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Meteorological Institute (meteorological + institute)
Selected AbstractsValidation of ECMWF (re)analysis surface climate data, 1979,1998, for Greenland and implications for mass balance modelling of the ice sheetINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2001Edward Hanna Abstract Climate (re)analysis products are potentially valuable tools, when properly verified, for helping to constrain the surface mass balance of the Greenland Ice Sheet (GIS). Monthly surface fields from European Centre for Medium-Range Weather Forecasts (ECMWF) operational- and re-analyses spanning 1979,1998 were validated using in situ data (surface air pressure and temperature, precipitation, cloud cover, short-/all-wave radiation, and wind speed/direction). These validation data are from coastal or near-coastal Danish Meteorological Institute (DMI) synoptic stations, inland Greenland Climate Network (GC-Net) and University of Wisconsin Automatic Weather Stations (AWSs), and two energy balance stations near the southern ice margin. The ECMWF analyses closely reproduce the seasonal patterns and interannual variations of much of the in situ data. Differences in the mean values of surface air pressure and temperature can mainly be ascribed to orography errors in the analyses' schemes, compared with the latest available accurate digital elevation model. Much of the GIS margin as modelled by ECMWF was too cold, on average by 4°C, and ECMWF precipitation averaged some 136% of the DMI station values. The misrepresentation of the (relatively) steep ice-sheet margin, which tends to be broadened and systematically over-elevated by several hundred metres, orographically reduced temperature and enhanced precipitation there in the ECMWF models. The cloud-cover comparison revealed not dissimilar annual mean cloud covers (ECMWF ,8%) but the ECMWF analyses had too little cloud and were too ,sunny' during the critical summer melt-season. ECMWF-modelled surface albedo in summer was ,11% lower than GC-Net values, which was mainly responsible for the disagreement of modelled surface short-wave radiation fluxes with observations. Model albedo and cloud errors need to be rectified if the analyses are to be used effectively to drive energy balance models of Greenland snowmelt. ECMWF wind speed averaged 66% (62%) of the DMI station (AWS) values. The validation results provide useful insights into how one can best improve the ECMWF Greenland climate data for use in glaciological and climatological studies. Copyright © 2001 Royal Meteorological Society [source] Monitoring and verifying cloud forecasts originating from operational numerical modelsMETEOROLOGICAL APPLICATIONS, Issue 3 2008Christoph Zingerle Abstract Weather satellites produce large amounts of observational data in real time. This information has high temporal and spatial resolution covering almost every region of the globe. The infrared (IR) window channels of operational meteorological satellites are sensitive to the clouds and to the underlying surface. Comparing the IR channel observations with synthetic satellite images is an effective way to evaluate the quality of cloud forecasts produced by numerical models. Assessment of potentially problematic features in the early stages of the forecast is essential in not only nowcasting and very short-range forecasting but also in a reliability check of a given numerical weather prediction model (NWP). A pre-operational real-time monitoring system is set up in the Finnish Meteorological Institute, using the observed and synthetic satellite images, and applying an entity-based verification method. Copyright © 2008 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] Hydrological ensemble prediction and verification for the Meuse and Scheldt basinsATMOSPHERIC SCIENCE LETTERS, Issue 2 2010Joris Van den Bergh Abstract We present the hydrological ensemble prediction system developed at the Royal Meteorological Institute (RMI) of Belgium to study the Meuse and Scheldt basins. An overview is presented of the hydrological model and the operational setup of the forecasting system. We present some results of a 3-year hindcast that was performed to verify the quality of the probabilistic forecasting system. The raw precipitation forecasts and streamflow forecasts are considered: we provide skill scores and relative economic value for various subcatchments of the Meuse and Scheldt basins. Copyright © 2010 Royal Meteorological Society [source] | ||||||||||