Temporal instability of temperature singularities in a long-term series at Prague-Klementinum

The recent study of meteorological singularities in the Czech Republic—?ezní?ková et al. (Theor Appl Climatol 88:179–192, 2007)—is supplemented with respect to findings concerning temporal stability of air temperature singularities. A long-term daily series at Prague-Klementinum is examined over 1881–2000, adopting the same statistical background for the detection of singularities. A procedure that reduces the dependence of results on the choice of a reference period is proposed. It is shown that nearly all temperature singularities found over the period since 1961 and/or the whole period of 1881–2000 are temporally unstable, and a lot of them should be treated as statistical properties of particular data samples (time periods) reflecting sampling variability rather than stable and recurrent anomalies related to distinct circulation patterns. The most important singularities are identified, occurring on 4 days in year only (around St. Médard’s Day, 8 June), and they are linked to intraseasonal variations in the occurrence of circulation patterns conducive to warm and cold temperature anomalies. A sharp increase (decrease) in the frequency of north (south) circulation types after 8 June leads to the most robust irregularity in the mean annual cycle of temperature.     

Natural and Anthropogenic Sources of Seismic,Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

Surveys in Geophysics - The record of seismic, hydroacoustic, and infrasonic waves is essential to detect, identify, and localize sources of both natural and anthropogenic origin. To guarantee...     

Periphyton and sphagnicolous protists of dystrophic bog lakes (Brandenburg, Germany): I. Annual cycles, distribution and comparison to other lakes

The periphyton of acid, dystrophic bogs was investigated. Glass-slides were exposed in four different bog lakes about 100 km north of Berlin, Germany, in order to examine the species composition and the annual cycle of the protist community. The annual cycles of the periphyton in bog lakes were comparable to those in other mesotrophic lakes: During the winter months small heterotrophic flagellates (HF) dominated the periphyton community. Besides that bacterivorous ciliates were present as typical pioneer species. At the end of the ice covering, almost exclusively unicellular green algae colonized the slides. In May high abundances of ciliates and choanoflagellates were observed. At the same time, a maximum of species was reached. From August to October peritrich ciliates significantly contributed to the periphyton. Their number decreased when early frosts occurred.

The four investigated bog lakes exhibit very similar species compositions, almost all of the species were present in each of the four lakes. Differences were only distinct concerning the dominance of some protistan groups. The largest deflections, however, occurred not between two lakes, but between two habitats within one lake: The upper 30 cm of the Sphagnum mat comprise two very different protistan communities, determined by a strong vertical zoning. Due to the different light and nutrient conditions, the slides of the upper region exhibited a denser colonization, mainly consisting of autotrophic cryptomonads and vagile ciliates. In contrast to this, the slides of the deeper region were mainly colonized by heterotrophic flagellates and sessile peritrich ciliates.     

Periphyton and sphagnicolous protists of dystrophic bog lakes (Brandenburg, Germany): II. Characteristic species and trophy of the lakes

Glass-slides were exposed in four different bog lakes located in great forest areas in Northern Germany, about 100 km north of Berlin, in order to examine the protist community of these dystrophic, acid lakes. Species composition and succession of the periphyton were studied during one year. The four investigated bog lakes exhibit similar species compositions, most of the species were present in each of the four lakes. The periphyton was composed of a great variety of protist species. Specimens of all major flagellated protists and of most of the ciliate taxa were found on the slides. Many of these species are ubiquitous. Some species, however, like the flagellates Spongomonas sacculus, Rhipidodendron huxleyi, Cyathobodo sp., and Pseudodendromonas vlkii as well as the ciliates Ophrydium hyalinum, Leptopharynx costatus, Uroleptus caudatus, and Platyophrya sphagni are found more frequently in acid waters. A regular and common occurrence of these species partly characterizes the acid Sphagnum bogs. Besides that, common species like Bodo spp., Cryptomonas spp., Goniomonas truncata, Chilodonella uncinata, Vorticella sp., and Cyrtolophosis mucicola are represented in the periphyton. Examinations of the testate amoebae in the Sphagnum mats show a very different species composition compared to earlier studies.

The investigated bog lakes revealed mesotrophic conditions. In the upper regions of the Sphagnum mats and in the center of the larger bog lakes, oligotrophic conditions still prevail. The lower regions of the Sphagnum mat and the smaller lakes, however, are influenced by the partly degradation of plants and the run-off water from surrounding land. In comparison to earlier studies, the species composition indicates a beginning eutrophication of the bog lakes. A direct anthropogenic impact can be excluded.     

Amplification of hydrological model uncertainties in projected climate simulations of the Upper Indus Basin: Does it matter where the water is coming from?

There is a growing appreciation of the uncertainties in the estimation of snow-melt and glacier-melt as a result of climate change in high elevation catchments. Through a detailed examination of three hydrological models in two catchments, and interpretation of results from previous studies, we observed that many variations in estimated streamflow could be explained by the selection of a best parameter set from the possible good model parameters. The importance of understanding changing glacial dynamics is critically important for our study areas in the Upper Indus Basin where Pakistan's policymakers are planning infrastructure to meet the future energy and water needs of hundreds of millions of people downstream. Yet, the effect of climate on glacial runoff and climate on snowmelt runoff is poorly understood. With the HBV model, for example, we estimated glacial melt as between 56% and 89% for the Hunza catchment. When rainfall was a scaled parameter, the models estimated glacial melt as between 20% and 100% of streamflow. These parameter sets produced wildly different projections of future climate for RCP8.5 scenarios in 2046–2075 compared to 1976–2005. Assuming no glacial shrinkage, for one climate projection, we found that the choice among good parameter sets resulted in projected values of future streamflow across a range from +54% to +125%. Parameter selection was the most significant source of uncertainty in the glaciated catchment and amplified climate model uncertainty, whereas climate model choice was more important in the rainfall dominated catchment. Although the study focuses on Pakistan, the overall conclusions are instructive for other similar regions in the world. We suggest that modellers of glaciated catchments should present results from at least the book-ends: models with low sensitivity to ice-melt and models with high sensitivity to ice-melt. This would reduce confusion among decision makers when they are faced with similar contrasting results.     

Compositional evolution of grossular garnet from leucotonalitic pegmatite at Ruda nad Moravou, Czech Republic; a complex EMPA, LA-ICP-MS, IR and CL study

Five distinct paragenetic, morphological and compositional types of grossular garnet (G1, G2, G3, G4, G5) were distinguished within the individual (sub)units of the zoned leucotonalitic pegmatite cutting serpentinized lherzolite with rodingite dikes at ??ár near Ruda nad Moravou, Staré Město Unit, Northern Moravia. Detailed study using Electron Microprobe Analysis, Laser Ablation Inductively Coupled Plasma Mass Spectrometry, Cathodoluminiscence and Infrared Spectroscopy revealed distinct compositional trends in major, minor and trace elements. The contents of Fe³⁺, Mn, Mg and Ti increase from early garnet (G1) in the outermost grossular subunit through the interstitial garnet (G2) in the leucocratic subunit to graphic intergrowths of quartz+garnet (G3) in the coarse-grained unit. Then these constituents decrease in inclusions of garnet (G4) from the blocky unit and large crystals of garnet (G5) from the quartz core. Some trace elements (V, Ni, Y) exhibit the same trends, only Be evidently increases in garnet from border zone to the centre. Fluorine has negative correlation with Fe³⁺ as well as some trace elements (Ta, Pb). Concentrations of H₂O in garnets, up to 0.22 wt.% H₂O, are comparable with spessartine-almandine garnets from the Rutherford No. 2 pegmatite, Virginia, and grossular garnets from high-temperature calc-silicate rocks (skarns). Water contents correlate positively with Fe³⁺, but inversely with F. The use of water contents in garnet to elucidate the fluctuations of activity of H₂O during the pegmatite formation is only limited; the incorporation of hydrous defects seems to be controlled instead by crystal-structural constraints. However, the sum of all volatile components (H₂O + F) increases about twice from the outermost subunit to the centre of the pegmatite body.     

Exploration of optimal time steps for daily precipitation bias correction: a case study using a single grid of RCM on the River Exe in southwest England

ABSTRACT

Bias correction is a necessary post-processing procedure in order to use regional climate model (RCM)-simulated local climate variables as the input data for hydrological models due to systematic errors of RCMs. Most of the present bias-correction methods adjust statistical properties between observed and simulated data based on a predefined duration (e.g. a month or a season). However, there is a lack of analysis of the optimal period for bias correction. This study attempted to address the question whether there is an optimal number for bias-correction groups (i.e. optimal bias-correction period). To explore this we used a catchment in southwest England with the regional climate model HadRM3 precipitation data. The proposed methodology used only one grid of RCM in the Exe catchment, one emissions scenario (A1B) and one member (Q0) among 11 members of HadRM3. We tried 13 different bias-correction periods from 3-day to 360-day (i.e. the whole of one year) correction using the quantile mapping method. After the bias correction a low pass filter was used to remove the high frequencies (i.e. noise) followed by estimating Akaike’s information criterion. For the case study catchment with the regional climate model HadRM3 precipitation, the results showed that a bias-correction period of about 8 days is the best. We hope this preliminary study on the optimum number bias-correction period for daily RCM precipitation will stimulate more research to improve the methodology with different climatic conditions. Future efforts on several unsolved problems have been suggested, such as how strong the filter should be and the impact of the number of bias correction groups on river flow simulations.

Editor M.C. Acreman Associate editor S. Kanae     

Performance assessment of evapotranspiration estimated from different data sources over agricultural landscape in Northern India

Accurate estimation of evapotranspiration is generally constrained due to lack of required hydrometeorological datasets. This study addresses the performance analysis of reference evapotranspiration (ETo) estimated from NASA/POWER, National Center for Environmental Prediction (NCEP) global reanalysis data before and after dynamical downscaling through the Weather Research and Forecasting (WRF) model. The state-of-the-art Hamon’s and Penman-Monteith’s methods were utilized for the ETo estimation in the Northern India. The performance indices such as bias, root mean square error (RMSE), and correlation (r) were calculated, which showed the values 0.242, 0.422, and 0.959 for NCEP data (without downscaling) and 0.230, 0.402, and 0.969 for the downscaled data respectively. The results indicated that after WRF downscaling, there was some marginal improvement found in the ETo as compared to the without downscaling datasets. However, a better performance was found in the case of NASA/POWER datasets with bias, RMSE, and correlation values of 0.154, 0.348, and 0.960 respectively. In overall, the results indicated that the NASA/POWER and WRF downscaled data can be used for ETo estimation, especially in the ungauged areas. However, NASA/POWER is recommended as the ETo calculations are less computationally expensive and easily available than performing WRF simulations.