History of Meteorology and Physical Oceanography Special Interest Group www.rmets.org/activities/groups/SIG/detail.php?ID=9 Newsletter 1, 2011 CONTENTS Mystery object ..........................................1 Why do they still teach that? .....................1 Letter written by G J Symons ...................3 MYSTERY OBJECT Do it yourself weather forecasting ............4 What is this device? Do any readers remember Subscriptions! ...........................................4 using one? See page 12. Snippet from an unexpected place ...........5 Annual Report for 2010 ............................6 Ernest Gold and geostrophy .....................7 Treasures in the Archive ...........................8 British Antarctic Expedition, Part III ..........9 No future for a meteorological society ....10 Reminiscences of Lerwick ......................11 Azores meteorological observatories ......14 Long ago and far away ...........................16 New publication ......................................16 Jehuda Neumann Memorial Prize ..........17 Sir Francis Galton ...................................17 Meeting report ........................................18 Forthcoming meetings ............................18 Recent publications ................................19 2010 members of the Group ...................20 WHY DO THEY STILL TEACH THAT? Farther west over the Indian Ocean, however, by Malcolm Walker westward of about 55°E, winds did indeed cross the equator on a regular basis, and quite In the latter years of the 1960s and early part of strongly, but there was no observational support the 1970s, my research interest was monsoons. for the concept of a persistent cross-equatorial When I embarked upon this research, I knew flow eastward of 55°E. It was perhaps true that little more about the subject than what I had mean winds were light southerly near the learned in geography lessons at school. Among equator over central parts of the Indian Ocean, my received knowledge was the belief that the but it did not follow that air was flowing south-east trade winds of the Indian Ocean northwards across the equator on a day-to-day cross the equator during the period June to basis throughout the SW monsoon season. September to become the south-westerly winds Observations did not support that notion. of the summer monsoon of southern Asia. So where had the idea come from that SE In the course of my research, I plotted many, trades cross from the southern hemisphere to many tephigrams for Gan, an RAF base in the the northern to become SW monsoon winds? southern Maldives at 00°40′S 73°E. Day after The answer to this question can be found in a day from June to September, winds were light substantial paper on monsoons by John Eliot, and variable and conditions convective. It was the Meteorological Reporter to the Government clear that air did not generally pass through Gan of India, published in the Quarterly Journal of en route to southern Asia. Rather, it tended to the Royal Meteorological Society in 1896 rise to the middle and upper troposphere in (Vol.22, pp.1-37). Eliot said that William Ferrel cumuliform clouds. Moreover, analyses of wet- had advanced the idea in A Popular Treatise on bulb potential temperature did not support the the Winds, published in 1890, and he named a idea of frequent cross-equatorial flow near Gan. number of distinguished meteorologists who had 1 agreed with Ferrel, among them W M Davis, mountain barrier, which can be the case in an R H Scott and the Hon Ralph Abercromby. anticyclone or when there is a warm front, occluded front or warm sector over the barrier. However, Eliot noted, his predecessor as The inversion becomes distorted over the lee Meteorological Reporter, H F Blanford, had held slopes, its altitude there decreasing abruptly the view that (in the words of Eliot), “there is, when the vertical profile of the wind speed throughout the whole period, a belt of calms and upstream becomes suitable. A phenomenon light winds over the equator, which serves as a called a ‘hydraulic jump’ takes place. The level species of reservoir or tank into which the SE of the inversion drops so much that air from Trades are absorbed, whilst from it on the north above the inversion reaches the atmospheric issue the SW to W winds of the rainy monsoon”. layer next to the ground. This air is warm and This view was supported by the German dry. Wherever stable air crosses a mountain meteorologist Wilhelm Meinardus in 1894. barrier, föhn development may occur. Eliot concluded from his study of the winds and An hydraulic jump is a phenomenon which may weather that occurred over southern Asia during occur when air is forced through a duct between 1893 that Blanford was correct so far as the pre- the ground and a marked temperature inversion. monsoon period was concerned but not for the Given an upstream wind of suitable speed and period June to September. Eliot was in fact direction, air moves rapidly (shoots) through the wrong, as we have now known for many years, duct. Such a flow begins and ends abruptly, and Blanford and Meinardus were right, so why starting when the speed and direction of the have elementary textbooks and the Web wind upstream is suitable for its maintenance, continued to promote a concept that has long ceasing when it is not. These speeds and been known to be incorrect? Deference to the directions are controlled by the synoptic-scale great and mighty of the past may be partly weather systems that are present at the time responsible (and are we prepared to question over the region in question. what the great and mighty of meteorology conclude nowadays?), but there is another It is often stated that the strong winds which factor, which I shall come to later in this article. occur over some coasts of the Antarctic are katabatic flows. In part, they are, but mostly they What else is taught in elementary meteorology are shooting flows. In general, katabatic flows courses that does not stand up to scrutiny? It is do not exceed about 20 knots anywhere in the sometimes said that the best way to learn world, but in the Antarctic at the foot of an ice something is to teach it. I was once in the slope near Commonwealth Bay (67°S 144°E) middle of a lecture to undergraduates about winds of 60 knots or more blow for about nine local winds and realized that the textbook föhn months of the year. Furthermore, apart from (foehn) explanation I was giving could not be occasional short-lived lulls, they blow wholly correct. remarkably steadily. Again, a marked The essence of this explanation is as follows. temperature inversion is an essential feature, When precipitation occurs over windward with air shooting through a duct formed between slopes, the temperature inside the rain clouds this inversion and the ground. falls with height at the saturated adiabatic lapse The bora, too, is often stated to be a katabatic rate. Moisture is lost from the air when flow. This strong, cold and gusty wind which in precipitation falls on the windward side of the winter descends to the Adriatic Sea from the mountain barrier, so the cloud base is higher on Dinaric Alps also tends to begin suddenly and the lee side than the windward side. Level for without warning. It is another example of a level, the air is warmer on the lee side because shooting flow. It is only in part a katabatic flow. the air which is descending warms at the dry adiabatic lapse rate. Another misconception concerning the climate of southern Asia is that the north-easterly I realized that this explanation did not account surface winds of winter result from cold air for the sudden onset of most föhn occurrences flowing out from an anticyclone over Mongolia or the magnitudes of the temperature increases and Siberia. It is certainly true that screen that occur on many föhn occasions. Moreover, it temperatures over Siberia are very low in winter, did not explain why a föhn can occur when skies but the notion that this cold air reaches India are cloudless over windward slopes! Why then and adjacent seas overlooks the fact that the do books (and now the Web) perpetuate an Tibetan Plateau, Himalayas and other obviously incorrect, or at best incomplete, mountains form a huge barrier. The cold air is explanation? very stable and does not readily cross such The occurrence of a föhn depends upon the formidable obstacles. presence of a temperature inversion over the 2 Moreover, the very existence of the winter Why do so many obvious misconceptions and anticyclone that is so often shown over north- shortcomings persist in elementary textbooks eastern Asia on charts of mean sea-level and on the Web? pressure is questionable. The land surface in Most books for schoolteachers are written by much of Mongolia is a kilometre or more above schoolteachers. It is the job of schoolteachers to sea level, so sea-level isobars there have little communicate accepted knowledge. Most meaning. And winds in the lower and middle teachers do not have the time or facilities to troposphere over eastern Asia are not advance knowledge. Not only that, textbooks consistent with outflow from Siberia. reflect the expectations of GCSE and A-level The NE winds over southern Asia in winter are examiners. In other words, the system is self- typical of the latitudes in question at that time of perpetuating. Until books for schoolteachers and year. They are, quite simply, NE trade winds. In the syllabuses they teach are influenced by winter, the atmospheric circulation over research workers who are able to put across southern Asia reverts to something akin to a new knowledge in school-friendly terms, Hadley Circulation. misconceptions and shortcomings will continue to be perpetuated. So far as the Web is Yet another misconception that is encouraged concerned, the less said the better.