July 2002

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

Mean daily maximum: 19.1
Difference from average: -0.2

Mean daily minimum: 10.6
Difference from average: +0.2

Mean air temperature: 14.9
Difference from average: 0

Absolute maximum: 25.5 (30th)

Absolute minimum: 5.1 (6th)

Mean grass minimum: 8.8

Absolute grass minimum: 3.8 (13th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.0

Mean soil temperature at 100cm depth: 14.7

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

Total for the month: 84
Difference from average: +32.1

Percentage of the average: 161%

Wettest day: 30.6 (31st)

Number of rain days (>0.25mm): 17

Number of wet days (=> 1mm): 13

3-month total rainfall to 31st July: 183.6
Difference from average: +27.7

6-month rainfall total to 31st July: 325.4
Difference from average: +28.9

12-month rainfall total to 31st July: 598.4
Difference from average: -50.6

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 74.5%

Sunshine
(all averages 1961 – 1990)

Total for the month: 118.5 hours
Difference from average: -36.4

Percentage of the average: 76.5%

Mean daily sunshine: 3.8 hours
Difference from average: -1.2

Sunniest day: 12.1 hours (13th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 817.4 hours
Difference from average: -27.6

Wind

The mean wind speed: 11.1 km/h [6kt]
Difference from average: -0.4 km/hr

The highest gust: 55.6 km/h [30kt] from 232° at 15:01 GMT on 8th

ISSN1350-483

Comments on July 2002
The mean air temperature was exactly equal to the long-term mean for July. Although this might seem a disappointing result, it is only four years since we had an even cooler July, but it was still below par compared to a year ago. As last month, sunshine was well below average; unlike June however, rainfall was well above average. All together, July 2002 was therefore rather unsatisfactory: dull, wet and only modestly warm.

I am as yet unable to make any detailed comments about the heavy rainfall on the 31st when the notable total of 30.6mm was recorded. Almost all of this seems to have fallen in the early hours of 1st August (the standard ‘rain day’ runs from 09:00 hours to 09:00 the next day) and I will hope to give more details in a later report.

Finally, there have been reports in the press recently that the first six months of 2002 have been the warmest on record in the northern hemisphere. Having checked the Durham Observatory record since 1850, I can confirm that this is true for Durham too. The average temperature of 8.57°C exceeds that for 1990 by fully 0.04°! The top ten values are as follows:

1999 – temperature: 8.05°C

1949 – temperature: 8.08°C

1868 – temperature: 8.10°C

1938 – temperature: 8.15°C

2000 – temperature: 8.17°C

1989 – temperature: 8.18°C

1992 – temperature: 8.30°C

1998 – temperature: 8.43°C

1990 – temperature: 8.53°C

2002 – temperature: 8.57°C

It is notable that most of these have occurred since 1989, and indeed only 2001 is absent from the last five years. The evidence of global warming is very clear in this regard.

Professor Tim Burt
Department of Geography
Durham University