December 2011

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 1990)

Mean daily maximum: 7.7
Difference from average: +1.1

Mean daily minimum: 2.3
Difference from average: +1.2

Mean air temperature: 5.0
Difference from average: +1.1

Absolute maximum: 12.9 (22nd)

Absolute minimum: -1.9 (9th)

Mean grass minimum: 0.3

Absolute grass minimum: -5.5 (9th)

Number of ground frosts: 15

Number of air frosts: 6

Mean soil temperature at 30cm depth: 6.0

Mean soil temperature at 100cm depth: 8.6

Rainfall
(all totals in millimetres; all averages 1961 – 1990)

Total for the month: 49.2
Difference from average: -8.2

Percentage of the average: 86%

Wettest day: 8.0 (30th)

Number of rain days (>0.25mm): 16

Number of wet days (=> 1mm): 15

3-month total rainfall to 31st December: 127.2
Difference from average: -44.8

6-month rainfall total to 31st December: 373.0
Difference from average: +26.8

12-month rainfall total to 31st December: 592.2
Difference from average: -56.8

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity:

Sunshine
(all averages 1961 – 1990)

Total for the month: 68.3 hours
Difference from average: +22.7

Percentage of the average: 150%

Mean daily sunshine: 2.2 hours
Difference from average: +0.7

Sunniest day: 6.3 hours (18th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 1364.3 hours
Difference from average: +35.1

Wind

The mast is still broken, we hope to replace it soon.

ISSN1350-483

Comments on December 2011
This was the 32nd equal warmest December in 162 years, easily into the upper quartile. The mean maximum temperature was the highest since 2005 and the mean minimum was the highest since 2002. The 12-month running mean for air temperature exceeded 10°C for the first none months of 2007 and the December 2011 mean is the highest 12-month mean since then. There has been a steady warming since the low point in December 2010 when the mean was 1.67°C lower, a very large difference. 2011 was the equal warmest year on record at Durham (with 2004): 9.96°C to two decimal places but 10°C to all intents and purposes!

December was another dry month, but not exceptionally so, 73rd lowest total in 162 years. Nine months have been below average in 2011 so the low total for the year is no surprise: 47th driest in 162 years. Sunshine hours were just above average, but there was less bright sunshine than in the previous three Decembers. Overall, 2011 had slightly more than average sunshine, but both 2006 and 2009 had higher totals.

Professor Tim Burt
Department of Geography
Durham University