Showing papers on "Longitude published in 1985"

The influence of the Hawaiian Archipelago upon the wind‐driven subtropical gyre in the western North Pacific

Abstract: In the middle of the Subtropical Gyre in the western North Pacific is the Subtropical Counter-current, comprised of at least three narrow bands of eastward geostrophic mean flow near 20°N, 24°N, and 26°N, each extending from the sea surface through the main pycrocline. The origin of these narrow bands of eastward mean flow has not previously been explained. In this study, these bands are shown in the mean to extend zonally from the Philippine Sea (i.e., 140°E) to the vicinity of the Hawaiian Archipelago (i.e., 160°W). East of there, they cannot be found. Therefore a hypothesis is presented wherein the Hawaiian Archipelago (extending from 19°N to 26°N near 165°W) is seen to act as an effective barrier, modifying the response of the western subtropical North Pacific to wind-driven effects in the eastern subtropical North Pacific and, in so doing, giving rise to these bands of eastward mean flow in the middle of the western Subtropical Gyre. A test of this hypothesis utilizes a Sverdrup [1947] model, driven by the annual, long-term, mean wind stress curl, constructed on a 2° latitude/longitude grid from synoptic (6 hourly) surface wind observations for the 13-year period 1968–1980. Two model simulations are conducted, one in the absence of the Hawaiian Archipelago and one in the presence of it. In the absence of the archipelago, none of the bands of eastward mean flow are simulated. In the presence of the archipelago, the narrow bands of eastward mean flow at 20°N, 26°N, and 24°N are simulated, although the latter band is very weak. These narrow bands of eastward flow are shown to occur in response to the deflection northward of the wind-driven geostrophic streamlines in the central subtropical North Pacific by the Hawaiian Archipelago.

The anomalous tracks of North Pacific drifting buoys 1981 to 1983

Abstract: Satellite tracked drogued buoys, initially deployed in August 1981 along 160°W south of the Aleutians, rather than recirculate in the Alaskan Gyre, slowly moved eastward to cross the North Pacific. Their trajectories contrast sharply with earlier buoy tracks in the region which all turned north into the Gulf of Alaska consistent with the pattern of mean annual 0/500 db dynamic topography. This marked difference in buoy trajectories is shown to be related to anomalies in the large-scale atmospheric pressure distribution rather than to anomalies in the oceanic geostrophic current. Comparisons between buoy and wind velocities reveal that the buoys respond to the wind-driven Ekman current. The anomalous buoy tracks and sea-level pressure patterns occurred in late 1981 and early 1982 just prior to the El Nino Southern Oscillation event of 1982 to 1983. During their anomalous eastward transit, the two southernmost buoys deployed almost 200 km apart in latitude behaved similarly with cross correlations of about 0.9 in their latitude, longitude displacements over a year. A third buoy crossing the same region three months later followed a path similar to the earlier two buoys, suggesting a stationary flow pattern over this period. The first two buoys finally turned north near the west coast of North America in late 1982 and rapidly continued northward near the coast in early 1983 with maximum velocities > 100 cm s−1. At the same time the third buoy shifted north and moved equally rapidly westward across the northern border of the Gulf of Alaska. Trajectories of buoys deployed in the autumn of 1982 suggest a return to the traditionally accepted circulation pattern of northward flow into the Gulf of Alaska at the eastern end of the North Pacific Current between 140° and 150°W.

Investigations on variations of the subtropical high in the Western Pacific during historic times

Abstract: In this paper the 500 mb circulation field over East Asia was reconstructed by means of a stepwise regression technique, based on the relationship between summer (June to August) rainfall in China and 500 mb level heights. As a result of this study, three indices for the subtropical high, the longitude of the west border, and the latitude of the north border and intensity for the period AD 1471–1980 were extracted from reconstructed 500 mb level heights.

Long-wave growth by baroclinic processes

Abstract: Results from an integration of a hemispherics spectral model, starting from a Northern Hemisphere climatological zonal mean state plus a small amplitude white noise perturbation are presented. Although there is no external forcing in this model, upper tropospheric, midlatitude long-wave fields of amplitude comparable to those observed in the atmosphere are produced. Two distinct generation mechanisms which are important in consecutive phases of the integration are investigated. The first type of long-wave growth is due to the interaction of the synoptic-scale systems, which vary in amplitude with longitude, with the “mean” flow in which they are embedded. The second long-wave development, which takes the form of an intensifying jet stream extending over 60° of longitude, can be interpreted in terms of linear instability of the zonal-mean flow involving one normal mode for each of zonal wavenumbers 1, 2 and 3. These modes are slowly growing and slow-moving, their superposition yields a growing dis...

Time switch with solar function

Abstract: PURPOSE:To facilitate the solar setting by including a means of setting and inputting the latitude and longitude of the set position and an arithmetic memory section for calculating the sunrise and sunset time everyday based on the latitude and longitude to reduce errors due to difference in the latitude. CONSTITUTION:With the east longitude and the north latitude read out of a second memory 10 as parameter, an auxiliary number M is read out of a fourth memory 13 while an auxiliary number N out of a fifth memory, the current date done out of a calendar/timepiece section 8 and the sunrise and sunset time T0 of the former Tokyo Astronomical Observatory, out of a third memory 12 are searched. With time difference P=(sunrise time - sunset time)/2 as parameter, an auxiliary number (n) is read out of a sixth memory 15 and the time T0, and the numbers M, N and (n) are substituted into the formula to calculate the sunrise and sunset time T at the set position, which are memorized into a first memory 9 as solar control time.

Large scale structures from topside sounding

Abstract: ISIS 2 orbits at an altitude of about 1400 km and sounds the ionosphere in the range from 0.1 MHz to 20 MHz. On analyzing a sequence of ionograms measured on April 26, 1971, covering a region from about −73° to 88° in geographic latitude along a trajectory that is mostly close to 80°W longitude, at about 1000 UT or about 5 a.m. local time, one finds large-scale structures in the spatial fluctuations of the electron density above the F peak. The structural features are analyzed by using isoelectronic contours, separating out trends in the data to obtain the spatial fluctuations in the altitude for various levels of electron density. The altitude variations for the various electron density levels strongly correlate, and spatial fluctuation waves are found on the order of 2000 km in scale size. Another example is shown for February 20, 1975, and is for an orbit that is in near conjunction with the Atmosphere Explorer C (AE-C) satellite. AE-C is at a much lower altitude, about 250 km, and measures, among many parameters, in situ ionization density. Comparison of the structures observed by ISIS 2 and AE-C in the electron density fluctuations relates features above and below the F peak; the same spatial wave system is found in the data of both satellites with scale sizes from about 600 km to more than 2000 km.

On simultaneous latitude longitude and azimuth determined by measured horizontal angles and time

Abstract: An observation equation is developed for the solution by least squares of Ney's Three Star Resection. The variance co-variance matrix is examined to determine the best observational conditions for a strong fix. The effect of systematic error in bubble correction is examined.

SAM 2 measurements of the polar stratospheric aerosol, volume 5

Abstract: The Stratospheric Aerosol Measurement (SAM) 2 sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric aerosol with a vertical resolution of 1 km. Representative examples and weekly averages of aerosol data and corresponding temperature profiles for the time and place of each SAM 2 mesurement (Oct. 1980 through Apr. 1981) are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are calculated. Seasonal variations and variations in space (altitude and longitude) for both polar regions are easily seen. Stratospheric optical depths are 0.002 to 0.003 for the Antarctic region and 0.005 to 0.006 at the beginning to 0.002 to 0.003 at the end of the time period for the Arctic region. The Northern Hemisphere values are quite large due mainly to the eruption of Mount St. Helens (46.2 deg N, 122.2 deg W) in May 1980. Polar stratospheric clouds at altitudes of about 20 km were observed during the Arctic winter. A ready-to-use format containing a representative sample of the fifth 6 months of data to be used in atmospheric and climatic studies is presented.

The Climatology of Upper Atmosphere Nitrogen Dioxide Revealed by LIMS Observations

Abstract: The LIMS experiment was launched on the Nimbus 7 satellite on October 24, 1978, for the purpose of sounding the middle atmosphere composition and structure One of the LIMS channels was centered spectrally in the 6 µm region to measure vertical profiles and the global distribution of nitrogen dioxide (NO2) mixing ratio The data reveal that NO2 is highly variable with altitude, latitude, longitude, and time Steep latitudinal gradients are observed in high latitude winter (“the NO2 Cliff”) when a wave number one pattern exists in the geopotential height field The daytime gradient under these conditions is less than that for the night The summer hemisphere column amount is considerably greater (by a factor of ~ 2) than in the winter hemisphere The largest mixing ratios occur at 4 mb at night (~ 20 ppbv) and 9 mb in the day (~7 ppbv) and the latitude region of the peak mixing ratio is skewed toward the southern hemisphere The mixing ratio variability is greater at night (by a factor of ~2 to 3) than in the day and there are significant long term changes revealed by mixing ratio time series analyses on a pressure versus time grid