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Statistical correlations with the Bristol
Meteorological Office site, that was less than two miles to the
North and was situated on top of a City Centre office block, were
generally good with rainfall and barometric data particularly close.
The site of the station is approximately 34 metres above sea level with the manual instruments mounted in a Stevenson screen. The screen is sited centrally in a small concreted garden area. A Snowdon rain gauge is mounted correctly in the ground but does not have the full open space required around it. A Davis Vantage Pro2 Plus automatic weather station (AWS) was added in May 2005 and this is mounted 4 feet above a concrete shelter. The wind data is gathered automatically from a Davis Vantage Pro2 Plus anemometer which is sited 3.3 metres (10 feet) above the house top.
Manual observational readings are still taken at approximately 0900 hours GMT every day for cloud cover and rainfall. Rainfall recorded in the Snowdon rain gauge taken at 09:00 GMT is entered for the previous day. The wind data is constantly logged and automatically reset at 24:00 hours GMT every day. The Davis rainfall tipping bucket was recalibrated in November 2005 and is now consistently under 3% under recording (an improvement from installation in May 2005 when 10% was more typically the norm).
Since the arrival of the Davis Vantage Pro2 Plus equipment in May 2005 temperatures, humidity and barometric pressure will be recorded from the new equipment. These figures will be more accurate and will be taken at exactly 09:00 GMT as the data is now logged to a computer.
By default the Davis equipment records every parameter for the 24 hour period 00:00 to 23:59 GMT. Data analysis will enable manual data extraction of temperatures and rainfall to 09:00 GMT. Due to the 0.2 mm (tipping bucket) measurements of precipitation recorded by the Davis equipment the Snowdon rain gauge will still be used due to its greater accuracy (see above).
Legend for the monthly data pages:
|Time = actual time GMT time that data was recorded.||Ave = Average temperature of last 24 hours max and min.|
|Temp = Temperature at the above time - degrees C.||Range = Difference between Max and Min temperature.|
|Min = Minimum temperature entered for the previous day - degrees C||pptn (mm) = Rainfall in millimetres entered for the previous day.|
|Max = Maximum temperature entered for the previous day - degrees.||Pressure (mb) = Barometric sea level pressure in millibars..|
|AF = Air frost recorded for last 24 hours.||Sf = Snowfall in last 24 hours.|
|GF = Ground frost recorded in last 24 hours - not currently collected.||Sl = Snow lying in last 24 hours (50% ground cover).|
|T = Thunder heard in last 24 hours.||H<5mm = Hailstones less than 5 millimetres in diameter.|
|AF = Air frost recorded in last 24 hours.||H>5mm = Hailstones greater than 5 millimetres in diameter.|
|Max Gust (mph) = Maximum gust in last 24 hours.||Cloud cover (Oktas) = Cloud cover observed in 8ths of the sky.|
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