Advances and visions in large-scale hydrological modelling: findings from the 11th Workshop on Large-Scale Hydrological Modelling

Large-scale hydrological modelling has become increasingly wide-spread during the last decade. An annual workshop series on large-scale hydrological modelling has provided, since 1997, a forum to the German-speaking community for discussing recent developments and achievements in this research area. In this paper we present the findings from the 2007 workshop which focused on advances and visions in large-scale hydrological modelling. We identify the state of the art, difficulties and research perspectives with respect to the themes "sensitivity of model results", "integrated modelling" and "coupling of processes in hydrosphere, atmosphere and biosphere". Some achievements in large-scale hydrological modelling during the last ten years are presented together with a selection of remaining challenges for the future

Seasonal characteristics of the relationship between daily precipitation intensity and surface temperature

Past studies have argued that the intensity of extreme precipitation events should increase exponentially with temperature. This argument is based on the principle that the atmospheric moisture holding capacity increases according to the Clausius-Clapeyron equation and on the expectation that precipitation formation should follow accordingly. We test the latter assumption by investigating to what extent a relation with temperature can be observed intraseasonally in present-day climate. For this purpose, we use observed and simulated daily surface temperature and precipitation over Europe. In winter a general increase in precipitation intensity is indeed observed, while in summer we find a decrease in precipitation intensity with increasing temperature. We interpret these findings by making use of model results where we can distinguish separate precipitation types and investigate the moisture content in the atmosphere. In winter, the Clausius-Clapeyron relationship sets a limit to the increase in the large-scale precipitation with increasing temperature. Conversely, in summer the availability of moisture, and not the atmosphere's capacity to hold this moisture, is the dominant factor at the daily timescale. For convective precipitation, we find a peak like structure which is similar for all subregions, independent of the mean temperature, contrary to large-scale precipitation which has a more monotonic dependence on temperature

Improved regional scale processes reflected in projected hydrological changes over large European catchments

For the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC), the recent version of the coupled atmosphere/ocean general circulation model (GCM) of the Max Planck Institute for Meteorology has been used to conduct an ensemble of transient climate simulations. These simulations comprise three control simulations for the past century covering the period 1860-2000, and nine simulations for the future climate(2001-2100) using greenhouse gas (GHG) and aerosol concentrations according to the three IPCC scenarios B1, A1B and A2. For each scenario three simulations were performed. The global simulations were dynamically downscaled over Europe using the regional climate model (RCM) REMO at 0.44A degrees horizontal resolution (about 50 km), whereas the physics packages of the GCM and RCM largely agree. The regional simulations comprise the three control simulations (1950-2000), the three A1B simulations and one simulation for B1 as well as for A2 (2001-2100). In our study we concentrate on the climate change signals in the hydrological cycle and the 2 m temperature by comparing the mean projected climate at the end of the twenty-first century (2071-2100) to a control period representing current climate (1961-1990). The robustness of the climate change signal projected by the GCM and RCM is analysed focussing on the large European catchments of Baltic Sea (land only), Danube and Rhine. In this respect, a robust climate change signal designates a projected change that sticks out of the noise of natural climate variability. Catchments and seasons are identified where the climate change signal in the components of the hydrological cycle is robust, and where this signal has a larger uncertainty. Notable differences in the robustness of the climate change signals between the GCM and RCM simulations are related to a stronger warming projected by the GCM in the winter over the Baltic Sea catchment and in the summer over the Danube and Rhine catchments. Our results indicate that the main explanation for these differences is that the finer resolution of the RCM leads to a better representation of local scale processes at the surface that feed back to the atmosphere, i.e. an improved representation of the land sea contrast and related moisture transport processes over the Baltic Sea catchment, and an improved representation of soil moisture feedbacks to the atmosphere over the Danube and Rhine catchments. [References: 41

925-39 Prenatal Hypertrophic Cardiomyopathy and its Association with Amniotic Fluid Insulin in Fetuses of Diabetic Mothers

The frequent presence of a disproportionate hypertrophic ventricular septum in infants of diabetic mothers, as well as its benign course, has been widely reported. This phenomenon has also been demonstrated in the fetus. The most accepted hypothesis to explain this disorder, yet to be proved in the prenatal period, is fetal hyperinsulinism due to inadequate control of maternal diabetes. This prospective controlled tra nsversal study was carried out to test the hypothesis that hypertrophic cardiomyopathy during prenatal life in diabetic pregnancies is related to fetal hyperinsulinism as assessed by amniotic fluid insulin levels. Sixty-five fetuses (37 of diabetic mothers and 28 of hypertensive mothers) were studied sequentially and non-intentionally. A comprehensive M-mode and cross-sectional Doppler echocardiogram, with color flow mapping, was performed within one week of the amniocentesis in every case. Fetal insulin levels and interventricular septum thickness were considered abnormal when their values were above 2 standard deviations, according to local nomograms. Statistical analysis utilized Student's “t” test, Fisher's exact test, ANOVA and Kruskal-Wallis test. The mean gestational age at the time of examination was 32.3±3.5 weeks (24–39 weeks) in the gestational diabetes group, 28.5±2.7 weeks (23–33 weeks) in the previous diabetes group and 30.6±3.1 weeks (25–36 weeks) in the control group. Mean septal thickness was 3.7 (2.2 to 6.3mm) in the group of diabetic mothers and 3.0 (2.0 to 4.3mm) in the control group (p<0.01). Mean fetal insulin levels was 14.7±16.8microlU/ml (3.2 to 75.3microlU/ml) in the group with diabetes and 6.4±3.3 microlU/ml (3.1 to 17microlU/ml) in the control group (p<0.01) Median insulin levels were 8.7 and 5.5microlU/ml in the diabetes and in the control group, respectively. Ten out of 37 fetuses of the diabetic group were considered to have hypertrophic cardiomyopathy (27%). while none of the fetuses of the control group showed increase in the septal thickness (p<0.01). A significant association between prenatal hypertrophic cardiomyopathy and fetal hyperinsulinism was demonstrated (p<0007).We conclude that there is association between the presence of hypertrophic cardiomyopathy during prenatal life and high levels of fetal insulin in diabetic mothers, thus justifying efforts to improve the glucemic control in pregnancies with this frequent complication

Significant individual variation between pathologists in the evaluation of colon cancer specimens after complete mesocolic excision

Background: After the introduction of complete mesocolic excision, a new pathological evaluation of the resected colon cancer specimen was introduced. This concept has quickly gained acceptance and is often used to compare surgical quality. The grading of colon cancer specimens is likely to depend on both surgical quality and the training of the pathologist. Objective: The purpose of this study was to validate the principles of the pathological evaluation of colon cancer specimens. Design: This was an exploratory study. Settings: The study was conducted in Aarhus, Denmark, and Leeds, United Kingdom. Patients: Colon cancers specimens were used. Main outcome measures: The agreement of gradings between participants was of interest. Four specialist GI pathologists and 2 abdominal surgeons evaluated 2 rounds of colon cancer specimens, each at 2 separate time points. Each round contained 50 specimens. After the first round, a protocol of detailed principles for the grading procedure was agreed on. Results from an experienced pathologist were considered as the reference results. Results: In the first round, the distribution of gradings between participants showed substantial variation. In the second round, the variation was reduced. Intraobserver agreement was mostly fair to good, whereas interobserver agreement was frequently poor. This did not significantly change from round 1 to round 2. Limitations: The small sample size of 100 specimens provided a very small number of specimens resected in the muscularis propria plane, which renders the evaluation of this group potentially unreliable. The evaluations were made on photos and not on fresh specimens. Conclusions: This study demonstrates significant variation in the pathological evaluation of colon cancer specimens. It demonstrates that it cannot be used in clinical studies, and care should be taken when comparing results between different hospitals

Frustration driven lattice distortion; an NMR investigation of Y2Mo2O7

We have investigated the 89Y NMR spectrum and spin lattice relaxation, T1, in the magnetically frustrated pyrochlore Y2Mo2O7. We find that upon cooling the spectrum shifts, and broadens asymmetrically. A detailed examination of the low T spectrum reveals that it is constructed from multiple peaks, each shifted by a different amount. We argue that this spectrum is due to discrete lattice distortions, and speculate that these distortions relieve the frustration and reduce the system's energy.Comment: To be published in Phys. Rev. Let

Production of biochars from crop residues for the remediation of trace elements contaminated soils

Biochar is the solid material obtained from thermochemical conversion of biomass under oxygen-limited conditions (pyrolysis), which can be applied as soil ameliorant [1]. In general, biochar properties are very heterogeneous due to the diverse pyrolytic conditions and the wide variety of organic residues used as feedstock [2,3]. This study intends to discern the relationship between feedstock, pyrolysis conditions and biochar properties with the goal of producing biochar with a high potential for the stabilization of trace elements in contaminated soils. For that purpose, biochars were produced using four different feedstock (rice husk, pruned olive trees, olive pit and “alperujo”, a byproduct of olive oil production) and two contrasting pyrolysis systems: a batch reactor (temperature ranged from 350 to 600 ºC; reaction time from 0.5 to 4 h under N2 atmosphere with a heating and cooling rate of XY K s-1) and a continuously feed reactor with a screw conveyor (Pyreka reactor; 500 ºC, residence time 12 min and N2 flux). Biochars were characterized by determining their pH, water holding capacity (WHC), elemental composition (C, H, N), ash content, internal structure by micro-computed tomography and chemical composition by field emission scanning electron microscopy with energy dispersive X-ray spectroscopy. To complete the characterization, Brunauer-Emmett-Teller specific surface area (SSABET; N2 adsorptive) and solid-state 13C-NMR spectroscopy were performed. Biochars produced in the batch reactor showed that pH, WHC, TC, SSABET, ash content and aromaticity increased with temperature and reaction time. Rice husk biochars showed the highest WHC (> 100%), while olive pit biochars the lowest ones. Rice husk and olive pit biochars had the highest aromaticity (between 75 and 91% of aryl carbon). The H/Cat ratio decreased with increasing pyrolysis temperature, which suggests an increase in the condensation degree of the aromatic structures. SSABET surface area ranged from 20 to 100 m2 g-1 and increased with temperature. Biochars produced in the batch reactor resulted in greater SSA values than Pyreka biochars. The pyrolysis conditions of 500 ºC and 2 h at the batch reactor resulted in similar biochars than those produced by the Pyreka reactor at 500 ºC and 12 min. Taking into account the necessity of applying biochar to soil for remediation purposes, we selected those biochars of high stability (ratio H/Cat ≤ 0.7 & high aromaticity by 13C NMR spectroscopy), great capacity for the sorption and stabilization of trace elements2 (SSABET ≥ 100 m2g-1; pH ≥9) and good potential to act as soil amendment (high WHC). The pyrolysis conditions finally selected were 500 ºC and 2 hours for the steel-batch reactor and 500 ºC and 12 min for the continuous reactor. At these conditions, rice husk biochars showed the most appropriate characteristics to be used as soil amendment for trace-elements contaminated soils

Effects of site dilution on the magnetic properties of geometrically frustrated antiferromagnets

The effect of site dilution by non magnetic impurities on the susceptibility of geometrically frustrated antiferromagnets (kagome and pyrochlore lattices) is discussed in the framework of the Generalized Constant Coupling model, for both classical and quantum Heisenberg spins. For the classical diluted pyrochlore lattice, excellent agreement is found when compared with Monte Carlo data. Results for the quantum case are also presented and discussed.Comment: 5 pages, 3 figure