Data from the University of Salford project "Hyrometeorological studies using a VPR".
This document describes the University of Salford data from the HYREX project. There are separate dataset descriptions for the common infrastructure dataset, the UKMO Unified Model data supplied by JCMM, and for the Chilbolton radar data.
The primary focus of this research project was to commission and deploy a mobile X band Vertically Pointing Radar (VPR) in the HYREX project area to support a high resolution study into the hydrometeorology of local rainfall systems. Of particular significance was an examination of the problems of bright band contamination of quantitative rainfall measurements from scanning weather radars. Large errors can result from the transmitted microwave intersecting water coated ice crystals at and immediately below the melting layer and thus generating larger reflected signals than would arise from ordinary raindrops.
The research programme was designed to further the understanding of bright band characteristics and dynamism and support the development of algorithms capable of modelling the consequences of variations in the vertical reflectivity profile on quantitative precipitation measurements. Hence the VPR data were integrated with other HYREX data sources including the Chilbolton, Cobbacombe and Wardon Hill radars as well as the Salford low-cost C band MARS data (see Cluckie et al., 1995). The use of additional VPRs (one mobile and one located at the University of Salford) provided an opportunity to investigate the spatial variability of bright band characteristics through a number of transect experiments in north west England and via deployment in areas covered by the Chilbolton radar. Ground truth measurements were obtained from Transportable Weather Stations (TWS) and two drop counting raingauges (hydragauges) deployed alongside the VPRs. Data were also obtained from an acoustic radar and a disdrometer. Additional rainfall measurements from the dense raingauge network in the Brue catchment were also used.
Three VPRs were used during the course of the project. Technical specifications may be found in Cluckie et al. (1992). For the period May - December 1994 data were collected in the north west of England from one device located at the University of Salford and two mobile devices which were deployed locally either at Warrington and Fazakerley or Davyhulme and Audenshaw (see Tilford et al., 1995). These combinations covered ranges of 43 and 17 kilometres respectively. From April - December the two mobile VPRs were operated in the HYREX region. Section 2.6 details the availability of all instrumentation operated by the Salford group during the HYREX period.
The VPR data consist of vertical reflectivity profiles at a resolution of 7.5 m and 4 seconds, and the files can be read using software available from Salford. The data quality is somewhat variable due to hardware and software modifications made during the course of the project and the unattended operation of the radars. No attempt has been made to quality control these data sets except in the case of specific events analysed by the Salford Group.
TWSs are operated alongside each of the VPRs and the availability of the data from these is outlined in Table 1. The stations record rainfall (0.1 mm tips) wind speed and direction, pressure, wet and dry bulb temperatures, humidity and net and solar radiation, all with a temporal resolution of 2 minutes.
The Hydragauge is a high resolution raingauge developed by the Atmospheric Physics Group, University of Auckland (Stow, 1993). The device operates by producing near-constant-size drops which are counted during a switch-selected time interval to give the rainfall rate. The nominal calibration of 160 drops per mm enables the gauge to measure rainfall intensities of up to approximately 200 mm per hr.
An RD-69 disdrometer (Joss and Waldvogel, 1970) was loaned by J.Goddard of Rutherford Appleton Laboratory for deployment alongside a VPR and the acoustic radar. The device records drop sizes over a range of 0.3 - 5.0 mm and stores data as the number of drops in each of 20 approximately exponentially distributed drop size classes over the given range. For the purposes of this study the temporal resolution was set to 1 minute.
The Auckland acoustic profiler (Bradley and George, 1994) transmits an 8l beam at 4250 Hz, 4300 Hz or 4350 Hz sine wave for 0.075 s from a 150 W array of 37 piezo-electric tweeters. These are then used as microphones for approximately 2 s which enables the signal reflected from inhomogeneities up to an altitude of 340 m to be observed. The returned signal is amplified and sampled at 10 bit resolution at a rate of 572 Hz over 20 m range gates.
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Date | Location | VPR | TWS | Hydragauge | Disdrometer | Acoustic
| | | | | | Radar
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| | | | | |
190495 - 030595 | Chilbolton | X | | X | |
| | | | | |
190495 - 030595 | Boscombe Down | X | X | X | |
| | | | | |
040595 - 240895 | Middle Wallop | X | X | X | |
| | | | | |
040595 - 100595 | Boscombe Down | X | X | X | X |
| | | | | |
110595 - 230595 | Boscombe Down | X | X | X | X | X
| | | | | |
240595 - 050695 | Boscombe Down | X | X | X | X |
| | | | | |
080695 - 140695 | Boscombe Down | X | | X | |
| | | | | |
230695 - 300695 | Boscombe Down | X | X | X | |
| | | | | |
010795 - 260795 | Boscombe Down | | X | X | X |
| | | | | |
270795 - 010895 | Boscombe Down | X | X | X | | X
| | | | | |
020895 - 090895 | Boscombe Down | | X | X | | X
| | | | | |
100895 - 140895 | Boscombe Down | X | X | X | | X
| | | | | |
150895 - 240895 | Boscombe Down | | X | X | | X
| | | | | |
250895 - 200995 | Middle Wallop | X | | X | |
| | | | | |
250895 - 200995 | Alhampton | X | | X | |
| | | | | |
210995 - 231195 | Middle Wallop | X | X | X | |
| | | | | |
210995 - 031095 | Alhampton | X | X | X | |
| | | | | |
041095 - 171095 | Alhampton | | X | X | |
| | | | | |
181095 - 211195 | Alhampton | X | X | X | |
| | | | | |
241195 - 211295 | Alhampton | X | | X | |
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Data analysis has been restricted to a number of individual storm events and consequently no general quality control measures have been undertaken. The use of any of the Salford datasets should be made with this in mind. Some guidance can be given as regards instrument failure and any potential error sources found during the course of routine maintenance. Most of the data held by Salford can be made available to any interested third parties although the use of VPR data by other researchers should be undertaken in collaboration with the Water Resources Research Group because of the technical issues detailed earlier.
The BADC holds the ancillary data, i.e. hydraguage and transportable weather station (TWS) files, plus image files of the radar data. Researchers wishing to use the data are encouraged to liaise with the PI group.
These data are world-readable, so they can be obtained via WWW from http://www.badc.rl.ac.uk/badc/hyrex/data/salford/ or by FTP (Note that you will need to register as a BADC/NEODC user before using this service - connect to ftp.ceda.ac.uk, log in with username and password and cd to directory badc/hyrex/data/salford).
The help file readme.txt gives details of file formats and contents. The hydragauge and TWS data are in ASCII files, while the radar images are held in GIF files.