High-level Stations Research Articles

The Altitudinal Gradients of Air Temperature in Southern Norway

Following from an earlier paper on the altitudinal gradients of temperature in the British Isles (Harding, 1978) a statistical study is made of the more extensive network of upland observations from southern Norway. The effects of altitude are found to be similar in the two regions: the mean values of the altitudinal gradients are the same and characteristic maximum in the spring is observable and is found to be more pronounced in the eastern half of the country. The larger number of high level stations in Norway allows a more complete description of the variability about the mean gradient, which shows a very significant seasonal variation.

Attenuation of solar radiation in the atmosphere

This paper presents the results of measurements of the solar radiant energy absorbed and scattered in the atmosphere. Since much of the information on solar irradiance at the ground is obtained by computation from extraterrestrial radiation data, it is important to know precisely the actual energy that is absorbed and scattered in its passage through the atmosphere for the accurate estimation of the radiant energy received at the ground. Various models exist for the estimation of daily totals of global solar radiation under clear sky and cloudy conditions, taking these effects into consideration and assuming average values for the ozone and water vapour content and the turbidity of the atmosphere. In the present investigation atmospheric attenuation of solar radiation has been calculated from measured values of ozone and water vapour content and turbidity in the atmosphere, at two stations Bangalore (950 metres above sea level) and Nandi Hills (1479 masl). Direct measurements of direct solar radiation for the whole spectrum and various spectral regions were made at Bangalore and Nandi using Ångström pyrheliometers fitted with broad-band pass filters during the clear months January–May 1979. Global solar radiation and sunshine duration measurements were also made at both stations. Using direct measurements of the total ozone and water vapour content and atmospheric turbidity, direct, diffuse and global solar radiation values at the ground were computed from extraterrestrial values of radiation for clear sky conditions. The results are compared with actual measurements and earlier observations of direct solar radiation at other high-level stations. The importance of atmospheric turbidity measurements in the computation of solar radiation is discussed.

Influence of Seasonal Variations of Temperature and Light on the Growth Rate of Cultures and Natural Populations of Intertidal Diatoms

Cultures of four benthic diatom species (Navicula salinarum, Amphiprora cf, paludosa, N. arenaria, Gyrosigma spenceni) were kept at the surface of a mudflat in order to measure division rates. During incubations in the period of December to June the mean temperature was the predominant factor regulating cell division rate. Immersion of the mudflat with very turbid tidal water was an important factor only at a low-level mudflat station during winter and early spring. Strong temperature fluctuations during incubations, with periods of frost in winter and periods of insolation during hot summer weather, did not interrupt growth of the cultures. Hence high temperatures and high irradiance values are unlikely to be the direct cause of the summer minimum in population density that is frequently observed in the estuary. After the winter minimum the increase in population density was measured at three levels of the mudflat. At the high-level station the density increased in January at still very low temperatures, whereas at the mid- and low-level stations this increase started in March. This observation indicates that the emersion time of the mudflat and hence its exposure to full daylight is an important factor in the development of the spring bloom. The density of the diatom populations in the 0.5 cm top layer of the sediment increased only at a very low rate (with maximum rates of ca. 0.1 doublings d-l). Low photosynthetic rates of natural diatom populations in the sediment core are the cause of these low doubling rates of natural populations on the mudflat. Dispersal of diatom cells into the sediment is probably responsible for the decreased photosynthetic rates and, consequently, for the low doubling rates of sediment-inhabiting diatoms.

Circumsolar Radiation as a Measure of the Turbidity of the Atmosphere Part 2

The paper is theoretical, based on experimental data. It treats field measurements of the circumsolar radiation in order to derive from them the variations of the turbidity of the atmosphere at the high level stations Table Mountain and Montezuma. A single relationship is derived for the circumsolar radiation as a function of the coefficient of turbidity beta.

Solar radiation measurements on Mauna Loa (Hawaii) and their bearing on atmospheric transmission

This paper presents the essential results of an analysis of solar radiation measurements carried out, during the period 1 March 1961 to 30 June 1962, at the Mauna Loa High-Altitude Observatory. The instrumental equipment comprised (a) a series of four Eppley precision filter pyranometers (the outputs of which were recorded continuously on strip-chart millivolt potentiometers) and (b) an Eppley normal incidence pyrheliometer (on an automatic equatorial mount) read at certain times during the day, corresponding to fixed solar elevations. The basic records were of total integral wavelength sun and sky radiation and its spectral components as defined by the wavelength intervals λ < 533, 533 – 613, 613 – 694 and λ < 694 mμ, and also of the integral wavelenght direct solar radiation. Of the detailed results of the Mauna Loa study, the following are emphasized. The maximum intensity of the direct solar radiation closely approaches the values previously measured at other very high-level stations such as Mt. Whitney, Pico de Teyde (Tenerife) and Mt. Everest, for conditions of extremely pure air, viz. about 1.67 cal cm −2 min −1. The spectral composition of the sun and sky radiation for cloudless skies appears to be remarkably constant, at all solar elevations. Infrared radiation (i.e. λ > about 700 mμ) constitutes 50.5 ± 1 percent of the total flux, which means that the energy of shorter wavelengths has a similar constant proportionality (49.5 ± 1 percent). It is found that at this altitude and in the exceptionally clear atmosphere characteristic of this location, the total daily radiation T, for cloudless conditions, is related to the corresponding solar noon value Q through the simple formula T = kQ a , where k = 0.512 and a = 1.60. Consequently, a similar relationship is valid for the two major spectral components. With regard to the influence of clouds, high and thin sheets like cirrostratus do not introduce significant changes in the relative composition of the total radiation. On the other hand, the presence of low cloud masses like cumulus seems to cause a decrease in the relative value of the longer wavelength radiation, to approximately 45 percent, corresponding to an increase of about 3 to 5 percent in the shorter wavelengths. The mean value derived for the Ångström atmospheric turbidity coefficient β is as low as 0.015. The atmospheric water-vapor absorption is found to be 0.13 cal cm −2 min −1, with a slight annual variation indicating a maximum in the summer months and a minimum in winter.

On the transposition of short duration rainfall intensity data in mountainous regions

Maximum rainfall amounts for various durations at low level and high level stations in an area exposed to the same general moisture inflow are compared. It is found that ratios between low level and high level values increase with durations. These ratios are used to obtain frequency analyses of maximum short duration rainfall for high level stations with a relatively short record from available long station records at the lower elevations.

The parameters of atmospheric turbidity

The methods for evaluating the atmospheric turbidity parameters, introduced by the present author in 1929-30, are subjected to a critical examination. A method first suggested by M. HEROVANU (1959) is here simplified and expanded, and used for deriving the named parameters in adherence to a procedure described by the present author in a previous paper in this journal (1961). The procedure is applied to the pyrheliometric observations at Potsdam in 1932-36, published by HOELPER (1939) A comparison between the frequency distribution of the coefficient of wave-length dependence α at the high level station Davos and the low level station Potsdam gives results which are discussed in detail. In all the figures of the present paper, where the turbidity coefficients occur, they are multiplied by 103.

Absorption of solar radiation by atmospheric aerosol, as revealed by measurements at the ground

Recorded values of global and diffuse solar radiation at the ground in cloudless conditions are compared with values computed for a clean atmosphere, taking into account Rayleigh scattering and absorption by H2O and O3. The diffuse radiation allows an estimate of the scattering by aerosol; the global radiation allows an estimate of the total attenuation. Aerosol absorption is thus obtained as the difference between the two estimates. An assumption of an angular distribution for aerosol scattering is involved; it is broadly justified by appeal to aircraft observations. In the course of the work comparison is made of the results of simple, single-scattering, and complex, multiple-scattering, computations of atmospheric transmission. For urban atmospheres (Kew, near London, and Vienna) aerosol absorption in excess of that due to H2O is found. For two island stations (Malta and Shetland) absorption comparable with that due to H2O is found. For selected very clear conditions at three high-level stations in Africa, and for mean conditions in the Antarctic, absorptions of two or three per cent are indicated. Examination of records of global illumination and of the direct solar radiation in three spectral bands at Kew suggests that the total attenuation and absorption by aerosol are very approximately non-selective there. These results are in broad agreement with recent direct measurements from aircraft. The method is capable of wide application, as global and diffuse solar radiation are now recorded at many stations.

A New Meteorological High-level Station in the Argentine Republic High-level Stations in Argentina

A New Meteorological High-level Station in the Argentine Republic High-level Stations in Argentina

Intensity and Polarisation of Skylight at Sunrise and Sunset

IT is now well-established that the illumination of the clear day-sky at high-level stations is almost entirely due to molecular scattering by the atmosphere. The remarkable changes in the character of skyillumination which take place when the sun approaches and gets below the horizon have been the subjects of study of a number of investigators and in recent years, particularly of Profs. Dorno1 and Gruner.2 Some of the phenomena, as for example, the changes of colour and polarisation of skylight and the appearance of the earth-shadow, occur in the clearest of weathers and at such high-level stations that their origin cannot be attributed to anything other than molecular scattering. Gruner has, indeed, shown that the observed changes of colour of skylight when the sun is near the horizon can be explained by scattering by a pure atmosphere.

Night Temperature on Mt. Etna

THE observatory on Mt. Etna is perched high up on a plateau of the volcano known as the Piano del Lago beneath the summit ridge, which rises about 1000 feet higher. It is sometimes noticed by the officials, who only reside a few days in each month, that a curious rise in temperature, amounting to a couple of degrees or so centigrade, occurs during the middle of the night, constituting a well-marked secondary nocturnal maximum in the diurnal variation of temperature. During a visit to the station in August 1920, Prof. Filippo Eredia noticed that the nocturnal inversion in the regular fall of temperature was associated with the arrival of sulphurous fumes from the crater, but notwithstanding the contemporaneous occurrence he does not attribute much causal connexion between the two phenomena. A dozen cases, as shown by thermograph records, are discussed by him in a paper contributed to vol. 31 (1922) of the Rendiconti della Reale Accademia Nazionale dei Lincei. Most of them occurred in the summer, and in conditions botif of calm and of wind of different forces and directions, chiefly N.E. and N.W. The calm cases with clear sky are shown to be analogous to similar nocturnal inversions in other mountain regions, and are attributed partly to the slow descent of air from the summit ridge whereby it is warmed by adiabatic compression, and partly to the latent heat of misty condensation due to the previous general nocturnal chilling of the atmosphere. This, however, is not quite convincing; the effects are too complex to be explained on a purely qualitative basis. The cases with strong wind are found to be associated with a great difference of temperature between the interior of Sicily and the eastern flanks of Etna, giving rise to a circulation which carries warmer air to the high-level station. At Catania on the coast near sea-level there are no corresponding night inversions of the diurnal range of temperature.

Atmospheric Pressure and Temperature.

IN Aus dem Archilv der deutschen Seewarte, 1911, No. 4, W. Brockmöller discusses the geographical distribution of the monthly range of oscillation of the barometer. So far as the southern hemisphere is concerned, the question was thoroughly investigated by Dr. W. J. S. Lockyer in a recent publication of the Solar Physics Committee, but Herr Brockmöller's treatment of the subject covers a wider area, and is based on a different definition of the “range.” He takes as the measure of this the mean value of the difference between the highest and lowest barometer readings for each month, and deals with a selection of stations, about 300 in all. After correcting the values for the periodic semi-diurnal variation, and for height above sea-level in the case of a few high-level stations, he plots the values for winter (December—February), and for summer (June—August), and obtains two very interesting charts, showing the isobaromertic lines, or lines of equal range. For the northern hemisphere he obtains also normals for different latitudes, and draws the isanomalies, or lines of equal departure from normal. The range is least, 3 or 4 mm., in the equatorial region, and greatest near the arctic circle, apparently diminishing again towards the pole. The outstanding features are the maxima, in both seasons, near Iceland and the Aleutian Islands, the regions of the “permanent cyclones.” The maxima are naturally much less intense in summer than in winter. Perhaps even more remarkable is the large value of the anomaly on the east coast of North America, where it is greater than at any other place. The effect is possibly due to the proximity of the division between the Labrador current and the warmer water of the North Atlantic, but it is deserving of further investigation.

THE PIC DU MIDI OBSERVATORY

IN a recent number of La Nature, M. L. Rudaux gave an interesting account of the present condition and operations of this important mountain station. France is well provided with high level stations, and the observations from seven of them are published daily in the Bulletin International of the French Meteorological Office. An account of the very favourable position of the Pic du Midi station, and of the almost insuperable difficulties experienced by its original founder, General de Nansouty, was given, in considerable detail, by M. R. Radau, in his useful little work on “Mountain Observatories” (Paris, 1876), and has been summarised by Mr. A. L. Rotch in the American Meteorological Journal. The summit, which has. an elevation of 2877 metres (the observatory being 17 metres lower), is situated on the outskirts of the Pyrenees, in lat. 42° 56′ N., and long. 2° 12′ W. of Paris, and affords one of the finest views in Europe. Towards the north an immense plain stretches as far as the eye can see, and to the north-west, on very clear days, the blue waters of the Atlantic are visible, at a distance of 160 km. It lies directly in the path of the great atmospheric disturbances which traverse the Bay of Biscay, while the summit mostly enjoys a clear and luminous atmosphere, being some 200 metres above the level at which thunderstorm clouds usually gather. These advantages early attracted the attention of astronomers and scientific men; M. F. de Plantade died in 1741 while observing at the ridge which has since taken his name.

Abstract of Paper on further Results of Mr Wragge's Ben Nevis Observations, taken in the year 1882

The more prominent results of Mr Wragge's work were discussed by Dr Buchan in a paper on the “Meteorology of Ben Nevis,” published in the Journal of the Scottish Meteorological Society (vol. vii. p. 4). The humidities at the intermediate stations on the hill-side have not, however, as yet been discussed. One reason for this was that, until Dr Herbertson and Mr H. N. Dickson carried out their researches on hygrometry at Ben Nevis Observatory, it was not known how far Glaisher's tables could be regarded as reliable at high-level stations. Their experiments, however, showed that for temperatures above 40°, Glaisher's factors could be used except when the air was excessively dry. As Mr Wragge's observations were taken between June and October, when the temperature was relatively high and the air nearly saturated, Glaisher's tables have been employed to compute the humidity and vapour pressure from the dry and wet bulb readings.

Atlantic Weather Charts

THE Meteorological Council has just issued a folio of synchronous weather charts for the North Atlantic Ocean and the adjacent continents, those now published forming the first part of a series which embraces the thirteen months from August 1, 1882, to August 31, 1883. The whole series is to be issued in four parts, Part 1 containing the charts from August 1, 1882, to November 7, 1882. Two charts are given for each day—one shows the barometer, wind, and weather, whilst the other gives the air- and sea-temperature, and weather, the weather being given on both charts for the purpose of easy comparison with other elements. The isobars, or lines of equal barometric pressure, are drawn for each tenth of an inch, and figures are given in the central areas of the several depressions to show the lowest reading of the barometer recorded by vessels passing through these disturbances. The direction and force of wind are shown by a system of arrows which fly with the wind, and the different forms of arrow exhibit very readily where the wind reaches the force of a gale, whilst the winds at high-level stations, where the elevation is 4000 feet or upwards, are indicated by red arrows. The air- and sea-temperatures are shown by different coloured isotherms, or lines of equal temperature, which are drawn for each 5° F. The weather, such as rain, fog, or mist, is shown by different methods of shading, and, as mentioned above, is given with each style of chart. The synchronous hour for which the observations are charted is noon Greenwich time, except in the case of air- and sea-temperature, where local noon has been taken in preference. No letterpress has been published with the charts except a few explanatory notes, in which it is stated that the study of the weather of Western Europe for many years has established in a manner that is beyond question that the atmospheric disturbances, on which the changes of weather are in a great measure, if not mainly, dependent, reach our western coasts after having passed for a longer or shorter distance over the Atlantic. The Meteorological Council undertook the investigation with a view to ascertaining as far as possible the conditions under which such disturbances either originate in or traverse the Atlantic, and the extent to which the direction of their course, their magnitude, and persistence, may be influenced by the general meteorological conditions of the area within which they are generated, or of the regions which surround that area.

High-Level Stations

IN NATURE, vol. xxxii. p. 17, I find the abstract of an address by Mr. Omond, on “Ben Nevis.” There are many points of interest, but I regret that one was not mentioned—viz. the exceedingly rapid decrease of temperature with elevation from Fort William to the Ben, anything nearly approaching, in middle latitudes, being only found on the Brocken, and all high-level stations of the Alps showing a much smaller decrease. At the Brocken, as well as at the Ben, the great difference from the Alps is not in summer, but in the colder months of the year. The reason seems to lie in the nearly constant winds, which bring air from below, which is cooled by ascension. The cases of great dryness of the air with descending currents in anticyclones in the colder months of the year, when isolated mountains are often much warmer than the valleys,1 are comparatively rare in the North of Scotland, but frequent in the Alps, and certainly must and do have a great influence on the mean temperature. Where they are frequent, as in the Alps—especially the eastern—the mean amount of decrease of temperature with elevation must be slower.

Meteorological Observations from Ben Nevis

A WEATHER REPORT from the Ben Nevis Observatory is now published daily, which gives the observations made at 9 a.m. and 9 p.m., these being the hours adopted by the Meteorological Societies of the British Islands, to which are added the highest and lowest temperatures, the amount of rain and snow in all cases where it is possible to measure it, the height of the snow on the plateau, measured by the snow gauge, the hours of sunshine, taken directly from the sunshine recorder, and the quantity of ozone, droughts, changes of wind, auroras, glories, halos, electrical and other phenomena, recorded as they occur. The record is strictly one of observations, and as these are made at the usual observing-hours, British meteorologists and all persons interested in the weather are thus afforded the means of comparing their own observations with those made at Ben Nevis Observatory, which is by far the most valuable high-level station we possess, as furnishing data of the first importance in the study of the weather changes of Europe. In the winter climate of the Ben, the problem of hygrometric observation is beset with formidable difficulties. With a view to the practical solution of these it is part of the winter's programme that Mr. Omond conduct a series of investigations with a hygrometer of a novel description specially designed by Prof. Chrystal for the purpose. In the meantime, and until the problem be solved, the word “Sat,” meaning saturation, is entered in the wet bulb column in all cases when the wet does not read lower than the dry bulb, it being evident that in such cases the air is all but, if not altogether, saturated. Indeed, a saturated atmosphere at all temperatures may be almost regarded as a persistent feature in the climatology of the Ben. Occasionally, however, as recently happened about Christmas and the New Year, a sudden change sets in, the clouds clear away, the sun blazes out in a sky of marvellous clearness,-and a dryness of air comes on such as is rarely if ever experienced at lower levels. In these circumstances the dry and wet bulb readings separate to a degree so extraordinary that Glaisher stables are no longer of any use in calculating the humidities of the air. As the periods of sudden and intense dryness of the atmosphere are intimately connected with the anti-cyclonic systems prevailing at the time in north-western Europe, it is not improbable that a careful record and study of them will lead to a more exact forecasting of some of our most important weather changes.

THE METEOROLOGICAL OBSERVATORY ON BEN NEVIS

THE importance of high-level stations in any satisfactory handling of the scientific and practical problems of meteorology which have now come prominently to the front, is everywhere recognised, and accordingly in almost all civilised countries such stations have been established, and their number is steadily increasing. On the continent of Europe, many of the more salient positions available for high-level stations are already occupied in France, Spain, Italy, Switzerland, Austria, Hungary, Germany, and Russia; and as regards other countries, the United States, Mexico, India, and our Australian colonies, have also established stations at great elevations, in an energetic prosecution of this important department of meteorology. Singularly enough, Great Britain alone stands aloof from participation in the general movement, and notwithstanding the heavy responsibility which her geographical position and vast pecuniary interests and resources impose upon her, none of the mountains that rear their heads in the very tracks of the storms which sweep over Europe from the Atlantic, is yet occupied by either observatory or station for systematic and Continuous observation of the weather, the highest station in these islands being Dalnaspidal, which is only 1450 feet above the level of the sea.

Intercolonial Meteorological Conference at Sydney

A METEOROLOGICAL Conference was held at Sydney in November last, the representatives of the different Colonies being Messrs. James Hector for New Zealand, Charles Todd for South Australia, R. L. J. Ellery for Victoria, and H. C. Russell for New South Wales, the last-named gentleman being chairman. The most cordial unanimity characterised the meeting, which lasted from the 11th to the 14th of the month, and the resolutions arrived at with a view to secure united action in their meteorological investigations and uniformity in the methods and times of observing and forms of publication augur well for the future of meteorology in the Australian Colonies. The whole question of weather telegrams was under anxious consideration. The system in present operation embraces only the Colonies of South Australia, Victoria, New South Wales, and Queensland, but a resolution was passed declaring it desirable to secure the co-operation of the Governments of Western Australia, Tasmania, and New Zealand in the system of inter-colonial weather telegrams. The facts pointed out by Mr. Todd as to the great regularity observed by the atmospheric disturbances in pursuing a course from west to east, and the statement by Dr. Hector that early notices could be sent from Queensland of the origin and progress of the dangerous and suddenly occurring cyclones that cross the northern part of New Zealand, sufficiently attest the practicability of the system of weather warnings and their practical value. For instance, the great storm which wrecked the Dandenong in. September, 1876, could have been telegraphed in sufficient time to have prevented the great loss of property which took place at the different ports along the coast of New South Wales. We have the greatest pleasure in noting a deliverance by the Conference to the effect that weather telegrams and forecasts shall in all cases depend upon the observations used for general meteorological and climatological statistics. Much emphasis was laid on the establishment of high-level stations with a more special view to the investigation of the winds; and the Conference recommended that there be established in each of the Colonies, upon a high mountain peak, a meteorological observatory for the special study of winds and other meteorological phenomena, the most desirable positions being Mount Lofty, in South Australia, 2,500 feet high; Kiandra, in New South Wales, 4,600 feet; Mount Wellington, in Tasmania, 4,000 feet; Mount Macedon, in Victoria, 3,500 feet; and in New Zealand, Tauhara Taupo, 4,600 feet, and Mount Herbert, 4,000 feet. We hope that the Governments of the different Colonies will vote the small sums which are required to carry out the resolutions of the Conference, the giving practical effect to which will certainly confer substantial advantages on commercial, shipping, and other interests, and contribute materially to a more satisfactory development of the meteorology of this important part of the globe.