NUMERICAL SIMULATIONS OF THE ELBE FLOOD CASE: SENSITIVITY TO INITIAL AND BOUNDARY DATA

Numerical experiments with the model chain of the German Weather Service are conducted to find the reasons for the bad performance of the operational precipitation forecast in the case of the Elbe flood in August 2002. The sensitivity to initial and to boundary data as well as to a new precipitation scheme and the horizontal model resolution is inspected. The greatest improvement concerning the amount and location of the predicted precipitation field is achieved by using ECMWF analysis data as initial fields. Also, the implementation of a precipitation scheme that allows the rain to be advected with the wind exhibits a positive effect. Last, the better resolution of the global model improves the rainfall forecast, whereas the better resolution of the regional model produces worse results

Synthesising, using, and correcting for telluric features in high-resolution astronomical spectra

We present a technique to synthesise telluric absorption and emission features both for in-situ wavelength calibration and for their removal from astronomical spectra. While the presented technique is applicable for a wide variety of optical and infrared spectra, we concentrate in this paper on selected high-resolution near-infrared spectra obtained with the CRIRES spectrograph to demonstrate its performance and limitation. We find that synthetic spectra reproduce telluric absorption features to about 2%, even close to saturated line cores. Thus, synthetic telluric spectra could be used to replace the observation of telluric standard stars, saving valuable observing time. This technique also provides a precise in-situ wavelength calibration, especially useful for high-resolution near-infrared spectra in the absence of other calibration sources.Comment: 11 pages, 11 figures, accepted for publication in A&A (updated version

Determination of Humidity and Temperature Fluctuations Based on MOZAIC Data and Parametrisation of Persistent Contrail Coverage for General Circulation Models

Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model

ZB MED - Information Centre for Life Sciences: An academic library as an engine for open access

ZB MED - Information Center for Life Sciences, Europe's most important medical library, outlines its view of the entire scope of open access: Since 2003 ZB MED has been intensely committed to open access. Beside the practical service of non-commercial user-friendly publication platforms for fast dissemination of scientific research results, ZB MED has gradually expanded its advisory services like FAQs, training sessions and scientific lectures since 2014. The library's strategic focus on integrating numerous open access publications into its catalogue is accompanied by the license department's commitment to enter into transformation contracts. Overall these various opportunities offered by ZB MED represent its claim to be the driving force for open Access in the field of life sciences.ZB MED - Informationszentrum Lebenswissenschaften, wichtigste europäische Medizin-Bibliothek, stellt in diesem Artikel sein gesamtinstitutionelles Open-Access-Angebot vor: Bereits seit 2003 engagiert sich ZB MED aktiv im Bereich Open Access. Neben dem praktischen Angebot alternativer, nicht-kommerzieller Publikationsplattformen zur leichten und schnellen Verbreitung wissenschaftlicher Forschungsergebnisse hat ZB MED seit 2014 zusätzlich sein Beratungsangebot z.B. durch detaillierte FAQs, Inhouse-Schulungen bei Partnern und Vorträge sukzessive ausgebaut. Die strategische Ausrichtung der Bestandsentwicklung, Open-Access-Publikationen in den Katalog aufzunehmen, wird durch das Engagement der Lizenzabteilung, Transformationsverträge zu schließen, ergänzt. ZB MED ist mit seinen Angeboten Motor für Open Access in den Lebenswissenschaften

High resolution modelling of snow transport in complex terrain using downscaled MM5 wind fields

Snow transport is one of the most dominant processes influencing the snow cover accumulation and ablation in high mountain environments. Hence, the spatial and temporal variability of the snow cover is significantly modified with respective consequences on the total amount of water in the snow pack, on the temporal dynamics of the runoff and on the energy balance of the surface. For the present study we used the snow transport model SnowModel in combination with MM5 (Penn State University – National Center for Atmospheric Research MM5 model) generated wind fields. In a first step the MM5 wind fields were downscaled by using a semi-empirical approach which accounts for the elevation difference of model and real topography, and vegetation. The target resolution of 30 m corresponds to the resolution of the best available DEM and land cover map of the test site Berchtesgaden National Park. For the numerical modelling, data of six automatic meteorological stations were used, comprising the winter season (September–August) of 2003/04 and 2004/05. In addition we had automatic snow depth measurements and periodic manual measurements of snow courses available for the validation of the results. It could be shown that the model performance of SnowModel could be improved by using downscaled MM5 wind fields for the test site. Furthermore, it was shown that an estimation of snow transport from surrounding areas to glaciers becomes possible by using downscaled MM5 wind fields

Application of a hydrometeorological model chain to investigate the effect of global boundaries and downscaling on simulated river discharge

In the current study, two regional climate models (MM5 and REMO) driven by different global boundary conditions (the ERA40 reanalysis and the ECHAM5 model) are one-way coupled to the uncalibrated hydrological process model PROMET to analyze the impact of global boundary conditions, dynamical regionalization and subsequent statistical downscaling (bilinear interpolation, correction of subgrid-scale variability and combined correction of subgrid-scale variability and bias) on river discharge simulation. The results of 12 one-way coupled model runs, set up for the catchment of the Upper Danube (Central Europe) over the historical period 1971-2000, prove the expectation that the global boundaries applied to force the RCMs strongly influence the accuracy of simulated river discharge. It is, however, noteworthy that all efficiency criteria in case of bias corrected MM5 simulations indicate better performance under ERA40 boundaries, whereas REMO-driven hydrological simulations better correspond to measured discharge under ECHAM5 boundaries. Comparing the hydrological results achievable with MM5 and REMO, the application of bias-corrected MM5 simulations turned out to allow for a more accurate simulation of discharge, while the variance in simulated discharge in most cases was better reflected in case of REMO forcings. The correction of subgrid-scale variability within the downscaling of RCM simulations compared to a bilinear interpolation allows for a more accurate simulation of discharge for all model configurations and all discharge criteria considered (mean monthly discharge, mean monthly low-flow and peak-flow discharge). Further improvements in the hydrological simulations could be achieved by eliminating the biases (in terms of deviations from observed meteorological conditions) inherent in the driving RCM simulations, regardless of the global boundary conditions or the RCM applied. In spite of all downscaling and bias correction efforts described, the RCM-driven hydrological simulations remain less accurate than those achievable with spatially distributed meteorological observations. © 2013 Springer-Verlag Berlin Heidelberg

Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model

Crucial role of obliquely propagating gravity waves in the quasi-biennial oscillation dynamics

​​​​​​​In climate modelling, the reality of simulated flows in the middle atmosphere is largely affected by the model's representation of gravity wave processes that are unresolved, while these processes are usually simplified to facilitate computations. The simplification commonly applied in existing climate models is to neglect wave propagation in horizontal direction and time. Here we use a model that fully represents the propagation of unresolved waves in all directions, thereby elucidating its dynamical effect upon the most important climate mode in the tropical stratosphere, i.e. the quasi-biennial oscillation. Our simulation shows that the waves in the equatorial stratosphere, which are known to drive this climate mode, can originate far away from the Equator in the troposphere. The waves propagating obliquely toward the Equator are found to play a huge role in the phase progression of the quasi-biennial oscillation as well as in its penetration into the lower stratosphere. Such waves will require further attention, given that current climate models are struggling to simulate the quasi-biennial oscillation down to the lower stratosphere, which may be needed to reproduce its observed impacts on the surface climate.</p