Royston (Iceni) Weather Station

Daily Weather Observations - March 2003

The weather in Royston in March was mild, dry and exceptionally sunny.

One of the outstanding features of the March weather was the absolute drought which endured from 13^th to 31^st March. Only 0.7 millimetres rainfall was recorded in the 5 days prior to the commencement of this period, thus making the ‘dry’ spell effectively 24 days in length. The drought ended on 1^st April, however, when a south-eastwards moving cold front brought 5.5 millimetres rainfall to Royston.

Total rainfall in March was 19.2 millimetres, which is 45% of the 30 Year (1971/2000) average. The number of "rain days" (0.2 millimetres or more) was only 3 which is the lowest such total in March in Royston since at least 1972. The monthly rainfall total itself was only the lowest since March 2000, however, when it was much drier with only 11.3 millimetres rainfall.

The wettest day in March was 5th when rainfall of 11.6 millimetres was recorded. On this day liberal deposits of orange/brown sand were washed out over Royston in this rainfall. A backward trajectory analysis of the air flow over the days preceding this event reveals the source of this fine sand to have been the deserts of Western Algeria and Mauritania, having been carried aloft by strong winds there.

Rainfall duration in the month was only 14.7 hours. No thunder was heard in March (thunder in March is only a 1 year in 4 possibility based on past records), and no snow or hail was observed to fall.

In yet another month (now 56 months in the last 75) the mean temperature was above average, mainly helped by the abundant sunshine (see below) raising day maximum temperatures to well above normal. Night frosts around mid-month pegged night minima back to average, however.

The mean daily maximum temperature in March was 13.1°C, which is 3.0°C above the 30 Year (1973/2002) average. This is the highest such value in the last 30 years in Royston, and is higher than the 30 Year April mean! The mean night minimum temperature of 3.3°C was exactly on the average.

The highest temperature recorded in March was 18.0°C which, despite the high mean maximum temperature, is not exceptional for March, having been equalled or exceeded in 6 out of the last 30 years. In contrast, the lowest day maximum temperature in the month was 7.0°C on 13^th. The lowest temperature of the month was –2.4°C on 22^nd, whilst the lowest grass minimum temperature was -5.5°C on 19^th. The highest night minimum temperature in March was 9.8°C on 5^th. In total 7 air frosts and 14 ground frosts occurred in March.

The mean earth temperature at 30 cms depth as measured at 0900 GMT daily was 7.0°C. The earth temperature extremes ranged from a minimum of 5.5°C on 3^rd to a maximum of 9.0°C on 31^st.

In addition to the drought mentioned above the other outstanding feature of the March weather was the very high sunshine total. The total sunshine of 197.9 hours (183% of the 30 Year (1961/1990) average) was higher than the 30 Year average for any month of the year! This high total was achieved despite sunshine running below average over the first 13 days of the month. Thereafter persistent anticyclonic conditions gave the clear skies responsible for the exceptional sunshine.

Only 1 day (29^th) in the month was completely sunless. This was more than compensated for over the next 2 days, however, with 11.6 hours sunshine on 30^th and 12.4 hours sunshine on 31^st. This latter figure was the highest daily sunshine total of the month.

The mean wind speed in March was 3.7 mph. The daily (00/00 GMT) mean wind speed ranged from a highest value of 12.4 mph on 8^th to a lowest value of 0.4 mph on both 19^th and 28^th. The highest wind gust speed recorded in the month was 41 mph on 8^th.

The monthly analysis of wind directions as observed at 0900 GMT daily was NORTH 3 days, NE 7, E 2, SE 0, S 4, SW 6, W 3, NW 2, and CALM (no discernible direction) 4.

The mean MSL air pressure in March was 1023.2 mB, which is approximately 8 mB above average, reflecting the strong anticyclonic influence. The highest and lowest air pressure readings recorded in March were 1043 mB and 1007 mB on 16^th and 2^nd respectively.

The mean relative humidity in March was 78.2%. The highest daily (00/00 GMT) mean relative humidity was 91.4% on 4^th, whilst the lowest daily mean relative humidity was 65.7% on both 19^th and 20^th. The absolute lowest relative humidity reading in March was 32% at 1425 GMT on 14^th and also at 1455 GMT on 27^th.

Fog (visibility < 1000 metres at 0900 GMT) was observed on 3 days ( 21^st, 22^nd and 28^th) in March. On 28^th visibility fell below the 200 metres threshold at 0900 GMT.

Met. Observer, Royston (Iceni) Weather Station

4^th March 2003

Royston Crow (Corvus Cornix)

Return to Daily Weather Observations - March 2003 header page