Showing papers on "Longitude published in 1982"

Variations in Surface Air Temperatures: Part 1. Northern Hemisphere, 1881–1980

Abstract: We have produced, using objective techniques, a long-term series of average Northern Hemisphere temperatures based on monthly mean station data gridded on a 5° latitude by 10° longitude grid. Difficulties in the estimation of this parameter are discussed, deficiencies in the currently available data base and possible effects on the estimated average are described, and monthly mean data are presented. Long-term trends and extremes are identified in the annual and seasonal data. All seasons show similar long-term trends, but there are noticeable differences on time scales of 10 years and less. For example, for winter temperature, the early 20th century warming peaked during the 1940's whereas the maximum in the other seasons was in the previous decade. Both the magnitude of the long-term trends and the year-to-year variability has been greatest in winter. There is evidence that the long-term cooling that characterized the 1940's, 1950's and 1960's has ended. Warming began in the mid to late 1960's ...

Auroral studies with a chain of meridian‐scanning photometers: 1. Observations of proton and electron aurora in magnetospheric substorms

Abstract: A chain of sensitive meridian-scanning photometers and all-sky cameras was operated during two new moon periods in 1978 to observe auroral proton and electron precipitation patterns with high time resolution (30 s). The latitude range was from 59.5/sup 0/ to 73.3/sup 0/N (invariant) with Churchill, Manitoba, as the northernmost of three stations. Intensity plots on a latitude-time scale were prepared, and from these, 14 auroral substorms over a broad range of local times were selected for analysis. Data from a widely spaced array of auroral zone and low-latitude magnetometers were used to determine substorm onset times and longitude sectors. Representative meridian intensity profiles of H/sub ..beta../lambda4861 and OIlambda5577 were then assembled as a function of invariant and local magnetic time to obtain a synthetic model of a typical substorm. It is found that the data are better ordered when the local magnetic time scale for the individual substorms is shifted so as to place the substorm origins at local magnetic midnight. While the results are in general agreement with earlier observations, the quantitative nature of the present data base leads to a more objective proton substorm model.

Space/time statistics of short‐term climatic variability in the western North Pacific

Abstract: Temperature observations routinely taken over a period of years are analyzed for information on the space/time statistical structure of the short-term, climate-related variability in the western North Pacific. Observations were taken by the RV Ryofu Maru, making winter hydrographic transects along/ 137°E from Japan to the equator each year from 1967–1974, and by the Japanese Far Seas Fisheries Agency, making 120 quasi-meridional bathythermograph sections between 125°E and 180° from Japan to the equator during 1968–1972. Meridional wave number spectra of subsurface temperature over the depth range 100–300 m are calculated from the sections. Spectra vary significantly between the tropical region south of 17.5°N and the subtropical region north of 17.5°N. In both regions, wave number spectra increase in spectral energy density as the inverse square of the wave number from wavelengths of 200–1200 km; this indicates that the spectra derive from a first-order, autoregressive process. Decorrelation scales associated with the first-order process are very different for the two regions. Evaluation of these parameters is obtained by fitting the observed wave number spectra with a model spectrum that is composed of a first-order autoregressive process and a white noise process. The best-fit decorrelation scale of the first-order process is 600 km in the tropics (south of 17.5°N) and 300 km in the subtropics (north of 17.5°N). The model permits the partition of temperature variance into climate-related signal variance, and noise variance that cannot be resolved by routine monitoring. The ratio of noise to signal variance is 0.3 in the tropics and 1.0 in the subtropics. Estimates of the time and zonal space decorrelation scales are determined from autocorrelation analysis of the Japanese Far Seas Fisheries Agency temperature data. Both north and south of 17.5°N, the decorrelation time scale in the subsurface temperature is approximately 6 months. The zonal decorrelation length scale in the subsurface temperature is approximately 10° longitude for the tropical region south of 17.5°N, but only about 2.5° longitude for the subtropical region north of 17.5°N. For equal time scales, it is shown that the spectral shapes and the latitudinal differences in zonal space scale are consistent with the representation of upper ocean thermal variability in terms of nondispersive baroclinic long waves (i.e., Rossby waves). Discussed are implications of this space/time statistical information on the design of monitoring networks used to detect shor-term climate-related variability in thermal structure.

El Niño and Tropical Pacific Ocean Surface Temperatures

Abstract: The spatial and temporal character of El Nino is explored with analyses of tropical Pacific Ocean surface temperatures for the period 1957–76. The data are derived from approximately 5×106 marine weather reports. Maps are illustrated which portray the initiation, maturation and decay of an “average” El Nino event. Empirical orthogonal functions of nonseasonal departures are displayed. The time coefficients of the dominant empirical functions are derived together with average departures for 18 regions which are usually 10° of latitude and 40–50° of longitude in size. Lag correlation and coherence-spectral analysts are carried out on all of the time series. The pattern of El Nino which is portrayed is that of a basinwide phenomenon with a time evolution lasting more than 24 months. During this evolution sea temperatures in the western Pacific tend to have departures of opposite sign to those in the cast. Variations in the eastern equatorial region are shown to precede those in the central equatoria...

Electric currents above Saint‐Santin: 2. Model

Abstract: We use Ohm's law and a combination of various local models of the electrodynamic parameters of the ionsphere derived from previous incoherent scatter studies (electric fields, neutral winds, ion composition, and ion neutral collision frequencies) to generate an empirical model of the local time and seasonal variations of the horizontal electric current flow above Saint-Santin (geographic latitude 44.1°N, geographic longitude 2.3°E). The various contributions to the total current (Hall and Pedersen contributions, neutral wind driven contributions, and electric field driven contributions) are explicitly obtained in this model. The local time variations of the two components of the total height-integrated horizontal current are compared with the Sr magnetic variation at our location. For all seasons the zonal component is weak, mainly as the result of equal and opposite contributions of the electric field and neutral winds. This result, which is consistent with the weak observed Sr variation of H, is expected for a station such as ours close to the latitude of the Sq focus where the current flow is essentially meridional. In contrast to the usual picture of the Sq system, which suggests a southward current in the morning and a northward current in the afternoon, our model meridional current is found to be always northward during the daytime. This surprising feature of the model is supported by the direct calculation of the current from the ion drifts on a series of individual days. Examination of the SR variation of the D component of ground magnetic variations shows that a north-south current asymmetry, though of smaller intensity, is also present in the magnetic variations. Both the net northward flow of charges revealed by the ionospheric data, and the observed discrepancy between calculated ionospheric currents and magnetic data, suggest that field-aligned currents must be flowing from the northern to the southern hemisphere in our longitude sector during a least part of the day. This situation seems to be quite different from the American sector, where no similar asymmetry has been detected in the average current flow over Millstone Hill. Explanations of these features will have to involve the possible effects of the inclination of the magnetic dipole of the earth with respect to its rotation axis, as well as of antisymmetric tidal modes, which are likely to produce, interhemispheric asymmetries and longitude variations.

The Effect of Model Resolution and Satellite Sounding Data on GLAS Model Forecasts

Abstract: The effect of horizontal model resolution on satellite data impact has been studied for two versions of the GLAS second-order general circulation model: the C-model with a 4-deg latitude by 5-deg longitude resolution and the F-model with a 2.5-deg latitude and 3-deg longitude resolution. It is found that the 48-72 h forecast skill of the GLAS model was significantly improved by the increased resolution. Initial state differences between the SAT and NOSAT cycles using the F-model were on the average smaller than the corresponding differences with the C-model. However, the F-model cycle differences exhibited a smaller scale structure and, in some cases, larger gradients.

Wave Instability in the Polar Region of Venus

Abstract: Infrared and radio observations of the upper cloud region of Venus indicate that the north polar region contains features of large thermal contrast. A cold collar, encompassing a region of temperature inversions, lies between latitudes of about 65 and 75 deg, and a pair of warm features, separated by about 180 deg of longitude and centered near 80 deg latitude, rotate about the pole with a period of about 2.9 days. It is shown that the cold temperatures associated with the inversions lead to an enhancement in the mean zonal wind in a localized area near the pole, and that this enhancement makes the mean flow barotropically unstable. Since data for this region are limited, a model for the thermal structure has been used for calculating growth times and phase periods of the unstable modes. Choosing model parameters to agree as closely as possible with available data, it has been determined that the rotating warm features are likely to be manifestations of barotropically unstable waves.

An investigation of the causes of abnormal quiet days in Sq (H)

Abstract: Summary. From a study of ‘abnormal quiet days’ (AQDs) along the 0° meridian between 14 and 60° N, it was found (Butcher & Brown) that the minimum in H at stations on the poleward side of the Sq (H) focus was formed by a small negative substorm event when the normal Sq (H) amplitude was reduced by a superposed northward field. In this paper we consider both the AQD event and the superposed northward field as a function of longitude and also consider in more detail the latitude variation of the superposed northward field. From such a study it is concluded that: (1) the AQD event is definitely due to a small magnetospheric substorm event; (2) the superposed northward field varies smoothly with longitude falling to zero some 110° from the longitude of its maximum amplitude; (3) the superposed northward field has a variation with geomagnetic latitude tending to zero near 20° and 70°N with a maximum near 55° N in summer and 35° N in winter; (4) there is some evidence that the effect of the IMF penetrates into the mid-latitude E-region and its effect is latitude-dependent. Although the evidence supports the suggestion that the currents responsible for the superposed northward field flow in the E-region no suggestion as to the origin of the driving force of the currents is forthcoming.

Comparison of Year-Average Latitude, Longitude and Pressure of the Four Centers of Action with Air and Sea Temperature, 1899–1978

Abstract: The average latitude, longitude and central pressure of the four centers of action (Icelandic low, Aleutian low, Azores high, Pacific high) have been estimated for each of the 80 years of the Northern Hemisphere Historical Weather Map Series (1899–1978), and compared with year-average values of Northern Hemisphere surface temperature (NHST) and sea surface temperature (SST) in the region 0–10°S, 180–90°W of the equatorial eastern Pacific. Inasmuch as NHST and SST have been positively correlated during the 80-year period, their relations with the centers of action have been estimated using partial correlation coefficients. While there has been a tendency for northward displacement of all four centers of action at time of hemispheric warming, none of the partial correlations is significant at the 95% level, taking into account the serial correlation of the data. However, the correlation (r) of 0.31 in the case of the Aleutian low is on the verge of significance, and the correlation of 0.33 in the c...

Motions in Sunspots Like Torsional Oscillations

Abstract: To study the rotation of sunspots, we selected the observational data for one group, namely for group which crossed the central meridian in October 4, 1974. This group was located in the southern hemisphere of the Sun (φ ≈ −60). It consisted of two large sunspots: preceding N-polarity spot and following S-polarity spot were separated by ∆L ≈ 90 in longitude. The magnetic field strength of both sunspots was approximately the same, i.e. about 2500G.

Mappings of energetic electron precipitation following substorms using the satellite bremsstrahlung technique

Abstract: With an array of collimated cadmium telluride spectrometers on a spinning polar-orbiting satellite (P78-1) a study has been made of the energetic bremsstrahlung X ray ( > 21-keV) patterns following substorms. From an altitude of ∼600 km, X rays emanating from a wide range of magnetic local times can be observed and the local time profiles mapped on a given pass of the satellite across either polar cap. Pronounced longitude variations in the X ray intensities and hence in the precipitating electron fluxes were observed in the daytime sector at various delay times after the onset of substorms near local midnight. The longitude profile features were found to persist over time periods of at least a few minutes. Longitude variations in the energy spectra of the bremsstrahlung X rays were also obtained, and in several cases the spectra were found to be harder at later local times after midnight, although no consistent trends were evident. Coordinated measurements of electrons from the SCATHA satellite at near-synchronous orbit revealed enhancements in the fluxes of trapped electrons on the dayside at the times of the X ray events, indicating a correlation between the trapped and precipitating electron fluxes. Additional information on the longitude profiles of electron precipitation was obtained from riometer measurements in the Danish chain, which also provided complete time histories at the station longitudes. The longitude distributions of energetic electron precipitation as inferred from satellite X ray intensity and from riometer absorption measurements show very good agreement. The riometer absorption at the Narssarssuaq station with an L value of 7.3, comparable to the SCATHA values, was found to be very similar in time profile to the trapped electron fluxes measured at SCATHA, showing a close association between the trapped and precipitating fluxes of electrons.

Electric currents above Saint-Santin; Part II: Model

Abstract: We use Ohm's law and a combination of various local models of the electrodynamic parameters of the ionsphere derived from previous incoherent scatter studies (electric fields, neutral winds, ion composition, and ion neutral collision frequencies) to generate an empirical model of the local time and seasonal variations of the horizontal electric current flow above Saint-Santin (geographic latitude 44.1 oN, geographic longitude 2.3oE). The various contributions to the total current (Hall and Pedersen contributions, neutral wind driven contributions, and electric field driven contributions) are explicitly obtained in this model. The local time variations of the two components of the total height-integrated horizontal current are compared with the Sr magnetic variation at our location. For all seasons the zonal component is weak, mainly as the result of equal and opposite contributions of the electric field and neutral winds. This result, which is consistent with the weak observed Sr variation of H, is expected for a station such as ours close to the latitude of the Sq focus where the current flow is essentiallym eridionalI.n contrast o the usualp ictureo f the Sqs ystem,w hichs uggestas southward current in the morning and a northward current in the afternoon, our model meridional current is found to be always northward during the daytime. This surprising feature of the model is supported by the direct calculation of the current from the ion drifts on a series of individual days. Examination of the SR variation of the D component of ground magnetic variations shows that a north-south current asymmetry, though of smaller intensity, is also present in the magnetic variations. Both the net northward flow of charges revealed by the ionospheric data, and the observed discrepancy between calculated ionospheric currents and magnetic data, suggest that field-aligned currents must be flowing from the northern to the southern hemisphere in our longitude sector during a least part of the day. This situation seems to be quite different from the American sector, where no similar asymmetry has been detected in the average current flow over Millstone Hill. Explanations of these features will have to involve the possible effects of the inclination of the magnetic dipole of the earth with respect to its rotation axis, as well as of antisymmetric tidal modes, which are likely to produce, interhemispheric asymmetries and longitude variations.

On the latitude of the Sq(H) focus at sunspot minimum

Abstract: Summary. The latitude of the Sq(H) focus along the 0° longitude meridian in the northern hemisphere has been determined for all the quiet days, as determined from the aa indices, for the sunspot minimum years 1963–64–65. It is shown that: (a) most of the large variability of the focus latitude is due to the effect of a superposed northward magnetic field that is present on AQDs and which tends to move the apparent focus latitude poleward in the northern hemisphere, and (b) a smaller equatorward motion is caused by the negative AQD events that occur in the 0830–1330 LT range. When these two classes of days are removed from the data set, the focus latitude is found to be completely contained within the range 36°-48° for the months March-October with an average value of 41.5 ± 2.3, whilst in winter the range is larger with an average value of 36.7 ± 3.4. However, since the magnitude of the superposed northward field is longitude-dependent, it may be present even on days not classed as AQDs. It is shown that much of the variability in the focus latitude of the normal days along the 0° longitude meridian is caused by variations in the amplitude of the superposed northward field.

A shipborne magnetic survey in Hudson Bay

Abstract: A marine magnetic total-field survey of Hudson Bay was conducted from 1975 to 1978. Approximately 62 000 line-km of data, or 35 000 five-minute averages, were acquired. The data were corrected for secular variation by means of a polynomial in latitude, longitude, and time, first fitted to annual mean differences from nine observatories and then integrated over time. The data were corrected for diurnal and transient variations by means of a linear interpolation, over geomagnetic latitude, of running hourly mean values from two neighbouring magnetic stations (numbering seven in all). Crossover differences are analysed in terms of a mixture of normal distributions resulting from the intermittent transient variations, and indicate the effectiveness of the corrections. The variance of the data is reduced, as a result of the corrections, by 87% during quiet periods and by 53% during disturbed periods, the weighted variance being reduced by 66%. Navigational accuracy is estimated, from a novel method utilizing crossover differences and field gradients, to be approximately 300 m. Anomalies are presented in profile form, and discussed briefly.

The transverse mercator projection-simple but accurate formulae for small computers

Abstract: Two sets of formulae, simpler than those in current use but capable of considerable accuracy, are presented. One set is suitable for use at distances of up to 500 km from the central meridian in all latitudes up to about 74°; the other, the polar form, gives accurate results over any extent in longitude in latitudes as low as 50°.A formula for the inverse meridian arc is also given.

Survey system for ship speed by hyperbolic navigation method

Abstract: PURPOSE:To enable surveying of a ship speed without a time lag at an arbitrary point of time, by a method wherein, using a first-in first-out system memory, a ship speed is computed from a value which is most early written in the memory and a value which is written lastly. CONSTITUTION:Using a first-in first-out system memory FIFO, a latitude value and a longitude value, into which a hyperbolic data is converted by a centralized processing unit CPU, are written in the memory FIFO each time said conversion is made, and a reading of the latitude value and longitude value, which are most early written, and the latitude value and longitude value, which are written lastly, is obtained by the CPU. Through computatin of a distance between spots decided by each latitude value and longitude value, a ship speed can be found. This permits survey of a ship speed at the same period as a period which coordinate-converts the hyperbolic data into a latitude and a longitude, and enables an error to be enoughly reduced through arbitrary lengthening of a distance between two spots from which a ship speed is found.

PLTSYM: a FORTRAN computer system to plot Canadian symbol location maps for hydrogeochemical and stream-sediment reconnaissance data

Abstract: The PLTSYM system plots sample location maps on a line plotter at virtually any scale with data point values represented by one of 15 Canadian symbols. Sample location data can be in latitude/longitude or (X,Y) coordinate form. Five map projections are available for converting latitude/longitude into easting/northing coordinates. Data values can be sorted into classes using any one of four different class interval options.

Induction by long period geomagnetic variations in the Indian sub-continent

Abstract: In the present paper storm time variations and 27-day geomagnetic periodicity have been analysed to estimate the depth of the substitute conductor, assuming an infinitely (super) conducting core model of the earth. The advantage of using data from a restricted longitude range is that the uncertainties arising from lateral contrasts in the upper mantle and contributions from Sq current systems are considerably reduced. The result of the present analysis, which has been done in the time domain, gives a value of 522 km for the depth of the substitute conductor in case of storm time variations which rises to 870 km for 27-day recurrent storms. A higher value of the depth for 27-day variations indicate that the rise in conductivity inside the earth is not like a step function rather is a gradual one. The value of 522 km for storm time variations for the Indian region is smaller than the global average. This is natural to expect because the Indian sub-continent is known to be a tectonically active region.