# Weather Radar in Complex Orography
## 4 Solutions and Results
### Availability and Timeliness  
If the radar data are used for air traffic control, severe weather warnings or other safety-related applications, timeliness and availability are crucial. With an appropriate design and implementation of the data transmission and processing chain, the base products, including radar QPE, are ready for submission to the user within about one minute after the completion of a volume scan. The times are somewhat longer for enhanced products, such as thunderstorm nowcasts and heavy precipitation warnings, which also include data from other observation systems (a lightning detection network, rain gauges, satellites) and from the numerical weather prediction model. Table 1 shows timeliness statistics, as retrieved by the automatic real-time monitoring system, for different types of products of the Swiss radar network. The base and enhanced products include both single-radar and composite products of all the five radars. The antenna takes about ten seconds less than the nominal time to complete a volume scan. This time is enough to transmit and process all the base products, including radar QPE, for 50 percent of the cases, see the 50 th percentile in Table 1. For 90 percent of the time, the base products are ready within 8 s (90 th percentile), while for 99.95% of the time, they are ready within 60 s (last column). The times could be further reduced, if necessary, by means of parallel processing and a further optimisation of the processing chain. On a few days, and for a limited duration, the data transmission and processing took more than 300 s. These delays are related to planned interruptions of the central processing computer  
Figure 17: Ageing TR-limiter on the Weissfulhupigfel radar, as revealed by the automatic noise source measurements in the horizontal (red) and vertical (green) polarisations (\(y\)-axis to the left), the difference between the two (blue), and samples of the Sun’s signal obtained online during normal operation (black dots, \(y\)-axis on the right). for upgrades and security patches of server hardware, which are scheduled on days in which there is no significant precipitation. Satisfying the requirements of _availability_ is an even more demanding task. Users generally require radar information, such as QPE data and thunderstorm and heavy precipitation warnings, in real time, for all the regions in the country for 97, 99 or even \(>\)99% of the time. A single radar is not able to reach these numbers easily, and surely not in the case of a radar on a remote mountain site where a single failure that requires an intervention on site can easily last 2 or more days, because of long access routes. The interruption may be further prolonged as a result of weather restrictions of the cable car and difficult on-site working conditions. This should be added to the interruptions caused by preventive maintenance, which is usually scheduled twice a year. Whenever possible, preventive maintenance is performed under clear sky conditions, but this is not always possible, due to the weather conditions and limited flexibility. The high demands on availability can not be achieved by relying on a single radar.