# Weather Radar in Complex Orography
## 4 Solutions and Results
### Installation, Acceptance Testing and Lightning Protection  
The installation work of the Swiss radars had to be supported, to a great extent, by helicopters. Before starting the challenging civil work to install a new radar on a remote mountain peak, it is good practice to conduct detailed tests at the factory. Testing and fixing technical problems is far easier in a factory than at 3000 m above sea level. The Swiss radars were thoroughly tested on the roof of the supplier's factory as part of the formal acceptance process by analysing data injected by test equipment, reflections from a nearby tower, signals from the Sun, and echoes from precipitation, while operating the radar in the foreseen operational configuration. During the factory tests, which lasted several weeks, the hardware monitoring parameters were recorded in real time and various aspects were analysed.  
Another novel element for acceptance testing was a 6-month test period in operational mode, which started upon completion of the site acceptance test at the end of commissioning. The 6-month operational test was followed by a final 4-month test of the whole network. Throughout the acceptance testing, the combination of different pieces of complementary equipment and sources of information proved to be a good strategy. In addition to standard tests, MeteoSwiss deployed an external receiver and an external transponder, and implemented numerous experiments to gain as much information about technical and functional performance of the radar as possible. The transponder can introduce a time delay, which allows the signal to be moved to a silent gate, with no clutter contamination. It can also add a shift to the Doppler frequency and change the polarisation, which are interesting options to make independent measurements of the specifications of a new radar [133].  
Protection from lightning is another aspect that needs to be carefully thought through for radars on exposed mountain sites. A direct lightning strike can cause major damage to the radome [134] and the antenna, the repair of which could take several months. The damage caused by indirect lightning currents, which enter via the power or data line, is generally less serious, but locating and fixing the damage can be lengthy and complicated. Adequate protection from lightning is thus mandatory. On the other hand, it is desirable to avoid, as much as possible, any interference of lightning protection rods around the radome on the radar measurements. It has been shown that lightning poles can cause significant interference, in particular for polarimetric moments. Two groups of rods have been used to protect the Swiss radars from lightning, one is situated below the lowest point of the antenna, and the other one is located in the upper part of the radome, see Figure 13. With this design, the risk of interference is marginal and limited to the highest sweeps, which are less critical for quantitative rainfall estimation. To date, no interference has been witnessed in the measurements.  
Figure 12: Precipitation along a vertical north–south cross section through the Alps, as seen by the five Swiss radars. Reflectivity measurements from each radar were converted into equivalent rainfall rates using a fixed Z–R relation and then accumulated over the whole of 2016. All five panels use the same colour scale. Ideally, all the radars would show the same picture, that is, have the same values for all the locations on the cross section. However, this is not the case, because of severe shielding, clutter cancellation and broadening of the beam with distance. The distance between the radar sites and the nearest point on the cross section is indicated after the name of each radar. For the position of the cross section, see the dashed line in Figure 1.