Figure 6: Density map of blocking events extracted from the UCLA AGCM model data (1985-1989). impact of sea surface temperature anomalies on the rainfall over northeast brazil. Changes in Baroclinic Wave Activity during the Life Cycles of Low-Frequency Circulation Anomalies. Figure 3: Density map of cyclopresence during the northern winter from the ECMWF Advanced Analyses dataset. Figure 4: Den...

[1] Cirrus clouds play an important role both radiatively and dynamically in the tropics. Understanding the mechanisms responsible for the formation and persistence of tropical cirrus is an important step in accurately predicting cirrus in forecast and climate models. In this study, we compare ground-based measurements of cloud properties with those predicted by the ECMWF model at a location in...

A stand-alone sea ice model is tuned and validated using satellite-derived, basinwide observations of sea ice thickness, extent, and velocity from the years 1993 to 2001. This is the first time that basin-scale measurements of sea ice thickness have been used for this purpose. The model is based on the CICE sea ice model code developed at the Los Alamos National Laboratory, with some minor modi...

We present a new statistical method to optimally link local weather extremes to large-scale atmospheric circulation structures. The method is illustrated using July-August daily mean temperature at 2m height (T2m) time-series over the Netherlands and 500 hPa geopotential height (Z500) time-series over the Euroatlantic region of the ECMWF reanalysis dataset (ERA40). The method identifies pattern...

A convective cloud field model (CCFM) is substituted for a standard mass flux parameterisation of convective clouds in a limited area atmospheric model (REMO) and is tested for a whole annual cycle (July 1997 to June 1998) over the West Pacific Maritime Continent. REMO with CCFM is run in 0.5-degree resolution and the model at the lateral boundaries is forced 6-hourly by ECMWF reanalysis data. ...

Two new developments in extracting wind information by tracking of clouds or water vapour features are increasing the spatial coverage and providing quality estimates for individual observations. The transition from low density to high density wind observations of both GOES satellites led to first experiences with increased spatial coverage in NWP centres. The relative impact of low density and...

During the last years the European Centre for MediumRange Weather Forecasts (ECMWF) released new editions of the wave model WAM. The latest model version has been evaluated on both wave height and spectrum in close and shallow seas as well as in open oceans. The purpose of this work is twofold: First to discuss some evaluation results concerning the model performance and secondly to study the s...

Operational wave data assimilation at ECMWF started with ERS-1 radar altimeter wave heights on 15 August 1993. This had a significant impact on the wave model analysis and forecast. The impact of wave data assimilation based on the ECMWF experience is presented. This includes the impact of assimilation of ERS radar altimeter and synthetic aperture radar and ENVISAT radar altimeter-2 wave data. ...

Since the beginning of the ERS-1 mission, ECMWF is involved in the global validation and long-term performance monitoring of the wind and wave Fast Delivery products that are retrieved from the Radar Altimeter (RA), the Synthetic Aperture Radar (SAR) and the Active Microwave Instrument (AMI), on-board the ERS spacecrafts. Their geophysical content is compared with corresponding parameters from ...