Home About us Contact
|
Home About us Contact | ||
|
|
||
Lateral Boundary Conditions (lateral + boundary_condition)
Selected AbstractsRole of lateral mantle flow in the evolution of subduction systems: insights from laboratory experimentsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004Francesca Funiciello SUMMARY We present 3-D laboratory experiments constructed to investigate the pattern of mantle flow around a subducting slab under different boundary conditions. In particular we present a set of experiments, characterized by different conditions imposed at the trailing edge of the subducting plate (that is, plate fixed in the far field, plate detached in the far field, imposed plate motion). Experiments have been performed using a silicone slab floating inside a honey tank to simulate a thin viscous lithosphere subducting in a viscous mantle. For each set, we show differences between models that do or do not include the possibility of out-of-plane lateral flow in the mantle by varying the lateral boundary conditions. Our results illustrate how a subducting slab vertically confined over a 660-km equivalent depth can be influenced in its geometry and in its kinematics by the presence or absence of possible lateral pathways. On the basis of these results we show implications for natural subduction systems and we highlight the importance of suitable simulations of lateral viscosity variations to obtain a realistic simulation of the history of subduction. [source] Effects of urbanization on the land sea breeze circulation over the Pearl River Delta region in winterINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2010Xi Lu Abstract In this study, the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Model (MM5) was used to investigate the effects of urbanization on land,sea breezes (LSBs) in the Pearl River Delta (PRD) region, which is a rapidly developing area located in southern China. LSBs in the 2003/2004 winter were simulated utilizing an approach in which the NCEP Final Analysis data averaged in the 2003/2004 winter is used as initial and lateral boundary conditions for the model. The simulated surface winds are shown to be capable of reproducing the basic features and diurnal variation of the LSBs. Sensitivity experiments with changes in land uses were performed with this model. Results of these experiments show that urbanization in the PRD region can have significant effects on the patterns of the LSBs and circulation in the region. In particular, it has been shown that the urbanization of Shenzhen (a major city located in the eastern coast of the PRD and neighbouring to the north of Hong Kong) may significantly enhance the sea breeze to the west of Hong Kong in the early afternoon. This may enhance the low-level convergence in Hong Kong and may worsen the air pollution problem there. On the other hand, the effects of urbanization in the western coast of the PRD region are relatively local and LSBs on the eastern PRD are generally not affected. Copyright © 2009 Royal Meteorological Society [source] Simulation of New Zealand's climate using a high-resolution nested regional climate modelINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2007Frank Drost Abstract A regional climate model (RCM) for New Zealand has been developed. The RCM is embedded within a GCM and both models are run under pre-industrial conditions. Seasonal mean output of the RCM is compared against NCEP data and the New Zealand national climate database. Regional and seasonal aspects of modelled surface temperature and precipitation are to a large extent simulated correctly. The main anomalies are related to the difficulty of incorporating New Zealand's orography appropriately and to the initial and lateral boundary conditions, which were supplied by the GCM. The largest anomalies occur over the Southern Alps, where the modelled temperatures are too low and where the amount of precipitation is too high. Many parts of the east coasts in both the North and South Island are too warm and too dry. Correlation patterns of temperature and precipitation with mean sea-level pressure differ considerably from the equivalent patterns constructed from NCEP data, but do show in general the dominant relationships between wind direction and temperature and precipitation. Copyright © 2006 Royal Meteorological Society [source] Limited-area ensemble predictions at the Norwegian Meteorological InstituteTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 621 2006Inger-Lise Frogner Abstract This study aims at improving 0,3 day probabilistic forecasts of precipitation events in Norway. For this purpose a limited-area ensemble prediction system (LAMEPS) is tested. The horizontal resolution of LAMEPS is 28 km, and there are 31 levels in the vertical. The state variables provided as initial and lateral boundary conditions for the limited-area forecasts are perturbed using a dedicated version of the European Centre for Medium-Range Weather Forecasts (ECMWF) global ensemble prediction system, TEPS. These are constructed by combining initial and evolved singular vectors that at final time (48 h) are targeted to maximize the total energy in a domain containing northern Europe and adjacent sea areas. The resolution of TEPS is T255 with 40 levels. The test period includes 45 cases with 21 ensemble members in each case. We focus on 24 h accumulated precipitation rates with special emphasis on intense events. We also investigate a combination of TEPS and LAMEPS resulting in a system (NORLAMEPS) with 42 ensemble members. NORLAMEPS is compared with the 21-member LAMEPS and TEPS as well as the regular 51-member EPS run at ECMWF. The benefit of using targeted singular vectors is seen by comparing the 21-member TEPS with the 51-member operational EPS, as TEPS has considerably larger spread between ensemble members. For other measures, such as Brier Skill Score (BSS) and Relative Operating Characteristic (ROC) curves, the scores of the two systems are for most cases comparable, despite the difference in ensemble size. NORLAMEPS has the largest ensemble spread of all four ensemble systems studied in this paper, while EPS has the smallest spread. Nevertheless, EPS has higher BSS with NORLAMEPS approaching for the highest precipitation thresholds. For the area under the ROC curve, NORLAMEPS is comparable with or better than EPS for medium to large thresholds. Copyright © 2006 Royal Meteorological Society [source] High-resolution limited-area ensemble predictions based on low-resolution targeted singular vectorsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 582 2002Inger-Lise Frogner Abstract The operational limited-area model, HIRLAM, at the Norwegian Meteorological Institute is used at 0.25° latitude/longitude resolution for ensemble weather prediction over Northern Europe and adjacent parts of the North Atlantic Ocean; this system is called LAMEPS. Initial and lateral boundary perturbations are taken from coarse-resolution European Centre for Medium-Range Weather Forecasts global ensemble members based on targeted singular vectors (TEPS). Five winter and five summer cases in 1997 consisting of 20 ensemble members plus one control forecast are integrated. Two sets of ensembles are generated, one for which both initial and lateral boundary conditions are perturbed, and another with only the initial fields perturbed. The LAMEPS results are compared to those of TEPS using the following measures: r.m.s. ensemble spread of 500 hPa geopotential height; r.m.s. ensemble spread of mean-sea-level pressure; Brier Skill Scores (BSS); Relative Operating Characteristic (ROC) curves; and cost/loss analyses. For forecasts longer than 12 hours, all measures show that perturbing the boundary fields is crucial for the performance of LAMEPS. For the winter cases TEPS has slightly larger ensemble spread than LAMEPS, but this is reversed for the summer cases. Results from BSS, ROC and cost/loss analyses show that LAMEPS performed considerably better than TEPS for precipitation, a result that is promising for forecasting extreme precipitation amounts. We believe this result to be linked to the high predictability of mesoscale flows controlled by complex topography. For two-metre temperature, however, TEPS frequently performed better than LAMEPS. Copyright © 2002 Royal Meteorological Society [source] | ||||||||||