Surface energy balance on the Antarctic plateau as measured with an automatic weather station during 2014

AWS data during 2014 collected at PANDA-N station, on the East Antarctica Plateau, are analysed. Net Short Wave Radiation (QSWR), net Long Wave Radiation (QLWR), sensible (QH), latent (QL) and subsurface or ground (QG) heat fluxes are computed. Annual averages for QSWR, QLWR, QH, QL and QG of 19.65, −49.16, 26.40, −0.77 and 3.86 W·m−2 were derived based on an albedo value of 0.8. QSWR and QH are the major sources of heat gain to the surface and QLWR is the major component of heat loss from the surface. An iterative method is used to estimate surface temperature in this paper; surface temperature of snow/ice is gradually increased or decreased, thereby changing longwave radiation, sensible, latent and subsurface heat fluxes, so that the net energy balance becomes zero. Mass loss due to sublimation at PANDA-N station for 2014 is estimated to be 12.18 mm w.e.·a−1; and mass gain due to water vapour deposition is estimated to be 3.58 mm w.e.·a−1. Thus the net mass loss due to sublimation/deposition is 8.6 mm w.e.·a−1. This study computes surface energy fluxes using a model, instead of direct measurements. Also there are missing data especially for wind speed, though 2 m air temperature data is almost continuously available throughout the year. The uncertainties of albedo, wind speed and turbulent fluxes cause the most probable error in monthly values of QLWR, QH, QL, QG and surface temperature of about ±4%, ±20%, ±50%, ±11% and ±0.74 K respectively

A new WMO Guide for the measurement of cryospheric variables

Comunicación presentada en: TECO-2018 (Technical Conference on Meteorological and Environmental Instruments and Methods of Observation) celebrada en Amsterdam, del 8 al 11 de octubre de 2018.The Global Cryosphere Watch (GCW) is being developed by the WMO as a mechanism for providing dependable data, information, and analysis on the past, current, and future state of the cryosphere. To achieve its goals, GCW promotes consistent and sustainable measurements, of demonstrated quality, of all cryospheric components such as solid precipitation, snow, glaciers and ice caps, ice sheets, ice shelves, icebergs, sea ice, lake and river ice, and permafrost and seasonally frozen ground. As part of the GCW Observations Working Group, a Best Practices team was tasked with compiling an authoritative guide on measurement best practices for cryospheric variables for use at the GCW CryoNet stations as well as broader applications involving cryospheric observations. Recognizing the complexity and diversity of this task, the first priority has been given to the development of best practices for snow, sea ice, and glaciers. The intent of the guide proposed by GCW is to fill a void where current measurement guidelines are incomplete or fragmented and to compile and update existing measurement procedures to reflect current technologies and associated recommendations. For example, results from the recently completed WMO Solid Precipitation Inter-Comparison Experiment (SPICE) are incorporated to add recommendations on the automated measurement of snow on the ground. The Guide for the Measurement of Cryospheric Variables will include specific chapters for each component of the cryosphere and a general chapter reflecting broader aspects of cryosphere observations. These will be published in conjunction with the Guide to Meteorological Instruments and Methods of Observation, WMO-No. 8, as it evolves to broaden its scope to include the full spectrum of observations within the context of the Integrated Global Observing System. This will ensure that the information will be widely accessible and used by the community. This presentation will provide an introduction to the new Guide for the Measurement of Cryospheric Variables and most recent developments

Drift of pancake ice floes in the winter Antarctic marginal ice zone during polar cyclones

High temporal resolution in situ measurements of pancake ice drift are presented, from a pair of buoys deployed on floes in the Antarctic marginal ice zone during the winter sea ice expansion, over 9 days in which the region was impacted by four polar cyclones. Concomitant measurements of wave-in-ice activity from the buoys are used to infer that the ice remained unconsolidated, and pancake ice conditions were maintained over at least the first 7 days. Analysis of the data shows (i) the fastest reported ice drift speeds in the Southern Ocean; (ii) high correlation of drift velocities with the surface wind velocities, indicating absence of internal ice stresses >100 km from the ice edge where remotely sensed ice concentration is 100%; and (iii) presence of a strong inertial signature with a 13 hr period. A Lagrangian free drift model is developed, including a term for geostrophic currents that reproduce the 13 hr period signature in the ice motion. The calibrated model provides accurate predictions of the ice drift for up to 2 days, and the calibrated parameters provide estimates of wind and ocean drag for pancake floes under storm conditions

Comparing methods of measuring sea-ice density in the East Antarctic

Remotely sensed derivation of sea-ice thickness requires sea·ice density. Sea-ice density was estimated with three techniques during the second Sea Ice Physics and Ecosystem eXperiment (SIPEX-II, September-November 2012, East Antarctica). The sea ice was first-year highly deformed, mean thickness 1.2 m with layers, consistent with rafting, and 6-7/10 columnar ice and 3/10 granular ice. Ice density was found to be lower than values (900-920 kg m⁻³ used previously to derive ice thickness, with columnar ice mean density of 870 kg m⁻³. At two different ice stations the mean density of the ice was 870 and 800 kg m⁻³, the lower density reflecting a high percentage of porous granular ice at the second station. Error estimates for mass/volume and liquid/solid water methods are presented. With 0.1 m long, 0.1 m core samples, the error on individual density estimates is 28 kg m⁻³. Errors are larger for smaller machined blocks. Errors increase to 46 kg m⁻³ if the liquid/solid volume method is used. The mass/volume method has a low bias due to brine drainage of at least 5%. Bulk densities estimated from ice and snow measurements along 100 m transects were high, and likely unrealistic as the assumption of isostatic balance is not suitable over these length scales in deformed ice

SIPEX-2: A study of sea-ice physical, biochemical and ecosystem processes off East Antarctica during spring 2012

This editorial introduces a suite of articles resulting from the second Sea Ice Physics and Ecosystems eXperiment(SIPEX-2) voyage by presenting some background information on the study areaandAntarcticsea-ice conditions,and summarising the key findings from the project.Using the Australian iceb reaker RV Aurora Australis, SIPEX-2 was conducted in the area between 115–125°E and 62–66°S off East Antarctica during September to November 2012. This region had been sampled during two previous experiments,i.e. ARISE in 2003 (Massom etal.,2006a) and SIPEX in 2007(Worbyetal.,2011a). The 2012 voyage combined traditional and newly developed sampling methods with satellite and other data to measure sea-ice physical properties and pro- cesses on large scales,which provided context for bio geochemical and ecological case studies. Thes pecific goals of the SIPEX-2 project were to:(i)measure the spatial variability in sea-ice and snow-cover properties over small-to regional-length scales;(ii) improve understanding of sea-ice kinematic processes;and(iii) advance knowledge of the links between sea-ice physical characteristics,sea-ice biogeochemical cycling and ice-associated food-web dynamics.Our field-based activities were designed to inform modelling approaches and to improve our capability to assess impacts of predicted changes in Antarctic sea ice on Southern Ocean biogeochemical cycles and ecosystem function

A U-HPLC-ESI-MS/MS-based stable isotope dilution method for the detection and quantitation of methotrexate in plasma

INTRODUCTION: High-dose methotrexate (MTX) is used in the treatment of proliferative diseases such as acute lymphoblastic leukemia. Therapeutic drug monitoring of plasma MTX is important to monitor efficacy and adverse events. The authors aimed to develop a liquid chromatography, electrospray ionization, tandem mass spectrometry (LC-ESI-MS/MS)-based method to determine MTX in plasma for therapeutic drug monitoring and pharmacokinetic studies. METHODS: Samples were analyzed using a Waters Acquity UPLC and Quattro Premier XE. A Waters Acquity UPLC BEH C18 column (2.1 mm x 100 mm, 1.7 μm) was used running an isocratic mobile phase of 21% methanol and 10 mM ammonium bicarbonate. The electrospray was operated in the positive ionization mode monitoring the following mass transitions: m/z 455.2 > 308.2 for MTX and m/z 458.2 > 311.2 for MTXd3. The analysis combined straightforward sample preparation, consisting of dilution and protein precipitation, with a 3-minute run time. RESULTS: The method was linear up to 50 μM (r > 0.99), and the coefficient of variation was 1:10, was 5 nM. Method comparison with the Abbott TDx fluorescent polarization immunoassay (FPIA) showed excellent agreement, and a small but significant negative constant bias was detected (LC-MS/MS = 0.98 x FPIA - 7.3). CONLUSIONS: The authors developed a specific and sensitive stable isotope dilution LC-ESI-MS/MS method to monitor MTX concentrations in plasma within the clinically relevant range. The method can be easily applied in clinical laboratories because it combines straightforward sample pretreatment with LC-MS/MS. Copyrigh

Multicentre evaluation of the Roche Elecsys® Active B12 (holotranscobalamin) electro-chemiluminescence immunoassay

Background: Vitamin B12 deficiency is a common disorder. In circulation, vitamin B12 is bound to transcobalamin (holotranscobalamin), which is considered the active form of cobalamin. The objective of this study was to evaluate the analytical performance of the Roche Elecsys Active B12 immunoassay. Methods: Limit of quantification and linearity were assessed according to CLSI EP17-A2 and EP-6A guidelines. Precision and bias of Roche Active B12 test against Architect ci8200 (Abbott) were performed according to CLSI EP-5 A3 guideline at three Euro

Participation, retention, and associated factors of women in a prospective multicenter study on Chlamydia trachomatis infections (FemCure)

Prospective studies are key study designs when attempting to unravel health mechanisms that are widely applicable. Understanding the internal validity of a prospective study is essential to judge a study's quality. Moreover, insights in possible sampling bias and the external validity of a prospective study are useful to judge the applicability of a study's findings. We evaluated participation, retention, and associated factors of women in a multicenter prospective cohort (FemCure) to understand the study's validity.Chlamydia trachomatis (CT) infected adult women, negative for HIV, syphilis, and Neisseria gonorrhoeae were eligible to be preselected and included at three sexually transmitted infection (STI) clinics in the Netherlands (2016-2017). The planned follow-up for participants was 3 months, with two weekly rectal and vaginal CT self-sampling and online questionnaires administered at home and at the clinic. We calculated the proportions of preselected, included, and retained (completed follow-up) women. Associations with non-preselection, noninclusion, and non-retention (called attrition) were assessed (logistic and Cox regression).Among the 4,916 women, 1,763 (35.9%) were preselected, of whom 560 (31.8%) were included. The study population had diverse baseline characteristics: study site, migration background, high education, and no STI history were associated with non-preselection and noninclusion. Retention was 76.3% (n = 427). Attrition was 10.71/100 person/month (95% confidence interval 9.97, 12.69) and was associated with young age and low education. In an outpatient clinical setting, it proved feasible to include and retain women in an intensive prospective cohort. External validity was limited as the study population was not representative (sampling bias), but this did not affect the internal validity. Selective attrition, however (potential selection bias), should be accounted for when interpreting the study results