Royston (Iceni) Weather Station
Monthly Weather Review - March 2000
It was a very dry March in Royston, and milder and a little sunnier than normal.
March is the second driest month of the year (after February) in Royston and this year the month more than lived up to its reputation in this respect by producing only one quarter of its long term average rainfall.
Total rainfall in March was only 11.3 millimetres (0.44 inches), which is 26% of the 35 Year (1961/1995) average. The number of "rain days" (0.2 millimetres or more) was 9, whilst the wettest day was 2nd with 4.3 millimetres (0.17 inches) rainfall. It was the driest March since 1997 only as that year experienced an even drier March (8.1 millimetres rainfall). Rainfall duration in the month was 19.4 hours.
The month was snow, hail and thunder free, but a relatively unusual rainfall event did take place in the early hours of 24th. On the morning of 24th Royston woke up to a light covering of orange/brown fine sand which had been washed out in the overnight rain. The most likely source of this deposit is from sandstorms in the Sahara Desert which carried fine particles high into the atmosphere before being transported northwards. The synoptic situation at the time was ideal for just such an occurrence with a long fetch of winds from North Africa and a rainfall here which was light enough to preserve the evidence so to speak.
Temperatures were once again a significant feature of the weather even though no records were broken. This is because an above average mean temperature resulted in March being the 31st month out of the last 39 (i.e. since January 1997) to experience above average temperatures. A colder spell at the end of the month, however, served as a reminder why the recent winter was mild without any severe spells. A north to north-easterly wind set in on 27th and brought in cold air from northern Europe over a relatively cold North Sea, whereas the winter weather (and indeed much of March) was dominated by air masses originating over the much warmer Atlantic Ocean.
The mean daily maximum temperature in March was 11.6°C (52.9°F), which is 1.7°C above the 25 Year (1973/1997) average. The highest temperature recorded was 16.5°C (61.7°F) on 8th. The lowest day maximum temperature occurred on 29th when a value of only 6.5°C (43.7°F) was recorded, whilst the maximum temperature was little better on 28th and 30th at 7.6°C (45.7°F).
The mean night minimum temperature was 4.5°C (40.1°F), which is 1.4°C above average. The coldest night of the month was 4th when the temperature dropped to –2.0°C (28.4°F). The lowest grass minimum temperature of –5.6°C (21.9°F) also occurred on this date.
During March there was only 1 air frost and air frost duration was correspondingly low at only 7.3 hours. A total of 9 ground frosts occurred, however.
The mean earth temperature at 30 cms depth as recorded at 09 GMT daily was 7.8°C (46.0°F). The highest earth temperature recorded in the month was 9.0°C (48.2°F) on 24th and 25th, and the lowest 5.0°C (41.0°F) on 5th.
Once again Royston enjoyed a month with above average sunshine making March the 7th consecutive sunnier than average month. Total sunshine of 120.4 hours was 111% of normal. The sunniest day of the month was 12th with 11.0 hours. Other days with over 10 hours sunshine were 15th (10.4 hours) and 21st (10.4 hours). Five days (2nd, 17th, 20th, 29th and 30th) in the month were completely sunless.
Although March is traditionally a windy month it was not particularly so this year with a mean wind speed of 5.4 mph, the lowest monthly value so far this year. However, a maximum gust speed of 58 mph did occur on 3rd. The highest daily (00/00h) mean wind speed was 13.4 mph on 8th, whilst the lowest daily mean wind speed was 0.6 mph on 31st.
As regards wind directions observed daily at 09 GMT these were as follows: N 5, NE 2. E 0, SE 1, S 1, SW 7, W 8, NW 6, CALM 1.
The mean MSL air pressure throughout the month was 1021.1 mb, which is approximately 6 mb above average. The highest pressure reading observed was 1038 mb on 19th and the lowest 998 mb on 3rd.
The mean relative humidity in March was 81.0%. The highest daily (00/00h) mean relative humidity was 91.6% on 29th and the lowest daily mean relative humidity was 70.2% on 4th.
Fog hardly featured in March, there being just one day (22nd) when the visibility reduced to below 1000m at the 09 GMT observation hour.
Richard Barker
Richard Barker
Met Observer, Royston (Iceni) Weather Station
4th April 2000
Royston Crow (Corvus Cornix)
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