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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.


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TL;DR: In this paper, the authors compare the He and combined O + Ne flow distributions for two interstellar flow passages in 2009 and 2010 with an analytical calculation, which is simplified because the IBEX orientation provides observations at almost exactly the perihelion of the gas trajectories.
Abstract: Neutral atom imaging of the interstellar gas flow in the inner heliosphere provides the most detailed information on physical conditions of the surrounding interstellar medium (ISM) and its interaction with the heliosphere. The Interstellar Boundary Explorer (IBEX) measured neutral H, He, O, and Ne for three years. We compare the He and combined O + Ne flow distributions for two interstellar flow passages in 2009 and 2010 with an analytical calculation, which is simplified because the IBEX orientation provides observations at almost exactly the perihelion of the gas trajectories. This method allows separate determination of the key ISM parameters: inflow speed, longitude, and latitude, as well as temperature. A combined optimization, as in complementary approaches, is thus not necessary. Based on the observed peak position and width in longitude and latitude, inflow speed, latitude, and temperature are found as a function of inflow longitude. The latter is then constrained by the variation of the observed flow latitude as a function of observer longitude and by the ratio of the widths of the distribution in longitude and latitude. Identical results are found for 2009 and 2010: an He flow vector somewhat outside previous determinations (λISM∞ = 79. ◦ 0+3 . 0(−3. ◦ 5), βISM∞ =− 4. 9 ± 0. 2, VISM∞ = 23.5 + 3.0(−2.0) km s −1 , THe = 5000–8200 K), suggesting a larger inflow longitude and lower speed. The O + Ne temperature range, T O+N e = 5300–9000 K, is found to be close to the upper range for He and consistent with an isothermal medium for all species within current uncertainties.

191 citations

Journal ArticleDOI
TL;DR: In this paper, the first 40-year global wave simulation derived from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NRA) surface wind fields was described.
Abstract: This study describes the first 40 year global wave simulation derived from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NRA) surface wind fields. The NRA 10 m wind fields were input into a deep water version of a proven spectral ocean wave model adapted onto a global grid of spacing 1.25° in latitude by 2.5° in longitude. In situ and satellite wind and wave data sets were used to evaluate the hindcast skill. The validation showed excellent agreement not only in terms of bias and scatter but over the entire frequency distribution out to 99th percentiles of both winds and waves. A global trend analysis showed statistically significant areas of both increasing and decreasing winds and waves. The increasing trend in the northeast Atlantic and decreasing trend in the central North Atlantic are particularly well defined and consistent with changes reported in previous studies, which were linked to changes in the North Atlantic Oscillation. The trend analysis highlighted the difficulty in separating creeping inhomogeneities in the NRA winds from real climate change, illustrating the need to use homogeneous in situ measured data to confirm trends derived from model output. The trends derived from the hindcast seem reasonable in the Northern Hemisphere and may provide a good upper bound to true trends in the wind and wave climate.

187 citations

Journal ArticleDOI
TL;DR: In this paper, the development of a daily historical European-North Atlantic mean sea level pressure dataset (EMSLP) for 1850-2003 on a 5° latitude by longitude grid is described.
Abstract: The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and...

187 citations

Journal ArticleDOI
TL;DR: In this paper, a new longitude system was proposed based on ∼2 years of Cassini observations of the kilometric radio emissions and accounts for the variable radio period (SLS2) valid over the time interval from day 001, 2004 through day 240, 2006.
Abstract: [1] The period of Saturn kilometric radiation modulation as determined by Voyager forms the basis for a longitude system (SLS) recognized by the International Astronomical Union However, Ulysses and Cassini observations have shown that this modulation period varies by the order of one percent on timescales of a few years and, hence, does not represent the internal rotation period of the planet A new longitude system was proposed based on ∼2 years of Cassini observations of the kilometric radio emissions and accounts for the variable radio period (SLS2) valid over the time interval from day 001, 2004 through day 240, 2006 Early uses of this longitude system have revealed a number of magnetospheric phenomena which appear to be locked to the radio period, such as variations in the external magnetic field, the plasma density in the inner magnetosphere, and enhanced intensities of energetic ions Analysis of the radio emissions since the new system was proposed revealed that the radio period continued to evolve, even showing a second, shorter period at times The subsolar longitude of the peak of Saturn kilometric radio emissions begins to deviate from that given by the SLS2 system almost immediately after the previous analysis interval Here, we provide a definition for SLS3, an extension to the longitude system valid over the interval from day 001, 2004 through day 222, 2007 based on variable period radio emissions

181 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the coupling between the troposphere and lower thermosphere due to upward-propagating tides using temperatures measured from the SABER instrument on the TIMED satellite.
Abstract: Coupling between the troposphere and lower thermosphere due to upward-propagating tides is investigated using temperatures measured from the SABER instrument on the TIMED satellite. The data analyzed here are confined to 20-120 km altitude and +/-40 deg latitude during 20 July 20 September, 2002. Apart from the migrating (sun-synchronous) tidal components, the predominant feature seen (from the satellite frame) during this period is a wave-4 structure in longitude with extrema of up to +/-40-50 K at 110 km. Amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time, and as the wave(s) responsible for this structure vary with time. The primary wave responsible for the wave-4 pattern is the eastward-propagating diurnal tide with zonal wavenumber s=3 (DE3). Its average amplitude distribution over the interval is quasi-symmetric about the equator, similar to that of a Kelvin wave, with maximum of about 20 K at 5 deg S and 110 km. DE3 is primarily excited by latent heating due to deep tropical convection in the troposphere. It is demonstrated that existence of DE3 is intimately connected with the predominant wave-4 longitude distribution of topography and land-sea difference at low latitudes, and an analogy is drawn with the strong presence of DE1 in Mars atmosphere, the predominant wave-2 topography on Mars, and the wave-2 patterns that dominate density measurements from the Mars Global Surveyor (MGS) spacecraft near 130 km. Additional diurnal, semidiurnal and terdiurnal nonmigrating tides are also revealed in the present study. These tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s=1 known to exist in the Southern Hemisphere during this period just prior to the austral mid-winter stratospheric warming of 2002.

179 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023240
2022432
202142
202042
201960
201851