Products

Up to seven parameters per station.

Per-station products. Every radar on the map delivers reflectivity. Most also deliver Doppler velocity, and the dual-polarisation networks add their polarimetric fields - but how many a station carries depends on what its national weather service publishes: from one parameter (Malta) to all seven (Slovakia). The files are decoded on the Duoradar server into compact grids; colouring and drawing happen on your own machine, in WebGL2.

Derived products. On top of the raw sweeps the map builds country composites, column maxima (MAX), constant-altitude slices (CAPPI) and echo tops (TOP) - merged in your browser from each country's own stations. The Europe-wide composite is the one product that arrives ready-made: it is produced by EUMETNET OPERA.

Per-station parameters

What a single radar measures.

DBZH

dBZ

Reflectivity

How much of the transmitted power the precipitation sends back - the basic measure of how intense rain, snow or hail is. Every other product starts from it.

Scale: -32 to 70 dBZ
Where: Every station, all 20 countries

VRADH

m/s

Radial Velocity

How fast the targets move toward or away from the radar (Doppler). Each scan can only measure up to its Nyquist velocity; faster motion folds over to the opposite sign. Values are shown exactly as delivered - no de-aliasing.

Scale: -50 to +50 m/s
Where: Every country except Malta and Romania (and Belgium's Helchteren radar)

WRADH

m/s

Spectrum Width

How much the measured velocities spread within one sample. Narrow means a steady flow; wide means turbulence, gusts or shear.

Scale: 0 to 30 m/s
Where: Czechia, Denmark, Estonia, the Netherlands, Slovakia, Sweden

ZDR

Differential Reflectivity

Compares the horizontal and vertical return. Large raindrops fall flattened, so rain reads positive; tumbling hail and dry snow read close to zero. It tells you the shape of the targets.

Scale: -8 to +8 dB
Where: Croatia, Czechia, Denmark, Estonia, Germany, the Netherlands, Slovakia

RHOHV

0…1

Correlation Coefficient

How similar the horizontal and vertical returns are - also written CC. Pure rain or snow sits close to 1; mixed precipitation, birds, insects or ground clutter pull it down.

Scale: 0 to 1
Where: Croatia, Czechia, Denmark, Estonia, Germany, the Netherlands, Slovakia

PHIDP

Differential Phase

The phase shift that builds up between the horizontal and vertical pulses as they travel through precipitation. It grows steadily through rain and is the basis for KDP.

Scale: -180 to +180°
Where: Czechia, Denmark, Estonia, Germany, the Netherlands, Slovakia

KDP

°/km

Specific Differential Phase

How fast PHIDP changes per kilometre. Strongly positive in heavy rain, and largely unaffected by how much signal the rain has already absorbed.

Scale: -1 to +5 °/km
Where: Slovakia

Germany publishes its polarimetric fields unfiltered (UZDR, URHOHV, UPHIDP) and Sweden its velocity unfiltered (UVRADH): these fill the whole scan circle, clear air and noise included, so they look busier than the filtered fields of other networks. Every elevation up to 45° can be viewed; steeper vertical soundings are left out because they cannot be drawn as a map.

Derived products

Built from the sweeps.

CMAX

dBZ

Europe-wide Maximum Reflectivity

The strongest reflectivity found in the vertical column above each point, merged from the national radar networks by EUMETNET OPERA and delivered as open data through MeteoGate.

Grid: 1 km cells, 3,800 × 4,400 km
Update: A new frame every 5 minutes, each built from 10 minutes of scans
History: Last hour; up to four hours in the settings

COMP

by elevation

Country Composite

One elevation from every radar of a country, merged into a single picture. A station whose newest sweep has not arrived yet keeps its previous one, marked as stale, so the country never goes blank between scans.

Grid: 500 m cells (1 km for Norway and the Netherlands)
History: The country's last 12 scan cycles

MAX

dBZ

Country Column Maximum

The country's own version of CMAX, computed from its stations' sweeps: every elevation of every radar that reaches a cell contributes, and the strongest value wins.

Grid: 500 m cells (1 km for Norway and the Netherlands)
Input: All elevations up to 45°

CAPPI

1.5 / 2 km

Constant Altitude Plan Position Indicator

A horizontal slice of reflectivity at a fixed altitude. For every cell the map works out how high each beam passes, then blends the sweeps just below and just above the target height. Where no such pair exists, the nearest sweep is used; beyond that the cell stays empty.

Heights: 1.5 km and 2 km
Rules: Blend when the two sweeps are at most 2.5 km apart; nearest sweep within ±1.2 km

TOP

Echo Top

The highest altitude at which reflectivity still reaches the chosen threshold, interpolated between the last beam above it and the first beam below. Tall tops mark strong, deep convection.

Threshold: 18, 30 or 40 dBZ (selectable)
Scale: 1.5 to 15 km; lower tops show in the lowest colour

Country composites, MAX, CAPPI and TOP are computed by your browser's graphics card from the stations' decoded sweeps - nothing is pre-rendered on a tile server. Beam heights use the standard 4/3 Earth-radius model, starting from each radar's own height above sea level.