The weather models are performing computations of the weather development on DMI’s supercomputer Cray-XT5, which is a very powerful computer installation. The weather models are computationally very demanding since the complicated physics and air movements of the atmosphere need to be programmed on the computer and calculated for a large number of grid volumes of the atmosphere. The computations (May 2009) are executed for 40 vertical levels up through the atmosphere while the horizontal number of grid points depend on the geographical setup.
At the surface the sea surface temperature is analysed daily. It does not change in the model on a given location throughout the weather forecast. Over land there is a special model to describe the evolution of both temperature and humidity at the ground during a forecast.
Before the start of a weather forecast the model needs to know the state of the atmosphere. To achieve this knowledge the weather parameters of the model are analysed together with different sorts of measurements from the atmosphere, e.g. from weather balloons (radiosondes) and from satellites. In the future, data from meteorological satellites and weather radar will be very important for the quality of the weather prediction.
The most important meteorological weather parameters produced by the weather model are wind, temperature, cloud cover and precipitation, but many other types of information are produced from the models to the customers of DMI.
In the table is shown the characteristics for the different models which individually need an external model to supply the needed weather information from outside to the model’s internal domain. The models of DMI-HIRLAM are coupled to the global model of the European Weather Centre ECMWF (European Centre for Medium range Weather Forecasts).
|
T15 |
M09 |
K05 |
S03 |
|
Number of vertical levels
|
40
|
40
|
40
|
40
|
|
Horizontal resolution
|
0,15° (16 km)
|
0,09° (10 km)
|
0,05° (5 km)
|
0,03° (3 km)
|
|
Time step
|
450 s
|
400 s
|
150 s
|
90 s
|
|
Boundary values
|
ECMWF
|
ECMWF
|
M09
|
M09
|
|
Forecast length
|
60 hours
|
60 hours
|
48 hours
|
54 hours
|
|
