The Impact of Waste Heat Release on Simulated Global Climate

The general circulation model of the United Kingdom Meteorological Office (UKMO) has been used to investigate the effects of thermal pollution from large-scale energy parks on climate. Two scenarios, with different locations for the energy parks, have been considered. Emphasis was placed on finding an estimate of model variability (on the basis of three control cases), so that the significance of the change caused by the heat release could be evaluated. As far as the model climatology is concerned, significant changes were produced by the energy parks. In addition, the location of the parks influenced the model response. The presently available models do not simulate climate in a completely realistic way so that the results of sensitivity experiments must be interpreted very carefully. At the present stage it can be said that the results call for further investigations

New method for the time calibration of an interferometric radio antenna array

Digital radio antenna arrays, like LOPES (LOFAR PrototypE Station), detect high-energy cosmic rays via the radio emission from atmospheric extensive air showers. LOPES is an array of dipole antennas placed within and triggered by the KASCADE-Grande experiment on site of the Karlsruhe Institute of Technology, Germany. The antennas are digitally combined to build a radio interferometer by forming a beam into the air shower arrival direction which allows measurements even at low signal-to-noise ratios in individual antennas. This technique requires a precise time calibration. A combination of several calibration steps is used to achieve the necessary timing accuracy of about 1 ns. The group delays of the setup are measured, the frequency dependence of these delays (dispersion) is corrected in the subsequent data analysis, and variations of the delays with time are monitored. We use a transmitting reference antenna, a beacon, which continuously emits sine waves at known frequencies. Variations of the relative delays between the antennas can be detected and corrected for at each recorded event by measuring the phases at the beacon frequencies.Comment: 9 pages, 9 figures, 1 table, pre-print of article published in Nuclear Inst. and Methods in Physics Research, A, available at: http://www.sciencedirect.com/science/article/B6TJM-4Y9CF4B-4/2/37bfcb899a0f387d9875a5a0729593a

Contribución al conocimiento de las epífitas vasculares del Área Natural Protegida “Reserva Ecológica Sierra de Otontepec”, Veracruz

Se presenta una contribución de la diversidad de epifítas vasculares del ANP Sierra de Otontepec, en tres tipos de vegetación: bosque mesófilo de montaña, bosque tropical perennifolio y acahual, en los municipios de Chontla y Citlaltepetl. Se encontró que este grupo de plantas está representado principalmente por las familias Bromeliaceae (26.4%) y Polypodiaceae (23.5 %), seguido de la familia Orchidaceae y Piperacea (14.7%). El BMM presento mayor riqueza de especies (46%), mientras que el BTP presento menor riqueza (23%) en comparación con el AC (31%). Se registraron dos especies en la NOM-059-SEMARNAT-2010, en la categoría de Amenazadas (Tillandsia imperialis y Prostecheae mariae). Este grupo de plantas se ven afectadas por la fragmentación y recolección ilegal, por lo que, se considera necesario generar conocimiento sobre las especies que se encuentran en la reserva

The wavefront of the radio signal emitted by cosmic ray air showers

Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above $10^{17}\,$eV and zenith angles smaller than $45^\circ$, we find that the radio wavefront of cosmic-ray air showers is of approximately hyperbolic shape. The simulations predict a slightly steeper wavefront towards East than towards West, but this asymmetry is negligible against the measurement uncertainties of LOPES. At axis distances $\gtrsim 50\,$m, the wavefront can be approximated by a simple cone. According to the simulations, the cone angle is clearly correlated with the shower maximum. Thus, we confirm earlier predictions that arrival time measurements can be used to study the longitudinal shower development, but now using a realistic wavefront. Moreover, we show that the hyperbolic wavefront is compatible with our measurement, and we present several experimental indications that the cone angle is indeed sensitive to the shower development. Consequently, the wavefront can be used to statistically study the primary composition of ultra-high energy cosmic rays. At LOPES, the experimentally achieved precision for the shower maximum is limited by measurement uncertainties to approximately $140\,$g/cm$^2$. But the simulations indicate that under better conditions this method might yield an accuracy for the atmospheric depth of the shower maximum, $X_\mathrm{max}$, better than $30\,$g/cm$^2$. This would be competitive with the established air-fluorescence and air-Cherenkov techniques, where the radio technique offers the advantage of a significantly higher duty-cycle. Finally, the hyperbolic wavefront can be used to reconstruct the shower geometry more accurately, which potentially allows a better reconstruction of all other shower parameters, too.Comment: accepted by JCA