Modelling variable glacier lapse rates using ERA-Interim reanalysis climatology: an evaluation at Vestari- Hagafellsjökull, Langjökull, Iceland

The near-surface air temperature lapse rate is an important tool for spatially distributing temperatures in snow- and ice-melt models, but is difficult to parameterize, as it is not simply correlated with boundary-layer meteorological variables, such as temperature itself. This contribution quantifies spring-autumn lapse rate variability over 5 years at Vestari-Hagafellsjökull, a southerly outlet of Langjökull in Iceland. It is observed that summer lapse rates (0.57 °C 100 m) are significantly lower than non-summer rates, and are also lower than the Saturated Adiabatic Lapse Rate (SALR), which is often adopted in melt models. This is consistent with reduced near-surface temperature sensitivity to free-atmosphere temperature change during the occurrence of melting. A Variable Lapse Rate (VLR) regression model is calibrated with standardized, 750 hPa temperature anomalies derived from ERA-Interim climatology, which is shown to be highly significantly correlated with near-surface temperatures. The modelled VLR overestimates cumulative June-September Positive Degree Days (PDDs) by 3% when used to extrapolate temperatures from 1100 to 500 m a.s.l. on the glacier, whereas the SALR overestimates cumulative PDDs by 14%. ERA-Interim data therefore appear to offer a good representation of free-atmosphere temperature variability over Vestari-Hagafellsjökull, and the modelling approach offers a simple means of improving lapse rate parameterizations in melt models. © 2012 Royal Meteorological Society

Lower gastrointestinal bleeding: incidence, etiology, and outcomes in a population-based setting.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.To investigate the incidence and outcomes of acute lower gastrointestinal bleeding (ALGIB) in a population-based setting and examine the role of drugs potentially associated with GIB.National University Hospital of Icelan

Inter-decadal variability in potential glacier surface melt energy at Vestari Hagafellsjokull (Langjokull, Iceland) and the role of synoptic circulation

The surface energy balance (SEB) of glaciers, although of considerable importance for understanding the melt response to climate change, is rarely analysed for more than a few melt seasons due to the logistical challenges of meteorological measurement campaigns on glaciers. Insight into low-frequency (inter-decadal) changes in the SEB in response to climate warming and variable atmospheric circulation patterns has thus been limited. Here this problem is addressed by using ERA-Interim reanalysis data to extend glacier-meteorological records at two locations on Vestari Hagafellsjökull (Iceland) for the period 1979–2012. Trend analysis is conducted for this series before the role of synoptic circulation in modulating surface energetics is investigated. The results indicate that potential melt energy has increased significantly throughout the period of simulation at both locations (by 19.7 and 32.4%), with the largest increase evident for the turbulent heat fluxes (36.3 and 93.1%). The synoptic conditions associated with the recent high melt rates on the proximate Greenland Ice Sheet (GrIS) do not result in similarly extreme melt conditions for our Icelandic location. We also find that the North Atlantic Oscillation Index is significantly correlated with the radiative and latent heat components of the SEB. This association remains hidden if the melt rate is assessed in isolation, highlighting the utility of the SEB approach presented here for assessing synoptic aspects of glacier-climate interactions

Conditioning temperature-index model parameters on synoptic weather types for glacier melt simulations

Temperature-index models are widely favoured as a pragmatic means of simulating glacier melt because of their generally good performance, computational simplicity and limited demands for in situ data. However, their coefficients are normally treated as temporally stationary, unrealistically assuming a constancy of the prevailing weather. We address this simplification by prescribing model coefficients as a function of synoptic weather type, in a procedure that utilizes reanalysis data and preserves the minimal data requirements of temperature-index models. Using a cross-validation procedure at Vestari Hagafellsjökull, Iceland, and Storglaciären, Sweden, we demonstrate that applying transient model coefficients, for three temperature-index models, results in statistically significant increases in the skill with which melt is modelled: Median simulation improvements in the Nash-Sutcliffe efficiency coefficient of 7.3 and 23.6% are achieved when hourly and daily melt totals are evaluated respectively. Our weather-type modelling approach also yields insight to processes driving parameter variability, revealing dependence that is consistent with a priori considerations of the surface energy balance. We conclude that incorporating weather types into temperature-index models holds promise for improving their performance, as well as enhancing understanding variability in coefficient values. © 2014 John Wiley & Sons, Ltd

Massive search of spot- and facula-crossing events in 1598 exoplanetary transit lightcurves

We developed a dedicated statistical test for a massive detection of spot- A nd facula-crossing anomalies in multiple exoplanetary transit light curves, based on the frequentist p-value thresholding. This test was used to augment our algorithmic pipeline for transit light curves analysis. It was applied to 1598 amateur and professional transit observations of 26 targets being monitored in the EXPANSION project. We detected 109 statistically significant candidate events revealing a roughly 2 : 1 asymmetry in favor of spots-crossings over faculae-crossings. Although some candidate anomalies likely appear non-physical and originate from systematic errors, such asymmetry between negative and positive events should indicate a physical difference between the frequency of star spots and faculae. Detected spot-crossing events also reveal positive correlation between their amplitude and width, possibly due to spot size correlation. However, the frequency of all detectable crossing events appears just about a few per cent, so they cannot explain excessive transit timing noise observed for several targets.Fil: Baluev, R. V.. Saint Petersburg State University; RusiaFil: Sokov, E. N.. Saint Petersburg State University; Rusia. Russian Academy of Sciences. Central Astronomical Observatory at Pulkovo; RusiaFil: Sokova, I. A.. Saint Petersburg State University; Rusia. Russian Academy of Sciences. Central Astronomical Observatory at Pulkovo; RusiaFil: Shaidulin, V. Sh.. Saint Petersburg State University; RusiaFil: Veselova, A. V.. Saint Petersburg State University; RusiaFil: Aitov, V. N.. Russian Academy of Sciences. Special Astrophysical Observatory; RusiaFil: Mitiani, G. Sh.. Russian Academy of Sciences. Special Astrophysical Observatory; RusiaFil: Valeev, A. F.. Russian Academy of Sciences. Special Astrophysical Observatory; Rusia. Russian Academy of Sciences. Crimean Astrophysical Observatory; RusiaFil: Gadelshin, D.R.. Russian Academy of Sciences. Special Astrophysical Observatory; RusiaFil: Gutaev, A. G.. Russian Academy of Sciences. Special Astrophysical Observatory; Rusia. KazanFederal University (Volga Region); RusiaFil: Beskin, G.M.. Russian Academy of Sciences. Special Astrophysical Observatory; Rusia. KazanFederal University (Volga Region); RusiaFil: Valyavin, G. G.. Russian Academy of Sciences. Special Astrophysical Observatory; Rusia. Russian Academy of Sciences. Crimean Astrophysical Observatory; Rusia. Saint Petersburg State University; RusiaFil: Antonyuk, K.. Russian Academy of Sciences. Crimean Astrophysical Observatory; RusiaFil: Barkaoui, K.. Université de Liège; Bélgica. Cadi Ayyad University; MarruecosFil: Gillon, M.. Université de Liège; BélgicaFil: Jehin, E.. Université de Liège; BélgicaFil: Delrez, L.. Université de Liège; BélgicaFil: Gumundsson, S.. Nes Observatory; IslandiaFil: Dale, H. A.. University of Emory; Estados UnidosFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Di Sisto, Romina Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Bretton, M.. Baronnies Provençales Observatory; FranciaFil: Wunsche, A.. Baronnies Provençales Observatory; FranciaFil: Hentunen, V. P.. Taurus Hill Observatory; FinlandiaFil: Shadick, S.. University of Saskatchewan; CanadáFil: Jongen, Y.. Observatoire de Vaison la Romaine; FranciaFil: Kang, W.. National Youth Space Center; Corea del SurFil: Kim, T.. National Youth Space Center; Corea del Sur. Chungbuk National University; Corea del SurFil: Pakštienė, E.. Vilnius University; LituaniaFil: Qvam, J. K. T.. Horten Videregående Skole; Norueg

Massive Search for Spot- A nd Facula-Crossing Events in 1598 Exoplanetary Transit Light Curves

We developed a dedicated statistical test for a massive detection of spot- A nd facula-crossing anomalies in multiple exoplanetary transit light curves, based on the frequentist p-value thresholding. This test was used to augment our algorithmic pipeline for transit light curves analysis. It was applied to 1598 amateur and professional transit observations of 26 targets being monitored in the EXPANSION project. We detected 109 statistically significant candidate events revealing a roughly 2 : 1 asymmetry in favor of spots-crossings over faculae-crossings. Although some candidate anomalies likely appear non-physical and originate from systematic errors, such asymmetry between negative and positive events should indicate a physical difference between the frequency of star spots and faculae. Detected spot-crossing events also reveal positive correlation between their amplitude and width, possibly due to spot size correlation. However, the frequency of all detectable crossing events appears just about a few per cent, so they cannot explain excessive transit timing noise observed for several targets