UK Wind Profiler Network: Preparation for operations and future requirements

Oakley, Tim & Nash, John

Met Office, Bracknell, Berkshire, UK

+44 (0)1344 855644 , +44 (0)1344 855897 (Fax),

Introduction.

The Met. Office operates four LAP3000 boundary layer wind profiler radars in the UK, located at Camborne and Dunkeswell in the South West of England, Aberystwyth in Wales and Wattisham on the East coast of England. A development project was tasked with demonstrating the capabilities of such a network and preparing the systems so that they could report wind measurements at a suitable quality and real time availability to be considered operational. From February 2001 observations from these sites have been routinely assimilated in the UK Met Office’s NWP models . The hand over process to operations will be completed during 2002.

Network.

Figure 1 details the current wind profiler network in the UK. Originally the sites were selected on the basis of providing a suitable ‘demonstration’ network ( approx. 100km separation) for investigations but should also have some existing infrastructure (reduced installation costs) and other instrumentation. Sites at Dunkeswell and Camborne (see Fig. 2) were selected as these were Met Office sites with existing surface/upper-air instrumentation and communications. Aberystwyth is a university site with a 46MHz wind profiler, which the Met Office have a contract for routine wind measurements. This site was selected to install the ‘development’ system, which would be used for testing new software/hardware, temporary relocation for trials/research campaigns but also providing routine observations for operations. The Wattisham system was originally installed at Pendine (South Wales), a site equi-distant between Abersytwyth and Dunkeswell. However as agreed in the hand over to operations process, the instrument was relocated to the East of the UK to provide wind measurements in the vicinity of a radiosonde station (Hemsby) which was being closed as part of an automation project.

The original ‘lease’ wind profiler was operated at 915MHz as this was the normal frequency for operations in the United States. In the UK this frequency is controlled by the Ministry of Defence and hence was available for use by the Met Office. Use of this frequency elsewhere in Europe is not possible. When the wind profiler network was expanded in 1999, the new systems were chosen to operate at the agreed European frequency of 1290MHz. Although maintaining systems at 2 frequencies has a higher maintenance cost, it has enabled the Met Office to compare the performance of the two systems. Subsequently it was discovered that both frequencies have restricted use in certain areas of the UK, due to other systems operating in the same band.

Figure 2 – Wind Profiler installed at Camborne, UK

Data availability and quality.

All wind profiler systems communicate in real-time, every 30 minutes, with the processing centre at Bracknell. Here the BUFR messages are processed and archived and routed to operations for NWP assimilation’s and dissemination on the GTS. Real-time displays (wind barbs) are provided on the Internet for forecasting/nowcasting use. Figure 3 below provide details of the data availability of the 4 systems since the beginning of 1999. Initially, whilst the network was running more as a demonstration, there were significant data loss due to hardware problems and lack of sufficient spares. However once the instruments had overcome the initial ‘start-up’ and improved infrastructure was in place, the availability improved significantly. Most of the problems occurring in the last year are related to communication failures (i.e. line faults) or to computer failures. This can be further improved by a greater redundancy of equipment (i.e. hot spares) but this will increase the running costs. The policy in the UK is to create an integrated upper-air observing network, whereby additional observations provide the redundancy in the event of a system failure. This should reduce the urgency to repair the equipment in the shortest possible time and the need to have extensive spares.


The wind measurements from the 4 UK systems have been available routinely to the operations (both NWP & Forecasters) since early 2001. Initially the measurements were only compared with the model fields both to demonstrate the quality of the measurements and for case studies to highlight the benefits of the additional, high temporal wind data. After a 12-month verification exercise, it was agreed that from February 2001 the UK wind profiler data (and associated European data) could be assimilated into the UK Global and Mesoscale models. Regular observation minus background (O-B) statistics are produced on a monthly and quarterly basis so that the performance of the systems can monitored. The table below details RMS statistics for the 3 wind profiler sites at Camborne (03807), Dunkeswell (03840) and Wattisham (03591). The statistics for the MST radar at Aberystwyth (03500) are included as a comparison. It can be seen that all systems have a similar performance ranging from 3 - 5.8m/s RMS differences. Higher values are observed at the upper levels for the boundary layer profilers, here the systems are invariable at the extent of their height range and the sample sizes are much smaller.

Hand over to operations.

After the success of the demonstration wind profiler network , a process needed to be agreed to transition these systems from development to operations. Although the procurement of these instruments did address the data requirements, build quality and system features of the wind profilers, additional, more operational issues were not addressed. Thus a transition document/process needed to be agreed to address the following issues:

  • Standard of installations.(electric’s, earthing, cabling, must meet Met Office standards)
  • Communications.( operational and support by central IT/Comms. group)
  • Technical support.( level of support provide by maintenance group and manufacturer)
  • Technical training.( level of training to engineers and network managers)
  • Documentation.( full documentation for ISO9000 etc.)
  • Spares.( agree suitable spares level + service level agreement)
  • User training.( training forecasters in the use of the data)
  • Long term support.( development support for testing/implementing new software/hardware)
  • Data archives(archiving policy and data access policy for research/commercial)

A number of these items were addressed during the demonstration phase and the target is to have these systems considered fully operational by the end of 2002. However this ‘hand over’ process is a complex programme requiring significant resource and is often overlooked when initiating projects and instrument trials for future observing systems.

Future

Figure 4 gives details of the UK Upper Air network planned for the end of 2002. Only two radiosonde stations will be staffed full time. Each of these stations will be responsible for checking and controlling the measurements from 2 Autosonde locations. The wind profiler on South Uist (NW of mainland Scotland) is planned to be in operation by the end of 2002. It will be a tropospheric wind profiler operating at 64MHz. It is the first Met Office wind profiler, which has been procured as a fully operational installation, supported for a period 10 years.

Among other advantages, wind profiler measurements provide network resilience in times of severe weather when Autosonde/Aircraft measurements might not be available. Real time, integrated, display of wind reports from radiosonde, aircraft’s and wind profilers have been developed to demonstrate this. These displays act as an important diagnostic tool for checking data quality and also investigating the mesoscale structure of upper air winds. At present these types of displays have not been fully developed for operational use and network management and are only updated twice per day.

The Met Office has also started to evaluate the benefits of additional remote sensing instrumentation collocated with the wind profilers. A real-time network of 8 GPS Water Vapour instruments is functioning, a relatively cheap 78GHz fmcw cloud radar has been developed in collaboration with the Rutherford Appleton Laboratory to provide a proof of concept ‘prototype’ and a 12 Channel Microwave radiometer has been initially deployed at the Camborne test site. The purpose of the current projects is to understand the measurement capability of the individual systems and then to investigate how the different types of measurements can be combined to provide profiles of temperature and humidity and cloud structure in the most cost-effective fashion. This will involve performing test evaluations with a more complete set of sensors than may be necessary for future operations.

It is clear that future ‘operational’ networks of integrated products not only rely on a detailed understanding of the remote sensing measurements (both real and derived) but also development and investment in reliable, real time communications and automated software displays tailored to the users. Work to develop the required infrastructure and software goes ‘hand in hand’ with the work in evaluating the instrument capabilities.