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.

NOAA-AVHRR detects thermal anomaly associated with the 26 January 2001 Bhuj earthquake, Gujarat, India

Abstract: The earthquake of 26 January 2001, USGS magnitude Ms = 7.9 and epicentre at 23°23′57″ latitude and 70°18′51″ longitude (figure 1), struck the state of Gujarat at 8:46 a.m. (IST) while India was cel...

The Moon’s physical librations and determination of their free modes

Abstract: The Lunar Laser Ranging experiment has been active since 1969 when Apollo astronauts placed the first retroreflector on the Moon. The data accuracy of a few centimeters over recent decades, joined to a new numerically integrated ephemeris, DE421, encourages a new analysis of the lunar physical librations of that ephemeris, and especially the detection of three modes of free physical librations (longitude, latitude, and wobble modes). This analysis was performed by iterating a frequency analysis and linear least-squares fit of the wide spectrum of DE421 lunar physical librations. From this analysis we identified and estimated about 130–140 terms in the angular series of latitude librations and polar coordinates, and 89 terms in the longitude angle. In this determination, we found the non-negligible amplitudes of the three modes of free physical libration. The determined amplitudes reach 1.296′′ in longitude (after correction of two close forcing terms), 0.032′′ in latitude and 8.183′′ × 3.306′′ for the wobble, with the respective periods of 1056.13 days, 8822.88 days (referred to the moving node), and 27257.27 days. The presence of such terms despite damping suggests the existence of some source of stimulation acting in geologically recent times.

Equatorial electrojet at African longitudes: first results from magnetic measurements

Abstract: . In the framework of the French participation in the International Equatorial Electrojet Year (IEEY), ten magnetotelluric stations were installed between November 1992 and November 1994 along a 1200-km-long meridian profile, between Lamto (latitude 6.2°N, Cote d'Ivoire) to the south and Tombouctou (latitude 16.7°N, Mali) to the north. These stations measured digitally the three components of the magnetic field and the two components of the telluric electric field, and operated over a period of 20 months. The magnetic data is used to study the features of the equatorial electrojet (EEJ) in West African longitude. The measurement of the telluric electric field variations will be presented elsewhere. Hourly mean values are used to study the morphological structure of the regular diurnal variation SR of the three components (H, D, and Z) of the earth magnetic field and to characterize the EEJ during magnetically quiet days. The occurrences of the counter-electrojet (CEJ) are set forth, emphasizing its seasonal variability. Assumed to be a current ribbon, the EEJ main parameters (the position of its center, its width, and the amplitude of its current density at the center) are determined. A preliminary analysis of the time variations of these parameters is presented over period of 20 months (from January 1993 to August 1994). Results are compared with those obtained during previous experiments of the same kind.

The Morphology of Northern Hemisphere Blocking

Abstract: The morphology of regional blocking in the Northern Hemisphere is discussed using the 40-yr ECMWF Re-Analysis (ERA-40) dataset and a measure of blocking based on the reversal at storm-track latitudes of meridional θ contrasts on a potential vorticity (PV) surface representative of the tropopause. The focus is on cyclonic and anticyclonic Rossby wave breaking that is inherent to the blocking development, and the extent to which this is determined by the climatological jet position and the ambient shears. More generally, the importance of the climatological planetary scale is discussed. The approach is mainly through composite behavior, but informed by consideration of many individual events. A diversity of behavior is found with longitude in both winter and summer, and there is a striking reversal of the sense of the wave breaking between the two seasons that is generally consistent with the difference in the jet locations. Preferred behaviors are found in various regions and seasons, and retrogre...

Lower stratospheric stationary waves and the longitude dependence of ozone trends in winter

Abstract: At northern midlatitudes, total ozone trends are largest in winter when the longitudinal distribution of ozone is highly asymmetric owing to dynamical forcing by stationary, planetary-scale waves. A distinct longitude dependence of these midlatitude trends for the 1979 to 1991 time period has previously been derived statistically from Nimbus 7 total ozone mapping spectrometer data. Here we apply a mechanistic ozone transport model to investigate the extent to which the geographic dependence of total ozone trends in January can be explained as being due to decadal changes in the amplitudes and phases of stationary planetary waves. Results indicate that most or all of the statistically derived geographic dependence can be explained in this manner. In support of the mechanistic model calculations, lower stratospheric geopotential height differences or anomalies between groups of Januaries near the end of the 1980s and near the beginning of the 1980s are inversely correlated with the geographic distribution of ozone trends. The observed decadal changes in upper tropospheric and lower stratospheric stationary wave properties are most probably a consequence of decadal climate variability in the troposphere.