Weather Radar — Europe

CMAX is the maximum reflectivity value (dBZ) found in the vertical column above each map location, built by merging all radar elevation sweeps and keeping only the highest value at each pixel. The Europe-wide CMAX is merged centrally by EUMETNET/OPERA into a single 1 km grid; a country MAX is the same product type, but computed in your browser from that country's station sweeps at 500 m (1000 m for NO/NL).

Per-station products:

DBZH — Reflectivity (dBZ): how much power came back; a measure of precipitation intensity.
VRADH — Radial Velocity (m/s): how fast the precipitation moves toward or away from the radar. Limited by each scan's Nyquist interval, and normalized per sweep.
ZDR — Differential Reflectivity (dB): compares the horizontal vs. vertical return. Raindrops fall flattened, so rain reads positive; hail tumbles and reads near zero. Tells you the shape of the drops.
RHOHV — Correlation Coefficient (CC, 0…1): how similar the horizontal and vertical returns are.
WRADH — Spectrum Width (m/s): how much the measured velocities spread within one sample. Narrow = steady wind; wide = turbulence, gusts or shear.
PHIDP — Differential Phase (degrees): phase shift between the horizontal and vertical pulses after passing through the precipitation; grows smoothly through rain. Used to correct rain-rate estimates.
KDP — Specific Differential Phase (deg/km): how fast PHIDP changes per kilometer. Strongly positive in heavy rain.

CAPPI (Constant Altitude Plan Position Indicator) is a horizontal slice of reflectivity data at one fixed altitude, built by interpolating between the elevation sweeps that pass through that height.

Echo Top finds the highest altitude at which reflectivity still equals or exceeds a chosen threshold — here, 18 dBZ.

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