TY  - JOUR
A1  - Böhm, Uwe
A1  - Kucken, M.
A1  - Hauffe, D.
A1  - Gerstengarbe, F. W.
A1  - Werner, P. C.
A1  - Flechsig, M.
A1  - Keuler, K.
A1  - Block, A.
A1  - Ahrens, W.
A1  - Nocke, T.
T1  - Reliability of regional climate model simulations of extremes and of long-term climate
N2  - We present two case studies that demonstrate how a common evaluation methodology can be used to assess the reliability of regional climate model simulations from different fields of research. In Case I, we focused on the agricultural yield loss risk for maize in Northeastern Brazil during a drought linked to an El-Nino event. In Case II, the present-day regional climatic conditions in Europe for a 10-year period are simulated. To comprehensively evaluate the model results for both kinds of investigations, we developed a general methodology. On its basis, we elaborated and implemented modules to assess the quality of model results using both advanced visualization techniques and statistical algorithms. Besides univariate approaches for individual near-surface parameters, we used multivariate statistics to investigate multiple near-surface parameters of interest together. For the latter case, we defined generalized quality measures to quantify the model's accuracy. Furthermore, we elaborated a diagnosis tool applicable for atmospheric variables to assess the model's accuracy in representing the physical processes above the surface under various aspects. By means of this evaluation approach, it could be demonstrated in Case Study I that the accuracy of the applied regional climate model resides at the same level as that we found for another regional model and a global model. Excessive precipitation during the rainy season in coastal regions could be identified as a major contribution leading to this result. In Case Study II, we also identified the accuracy of the investigated mean characteristics for near- surface temperature and precipitation to be comparable to another regional model. In this case, an artificial modulation of the used initial and boundary data during preprocessing could be identified as the major source of error in the simulation. Altogether, the achieved results for the presented investigations indicate the potential of our methodology to be applied as a common test bed to different fields of research in regional climate modeling
Y1  - 2004
SN  - 1561-8633
ER  - 
TY  - JOUR
A1  - Asghari, N.
A1  - Broeg, C.
A1  - Carone, L.
A1  - Casas-Miranda, R.
A1  - Palacio, J. C. C.
A1  - Csillik, I.
A1  - Dvorak, R.
A1  - Freistetter, F.
A1  - Hadjivantsides, G.
A1  - Hussmann, H.
A1  - Khramova, A.
A1  - Khristoforova, M.
A1  - Khromova, I.
A1  - Kitiashivilli, I.
A1  - Kozlowski, S.
A1  - Laakso, T.
A1  - Laczkowski, T.
A1  - Lytvinenko, D.
A1  - Miloni, O.
A1  - Morishima, R.
A1  - Moro-Martin, A.
A1  - Paksyutov, V.
A1  - Pal, A.
A1  - Patidar, V.
A1  - Pecnik, B.
A1  - Peles, O.
A1  - Pyo, J.
A1  - Quinn, T.
A1  - Rodriguez, A.
A1  - Romano, C.
A1  - Saikia, E.
A1  - Stadel, J.
A1  - Thiel, M.
A1  - Todorovic, N.
A1  - Veras, D.
A1  - Neto, E. V.
A1  - Vilagi, J.
A1  - von Bloh, Werner
A1  - Zechner, R.
A1  - Zhuchkova, E.
T1  - Stability of terrestrial planets in the habitable zone of G1 777 A, HD 72659, G1 614, 47 Uma and HD 4208
N2  - We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial-like planets in their habitable zones (HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. For each of the five systems the 2-dimensional grid of initial conditions contained 80 eccentricity points for the Jovian planet and up to 160 semimajor axis points for the fictitious planet. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straightforward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e > 0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ. Studies such as this one are of primary interest to future space missions dedicated to finding habitable terrestrial planets in other stellar systems. Assessing the likelihood of other habitable planets, and more generally the possibility of other life, is the central question of astrobiology today. Our investigation indicates that, from the dynamical point of view, habitable terrestrial planets seem to be compatible with many of the currently discovered extrasolar systems
Y1  - 2004
UR  - http://www.aanda.org/
U6  - https://doi.org/10.1051/0004-6361:20040390
SN  - 0004-6361
ER  - 
TY  - JOUR
A1  - Werner, Klaus
A1  - Dreizler, S.
A1  - Heber, Ulrich
A1  - Rauch, Thomas
A1  - Fleming, T. A.
A1  - Sion, E. M.
A1  - Vauclair, G.
T1  - High resolution spectroscopy of two hot (pre-) white dwarfs with the Hubble space telescope : KPD 0005+5106 and RXJ 2117+3412
Y1  - 1996
ER  -