Counteracting Dropout Effects of Network Radar Replacements

Operational data from the German weather radar network, in combination with meteorological follow-up procedures, have become indispensible tools under the policy of the national German weather service, DWD. Forecast and warning production in the fields of meteorology, hydrology and aviation have been promoting the use of realtime radar data, and dropouts or misoperation of individual radars are no longer tolerated. Therefore, DWD is striving to increase radar availability from presently 95% to 98% as well as network areal coverage in the course of the network radars' replacement. On the other hand, site-specific construction measures as well as installation and testing inhibit simultaneous radar operation during relocation and replacement. The individual non-operation intervals are dictated by an ambitious time schedule, taking into consideration particular construction and climatic conditions as well as installation capabilities of both the manufacturer and DWD.

Consequently, efforts have been taken to minimize disruptions in temporal and spatial coverage and to maintain availability and data quality: 1) The range coverage of the quantitative mode has been increased from 130 km to 150 km. Thus, radars out of operation are largely being covered/overlapped by their neighbours. 2) If possible, neighbouring radars are not switched off at the same time. 3) At some locations, a new tower will be built at a distance sufficient to safely continue operating the "old" radar for a smooth crossover. 4) One of the DWD peculiarities to make sure of uninterrupted availability is the so-called "failsafe radar", a relocatable radar nearly identical to the operational ones (but for 2 deg beam width, and single polarization). Mounted on a folding tower, it is temporarily deployed where an old tower must be restructured on site or be replaced within safety distance.

These measures, their effects and the remaining risks of data or quality losses will be described here.