Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

Monthly tidal temperatures 20–120 km from TIMED/SABER

Abstract: [1] The SABER instrument on the TIMED satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides. However, the slow local time precession rate of TIMED can cause longer-term temperature variations to alias into the tidal signals. A new method of analyzing satellite data for tides has been developed to circumvent this difficulty, but at the expense of temporal resolution of the tidal fields, i.e., 120-day mean tidal structures are obtained. In this work, we apply this method to SABER temperature data to derive a series of 120-day mean tidal structures, extending between 20 and 120 km altitude, 50°S–50°N latitude, and centered on each month from September 2003 to September 2004. In addition to the migrating (Sun-synchronous) diurnal and semidiurnal tides, a number of nonmigrating tides are revealed in the SABER measurements. Some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s = 1. Other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection. Of the latter, the eastward propagating diurnal tide with s = 3 is dominant and is as large as the migrating diurnal tide during some months. Of particular interest is the wave-4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields. This feature is a result of the predominant wave-4 topography/land-sea longitude dependence at the surface, which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection. The ability of the global-scale wave model (GSWM) to approximate the observed tidal fields, including the wave-4 total tidal structures, is also assessed.

Global Distribution of Density Irregularities in the Equatorial Ionosphere

Abstract: We analyzed measurements of ion number density made by the retarding potential analyzer aboard the Atmosphere Explorer-E (AE-E) satellite, which was in an approximately circular orbit at an altitude near 300 km in 1977 and later at an altitude near 400 km. Large-scale (>60 km) density measurements in the high-altitude regions show large depletions of bubble-like structures which are confined to narrow local time, longitude, and magnetic latitude ranges, while those in the low-altitude regions show relatively small depletions which are broadly distributed in space. For this reason we considered the altitude regions below 300 km and above 350 km and investigated the global distribution of irregularities using the rms deviation ΔN/N over a path length of 18 km as an indicator of overall irregularity intensity. Seasonal variations of irregularity occurrence probability are significant in the Pacific regions, while the occurrence probability is always high in the Atlantic-African regions and is always low in the Indian regions. We find that the high occurrence probability in the Pacific regions is associated with isolated bubble structures, while that near 0° longitude is produced by large depletions with bubble structures which are superimposed on a large-scale wave-like background. Considerations of longitude variations due to seeding mechanisms and due to F region winds and drifts are necessary to adequately explain the observations at low and high altitudes. Seeding effects are most obvious near 0° longitude, while the most easily observed effect of the F region is the suppression of irregularity growth by interhemispheric neutral winds.

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 ...

Jupiter's main auroral oval observed with HST-STIS

Abstract: [1] An extended series of FUV images obtained on 7 days during winter 2000–2001, with fixed pointing, yielded highly accurate tracking of emisson features as Jupiter rotated. They provided newly detailed measurements of the degree of corotation of auroral emissions and their variations with changing central meridian longitude. This 2-month data set provides a statistical average location of the auroral emission and leads to the definition of new “reference ovals.” The overall auroral morphology pattern is shown to be fixed in System-III longitude and unchanged over a 5-year period. When arranged in central meridian longitude ranges, the images show a significant contraction of the northern main oval as the central meridian longitude increases from 115 to 255°. The main auroral oval brightness is globally very stable in comparison with its terrestrial counterpart. It is shown to vary with magnetic local time, increasing from noon to dusk and then decreasing again in the magnetic evening. Hectometric emissions observed simultaneously with Galileo and Cassini reveal interplanetary shocks propagating outward from the Sun which may be related to the contraction of the main auroral oval observed in the HST images taken on 14 December 2000. In addition, we find that a brightening and a significant contraction of the main oval observed on 13 January 2001 corresponded to a time of increased solar wind dynamic pressure.

Titan's rotation reveals an internal ocean and changing zonal winds.

Abstract: Cassini radar observations of Saturn9s moon Titan over several years show that its rotational period is changing and is different from its orbital period. The present-day rotation period difference from synchronous spin leads to a shift of ∼0.36° per year in apparent longitude and is consistent with seasonal exchange of angular momentum between the surface and Titan9s dense superrotating atmosphere, but only if Titan9s crust is decoupled from the core by an internal water ocean like that on Europa.