Showing papers on "Longitude published in 1979"

Large-Scale Aspects of Deep Convective Activity over the GATE Area

Abstract: Using digital IR data obtained by SMS I satellite, the large-scale behavior of convective activity was investigated over the tropical Atlantic within the GATE area. Spectral analysis has revealed the existence of two remarkable periodicities which show good association with the large-scale atmospheric field, namely, a 4-5 day mode and a diurnal mode. The area of the enhanced convection associated with the 4-5 day mode moves westward from Africa through the tropical Atlantic. Its mean phase speed turned out to be about 7° day-1 and the mean wavelength about 30° in longitude. The vertical structure of the corresponding disturbance, was investigated by the time-composite technique applied to upper air data over the GATE A/B area. The result shows that the enhancement of convection is associated with deep upward motion throughout the troposphere and southerly (northerly) winds in the lower (upper) troposphere. It also shows that the enhancement is accompanied by moistening in the cloud layer, while d...

Global model of longitude/UT variations in thermospheric composition and temperature based on mass spectrometer data

Abstract: Measurements of N2, O, He, and Ar densities from neutral gas mass spectrometers on four satellites and inferred O2 and H densities from an ion mass spectrometer have been combined to produce a model of longitude/UT variations in thermospheric neutral composition and temperature. The longitude/UT model is an extension of the mass spectrometer-incoherent scatter thermospheric model (Hedin et al., 1977) and uses spherical harmonic terms dependent on geographic latitude, longitude, and UT. The combined longitude and UT variations reflect the influence of the geomagnetic field but indicate that the variations may not simply be represented in magnetic coordinates.

Perturbation magnetic fields and current systems associated with eastward drifting auroral structures

Abstract: Magnetospheric substorms feature the development of distorted discrete auroral forms known as surges and loops. The westward traveling surge is known to expand in discrete steps into the evening sector, the western extremity of the surge acquiring a velocity of upward of 1 km/s in the early stages of its formation. Magnetic perturbations associated with the westward traveling surge are known to reach hundreds of nanotesla in the region below the surge form. In this study we report the existence of eastward traveling regions of large magnetic perturbations, whose velocities of propagation are in the range of 0.8–2 km/s. We find that the basic structures of these propagating perturbation regions are maintained over at least 12° of longitude, although the amplitude of the disturbance may vary considerably over that longitude range. We have modeled the eastward propagating disturbance by a three-dimensional current system of narrow longitudinal extent in which antiparallel Birkeland current sheets are linked by southward flowing current. We have used coincident riometer data to infer that the electrons responsible for E region ionospheric conductivity enhancements can also cause ionospheric absorption; this permits us to extimate the fluxes of energetic electrons responsible for the eastward propagating disturbance and thus to make a rough estimate of the equatorward electric field in the morning sector auroral oval. In particular, the longitudinal scale size of the eastward propagating structures is ∼5°–10° at 67.5°N.

Evidence for large-scale velocity features on the sun

Abstract: Giant velocity features on the solar surface are seen in line-of-sight velocity data from the Mount Wilson magnetograph Velocity amplitudes around 40 m/s are seen in features with dimensions about 15 deg in latitude and 30-60 deg in longitude These features are associated with solar activity The largest such feature accompanied the largest complex of activity in this interval, lived for about 16 rotations, and predated the first magnetic fields in the area by about two rotations A general pattern of upward motion at the equator is seen, and motions away from the earth at higher latitudes could represent a meridional flow toward the poles of the order of 20 m/s

Latitudinal beaming of Jupiter's low frequency radio emissions

Abstract: By comparing RAE-1 and IMP-6 satellite measurements of Jupiter's radio emission near 1MHz with recent Voyager-1 and 2 observations in the same frequency range, the properties of the low frequency radiation pattern over a 10 deg range of latitudes with respect to the Jovian rotation equator can be studied. These observations, which cover a wider latitudinal range than is possible from the earth, are consistent with many aspects of earlier ground-based measurements used to infer a sharp beaming pattern for the decameter wavelength emissions. Marked, systematic changes are found in the statistical occurrence probability distributions with system 3 central meridian longitude as the jovigraphic latitude of the observer changes over this range. Simultaneous observations by the two Voyager spacecraft suggest that the instantaneous beam width may be no more than a few degrees at times. The new hectometer-wave results can be interpreted in terms of a narrow, curved sheet at a fixed magnetic latitude into which the emission is beamed to escape the planet.

M 2 ocean tide parameters and the deceleration of the Moon's mean longitude from satellite orbit data

Abstract: An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

Differential solar rotation depends on solar activity

Abstract: SUNSPOTS have long been used as tracers to determine the rotation rate of the Sun Scheiner1 noted 250 years ago that low-latitude sunspots rotate more rapidly than those at high latitude (‘differential rotation’) In a recent review, Howard2 stressed the limitations of the sunspot technique for determining rotation rate and differential rotation, as long-lived spots may have substantial individual motions, random and systematic, in both longitude and latitude For example, leading and following spots of a sunspot group diverge early in the group's lifetime3; rotation rates for isolated (‘unipolar’) spots and groups differ, with group rates depending on the shape of the group4 Another problem in using sunspots is the Wilson effect, a surface depression of the spot causing errors in longitude estimates away from the central meridian Despite these difficulties, spots have been used previously to establish that there is no secular variation in rotation rate and differential rotation, nor any variations with phase of the solar cycle5, the only possible exception being during long-term disruptions in the solar activity cycle mechanism6 We present here evidence to suggest that the first of these conclusions is incorrect, and that differential rotation does depend on the amplitude of the solar cycle, at least for unipolar spots

Midsummer stratospheric NO2 at latitude 45°S

Abstract: Ground based measurements of stratospheric nitrogen dioxide during morning and evening twilight have been made at Lauder, New Zealand, 169°40′E longitude and 45°04′S latitude during January and Feb...

Interplanetary Magnetic Field Polarity and the Size of Low-Pressure Troughs Near 180°W Longitude

Abstract: The relationship between interplanetary magnetic field polarity and the area of low pressure (300 mbar) troughs near 180 deg W longitude is examined. For most of the winters from 1951 to 1973, the trough size, as indicated by the vorticity area index, is found to be significantly greater when the interplanetary magnetic field is directed away from the sun than when the field is directed towards the sun. This relationship is shown to hold for various combinations of winters and for most months within a winter, and be most pronounced at the time when polarity was determined. It is suggested that the phenomenon is caused by merging of interplanetary magnetic field lines, when polarity is directed away from the sun, with geomagnetic field lines in the Northern Hemisphere (where these measurements were made), allowing energetic particle fluxes to have access to the north polar region

Seasonal displacement and deformation of the Earth by the atmosphere

Abstract: Mass transports on the surface impart a space motion to the earth. The shift induced by seasonal atmospheric pressure variations is calculated. The magnitude of the displacement is approximately 1.6 | cos [(sun - 9°)] | mm where (sun) is the sun's longitude measured from the beginning of the year. The motion is thus too small to be detected at present. Deformations of a model earth caused by atmospheric loading are estimated. The seasonal distortions over parts of Asia and Greenland approach the lcm measuring goal of the new laser ranging techniques and exceed it over the Antarctic continent. They are not generally significant in other parts of the globe. The results are depicted in contour form on world maps for each of the four seasons.

Recent Change of the Northern Hemisphere Mean Surface Air Temperature Estimated by Optimum Interpolation

Abstract: The optimum interpolation method, which allows ready estimates of the error of interpolation, is applied to a network of monthly mean surface air temperature at 370 stations to the north of 25°S, for 324 months from January 1951–December 1977 The temperature deviations from the 25-year mean at grid points on 30° longitude (45° longitude at 80°N only) and 10° latitude intersections are determined for each month From a set of these grid-point values, time series of longitudinal distributions at 60 and 30°N, and of spatial means over 30° latitudinal zones 90–60°N, 60–30°N and 30–0°N are given In addition 12- and 36-month running means of the Northern Hemisphere mean are presented, together with the 95% confidence limits for the error, which are estimated as less than 005 and 003°C, respectively Some significant fluctuations are noticed

The observed zonal wind cycle in the southern hemisphere stratosphere

Abstract: Zonal winds in the stratosphere for a period of 20 years have been analysed at nine stations between 7°S and 66°S centred on the longitude of eastern Australia. The amplitude, period and phase of the third (‘quasi-biennial’) cycle are determined. Although a coherent pattern emerges in the variation of period with latitude and height it is concluded that, at least in the tropics, the representative period is 832 days (27.35 months). The well-known maximum in amplitude of this third cycle in the tropics decreases to a minimum at about 30°S but increases again polewards, reaching a maximum at about 50°S at the highest levels of observation (6mb). The phase of the cycle ‘leads’ at high levels and low latitudes and also at the height and latitude of the polar night jet. Below these maxima there is a downward propagation of the cycle but little phase variation with height exists in middle latitudes. For the tropics, the variation with latitude of amplitude and phase is consistent with lateral diffusion of a forced equatorial cycle, with eddy diffusion coefficients of 1 × 109cm2s−1 at 80mb, decreasing to 3 × 108cm2s−1 at 25mb.

A large-beam sky survey at millimeter and submillimeter wavelengths made from balloon altitudes.

Abstract: A survey has been made of a quarter of the celestial sphere from balloon altitudes with a telescope having a 1.6-deg beamwidth and two spectral bands: 3-10 kaysers and 10-25 kaysers. The limiting sensitivity of the survey was 10,000 Jy. The galactic disk was detected from 358 to 45 deg galactic longitude. The total far-infrared flux from several regions on the galactic plane measured in this survey is 5-10 times larger than that observed by others using smaller beamwidths and small-amplitude spatial chopping, indicating that a substantial part of the emission comes from extended sources. Two other extended sources were also observed, one in the Cygnus region and the other a spur running off the galactic plane at 130 deg galactic longitude toward the north celestial pole. In addition, lower limits for the spectral index of interstellar dust emission are presented.

Associations between Sea Surface Temperature Gradient and Overlying Mid-Tropospheric Circulation in the North Pacific Region

Abstract: An attempt was made to verify and further investigate a proposed relationship between the location of the maximum east-west sea surface temperature anomaly gradient (ΔSSTA) and the location of the maximum meridional component of the anomalous 700 mb geostrophic wind (VgA) in the North Pacific on a monthly and seasonal time scale. Previous empirical studies, mostly of a case study type, had suggested collocation of maximum values of these variables in the same time period, particularly during the cold seasons. Using 31 years of monthly sea surface temperature and 700 mb height data for the North Pacific, the two variables wore computed for each month and 3-month periods for each 10° longitude sector from 125°W to 155°E, and for each of three latitude bands (55–40°N, 40–25°N, 55–25°N). From these calculations, the spatial relationships of the two variables wore determined by counting frequencies of the collocation of maximum VgA and ΔSSTA for each month or season and latitude band, and by computing...

The Depth Variability of Meridional Gradients of Temperature, Salinity and Sound Velocity in the Western North Pacific

Abstract: In the western North Pacific, meridional gradients of temperature, salinity and sound velocity show considerable variation with depth. Gradients of frontal intensity (more than three times the rms value) occur in the upper 600 m of the ocean. Fronts in the surface layer are spaced at irregular intervals. Many deep fronts have no surface manifestation and are spaced at intervals between 300 and 600 km. A spectral analysis of the meridional gradients as functions of depth and longitude was carried out for the wavenumber range between 0 and 13.4 cycles per 1000 km (c.p. 1000 km). The shape of the power density spectra strongly depends on depth. In the upper 150 m the shape is irregular. Between 300 and 600 m, the spectra show a well-defined peak between 1.5 and 3.3 c.p. 1000 km and a sharp decrease in power beyond 10 c.p. 1000 km. While the shape of the power density spectra shows little variation with longitude, there is a substantial decrease in the total power when crossing the Emperor seamount c...

Results of a 36-hour storm surge prediction of the North Sea for 3 January 1976 on the basis of numerical models

Abstract: To explore the feasibility of forescasting North Sea storm surges by integrating numerically a combined atmospheric-oceanographic physical model, the severe storm and the resulting water levels occurring on 3 January 1976 were simulated as a first step into this direction. For this purpose, the atmospheric model was run with a resolution of 8 levels in the vertical and a horizontal grid spacing of 1.4° in latitude and 2.8° in longitude on the hemisphere. The initial conditions are based upon observations of 2 January 1976, 12 GMT, i.e. about 24 hours before the storm reached its greatest intensity in the southern parts of the North Sea. The surface wind predicted by the atmospheric model was converted into stress values through a bulk formula which then entered the vertically integrated North Sea model, to yield the desired water elevations in a 22 km-grid. Moreover, also the observed wind, stemming from a careful re-analysis of the storm situation, was handled in the same way. The numerically obtained results were compared with gauge measurements at a number of coastal stations.

The Behavior of Tropical Ozone During the Stratospheric Warming of March–April 1976

Abstract: The backscatter ultraviolet spectrometer on the Atmosphere Explorer-E satellite obtained ozone data for the upper stratosphere and lower mesosphere from an equatorial orbit near the time of the March-April 1976 stratospheric warming. A simple inversion technique allows the extraction of information on the absolute ozone abundance and its longitudinal variation from the measured radiances. Between altitudes of 35 and 60 km tropical O3 in constant pressure layers exhibits increased spatial variations on length scales of 20 to 30 deg in longitude after the onset of the polar warming, indicating enhanced wave activity. One week after the polar vortex breakdown, upper stratospheric O3 begins a relaxation toward the unperturbed state, while that in the lower mesosphere continues to show maximum variations near + or 10% of the longitudinally averaged value. Although the degree of horizontal structure increases during the warming, the absolute O3 amounts averaged over longitude between 35 and 60 km in altitude remain nearly constant in time. The observed behavior is consistent with that expected from enhanced vertical transport of O3 in the tropics with accompanying adiabatic temperature changes which alter the chemical loss rate.

Compilation of 1:500 000 reconnaissance mapping in the Precambrian of the Evighedsfjord – Søndre Strømfjord – Itivdleq region, southern West Greenland

Abstract: The three years reconnaissance mapping programme for the 1:500 000 map sheet Frederikshab Isblink - Sondre Stromfjord (Allaart et al., 1977,1978) was completed during the 1978 summer season. This summer's activity was concentrated in the area between Evighedsfjord and the northem boundary of the map sheet at latitude 66°45'N, and west of longitude 51°30'W (fig. 26). The area north-east of the Sukkertoppen Iskappe was reconnoitred during the summer of 1969 (Eseher et al., 1970). The area around Itivdleq and further north has been mapped more recently by geologists from the University of Liverpool under the direction of J. Watterson (1974). The mapping team in 1978 comprised two geologists based on the GGU cutter J. F. Johnstrup; periodic reconnaissance with Jet Ranger and Bell 204 helicopters was undertaken. The guidance of J. Watterson in the area around Itivdleq and Kangerdluarssuk fjords was greatly appreciated.

Terrestrial and Celestial Cartography

Abstract: : World Data Bank I has been reordered in such a way that the latitudes where coastlines cross meridians are sorted in order of latitude for each minute of longitude. Whether a satellite position is over sea or over land is determined by the parity of the next lower crossing. Stellar data on distance and velocity as well as direction are given in a small catalog. Boundary data for moon maria, constellations, and the Milky Way are given in a set of files. (Author)

Rapporti tra distribuzione della vegetazione in piani altitudinali teorici, loro contenuti reali e zonazione: esempi critici nei due emisferi

Abstract: Relations between distribution of vegetation in theoretical altitude belts, their real contents and zones: critical examples in the two hemispheres. – The terminologies used by different Authors in the description of the altitude and longitude successions are reviewed, mentioning the most important concepts. As an example, critical cases chosen in the two hemispheres are illustrated. In the case of South America, to the south of 41st parallel, South Africa, Tasmania and New Zealand, the Author shows that zones develops in longitudinal direction and not according to the latitude as in the case in the boreal hemisphere.