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14
METEOROLOGICAL OBSERVATIONS.
I am indebted to Sir H. Spencer Jones, F.R.S., Astronomer
Royal, for the following meteorological data for the year ended
December, 1947.
The mean temperature for the year was 50.6° which is 0.9°
higher than the average for 100 years 1841-1940. The highest
temperature in the shade was 95.7°, registered in an open screen,
facing north, on June 3rd, which was thus the warmest June day
ever recorded at the Observatory.
Temperatures exceeding 90° were recorded on 9 days. These
included two instances of four consecutive days (May 31st to June
3rd and August 15th to 18th) a circumstance without previous
example at Greenwich. May, August and September were exceptionally
warm months. The thermometer reached 70° on every day in
August, and this also has no previous example in the Observatory
registers.
The lowest temperature was 9.0°, which occurred on February
24th. There were 71 days on which the thermometer gave readings
below freezing point, 18 in January, 26 in February, 18 in March,
1 each in April and October, and the rest in November and December.
On the whole, February was the coldest month since February 1895
when, although a slightly lower temperature occurred at night
on one occasion, day temperatures were in general a little higher
than in February 1947. Snow lay on the ground practically throughout
the month.
The mean daily horizontal movement of the air was 244 miles,
41 miles below a fifty years' average. The greatest daily movement
was 675 miles (April 23rd) ; the greatest hourly movement was 52
miles (March 16th), the greatest wind pressure 35.0 lbs to the square
foot occurring on the same day.
The duration of bright sunshine was 1400.6 hours—a little
below average. The sunniest day was May 28 when 14.8 hours,
representing 92 per cent of the possible total, were registered.
There were 88 entirely sunlese days, 73 of which occurred in the
winter months November to March.
The total rainfall was 20.296 inches, 3.03 inches below a 100
years' average. The March total of 5.22 inches surpassed by more
than 1 inch any previous fall in March during the 132 years of
Greenwich records. On the other hand the rainfall during the last
six months of the year—6.26 inches—was lower than in any previous
instance, the nearest example being 6.59 inches in 1921.
The period from August 6 to September 7th inclusive comprised