Progress Report on the Global Data Processing System 1999

European Centre for Medium-Range Weather Forecasts

On 9 March, the reference, T_L319 model had its vertical resolution extended from 31 to 50 levels (Figure 1); extra resolution was mainly in the stratosphere and mesosphere, with the model top moved from 10hPa to 0.1hPa.

On 5 May, raw MSU (NOAA14) and AMSU (NOAA15) radiance were introduced in the data assimilation;

On 13 July, winds from the NOAA/FSL Demonstration Network of Profilers were activated in the data assimilation; a screen-level humidity and temperature analysis is now used for the optimum interpolation of soil temperature and water content; a new bias correction scheme for radiosonde temperatures was activated, as well as a new numerical scheme for the physical tendencies;

On 12 October, the reference model vertical resolution was further extended from 50 to 60 levels, while the EPS was extended from 31 to 40 levels; in both cases extra levels are mainly in the Planetary Boundary Layer (Figure 2); a new parameterisation of precipitation accounting for cloud and precipitation partial overlap was introduced; the prescribed model background error statistics used in data assimilation were revised using an ensemble of perturbed analyses; a 1D-var assimilation of SSMI winds was activated;

The computer equipment in use at the end of 1999 is summarised in Table 1.

The observational data used in the operational analysis (cf para. 5 below) undergo a quality control in near real-time, after having been decoded. Each observation is subject to a number of tests:

(i) The parameter values are compared with gross limits for the parameter. Limits depend on latitude and, for surface parameters, also on the season of the year.

4.    MONITORING OF THE OBSERVING SYSTEM

The operational monitoring of all data types continues to provide the basis for decisions on the operational use of the data. The quality of observations is monitored in non real-time, based on statistics of the departures between the data and the operational 6-hour forecasts and analyses. All data types used in the data assimilation system are monitored in that way.

Results are published in a monthly Global Data Monitoring Report, provided to GDPS centres participating in data monitoring activities and to the WMO Secretariat (further copies can be obtained from ECMWF on request). Feedback is also provided directly to data producers.

The Centre has continued to fulfil its rôle of lead centre for radiosonde and pilot data monitoring as requested by WMO, including co-ordination and liaison with other lead centres.

Smallest half-wavelength resolved:

63 km (triangular spectral truncation 319)

Time-step: 20 minutes

Numerical scheme:

Semi-Lagrangian, semi- implicit time-stepping formulation.

Number of grid points in model:

8,300,760 in upper-air, 553,384 in land surface and sub- surface layers. The grid for computation of physical processes is a reduced, linear Gaussian grid, on which single- level parameters are available. The grid spacing is close to 62km.

Variables at each grid point (recalculated at each time-step):

Wind, temperature, humidity, cloud fraction and water/ ice content (also pressure at surface grid-points)

Physics:

orography (terrain height and sub-grid-scale), drainage, precipitation, carbon dioxide, temperature, ground humidity, snow-fall, snow-cover & snow melt, radiation (incoming short-wave and out-going long-wave), friction (at surface and in free atmosphere), sub-grid-scale orographic drag - gravity waves and blocking effects, evaporation, sensible & latent heat flux, oceanic waves.

Analysis: Mass & wind (four-dimensional variational multi- variate analysis on 31 model levels)

Humidity (four-dimensional variational analysis on model levels up to 250 hPa)

Surface parameters (sea surface temperature from NCEP Washington analysis, sea ice from SSM/I satellite data), soil water content, snow depth, screen level temperature and humidity

Data used: Global satellite data (SATOB, (A)TOVS, ERS2, SSM/I), Global free-atmosphere data (AIREP, AMDAR, TEMP, PILOT, TEMP/DROP, PROFILERS), Oceanic data (SYNOP/SHIP, PILOT/SHIP, TEMP/SHIP, DRIBU), Land data (SYNOP). Data checking and validation is applied to each parameter used. Thinning procedures are applied when observations are redundant at the model scale.

Initial perturbations generated from singular vectors at T42 resolution. 10-days forecasts are perturbed through random perturbations of the physical tendencies (stochastic physics).

50 ensemble members at TL159 resolution (linear grid), 40 levels

via a dedicated telecommunications network (mainly 64,000 bits per second) connecting the ECMWF system with the computer systems in the meteorological services of the 17 Member States and four co- operating States

dissemination requirements updated (and repeat transmissions requested) by individual Member States

via the Global Telecommunications System, network (50 to 64,000 bits per second) operated under the World Weather Watch of the World Meteorological Organization, connecting the meteorological services of all countries of the world

Parameters:

Free atmosphere:

A     Geopotential height at 500 hPa

B Temperature at 850 hPa

C Wind at 850 & 200 hPa

Surface:

D Mean-sea-level pressure

Time-steps:

A, B, C, D: one analysis time-step (12 UTC current day)

A, B, D (NH,SH): seven forecast time-steps (24 to 168 hours at 24-hour intervals)

C (tropics): five forecast time-steps (24 to 120 hours at 24-hour intervals)

5 x 5 degrees (dissemination in code GRID) and 2.5 x 2.5 degrees (dissemination in code GRIB)

 

Dissemination to the African Centre of Meteorological Applications for Development (ACMAD):

via METEOSAT MDD Specific parameters for the African region

 

A range of ECMWF products are sent daily to the Meteorological Product Extraction Facility at EUMETSAT to aid in retrieving cloud motion winds from METEOSAT. The ECMWF products are used for calculation of sea surface temperature and to assign cloud top heights to pressure levels.

A range of ECMWF products are sent daily to ESA to aid in processing data from the ERS satellites.

 

The processes forming the operational suite and the research experiments are managed and controlled by a Supervisor - Monitor - Scheduler (SMS) system. Many suites can be controlled under one SMS; alternatively, several versions of SMS may run simultaneously.

 

Demand for data from the Centre's archives of grid products, provided for research by ECMWF data services, continued to grow. A brochure describing available services can be obtained from ECMWF on request.

 

Average of the monthly WMO/CBS standard scores for 1999: