"RADAR" is an acronym (english, RAdio Detection And Ranging) quite self explanatory, since it shows that radars do detect and locate targets while sending radio frequency electromagnetic waves into the atmosphere.
Radars that we use in meteorology, namely the ones that IPMA exploits, scan atmospheric volumes in a way that supports weather forecasters regarding the accomplishment of their activities; for instance, they are used to identify where and how much will rain, in the short term and, sometimes, to identify severe weather phenomena signatures. These radars supply wind information, as well. Currently, Coruche/Cruz do Leão and Loulé/Cavalos do Caldeirão form the portuguese weather radar network.
C band Doppler weather radar systems (aproximately 5cm wavelength), as the ones we exploit, measure:
dBZ is the reflectivity unit. The physical meaning of this unit is very hard to interpret; nevertheless, one can think of larger Z values to correspond to larger drops and/or larger hail stones.
dBZ turns into mm/h as long as reflectivity is converted into rainfall intensity. In this case, the physical meaning of the unit is the same than the one we get from surface classic weather stations. Radar observation is discrete; so, should radar observation be performed with 5 minutes interval and, for instance, a value of 15 mm/h is recorded by the radar on every observation performed in one hour period, it can be assumed to have a 15 mmm rainfall acumulated value (rainfall intensity assumed to be uniform during the time betwen observations.
The speed unit is m/s.
Currently, our Web page presents the following products:
Maximum returns of Reflectivity (dBZ) – available for each radar location every 30 minutes -, Rainfall Intensity (mm/h) – available for the radar composite every 30 minutes – and Hourly rainfall accumulation (mm) – available both for each radar location and for the radar composite every 30 minutes.
In every product there is an image scale, where cold colors (blueish) are associated with the lower values and warm colors (redish) to the higer ones.