Hawking, S. (1991) Author joins debate over corn circle. Cambridgeshire Eoening News, 30 September 1991

Kikuchi, T., Snow, J.T. and Meaden, G.T. (1992) Nanoburst: Microburst by a spiral vortex of micrometeorological scale. J. Meteorol. VK, 17, pp. 109-115

Meaden, G.T. (1987) An anticlockwise spiral- circle in a cereal crop. J. Meteorol., 12, pp. 44-51 - (1991) The goddess of the stones: The

language of the megaliths. Souvenir Press, London - (1992) The Stonehenge solution. Souvenir

Press, London Thorn, A. (1967) Megalithic sites in Britain.

Oxford University Press

Blocking Frequencies over Europe In his study of very warm years, Murray

(Weather, 47, pp. 98-103) asks an interesting question in his concluding remarks, namely will blocking over and near north-west Europe be less frequent, or less intense with global warm- ing than in recent decades?

Since the general circulation models used to predict the effects of greenhouse gas warm- ing point to the most distinct and largest warm- ing in winter and spring, perhaps these are the seasons when it would be expected that circulation changes might be most in evidence. A study by Bardossy and Caspary (1990) of European atmospheric circulation patterns from 1881 to 1989 finds that “the frequencies of zonal circulations have increased in December and January and decreased in April and May since about 1973”. There has also been a rapid decrease of easterly circulation types, par- ticularly in winter since about 1980. Trenberth (1991) in a comparison of mean sea-level press- ures for November-March 1980-86 versus 1946-77 notes falls of about 2 mbar near Ice- land and rises of similar magnitude over Spain,

thus increasing the zonal gradient over the east- ern Atlantic.

By contrast Lough et al. (1983) showed that the number of European blocking anti- cyclones increases in a warm period. More recently Pitrovranov and Jager (1990) have used a statistical approach to determine the frequencies of circulation regimes and North- em Hemisphere average temperature. They find that hemispheric warming is associated with more meridional and blocked circulations in winter, but a decrease of blocking activity in summer.

The detecting of climate change as a result of greenhouse warming has given a new urgency to monitoring closely contemporary atmospheric circulation patterns. Confirmation is needed as to whether these recent signs of change to a more zonal circulation are main- tained. Dept. of Geography, A. H. PERRY University College of Swansea

REFERENCES

Bardossy, A. and Caspary, H. J. (1990) Detec- tion of climate change in Europe by analys- ing European atmospheric circulation patterns from 1881-1989. Theor. Appl. Climatol., 42, pp. 155-167

Lough, J. M. el al. (1983) Climate and climate impact scenarios for Europe in a warmer world. J Climatol. Appl. Meteorol., 22, pp. 1673-1684

Pitrovranov, S. and Jager, J. (1990) Climate: Grosswetterlagen approaches. In: Solo- man, A. and Kauppi, L. (Eds.) Toward ecological sustainability in Europe. Inter- national Institute for Applied System Analysis, pp. 31-41

Trenberth, K. E. (1991) Recent climate changes in the N hemisphere In: Schle- singer, M. (Ed.) Greenhouse gas induced climatic change, Elsevier Press, pp. 377- 390

CORRECTION On page 159, line 9 of the May issue the date for poor air quality in London should

have been 13 December not the 23rd.

FIELD COURSE UNDERSTANDING MOUNTAIN WEATHER - A NEW FIELD COURSE HELD AT TY’R MORWYDD ADVANCED FIELD STUDY CENTRE, ABERGAVENNY

Ty’r Morwydd was pleased to welcome John George as the guest director of this residential course on the weekend of 3-5 A rill992. The course members included technical personnel from Bracknell Met. Office wgo are workin on the design of an automatic weather station for high mountain use, trainees for the dountaineering Instructor Award,

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and a would-be traveller to the mountains of central Asia. The course was designed to cater for a range of needs, and instruction by John Geor e was su ported by his excellent set of comprehensive lecture notes, together with visuaf materiar and videos from the Royal Meteorological Society and the Met. Office.

The weather was, if anything, too good for a course emphasising the changeability and hazards of mountain weather, with a ridge of high ressure movin over the area! Despite this, course members reached the summit of Pen $Gadair Fawr f W m ) and with the aid of sim le instruments sampled the environmental lapse rate and the changes in wind speed with aiitude, as well as topographically induced local funnelling effects.

Ty’r Morwydd is well appointed to support such courses, with excellent accommodation, library facilities, audio-visual equipment, automatic weather station and Dartcom weather satellite receiver. The centre caters for school and higher education groups as well as specialist adult courses such as John’s, and a second running of this ve successful course will take place on the weekend of October 17-18 1992. If an reaakrs are interested please contact: Howard Ray, Ty’r Monvydd Advanced Field Stud; Centre, Pen Y Pound, Abergavenny, Gwent, NP7 ~ U D . Tel: 0873 855959.

HOWARD RAY

MEETING REPORT JAMES RENNELL AND HIS PLACE I N OCEAN-ATMOSPHERE CIRCULATION STUDIES

This meetin arranged ‘ointly by the Specialist Group for the History of Meteorology and Oceanograpky and the bhallenger Society, and held at Southampton University on 14 March 1992, was one of the most interesting and instructive meetings I have attended for a long time.

The meeting traced the history of knowledge of the circulation of the Oceans from the mid-eighteenth century to the present day. James Rennell is probably little known to most meteorologists but he was a remarkable character. He went to sea in 1756 at the age of 14, became a midshipman at 18 and joined the East India Company tradin with India in the great sailin ships at 20. He was perhaps fortunate that the chronometertad been invented in 1761 ant th is enabled ships’ navi ators to determine their longitude accurately. For the first time, therefore, it was Possible, %y comparing actual ships’ positions with those deduced by dead reckoning, to arnve at some good estimates of Ocean currents. Rennell became fascinated b this type of work, perhaps because he had carried out a survey of Bengal for Sir Robert &ve while in India.

He was the first to produce maps of the ocean currents off South Africa in 1778 and later studied currents in many other parts of the world. He was perhaps lucky in that he retired from actual seagoing at the age of 36 and had a retirement lasting over 50 years in which he could analyse the available current data and produce various scientific works.

sthumously) in 1832 but he had also been very interested in the Arctic. Rennell was friendrwith Sir Jose h Banks, the President of the Royal Society, and through him learned of the work of Scoresty on Arctic ice. As a result his advice was sought on the possibility of finding a north-west passage but Rennell’s knowledge of the currents in that area made him very sceptical.

Rennell’s maps of the currents in the North Atlantic were remarkably good and his knowledge of the Gulf Stream was comprehensive and closely in accord with what is known today. European scientists had suggested in the early nineteenth century that variations of tem erature and salinity might have an effect on ocean currents. Until some 40 years after his feath in 1830, however, British scientists were satisfied with Rennell’s ideas that surface winds alone determined currents. It was late in the nineteenth century before the general acceptance of the importance of temperature and salinity in ocean circulation was fully realised.

We were brought right up to date by the Chairman, Professor Henry Charnock, who described how theory predicted that there must be a current in the opposite direction under the Gulf Stream. With the development of the Swallow neutral buo ancy float it has been possible to demonstrate that this is the case. However, other preictions of deep ocean circulation have not always been verified and much remains to be learned about this important subject.

All the speakers and the organisers of this meeting are to be congratulated on a splendid day which was enjoyed by some 40 persons including descendants of James Rennell.

R. A. S. RATCLIFFE

Perhaps the best known is his book on the Gulf Stream published (

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