Asko Huuskonen, FMI:

Radar Siting

Introduction: Siting a radar is a task in which the following points at least need to be taken into account or they have an effect on the decision. Only in rare cases one can follow the list step-by-step. Usually several of the items have to be considered simultaneously, although the items on top should be considered first.

- Network planning: the location of the radar as part of the (inter)national radar network. This task is easier if a fully new network is designed. Adding radars to an existing network may require that some radars are simultaneously moved. Savings will occur if the network is designed in co-operation with the neigbouring countries. Network planning is presently an important issue in Norway, where up to 6 radars are to be built, and to some extend in Sweden, where radars have recently been moved to new locations. One radar is needed to complete the Finnish network. A good location for the radar has been found.

- Location: The radar horizon should be unobscured, to the extent possible determined by the local orography. If the surrounding country is flat, as in Finland and most of Sweden, it is possible to find a location so that no (or very tiny) blocked sectors exist and so that the location is not too far from the optimal location based on the network planning. Such a location is the best for all the uses of the radar data. In mountaneous regions such locations are found only on mountain tops, but such a location is problematic for many of the points considered below. Thus an unobscured horizon is only one of the things which determine the radar location. The location also affects the building cost of the radar, if the site is not accessible by a lorry. If very strong winds (>50 m/s) are expected, the tower and the radome may need to be more sturdy (and thus more expensive). A remote location also increases the cost of electricity lines and the computer connections. It will also increase the cost of maintenance trips and will lengthen the delay of starting the maintenance.

- Permissions: Several permissions are needed for the building and operation of the radar. Most notable are the building permission from the local authority, transmitting licence from the frequency authority and the permission from the authority responsible for the radiation safety. The local communities also have a say in the acceptance. A radar may be a disturbing feature as part of the scenery or a radar is not wanted to the surroundings because of the radiation safety issues. The future building around the radar site has to be discussed with the local authority and explain that obscuring buildings, masts etc. decrease the value of the radar.

- Meteorology and uses of data: One puts the radar where most of the users are. There is a denser network in southern Finland compared to that in the northern Finland. In mountaneous countries (Norway) one weights the importance of servicing general forecasting to that of servicing hydrology. Locations at the airports should be avoided, because such a location is not the best one to support the aviation. There are other things which have an effect on the data quality. The amount of ground clutter and sea clutter. The probability of ducting and anaprop. These are usually things one has to live with and to try to eliminate from the data to the best possible extent.. The other factors are more determining for the siting and take precedence.