению особенностей урбанистического хронотопа в поэзиях Ю. Андруховича, А. Ирванца, В. Неборака. Так, в творчестве Ю. Андруховича были выявлены такие модификации урбанистического хронотопа, как топографический с доминантами Львова и Станислава и карнавальный Город; в поэзиях В. Неборака вариации урбанистического хронотопа осуществляются при помощи использования традиционных атрибутов города, а также собственно городских слоев населения; урбанистический хронотоп поэзий А. Ирванца наименее материализован и тяготеет к психологически-метафизическому. Ключевые слова: пространственно-временное единство, хронотоп, топос, урбанистичность, карнавальность.The article is dedicated to the study of the urbanism chronotope’s particularities in Yu. Andruhovicha, A. Irvanca, V. Neboraka poetry. So in Yu. Andruhovich’s work. Such modification urbanism chronotope as topographical one with the Livov and Stanislav’s dominant and the carnival one. In V. Neboraka’s variations of urbanism chronotope are realized using the traditional city attributes and town population layers as well. A. Irvanc’s poetry urbanism chronotope is less materialired and strongly attracted by psychological-metaphysical one. Keywords: space-time unity, chronotope, urbanism, carnivalization

Power to participants: methodological and ethical reflections from a decade of adolescent advisory groups in South Africa

Whilst the HIV response has made significant progress in increasing representation of adults affected by HIV, the meaningful inclusion of children and adolescents has lagged. But this may be a pivotal moment of change. We report on a decade of conducting adolescent advisory groups in South Africa, to reflect on youth advisory processes. Data was collected from 2008 to 2018 from adolescent advisors (n = 60) and researchers (n = 25), and included feedback sessions, social media, anonymous “post-boxes” and interviews. Findings include the value of adolescent involvement in multiple stages of research co-creation and engagement in policy processes, the need for a safe environment and supporting adolescents living in extreme vulnerability. We also discuss the reconfiguring of power and personal relationships, and logistical and financial needs of adolescent advisory groups. Findings suggest that adolescent co-creation of research is feasible, even with very vulnerable adolescents, although ethical considerations need to be carefully addressed. Benefits include increased methodological rigour, enhanced adolescent acceptability of research and the recalibration of research dynamics for the empowerment of their target beneficiaries. Future studies could benefit from meaningfully involving adolescents through youth advisory groups

Listening to health workers: lessons from Eastern Uganda for strengthening the programme for the prevention of mother-to-child transmission of HIV

<p>Abstract</p> <p>Background</p> <p>The implementation and utilization of programmes for the prevention of mother-to-child transmission (PMTCT) of HIV in most low income countries has been described as sub-optimal. As planners and service providers, the views of health workers are important in generating priorities to improve the effectiveness of the PMTCT programme in Uganda. We explored the lessons learnt by health workers involved in the provision of PMTCT services in eastern Uganda to better understand what more needs to be done to strengthen the PMTCT programme.</p> <p>Methods</p> <p>A qualitative study was conducted at Mbale Regional Referral Hospital, The AIDS Support Organisation (TASO) Mbale and at eight neighbouring health centres in eastern Uganda, between January and May 2010. Data were collected through 24 individual interviews with the health workers involved in the PMTCT programme and four key informants (2 district officials and 2 officials from TASO). Data were analyzed using the content thematic approach. Study themes and sub-themes were identified following multiple reading of interview transcripts. Relevant quotations have been used in the presentation of study findings.</p> <p>Results</p> <p>The key lessons for programme improvement were: ensuring constant availability of critical PMTCT supplies, such as HIV testing kits, antiretroviral drugs (ARVs) for mothers and their babies, regular in-service training of health workers to keep them abreast with the rapidly changing knowledge and guidelines for PMTCT, ensuring that lower level health centres provide maternity services and ARVs for women in the PMTCT programme and provision of adequate facilities for effective follow-up and support for mothers.</p> <p>Conclusions</p> <p>The voices of health workers in this study revealed that it is imperative for government, civil society organizations and donors that the PMTCT programme addresses the challenges of shortage of critical PMTCT supplies, continuous health worker training and follow-up and support for mothers as urgent needs to strengthen the PMTCT programme.</p