bluuebunny/crossref_metadata_2025 huggingface dataset:
The artificial production of carbon dioxide and its influence on temperature
Authors: Callendar G. S.
Published: July 2010

By fuel combustion man has added about 150,000 million tons of carbon dioxide to the air during the past half century. The author estimates from the best available data that approximately three quarters of this has remained in the atmosphere.

The radiation absorption coefficients of carbon dioxide and water vapour are used to show the effect of carbon dioxide on “sky radiation.” From this the increase in mean temperature, due to the artificial production of carbon dioxide, is estimated to be at the rate of 0.003°C. per year at the present time.

The temperature observations a t zoo meteorological stations are used to show that world temperatures have actually increased at an average rate of 0.005°C. per year during the past half century.
The oxford expedition to North East Land, 1935‐36. General meteorology
Authors: Hamilton R. A.
Published: July 2010

The Expedition maintained a station for a year at 80° 23′ N. 19° 31′ E. on the NTIV. coast of North East Land, and other stations for shorter periods on the west coast and on the ice cap in the interior of the country.

This paper gives monthly means and extreme values of the usual meteorological elements, as observed a t these various stations together with a general comparison between them.

Although there is reason to believe that the winter was an unusually mild one, the observations seem t o disprove the tradition of continual gales, a wind velocity of 12 to 14 m.p.h. being maintained during the dark time. Sudden large fluctuations in temperature occurred in the winter and spring, changes of 30° F. being recorded in one day. In spite of the high latitude, temperatures above 15° F. were recorded during every month of the year. An almost constant feature of the summer weather was the mist which enveloped the ice‐cap station (1,700 ft.) and which was usually observed about 300 ft. up on the hills near the Base Camp.
Meteorological observations of the British East Greenland expedition, 1935‐36, at Kangerdlugssua, 68° 10′ n., 31° 44′ w.
Authors: Manley Gordon
Published: July 2010

Systematic and detailed meteorological observations were maintained by the British East Greenland Expedition, 1935‐36, under the leadership of L. R. Wager. The expedition's coastal base was at Kangerdlugssuak (68° 10′ N.) in a region, previously little known, which is of distinct meteorological interest. The records have been discussed in some detail and compared with those of Danish stations, and those of a previous Norwegian expedition; the courtesy and help of the Danish and Norwegian authorities is gratefully acknowledged. The British observations, reduced and tabulated, are available at the Royal Metcorological Society; summaries only are appended here, by reason of lack of space. Conclusions are reached with regard to the meteorological characteristics of the region, notably the occurrence of fjord gales and precipitation. It is hoped that the general discussion of this excellent set of observations will be of value to others working on the problems 01 Greenland meteorology. Maps and photographs will be found, accompanying the general account of the espedition, in the Geographical Journal, Vol. 90, November, 1937.
Cloud forecasting: The daily use of the tephigram
Authors: Poulter R. M.
Published: July 2010

For air‐survey work and other specialised daylight flying it is important to know for some hours ahead in fine weather the amount of the sky that will be covered by cloud and the height at which the cloud will exist. Readings of the dry‐ and wet‐bulb thermometers at 50 mb. intervals provide information which, when plotted on a tephigram or similar diagram, enables a forecaster to predict with useful accuracy the amount, height and thickness of clouds during the day. Temperature and dew‐point at 4 ft. in the forecast area and the probable rise of temperature arc required to give the height of potential condensation, while the relation between the condensation temperature and the temperature of the environment is the criterion for cloud formation.

Cloud thickness is judged by the relation between the saturation adiabatic through the condensation point and the actual temperatures above, while cloud amount is estimated by the relative humidity of the environment a t the condensation level.

The application of this technique to the various situations met in day‐to‐day forecasting is described and illustrated.
Atlantic flight and its bearings on meteorology
Authors: Entwistle F.
Published: July 2010

The development of long‐distance air routes in recent years has necessitated the expansion of meteorological services in different countries and, in certain cases, the establishment of organised meteorological services where none existed previously. A position is thus being approached gradually in which an organised system of meteorological observations will exist over the greater part of the globe, and material for a study of world meteorology, to an extent hitherto unknown, will be available to investigators.

In the case of the long trans‐ocean air routes which are projected, a special study of prevalent meteorological conditions from the point of view of aviation is necessary. The fundamental data in such cases are supplied by observations from selected ships which bridge the gaps between the fixed continental observing stations and so contribute to the world network.

Certain of the meteorological problems which have arisen, owing to the proposed establishment of a regular trans‐Atlantic air service, are discussed both from the point of view of aviation requirements and also as contributing to meteorological knowledge. A brief account is also given of the organisation devised to ensure an adequate meteorological service for trans‐ocean flights.
Report on the phenological observations in the British Isles from December, 1936, to November, 1937. no. 47
Authors: Gunton H. C.
Published: July 2010

New organisation for phenological‐ecological research. Modifications in analysis and presentation of results; comparison of past and new methods; plants and insects.

Explanatory: arrangement of tables, appendices and diagrams. New diagrams showing phenological events and meteorological factors in juxtaposition.

Ecological aspects.

Conclusions and proposals for further progress.
The partition of a region into rainfall districts: With special reference to South Africa
Authors: Schumann T. E. W. , Hofmeyr W. L.
Published: July 2010

A method is here presented for dividing any region into a number of rainfall districts on the basis of seasonal distribution of precipitation. This is accomplished by drawing on a map of the region two systems of lines of equal “phase” and equal “relative amplitude,” which are measures respectively of the epoch of maximum rainfall and of the normal fluctuation which occurs in the course of a year. A map of the Union of South Africa is reproduced showing rainfall districts obtained by this method.
The lunar atmospheric tide at Accra, Gold Coast, Africa
Authors: Chapman S.
Published: July 2010

The lunar atmospheric tide has hitherto been determined at two stations on the African continent, Helwan and Kimberley. A new determination has now been made from about three years' bi‐hourly data for the tropical African station, Accra (5° 33′ N., 0° 12′ W.). The annual mean amplitude of the lunar tidal variation of pressure is found to have the rather small value 45 microbars; the phase angle, 72°, implies that the high (lunar) tide in the atmosphere over Accra occurs about half an hour after the moon's transit; this phase lag is quite normal.
The mechanism of thundery conditions at Karachi
Authors: Mal S. , Desai B. N.
Published: July 2010

Weather conditions and aeroplane ascents at Karachi between June 22 and July 2, 1936, have been examined for understanding the mechanism of thundery conditions which prevailed there during that period. It is observed that thundery conditions occurred when the characteristic monsoon inversion was absent and there was a sufficiently deep layer of air which when raised to a certain level either by insolation, arrival of sea air, or convergence of winds, released an appreciable amount of energy of latent instability.
Katabatic winds and the prevention of frost damage
Authors: Cornford C. E.
Published: July 2010

A new instrument for recording air movements of low velocity and air temperature fluctuations, and a portable anti‐radiation screen, suitable for a grass minimum thermometer, are described.

Experiments are described showing that certain conditions must be fulfilled in making a just comparison between the air temperature in an orchard‐heated plantation and in an unheated plantation.

Observations of air currents on hillsides on radiation nights are presented, which show that two winds exist, the “hilltop” wind and the katabatic wind. The effect of each on the other in certain localities is described. It is shown that the hilltop wind is able, on the higher part of a slope facing it, to push uphill the air in the first 10 ft. or so above the ground, and at a lower level to neutralise the force of the katabatic wind, producing a calm belt on the slope.

Experiments designed to demonstrate the magnitude of air temperature differences caused by differences in the vegetative cover of the soil alone, by differences in altitude alone, and by a third unknown factor, are described.

Evidence is presented showing that when a katabatic wind moves down a slope its temperature does not necessarily decrease.

It is indicated how the new information may be applied to the problem of preventing frost damage to crops.
A practical method of determining the visibility number v at night
Authors: Gold Ernest
Published: July 2010

The paper contains an account of a method of ascertaining the visibility number V of the International Scale of Visibility from observations of lights at fixed distances smaller than the actual distance of visibility. The method depends on the use of a meter with a filter in which the obscuring power varies continuously from zero to a value large enough to obscure the selected lights when the atmosphere is clear. The construction of the meter and its method of use are described. A unit of obscuring power is defined such that 100 units reduce the intensity of light to 1/1000th part of its incident value. This unit is of a convenient practical size for use in the graduation of the meter. In view of its utility the name “nebule” is proposed for this unit.

The paper also contains an account of a method of estimating the distance of “sure” visibility of lights of different candle power at different distances in conditions of atmospheric turbidity corresponding with the different numbers of the standard scale of visibility, and suggestions for the construction of a more logical scale of visibility than the existing International Scale.
High latitude ozone measurements
Authors: Hamilton R. A. , Dobson G. M. B.
Published: July 2010

Observations were made at North‐East Land to determine the amount of ozone in the upper atmosphere by measuring the absorption of the ultra‐violet light in the spectrum of the Pole star. A quartz spectrograph was used and the spectra were examined by a photometer. The densities of the spectra for wave length 3,290 and 3,092 A were compared with the equal densities on an image on the plate of a source of light whose intensity varied along the image according to a known law. The constants were determined by carrying out a similar experiment at Oxford at night when the amount of ozone on the previous and following days had been measured by the standard method. Trouble was caused by the fogging of the plates caused by auroral light, but this was corrected for by a statistical method. The mean error of each determination was of the order of 30×10‐3 cms., but the day‐to‐day fluctuation was found to be far greater than this and than the fluctuation observed in lower latitudes. There was no apparent connection between the amount of auroræ and the amount of ozone. The results show that the autumn fall in the amount of ozone, observed at all latitudes is continued through the winter and is followed by a sudden rise in spring.
Ecological aspects of meteorology
Authors: Salisbury E. J.
Published: July 2010

The relative importance of extreme and mean climatic conditions in respect to their influence upon the persistence of species. The biological significance of temperature summations. The importance of absolute minima, even when infrequently paralleled, in influencing geographical distribution. Frost severity in relation to the survival of “winter annuals” and of “summer annuals.” Maximum temperatures and their effect upon flower and seed production. The nature of the soil surface and its effect upon air temperatures.

The influence of meteorological conditions upon plant life as modified by the biology of the species. The importance of katabatic winds in modifying temperatures affecting plant life.

Duration and intensity of sunshine as they effect reproduction; photoperiodism.

Precipitation and its role: (1) as a source of raw material; (2) as an erosion agent; (3) in leaching. The significance to plant life of the seasonal incidence and intensity of precipitation.

Meteorological factors as influencing soil development and the extent of their modification by the plant covering.

Ecological aspects of wind; its direct and indirect effects.

The influence of meteorological factors on the conditions of life in relation to the time factor as illustrated by dune soils. Edaphic succession.
Report on the phenological observations in the British Isles from December, 1937, to November, 1938 no. 48
Authors: Gunton H. C.
Published: July 2010

Development of organisation. Meetings of the Main Conference and Executive Committee; steps taken. Presentation of records. The weather of 1938 and its effects. Explanation of diagrams. Conclusions; general principles. Evidence with reference to a dominant factor in relation to the responses to meteorological conditions.
The seasonal and geographical distribution of absolute drought in England
Authors: Lewis Lilian F. , Bilham E. G.
Published: July 2010

A section of British Rainfall has been devoted to absolute droughts since 1888, but the data have not hitherto been summarized in order to determine which areas in England are most subject to drought and in what season of the year absolute droughts may be expected to occur most frequently. In a preliminary investigation it was found that absolute droughts were comparatively rare and an exhaustive research was therefore not attempted but attention was confined to selected stations with long and reliable records. Complete lists of absolute droughts at six stations during periods of from 80 to 95 years and at three other stations over periods from 43 to 52 years are included in the tables. The data reveal three notable facts:—(1) The large number of absolute droughts experienced in south‐east England and the southern midlands compared with the number in north‐east England, although the average annual rainfall is approximately the same in each case; (2) the greater number of absolute droughts recorded at Liverpool than at Stonyhurst, due to the shelter afforded to Liverpool from the moist south‐west winds by the Welsh mountains and the greater height of Stonyhurst above mean sea level; (3) the larger number of absolute droughts experienced on the south‐east coast compared with the number on the more unsettled south‐west coast. The information was next analysed in order to investigate the seasonal incidence of absolute drought. The method adopted was to start with January 1 and count the number of occasions when that day formed part of an absolute drought at a given station. The process was repeated for January 2, January 3, and so on throughout the year. The results are shown graphically on a single diagram, with the days of the year as abscissæ and the number of occasions of absolute drought as ordinates. Finally the odds to one against a “drought‐day” (a day which has been included in a period of absolute drought) were evaluated for each calendar month at each station.
The distribution of wet‐bulb potential temperature in four selected cyclones
Authors: Firesah A. M.
Published: July 2010

The distribution of wet‐bulb potential temperature has been investigated in four cyclones, each by means of serial sounding balloon ascents made at one station. The results are plotted as though they represented observations along a vertical cross‐section through the moving cyclone. Lines of equal wet‐bulb potential temperature are drawn, and these are found to show a characteristic form of distribution at warm fronts, cold fronts and occlusions. At warm fronts the lines are closely crowded together. At cold fronts they show a nose raised some kilometres above the ground, the wet‐bulb potential temperature decreasing with height in the air below the nose. The air in this region usually shows marked latent instability capable of being realised after only relatively small upward displacement. At occlusions the lines of equal wet‐bulb potential temperature have a pronounced V‐shaped form.
Some factors influencing the development and occlusion of warm sectors
Authors: Douglas C. K. M.
Published: July 2010

The initial formation of a warm sector is attributed mainly to geostrophic motion, associated firstly with external systems and secondly with deformation of the warm air mass. The occlusion process is due to a combination of convergence with a suitable distribution of geostrophic motion. The concentration of convergence ahead of the warm front is attributed mainly to the isallobaric effect and not to curvature.
A dutch radio‐meteorograph
Authors: Insje C. M. A. , van Soest J. L.
Published: July 2010

This paper contains an account of the radio‐meteorograph which has been developed in Holland in order to secure accuracy, lightness and cheapness. Following Moltchanov's principles it sends out letters in the Morse code which can be received on an ordinary shortwave receiving set. One valve is employed. The signaller is driven by a small electric motor and the set is operated by either one or two 4 1/2 volt flashlight batteries according to the height to be reached. The total weight with two batteries is 585 grams. Experience shows that a very large proportion of the radio‐meteorographs are recovered in good condition, fit for further use.
On the determination of sea‐level isotherms with special reference to south africa
Authors: Schumann T. E. W. , le Roux J. J.
Published: July 2010

The first part of this paper contains a discussion of the application of the method of least squares for calculating vertical temperature gradients and thus reducing temperatures as recorded at station level, to sea level.

The second part is devoted to a discussion of the results arrived at. Apart from South Africa, the lapse rates for India and the Western and Eastern U.S.A. were also calculated, forty or fifty representative stations being selected in each area. For South Africa the temperature‐influencing factors of altitude, latitude and rainfall are considered simultaneously, whereas for India and the U.S.A. only the factors of altitude and latitude are taken into account.

The values both of the lapse rate and of the variation of temperature with latitude are represented graphically, and explanations are offered for their seasonal variations.
Variations in annual, seasonal and monthly rainfall over the British Isles, 1870‐1939
Authors: Glasspoole John
Published: July 2010

The paper includes statistics of the general monthly rainfall over the British Isles, both in inches and as percentages of the average, for the seventy years 1870‐1939. The general trend of the variations is shown by diagrams of ten‐year means for each month, based on the similar statistics for England and Wales, Scotland and Ireland separately. Similar diagrams are given to show the variations for the winter half‐year, summer half‐year and seasonal year separately.
Evaporation‐loss per month over drainage areas, II. Loss over three areas
Authors: Lloyd David
Published: July 2010

The data from three more large drainage areas are examined by the same method as in the former paper on this subject. The results show again that the variations in loss can be largely associated with variations in rainfall and temperature. It is also demonstrated that, with similar climatic conditions, the loss increases as the sub‐surface has increasing permeability.
The frequency‐distribution through the year of abnormally high and low daily mean temperatures at Greenwich observatory
Authors: Hawke E. L.
Published: July 2010

This paper presents the results of an analysis of thermometric records at Greenwich Observatory over the period 1841‐1936 undertaken with the object of ascertaining the number of occasions on which each day of the year gave a mean temperature above and below the smoothed average value to specified extents. Days with positive departures of at least 10°F. and 15°F. are classed as “warm” and “very warm,” and those with corresponding negative departures as “cold” and “very cold,” respectively. Diagrams and tables referring these several categories to the seasons and calendar months, as well as to pentads and individual dates, are given and discussed. It is shown that the average year contains 17·5 “warm” days, 0·7 “very warm” days, 11 “cold” days, and 1·3 “very cold” days; that the winter months December to February provide 43 per cent of the “warm” days, 53 per cent of the “cold days,” and 86 per cent of the “very cold” days; that there is an entire absence of “very cold” days from March 17 to November 15; and that only three “cold” days are on record for August. Instances, 15 in all, of very exceptional heat and cold, represented by daily mean temperatures at least 20°F. above and below the average, are also listed, special reference being made to the single extant case of a positive departure so great as 20°F. (May 22, 1922). Explanations are advanced for anomalies brought to light by the investigation.
The eddy diffusivity and the temperature of the lower layers of the atmosphere
Authors: Cowling T. G. , White A. , Chapman S.
Published: July 2010

Methods of calculating the eddy diffusivity κ are discussed. It is shown that methods which assume that κ can be regarded as independent of the height, even through a shallow layer, lead to erroneous results: in consequence the frequent use in the literature of the approximate equation of transfer of heat κθ||=θ is to be deplored. It is also shown that there is a large diurnal variation of κ at any level, and that neglect of this may also lead to incorrect and discordant results. Using the values obtained for κ, it is shown that certain features of the temperature variation cannot be explained by convection alone, and it is suggested that they may possibly be due to radiation.
Model predictions of neutrally stratified planetary boundary layer flow over ridges
Authors: Taylor P. A.
Published: July 2010

A numerical model of the local flow above an infinite series of two dimensional ridges is used to investigate the extent to which form drag on the ridges is balanced by reductions in surface shear stress compared to that for a plane surface. With a constant eddy viscosity Mason and Sykes (1979) results an confirmed and there is only a relatively small net increase in the horizontal force on the terrain due to the presence of topography. A larger increase is found when height dependent eddy viscosities are used. the nature of velocity defects produced by individual ridges are examined for the two cases.
On the distribution of mean radiative cooling at the top of a stratocumulus‐capped mixed layer
Authors: Deardorff James W.
Published: July 2010

The fraction, r, of the net in‐cloud radiative flux difference existing within the mean capping inversion of a stratocumulus‐topped mixed layer is calculated, assuming an exponential diminution of radiative flux below local cloud‐top height. Its dependence upon hoλ and Δh/ho is presented, where ho is the depth of the well‐mixed portion of the boundary layer, λ is the radiative extinction length, and Δh is the thickness of the mean capping inversion, or entrainment zone, within the context of ensemble averaging or horizontal averaging. the calculation makes use of laboratory observations on the distribution of mixed‐layer matter within the entrainment zone of a convectively mixed layer. the fraction r is shown to vary widely between its limits of 0 and 1 and under different configurations of stratocumulus mixed layers.

For a given net radiative flux at the top of the cloud, it is shown that changes in λ and r have a modest effect upon the buoyancy flux profile and a strong effect upon the entrainment rate. Buoyant production of turbulence within the well‐mixed layer is found to be maximized when r lies in the vicinity of 0.3.
Statistical prediction of continental planetary albedo
Authors: Linder David I. , Stouffer Ronald J. , Cahir John J. , Panofsky Hans A.
Published: July 2010

Regression equations have been derived for albedo in the United States, summer and winter, as a function of conventional meteorological variables of the type that might be available from a numerical model. For monthly mean patterns, the variance reduction was from 60% in summer to 84% in winter on test samples. On a day to day basis, the reduction of variance was from 45% in summer to 55% in winter. Still, errors of estimate are smaller in summer than in winter.

The principal predictors were the mean relative humidity below 500 mb, and the pole‐ward meridional wind component aloft. In addition, a snow‐cover variable was needed in winter. Dynamic predictors, such as vorticity advection or vertical velocity, had relatively little skill and did not enter the equations consistently. Also, stability parameters played an unimportant part.
Maximum entropy production states in quasi‐geostrophic dynamical models
Authors: Shutts G. J.
Published: July 2010

Mathematical expressions for the time‐mean production rate of statistical, hydrodynamical entropy are introduced in the context of the two‐level quasi‐geostrophic equations and Gibbsian thermodynamics. These form the basis of an investigation into the hypothesis put forward by Paltridge that the climatic‐mean fields are those which maximize this quantity. the entropy production rate is treated as a functional of the surface wind field (obtained by linear extrapolation) and the temperature field as defined in the two‐level equations of quasi‐geostrophic dynamics. Using the calculus of variations, two coupled second‐order differential equations are obtained for these fields and they are solved analytically and numerically for betaplane and spherical‐polar geometries respectively. A global torque constraint is applied using the method of Lagrange multipliers.

The zonal‐mean surface wind equation derived is found to be identical to Green's surface wind equation obtained from his vorticity transfer theory, apart from the redefinition of some empirical constants. an important difference regarding the method of satisfaction of the torque constraint results in realistic surface winds in spherical geometry in contrast to those found by White (1977) using an extension of Green's original work.

The extremal flow field of an equivalent barotropic model of a wind‐driven ocean basin circulation is also investigated and is found to resemble a superposition of Fofonoff's non‐linear inertial solution and a wind stress forced circulation.
The response of numerical weather prediction systems to fgge level iib data. Part I: Analyses
Authors: Hollingsworth By A. , Lorenc A. C. , Tracton M. S. , Arpe K. , Cats G. , Uppala S. , Kållberg P.
Published: July 2010

We present an intercomparison of analyses of the main FGGE level IIb dataset with three advanced analysis systems. the aims of the work are to estimate the extent and magnitude of the differences between the analyses; to identify the reasons for the differences; and, finally, to estimate the significance of the differences for forecast skill. We restrict ourselves primarily to a consideration of the extra‐tropical analyses. the subject of tropical analyses merits separate treatment.

We discuss objective evaluations of analysis quality, such as fit to observations, statistics of analysis differences, and mean fields. In addition we place substantial emphasis on subjective evaluation of a series of case studies which were selected to illustrate the importance of different aspects of the analysis procedures, such as quality control, data selection, resolution, dynamical balance, and the role of the assimilating forecast model. In some cases the forecast models are used as selective amplifiers of analysis differences to assist in deciding which analysis was more nearly correct in the treatment of particular data. In part II we consider the overall impact of the analysis differences on forecast quality, and the implications for predictability.

In general the analysis systems draw reasonably well to the data, although each system has its own characteristics in this regard. the root mean square differences between the analyses are of the expected order of magnitude, although there are clear differences in the closeness of agreement between different pairs of analyses. Systematic differences arising from particular components of the assimilation suites can be identified.

The discussion of the case studies highlights those areas where differences of approach to the analysis problem have led to significant differences in the analyses. Some of the case studies suggest strongly that analysis differences in the vicinity of active baroclinic zones are of particular importance. In order to validate these suggestions in one case, we present an experiment where one analysis is transplanted, locally, into another, to show that large differences in the medium‐range forecasts are attributable to localized differences in the analyses.

The results presented here, together with the forecast verification results of part II, suggest that in some cases uncertainties in the analysis are a major contributor to the loss of forecast skill in the medium range.
A study of the impact of aircraft wind observations on a large‐scale analysis and numerical weather prediction system
Authors: Barwell B. R. , Lorenc A. C.
Published: July 2010

An observing systems experiment to assess the impact of aircraft observations on analyses and forecasts from a numerical model is described. Parallel runs with and without aircraft observations show significant analysis differences in the upper troposphere over northern hemisphere oceans, the aircraft giving a better representation of jet strengths and less reliance on poorer quality observations. This positive impact extends to the shape and position of upper tropospheric features in forecasts from these analyses though the magnitude of the improvements is somewhat less.

These results are in broad agreement with those from a similar experiment carried out at the European Centre for Medium Range Weather Forecasts. Some differences attributable to the response of the different analysis schemes used are discussed in the light of geostrophic adjustment theory and are studied further using model forecasts from perturbed initial conditions. These studies suggest that beneficial effects on forecasts can be achieved by distributing single‐level data throughout several model levels and using wind observations to update the rotational component of the wind field.

A simple linearized theoretical model supports these conclusions and is used to investigate the effects of the repeated insertion analysis procedure used in our experiments. This effectively suppresses the generation of high frequency waves but shows undesirable effects in the presence of a large mean advective velocity.
Potential vorticity in the stratosphere derived using data from satellites
Authors: Clough S. A. , Grahame N. S. , O'Neill A.
Published: July 2010

Maps of Ertel's potential vorticity, Q, are computed on an isentropic surface in the middle of the stratosphere. They are derived using data from stratospheric sounding units on board NOAA satellites. the reliability of the maps is demonstrated mainly by conservation of Q that is shown in successive analyses, and by the close agreement obtained using independent data from two satellites.

The maps are used to follow the movement of material during the course of strong disturbances which occurred in December 1981. They clearly show the breaking of planetary waves in the stratosphere, an inherently nonlinear process. the effect of wave breaking on the structure of the westerly vortex is considered. Any mixing of Q on isentropic surfaces during wave breaking is shown to be far from complete in the examples studied.

The behaviour of diagnostics based on zonal averaging, such as the Eliassen‐Palm flux, is accounted for by local changes in the distribution of Q. the implications of our findings for the study of stratospheric dynamics are discussed.
The frontal transition zone and microphysical properties of associated clouds
Authors: Ryan B. F. , King W. D. , Mossop S. C.
Published: July 2010

A study of the cloud structure and precipitation in the transition zone of cold fronts over western Victoria shows that the important precipitation parameters, such as cloud top temperature and depth, are determined synoptically. Pre‐frontal clouds experience slow uplift over substantial depths; this results in cold deep clouds with lifetimes of the order of tens of hours. In the post‐frontal clouds the uplift is mesoscale and shallow and causes short‐lived cloud elements.

These dynamic and thermodynamic featurea determine the cloud microphysics and largely the associated rainfall. Precipitation in pre‐frontal clouds forms mostly through lightly rimed ice crystals produced at low temperatures; the process can be very efficient in glaciating the cloud but not necessarily efficient in producing ice crystals large enough to survive the fall to the surface. In the post‐frontal systems the ice crystals are produced at much higher temperatures in the presence of higher liquid water contents and the precipitation depends very strongly on cloud depth and duration.
Isotopic study of hail: The δd‐δ18O relationship and the growth history of large hailstones
Authors: Jouzel Jean , Merlivat Liliane , Federer Bruno
Published: July 2010

Simultaneous deuterium and oxygen‐18 measurements were performed on three large hailstones. On a δD‐δ18O diagram, the representative points of the samples are generally shifted to the right compared with the curve calculated for the cloud liquid phase, especially for clear layers. This effect is due to evaporation of collected water between times of collection and freezing. A theoretical model is developed for both the wet and dry growth regimes which satisfactorily explains the experimental results.

In the framework of the same study, interpretation of radial variations of deuterium content for eleven large hailstones from three storms is presented. the trajectories are reconstructed using the ICM isotopic cloud model which gives more realistic results than the adiabatic model used earlier. Its application shows that the most common growth temperatures are for the layers between ‐15° and ‐20°C and that all the studied graupel embryos originate from around the ‐15°C isotherm. There is good agreement between calculated and estimated updraught speeds and between structural, crystallographic and isotopic features which when combined can serve as a quantitative tool to study both hailstone growth regimes and hailstone trajectories.
On the influence of different radiation parametrizations on model‐generated radiation fields
Authors: Morcrette Jean Jacques , Geleyn Jean Francois
Published: July 2010

Radiation fields for 10‐day forecasts with the operational ECMWF model using three different radiation schemes are presented. Simultaneous measurements of the radiation budget at the top of the atmosphere derived from TIROS‐N AVHRR data are compared with the computed budgets. Initial values of the radiation fields computed by the three schemes are compared and large intrinsic differences are found. Discrepancies in the heating rate profiles are located in the stratosphere and in the tropical lower layers. Land‐sea contrasts in the maps of outgoing longwave fluxes, related to differences in cloudiness, vary from one scheme to another, and are usually smaller than those derived from satellite measurements. Over the 10‐day period of integration, all three schemes lead to similar changes in the cloud fields, with a decrease over the ITCZ and an increase at high latitudes. This effect can be related to deficiencies in the hydrological cycle of the global model. Despite relatively large differences between the initial values of the radiation fields, compensating mechanisms are such that the computed fields, averaged over the 10 days, show smaller deviations from the observed fields.
Solar tides in the middle atmosphere. I: Description of satellite observations and comparison with theoretical calculations at equinox
Authors: Brownscombe J. L. , Nash J. , Vaughan G. , Rogers C. F.
Published: July 2010

In recent years several refinements have been made in the numerical computation of solar atmospheric tides between 30 and 60 km. Although comparisons have been made with winds observed by rockets it has not been possible until now to test these predictions against a globally extensive set of observations. In this paper we describe techniques for obtaining such observations from measurements made by the stratospheric sounding units (SSU) on the TIROS‐N series of satellites. These unique data are compared with calculations of the radiance variations expected from the SSU based on classical tidal theory at equinox.
The production and dispersal of marine aerosol
Authors: Exton H. J. , Latham J. , Park P. M. , Perry S. J. , Smith M. H. , Allan R. R.
Published: July 2010

This paper describes an extensive series of aerosol experiments conducted from a coastal site on the island of South Uist in the Outer Hebrides. Measurements at this site are shown to be reasonably representative of open ocean conditions. Aerosol size distributions (0.08 < radius, r, < 23.5 m̈m) and basic meteorological parameters were measured under both continental and maritime conditions. In all cases wind speed was found to have a dominant effect on aerosol characteristics; the volumetric loading, V(m̈m3 cm−3), increased rapidly with wind speed U(ms−1) according to ln(V) = bU + A, where, for the larger aerosol b ≈ 0.2 sm−1 and A ≈ 4. the size distributions could be principally divided into two ranges at r ≈ 0.5 m̈m, the lower corresponding to long‐range aerosol and the higher to particles produced locally, by bubble bursting at the sea surface. Results of the S. Uist experiments are compared with each other and with those of other workers.

Other findings include a general but not exclusive insensitivity of aerosol characteristics to the range of relative humidity experienced at S. Uist; a decrease of aerosol concentrations, n, with altitude; and an inverse relationship between n and mixing height.
Ozone photochemistry in the antarctic stratosphere in summer
Authors: Farman J. C. , Murgatroyd R. J. , Silnickas A. M. , Thrush B. A.
Published: July 2010

Ozone photochemistry over Antarctica in summer has been examined using a 1‐D model. With diffusive transport alone, the predicted ozone decay rates from the December (summer) solstice to the March (autumn) equinox were found greatly to exceed observed rates. In order to obtain broad agreement between calculated and observed ozone amounts, it was necessary to include the effects of a slow downward mean velocity. the velocities used, a few tens of metres per day, are compatible with a Lagrangian mean circulation pattern derived from thermodynamic considerations and from GCMs.

The rates of change of ozone amounts computed for 75°S decrease abruptly following the change from continuous to interrupted photolysis when the sun first sets (in mid‐February) after the long polar day of midsummer. In the polar day regime, N2O5 concentrations are depressed strongly, and CIONO2 concentrations moderately, relative to those in regions subjected to diurnal interruption of photolysis. the effects on the diurnal variations of ozone and other minor constituents are described.
A model study of some aspects of soil hydrology relevant to climatic modelling
Authors: Hunt B. G.
Published: July 2010

A considerable international effort is being made to improve all aspects of the physical processes represented in numerical models of climate. This particular paper is concerned with one of those aspects, namely the manner in which soil hydrology is included in such models and how it affects climate. For this purpose a 1‐dimensional radiative‐convective model has been coupled with various soil hydrology formulations. This simple approach has the combined advantages of permitting a self‐consistent energetic evaluation of the impact of the moisture content of the soil, and of providing a very economical means for investigating the model's response to perturbations in selected variables. Three soil hydrology parametrizations suitable for use in climatic models were compared, and their individual characteristics illustrated. A method devised by J. W. Deardorff was judged to be superior and was therefore used in the subsequent experiments. These experiments were designed to clarify the role of soil moisture and its variability on the model's surface temperature and surface heat fluxes. the approach adopted permitted individual responses to be followed in great detail, and highlighted the potential role of the model for assisting in the design and subsequent analysis of appropriate experiments using climatic models. Importantly, the results illustrate the limitations of current formulations for surface hydrology used in climatic models, and the need for better parametrizations to be developed.
Modification of turbulence characteristics in flow over hills
Authors: Zeman Otto , Jensen Niels Otto
Published: July 2010

A new model has been developed to investigate turbulence in flows over two‐dimensional hills: the von Mises transformation was applied in mean momentum equations, and turbulence equations (second‐order‐closure type) were solved in a coordinate system aligned with streamlines; the hill perturbation pressure was calculated by means of potential flow theory. the model predictions were compared with some experimental results from the Askervien Hill project with good agreement. It was found that apart from rapid distortion the curvature of streamlines has an important dynamical effect on turbulence. the curvature effect is shown to be particularly pronounced in the vicinity of the inner layer height on the hill top, where it attenuates turbulence. Overall, the salient features of the hill top turbulence profile were successfully explained by analysing the turbulence conservation equations in streamline coordinates.
The two‐dimensional dynamics of West African squall lines
Authors: Dudhia J. , Moncrieff M. W. , So D. W. K.
Published: July 2010

The two‐dimensional dynamics of multicell and unicell squall lines are examined using a numerical model. Both types feature a convective jump updraught with extensive, deep, rearward‐extending anvils. the multicell case contains travelling convection cells and is unsteady but persistent, whereas the unicell case is quasi‐steady.

In the multicell case, an extensive density current is produced by the evaporation and drag of rain falling from a succession of convection cells which travel rearwards relative to the density current head. the circulation within the density current is complex and consists of three mutually interactive branches: a rotor, a cold downdraught, and a subsidence region.

In the unicell case, a density current is not produced and the updraught is forced by a propagating wave of elevation, generated as an interaction between the updraught, water loading and evaporation in a very localized area.

The squall line structure is compared with other models and it is shown that certain propagating two‐dimensional tropical and mid‐latitude squall lines are dynamically similar, their detailed structure being controlled by the inflow wind profile.

The multicell case is compared with a quasi‐two‐dimensional West African squall line which occurred on 22 June 1981 during the Convection Profonde Tropicale (COPT 81) experiment performed in the northern part of the Ivory Coast. Good agreement is found between the model and the observations, and hence the dynamics of the observed squall line is quantified. the unicell case, in which a density current and conventional downdraughts are absent, has yet to be identified in atmospheric observations.
An analytic model of the heat‐induced tropical circulation in the presence of a mean wind
Authors: Phlips P. J. , Gill A. E.
Published: July 2010

A linear analytic model of the response of the tropical troposphere‐in the presence of a uniform zonal mean wind‐to an isolated region of deep heating is presented. the O(1) components of the response are the long Kelvin and planetary waves. as found in earlier work by Matsuno, Gill, and others. the behaviour of these modes is a function of a non‐dimensional parameter which combines the damping time, the wave speed, the mean wind speed, and the length of the heating region. It is interpreted as the ratio of the heating region length to the wave decay distance. When this ratio is small the response consists of long waves propagating away from the heating region. But when it is large, disturbances are locally determined at each longitude, and the dynamics are those of two‐dimensional Hadley circulations.

In a westerly mean wind one also finds short stationary mixed and planetary waves downstream of the heating region. Their amplitude is small compared with the long waves, and proportional to U/LAH2 for small U, where U is the mean wind speed and LH the length of the heating region. In easterly mean winds the short stationary waves are replaced by inertial boundary layers at the edges of the heating region.
A Sequential Estimation Approach to Cloud‐Clearing For Satellite Temperature Sounding
Authors: Eyre J. R. , Watts P. D.
Published: July 2010

Temperature sounding of the troposphere using satellite‐borne infrared radiometers is complicated by the effects of clouds on the measured radiances. If accurate products are to be obtained these effects must first be detected and, if possible, corrections must be made for them in the retrieval procedures. This is normally done by converting the measured radiances to the ‘clear‐column’ values which would be observed from the same atmospheric profile in the absence of cloud—a process known as ‘cloud‐clearing’.

In this paper a review of cloud‐clearing methods is presented. Then a new approach to cloud‐clearing, based on the principles of optimal estimation, is developed and applied to data from HIRS (the High‐resolution Infrared Radiation Sounder) on the TIROS‐N/NOAA satellite series.

Preliminary estimates of clear‐column radiances and their expected errors are obtained at each HIRS spot by one of a number of methods, depending on the cloud characteristics. the properties of horizontal consistency expected in the clear‐column radiance field are then employed to improve the initial estimates using a sequential estimation procedure. This scheme is intended for implementation in the Local Area Sounding System of the Meteorological Office, which provides satellite soundings of high horizontal resolution for use in operational weather forecasting. Details of the new scheme, and of the old scheme which it replaces, are given. the improvements in clear‐column radiances are demonstrated by comparing the products of the old and new schemes with clear‐column radiances derived from coincident data of AVHRR (the Advanced Very High Resolution Radiometer).