Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Latitudo.
Articles de revues sur le sujet « Latitudo »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Latitudo ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
YUAN, YAN-MEI, et XIAO-FENG XUE. « Two new species of eriophyid mites (Acari : Eriophyidae) from Malaysia ». Zootaxa 4613, no 1 (4 juin 2019) : 152–60. http://dx.doi.org/10.11646/zootaxa.4613.1.8.
Texte intégralRésumé :
Two new species of the family Eriophyidae (Acari: Eriophyoidea) from Mount Trusmadi, Malaysia, are described and illustrated. They are Neodicrothrix grandcaputus sp. nov. on Stachyurus himalaicus (Stachyuraceae) and Latitudo asiaticis sp. nov. on Psychotria asiatica (Rubiaceae). Both of the two new species are vagrant on the lower leaf surface. No damage to the host was observed. In addition to the description, a key to species of Neodicrothrix is provided.
2
Vleck, Carol M., et Jessamyn A. Van Hook. « Absence of Daily Rhythms of Prolactin and Corticosterone in Adélie Penguins Under Continuous Daylight ». Condor 104, no 3 (1 août 2002) : 667–71. http://dx.doi.org/10.1093/condor/104.3.667.
Texte intégralRésumé :
Abstract Plasma prolactin and corticosterone levels were measured in free-living Adélie Penguins (Pygoscelis adeliae) at Torgersen Island, Antarctica (64°S latitude), at 4-hr intervals throughout the day during early January 1997 and examined for evidence of a 24-hr rhythm. At this season and latitude, natural daylight is continuous. No significant change in the plasma level of either corticosterone or prolactin was found across the day in this population. In contrast, hormone levels in birds at lower latitudes typically fluctuate between night and day. Our data would not have revealed circadian rhythms within individuals even if they exist, because each bird was only sampled once. The lack of hormone rhythms in the population, however, suggests that changes in light intensity at this latitude in the Antarctic summer are not sufficient to entrain, or perhaps even to maintain, circadian rhythms of individuals. Ausencia de Ciclos Diarios de Prolactina y Corticosterona en Pygoscelis adeliae bajo Luz Solar Continua Resumen. A principios de enero de 1997 en la Isla Torgersen, Antártica (latitud 64°S), se midieron cada 4 horas los niveles de prolactina y corticosterona en el plasma de Pygoscelis adeliae en busca de evidencia de un ciclo hormonal de 24 horas. Durante esta estación del año y a esta latitud, la luz solar es continua. No se encontraron cambios significativos en los niveles de prolactina ni de corticosterona en el plasma a través del día en esta población. En contraste, los niveles hormonales en aves en menores latitudes fluctúan típicamente entre el día y la noche. Aún si existiesen, nuestros datos no habrían revelado la existencia de ritmos circadianos para cada individuo, dado que cada animal fue muestreado una sola vez. Sin embargo, la ausencia de ciclos hormonales a nivel poblacional, sin embargo, indica que los cambios de luz a esta latitud en el verano antártico no son suficientes para sincronizar, o quizás ni siquiera para mantener, ritmos circadianos en los individuos.
3
Ortenberg, Veronica. « An Unknown Late Anglo-Saxon Text About old St Peter's in Rome ». Antiquaries Journal 70, no 1 (mars 1990) : 115–17. http://dx.doi.org/10.1017/s0003581500070347.
Texte intégralRésumé :
Ms Royal 2. B.V. in the British Library, London, is a tenth-century Psalter from Winchester, possibly from Nunnaminster. On the last folios of this MS (189-190) were added in the late tenth century, miscellaneous computistical entries, which include the years ofChrist, the ages of the world, the ages and generations, the numbering and reckoning of years and the number of years from the Creation to the foundation of Rome. Two texts, the ‘De longitudine mundi’ (fol. 189) and ‘Longitudo, latitudo et altitudo templi et tabernaculum (sic)’ (fols. 189randv) precede, and another, ‘De area Noe’ (fol. 189v) follows a short text entitled ‘De aedificatio (sic) ecclesie sancti Petri apostoli’ at folio 189v.With the exception of this last, all these texts are also found in a ninth-century MS, British Library, Cotton Vespasian B.VI (fols. 106-70). To the best of my knowledge, the ‘De aedificatio[ne]’ does not exist in any other manuscript, and there is no known source for it. The present note aims solely at bringing this text to light and providing an edition of it; an examination of its implications for English history and architecture will be provided elsewhere.
4
Ni, Qinbiao, Xiaoming Zhai, Guihua Wang et David P. Marshall. « Random Movement of Mesoscale Eddies in the Global Ocean ». Journal of Physical Oceanography 50, no 8 (1 août 2020) : 2341–57. http://dx.doi.org/10.1175/jpo-d-19-0192.1.
Texte intégralRésumé :
AbstractIn this study we track and analyze eddy movement in the global ocean using 20 years of altimeter data and show that, in addition to the well-known westward propagation and slight polarity-based meridional deflections, mesoscale eddies also move randomly in all directions at all latitudes as a result of eddy–eddy interaction. The speed of this random eddy movement decreases with latitude and equals the baroclinic Rossby wave speed at about 25° of latitude. The tracked eddies are on average isotropic at mid- and high latitudes, but become noticeably more elongated in the zonal direction at low latitudes. Our analyses suggest a critical latitude of approximately 25° that separates the global ocean into a low-latitude anisotropic wavelike regime and a high-latitude isotropic turbulence regime. One important consequence of random eddy movement is that it results in lateral diffusion of eddy energy. The associated eddy energy diffusivity, estimated using two different methods, is found to be a function of latitude. The zonal-mean eddy energy diffusivity varies from over 1500 m2 s−1 at low latitudes to around 500 m2 s−1 at high latitudes, but significantly larger values are found in the eddy energy hotspots at all latitudes, in excess of 5000 m2 s−1. Results from this study have important implications for recently developed energetically consistent mesoscale eddy parameterization schemes which require solving the eddy energy budget.
5
Li, Xiaoyong, Houpu Li, Guohui Liu, Shaofeng Bian et Chenchen Jiao. « Simplified Expansions of Common Latitudes with Geodetic Latitude and Geocentric Latitude as Variables ». Applied Sciences 12, no 15 (3 août 2022) : 7818. http://dx.doi.org/10.3390/app12157818.
Texte intégralRésumé :
Using the symbolic calculation program Mathematica and based on the power series expansions of the common latitude with geodetic latitude as a variable, power series expansions of the common latitude with geocentric latitude as the variable are derived. The coefficients of the two groups of formulas are based on the ellipsoid eccentricity e and the ellipsoid third flattening n, which make the expansions more uniform. Taking the CGCS2000 as an example, numerical analysis is applied to verify the accuracy and reliability of the derived power series expansions. By analyzing and calculating the truncation error of the common latitude based on ellipsoidal eccentricity e and the third flattening n expansion to different orders, we obtain simplified, practical formulas for the common latitude that satisfy the requirement of geodesic accuracy. Moreover, we show that the practical formula derived has higher calculation efficiency and easier dissemination, enriches the theory of map projection, and provides a basis for better display of remote sensing images.
6
Gao, PengXin, KeJun Li et QiXiu Li. « Latitude migration of solar activity at high latitudes ». Chinese Science Bulletin 53, no 1 (janvier 2008) : 8–11. http://dx.doi.org/10.1007/s11434-007-0422-7.
Texte intégral
7
Upadhyaya, H. D., K. N. Reddy, Sube Singh, C. L. L. Gowda, Mohd Irshad Ahmed et Senthil Ramachandran. « Latitudinal patterns of diversity in the world collection of pearl millet landraces at the ICRISAT genebank ». Plant Genetic Resources 12, no 1 (21 août 2013) : 91–102. http://dx.doi.org/10.1017/s1479262113000348.
Texte intégralRésumé :
The genebank at ICRISAT, Patancheru, India conserves a total of 19,063 pearl millet landraces from latitudes ranging from 33.00° in the Southern Hemisphere (SH) to 34.37° in the Northern Hemisphere (NH). In the present study, the NH was found to be the major region for growing pearl millet landraces (80.5%). More landraces were found at lower latitudes ( < 20°) in both hemispheres than at higher latitudes. The latitude range of 10°–15° in the NH and 15°–20° in the SH were found to be important source regions for the prevalence of pearl millet, with 39.6% and 13.1% in the world collection of landraces, respectively. Landraces from lower-latitude regions on either side of the equator varied widely for all traits. Landraces from the 5°–10°N latitude region flowered late and grew tall in the rainy and post-rainy seasons and produced more tillers. Landraces from the 10°–15°N latitude region produced few tillers and had long and thick panicles with larger seeds. Long-bristled bird-resistant landraces were considerable at latitudes of 10°–15°S and 20°–25°S. The minimum temperature at the collection sites was found to be one of the important factors for determining the patterns of the prevalence of pearl millet across the latitudes. Late-maturing, tall and high-tillering landraces from lower-latitude regions were better sources for fodder production. Early-maturing landraces producing long and thick panicles with large seeds from mid-latitude regions (15°–20°) in both hemispheres were useful for developing high-yielding cultivars. Using the latitudinal patterns of diversity in pearl millet landraces, missions may be launched to explore high-diversity, under-collected and threatened areas for the collection of materials of interest at latitudes of 15°–20°.
8
Chen, Yiding, Libo Liu, Huijun Le, Hui Zhang et Ruilong Zhang. « Responding trends of ionospheric F2-layer to weaker geomagnetic activities ». Journal of Space Weather and Space Climate 12 (2022) : 6. http://dx.doi.org/10.1051/swsc/2022005.
Texte intégralRésumé :
Geomagnetic activities frequently occur in varying degrees. Strong geomagnetic activities, which have been widely investigated, occur occasionally; they can cause distinguishable and significant disturbances in the ionosphere. Weaker geomagnetic activities frequently appear, whereas their effects are generally difficult to be distinguished from complex ionospheric variations. Weaker geomagnetic activities play important roles in ionospheric day-to-day variability thus should deserve further attention. In this study, long-term (longer than one solar cycle) measurements of the F2-layer critical frequency (foF2) were collected to statistically investigate ionospheric responses to weaker geomagnetic activities (Ap < 60). The responding trends of low- to high-latitude foF2 to increasing geomagnetic activity are presented for the first time; they are statistically evident. Both increasing and decreasing trends can occur, depending on latitudes and seasons. The trend gradually transits from high-latitude decreasing trends to equatorial increasing trends with decreasing latitude, and this transition is seasonally dependent. As a result, the trend has a seasonal difference at mid-latitudes. The responding trend is generally more distinct at higher latitudes and in the equatorial region than at mid-latitudes, and the responding intensity is largest at higher latitudes. Although theoretically, geomagnetic activities can disturb the ionosphere through multiple mechanisms, the morphology of the trend suggests that the frequent weaker geomagnetic activities modulate the high- to low-latitude ionosphere mainly through disturbing high-latitude thermospheric composition and further altering the thermospheric background circulation.
9
Myllys, M., N. Partamies et L. Juusola. « Latitude dependence of long-term geomagnetic activity and its solar wind drivers ». Annales Geophysicae 33, no 5 (28 mai 2015) : 573–81. http://dx.doi.org/10.5194/angeo-33-573-2015.
Texte intégralRésumé :
Abstract. To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level. We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57–61° in 1996 and at the latitudes 64–67° in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64–67°, the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57–61°, the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.
10
Sanchez-Marroquin, A., O. Arnalds, K. J. Baustian-Dorsi, J. Browse, P. Dagsson-Waldhauserova, A. D. Harrison, E. C. Maters et al. « Iceland is an episodic source of atmospheric ice-nucleating particles relevant for mixed-phase clouds ». Science Advances 6, no 26 (juin 2020) : eaba8137. http://dx.doi.org/10.1126/sciadv.aba8137.
Texte intégralRésumé :
Ice-nucleating particles (INPs) have the potential to remove much of the liquid water in climatically important mid- to high-latitude shallow supercooled clouds, markedly reducing their albedo. The INP sources at these latitudes are very poorly defined, but it is known that there are substantial dust sources across the high latitudes, such as Iceland. Here, we show that Icelandic dust emissions are sporadically an important source of INPs at mid to high latitudes by combining ice-nucleating active site density measurements of aircraft-collected Icelandic dust samples with a global aerosol model. Because Iceland is only one of many high-latitude dust sources, we anticipate that the combined effect of all these sources may strongly contribute to the INP population in the mid- and high-latitude northern hemisphere. This is important because these emissions are directly relevant for the cloud-phase climate feedback and because high-latitude dust emissions are expected to increase in a warmer climate.
11
Garvey, James E., et Elizabeth A. Marschall. « Understanding latitudinal trends in fish body size through models of optimal seasonal energy allocation ». Canadian Journal of Fisheries and Aquatic Sciences 60, no 8 (1 août 2003) : 938–48. http://dx.doi.org/10.1139/f03-083.
Texte intégralRésumé :
For fish at high latitudes, short growing seasons should constrain size-at-age, although the converse often occurs. We used a dynamic state variable model to find energy allocation strategies to length, fat, and ovaries that maximize expected egg production of largemouth bass (Micropterus salmoides). We determined how latitudes and rations affect optimal allocation and then simulated growth using optimal strategies. A theoretical reciprocal transplant explored how latitude-specific optimal strategies affected growth at other latitudes. At low ration, allocation and growth were similar among latitudes, with length selected in small individuals and reproductive tissue and fat in large counterparts. At high rations, low-latitude fish invested most energy to length and reproduction; high-latitude fish allocated to length during summer and fat during fall and developed ovaries earlier in the year. Transplants revealed that smaller size-at-age occurs in the north than in the south, consistent with field patterns for largemouth bass. Although northern strategies allowed fish to be successful in the south, southern strategies were unsuccessful in the north. Latitude-specific energetic adaptations may compromise success of fish transplanted beyond their native distribution.
12
KALSI, S. R., et S. R. HALDER. « Satellite observations of interaction between tropics and mid-latitudes ». MAUSAM 43, no 1 (30 décembre 2021) : 59–64. http://dx.doi.org/10.54302/mausam.v43i1.3318.
Texte intégralRésumé :
In certain seasons and over certain locations, the mid-latitude westerlies invade subtropical and tropical areas. Short wave perturbations moving in the broad mid-latitude westerlies amplify the. long wave troughs creating new baroclinic zones in relatively southern latitudes. These. baroclinic zones Interact .with the low-latitude circulations thus leading to development of new circulation pattern .In which low level easterlies extend northward over the Peninsula, central and northwest .India. The paper describes the role of short waves in the interaction between tropics and mid-latitudes and presents satellite data of a few sequences In which such Interactions have actually taken place.
13
Chen, Yiding, Libo Liu, Huijun Le et Hui Zhang. « Interhemispheric conjugate effect in longitude variations of mid-latitude ion density ». Journal of Space Weather and Space Climate 9 (2019) : A40. http://dx.doi.org/10.1051/swsc/2019039.
Texte intégralRésumé :
Earlier incoherent scatter radar measurements revealed upward topside ion fluxes in the summer and downward fluxes in the winter at mid-latitudes at night; a summer to winter interhemispheric coupling was accordingly inferred. However, this interhemispheric coupling through the plasmasphere is difficult to confirm directly from observations. A possible result induced by this coupling is interhemispheric conjugacy of the mid-latitude ionosphere. In this paper, interhemispheric conjugate effect in longitude variations of mid-latitude total ion density (Ni) is presented, for the first time, using the Defense Meteorological Satellite Program (DMSP) measurements; northern and southern Ni longitude variations at 21:30 LT are similar between magnetically conjugate mid-latitudes around solar minimum June Solstice of 1996. The conjugate effect after sunset also occurs around the June Solstice in other solar minimum years but disappears when solar activity increases. We suggested that mid-latitude interhemispheric coupling is responsible for the conjugate effect. Neutral wind induced ionospheric transport causes topside longitude variations via upward diffusion at summer mid-latitudes; this further induces similar longitude variations of topside Ni at winter mid-latitudes via the summer to winter interhemispheric coupling. The conjugate effect occurs only inside the plasmapause where magnetic flux tubes are closed and the plasma in these tubes can stably corotate with the Earth. The conjugate effect not only proves mid-latitude interhemispheric coupling through the plasmasphere, but also implies that neutral wind induced transport can affect ionospheric coupling to the plasmasphere at mid-latitudes.
14
Sun, Mingchen, Xiang Dong, Qinglin Zhu, Xuan Cheng, Hongguang Wang et Jiaji Wu. « Comparison and Analysis of Stellar Occultation Simulation Results and SABER-Satellite-Measured Data in Near Space ». Remote Sensing 14, no 19 (10 octobre 2022) : 5065. http://dx.doi.org/10.3390/rs14195065.
Texte intégralRésumé :
In this study, we analyze the accuracy of the stellar occultation technique to detect the oxygen number density and temperature in near space. Based on the validation of the algorithm related to stellar occultation using a single wavelength of 762 nm, the simulation and inversion are performed using the oxygen absorption A-band, and the results are compared with SABER observations to calculate the deviation. Then, the distribution of the detection accuracy with wavelength, latitude, and altitude is analyzed. The results show that the radiant transmittance of the basic observation varies significantly with wavelength and altitude, and it is not sensitive to a change of latitude. The inversion results of each wavelength at different latitudes can be combined, and it can be seen that the 754–769 nm band is preferred for oxygen and temperature detection. Therefore, analyzing the accuracy results of the specific wavelength 757.84 nm at different latitudes, the temperature accuracy can reach 0.1 K in the stratosphere at both low and high latitudes and 0.6–34 K at middle latitudes. The temperature detection accuracy in the mesosphere at each latitude reaches about a dozen K. The deviation of the inversion results at middle latitudes is larger in the thermosphere, and at the other two latitudes, it is about a few dozen K. From the analysis of relative deviation, excluding the deviation of 95–100 km, the deviation of other altitudes is within the ideal range, and the minimum can reach 0. The accuracy of the oxygen number density increases with latitude, and the relative deviation of the middle and high latitudes is around 10–20%. Based on the above results, it is concluded that the technique of starlight occultation exhibits high accuracy for detecting atmospheric parameters in the near space region, and the results lay the technical foundation for the independent development of stellar occultation.
15
Karpachev, Alexander. « Sub-Auroral, Mid-Latitude, and Low-Latitude Troughs during Severe Geomagnetic Storms ». Remote Sensing 13, no 3 (2 février 2021) : 534. http://dx.doi.org/10.3390/rs13030534.
Texte intégralRésumé :
The dynamics of ionospheric troughs during intense geomagnetic storms is considered in this paper. The study is based on electron density measurements at CHAMP satellite altitudes of 405–465 km in the period from 2000 to 2002. A detailed analysis of four storms with Kp from 5+ to 9− is presented. Three troughs were identified: sub-auroral, mid-latitude, and low-latitude. The sub-auroral trough is usually defined as the main ionospheric trough (MIT). The mid-latitude trough is observed equatorward of the MIT and is associated with the magnetospheric ring current; therefore, it is named the ring ionospheric trough (RIT). The RIT appears at the beginning of the storm recovery phase at geomagnetic latitudes of 40–45° GMLat (L = 1.75–2.0) and exists, for a long time, at the late stage of the recovery phase at latitudes of the residual ring current 50–55° GMLat (L ~ 2.5–3.0). The low-latitude trough (LLT) is discovered for the first time. It forms only during great storms at the latitudes of the internal radiation belt (IRB), 34–45° GMLat (L = 1.45–2.0). The LLT’s lowest latitude of 34° GMLat was recorded in the night sector (2–3 LT). The occurrence probability and position of the RIT and LLT depend on the hemisphere and longitude.
16
Lan, Ting, Chunhua Jiang, Guobin Yang, Fei Sun, Zhenyun Xu et Zhong Liu. « Latitudinal Differences in Spread F Characteristics at Asian Longitude Sector during the Descending Phase of the 24th Solar Cycle ». Universe 8, no 9 (14 septembre 2022) : 485. http://dx.doi.org/10.3390/universe8090485.
Texte intégralRésumé :
By using ionosonde data recorded at Chiang Mai (18.8° N, 98.9° E, magnetic latitude is 9.1° N), Puer (22.7° N, 101.1° E, magnetic latitude is 12.9° N), and Leshan (29.6° N, 103.7° E, magnetic latitude is 19.8° N), the statistical features of different types of spread F (SF) occurrence at low and middle latitudes were analyzed in this study. The results showed that the SF occurrence had obvious local time, latitude, and SF-type variations. The range spread F (RSF) occurrence in equinox months decreased with the increase in latitude, while the frequency spread F’s (FSF) occurrence rate in the summer months increased and the onset time of FSF became earlier when the latitude increased. The generation of SF depends on the SF type. A plasma bubble excited by the generalized Rayleigh–Taylor instability (GRT) at the equator is more likely to produce RSF, while nighttime medium-scale traveling ionospheric disturbances (MSTIDs) induced by Perkins instability at middle latitudes is the main reason for the generation of FSF.
17
Yizengaw, E., E. A. Essex et R. Birsa. « The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm ». Annales Geophysicae 22, no 8 (7 septembre 2004) : 2765–73. http://dx.doi.org/10.5194/angeo-22-2765-2004.
Texte intégralRésumé :
Abstract. The ionospheric storm evolution process was monitored during the 22 September 1999 magnetic storm over the Australian eastern region, through measurements of the ionospheric Total Electron Content (TEC) from seven Global Positioning Systems (GPS) stations. The spatial and temporal variations of the ionosphere were analysed as a time series of TEC maps. Results of our analysis show that the main ionospheric effect of the storm under consideration are: the long lasting negative storm effect during a magnetic storm at mid-latitude regions; the strong, positive disturbances during the storm's main phase at auroral latitude regions; the effects of storm-induced equatorward directed wind causing a positive disturbance at high and mid-latitude stations with appropriate time shift between higher and lower latitudes; daytime poleward movement of depleted plasma that causes temporary suppression of the equatorial anomaly during the start of the storm recovery phase; and prompt penetration of eastward electric fields to ionospheric altitudes and the production of nearly simultaneous TEC enhancement at all latitudes. In general, we found dominant negative disturbance over mid and high latitudes and positive disturbance at low latitudes. A comparison of storm-time behaviour of TEC determined from GPS satellites, and foF2 derived from ionosondes at a range of latitudes, showed reasonable agreement between the two independent measurements.
18
Jensen, J. W., et B. G. Fejer. « Longitudinal dependence of middle and low latitude zonal plasma drifts measured by DE-2 ». Annales Geophysicae 25, no 12 (2 janvier 2007) : 2551–59. http://dx.doi.org/10.5194/angeo-25-2551-2007.
Texte intégralRésumé :
Abstract. We used ion drift observations from the DE-2 satellite to study for the first time the longitudinal variations of middle and low latitude F region zonal plasma drifts during quiet and disturbed conditions. The quiet-time middle latitude drifts are predominantly westward; the low latitude drifts are westward during the day and eastward at night. The daytime quiet-time drifts do not change much with longitude; the nighttime drifts have strong season dependent longitudinal variations. In the dusk-premidnight period, the equinoctial middle latitude westward drifts are smallest in the European sector and the low latitude eastward drifts are largest in the American-Pacific sector. The longitudinal variations of the late night-early morning drifts during June and December solstice are anti-correlated. During geomagnetically active times, there are large westward perturbation drifts in the late afternoon-early night sector at upper middle latitudes, and in the midnight sector at low latitudes. The largest westward disturbed drifts during equinox occur in European sector, and the smallest in the Pacific region. These results suggest that during equinox SAPS events occur most often at European longitudes. The low latitude perturbation drifts do not show significant longitudinal
19
Lin, Jiaqi, Feng Wang, Linhua Deng, Hui Deng, Ying Mei et Yangfan Xie. « The Temporal and Spatial Behaviors of CME Occurrence Rate at Different Latitudes ». Astrophysical Journal 932, no 1 (1 juin 2022) : 62. http://dx.doi.org/10.3847/1538-4357/ac6f54.
Texte intégralRésumé :
Abstract The statistical study of the coronal mass ejections (CMEs) is a hot topic in solar physics. To further reveal the temporal and spatial behaviors of the CMEs at different latitudes and heights, we analyzed the correlation and phase relationships between the occurrence rate of CMEs, the coronal brightness index (CBI), and the 10.7 cm solar radio flux (F10.7). We found that the occurrence rate of the CMEs correlates with the CBI relatively stronger at high latitudes (≥60°) than at low latitudes (≤50°). At low latitudes, the occurrence rate of the CMEs correlates relatively weaker with the CBI than the F10.7. There is a relatively stronger correlation relationship between CMEs, the F10.7, and the CBI during Solar Cycle 24 (SC24) than Solar Cycle 23 (SC23). During SC23, the high-latitude CME occurrence rate lags behind the F10.7 by 3 months, and during SC24, the low-latitude CME occurrence rate leads the low-latitude CBI by 1 month. The correlation coefficient values turn out to be larger when the very faint CMEs are removed from the samples of the CDAW catalog. Based on our results, we may speculate that the source regions of the high/low-latitude CMEs may vary in height, and the process of magnetic energy accumulation and dissipation is from the lower to the upper atmosphere of the Sun. The temporal offsets between different indicators could help us better understand the physical processes responsible for the solar-terrestrial interactions.
20
de Jong, Jelte T. A., Brian Yanny, Hans-Walter Rix, Eric F. Bell et Andrew E. Dolphin. « Mapping low-latitude stellar substructure with SEGUE photometry ». Proceedings of the International Astronomical Union 4, S254 (juin 2008) : 121–26. http://dx.doi.org/10.1017/s1743921308027488.
Texte intégralRésumé :
AbstractEncircling the Milky Way at low latitudes, the Low Latitude Stream is a large stellar structure, the origin of which is as yet unknown. As part of the SEGUE survey, several photometric scans have been obtained that cross the Galactic plane, spread over a longitude range of 50° to 203°. These data allow a systematic study of the structure of the Galaxy at low latitudes, where the Low Latitude Stream resides. We apply colour-magnitude diagram fitting techniques to map the stellar (sub)structure in these regions, enabling the detection of overdensities with respect to smooth models. These detections can be used to distinguish between different models of the Low Latitude Stream, and help to shed light on the nature of the system.
21
Tian, Wenshou, Yuanpu Li, Fei Xie, Jiankai Zhang, Martyn P. Chipperfield, Wuhu Feng, Yongyun Hu et al. « The relationship between lower-stratospheric ozone at southern high latitudes and sea surface temperature in the East Asian marginal seas in austral spring ». Atmospheric Chemistry and Physics 17, no 11 (8 juin 2017) : 6705–22. http://dx.doi.org/10.5194/acp-17-6705-2017.
Texte intégralRésumé :
Abstract. Using satellite observations, reanalysis data, and model simulations, this study investigates the effect of sea surface temperature (SST) on interannual variations of lower-stratospheric ozone at southern high latitudes in austral spring. It is found that the SST variations across the East Asian marginal seas (5° S–35° N, 100–140° E) rather than the tropical eastern Pacific Ocean, where ENSO occurs, have the most significant correlation with the southern high-latitude lower-stratospheric ozone changes in austral spring. Further analysis reveals that planetary waves originating over the marginal seas in austral spring can propagate towards southern middle to high latitudes via teleconnection pathway. The anomalous propagation and dissipation of ultra-long Rossby waves in the stratosphere strengthen/cool (weaken/warm) the southern polar vortex, which produces more (less) active chlorine and enhances (suppresses) ozone depletion in the southern high-latitude stratosphere on one the hand and impedes (favors) the transport of ozone from the southern middle-latitude stratosphere to high latitudes on the other. The model simulations also reveal that approximately 17 % of the decreasing trend in the southern high-latitude lower-stratospheric ozone observed over the past 5 decades may be associated with the increasing trend in SST over the East Asian marginal seas.
22
Laurel, Benjamin J., et Ian R. Bradbury. « “Big” concerns with high latitude marine protected areas (MPAs) : trends in connectivity and MPA size ». Canadian Journal of Fisheries and Aquatic Sciences 63, no 12 (1 décembre 2006) : 2603–7. http://dx.doi.org/10.1139/f06-151.
Texte intégralRésumé :
The success of marine protected areas (MPAs) as fisheries management tools in tropical latitudes has generated interest in their applicability and potential elsewhere. Here we suggest that dispersal and gene flow in marine fish populations (a primary biological consideration for marine reserve design) increases with latitude. For example, north temperate fish species at latitudes between 40° and 45° had about three times greater dispersal potential (planktonic larval duration (PLD), n = 96 species) and genetic homogeneity (FST, n = 100 species) than fish species near equatorial regions. Using the PLD and FST relationships, dispersal increases at a rate of ~8% per degree of latitude north or south of the equator. Therefore tropical MPAs should not serve as direct scalar templates in other regions, but rather should be used as a basis against which higher-latitude MPAs should be scaled. However, a review of 429 existing MPAs indicates that no such changes in reserve size have been implemented with respect to latitude. Fisheries managers must be prepared and willing to implement MPAs at large scales in high latitudes, either as single reserves or in a network, or else we lose the legitimacy of a new and promising management tool for conserving marine biodiversity in cold ocean regions.
23
Singh, Jagdev, M. Priyal, G. Sindhuja et B. Ravindra. « Variations in Ca-K line profiles and Ca-K line features as a function of latitude and solar cycle during the 20th century ». Proceedings of the International Astronomical Union 13, S340 (février 2018) : 23–26. http://dx.doi.org/10.1017/s1743921318001540.
Texte intégralRésumé :
AbstractThe analysis of the Ca-K line spectra as a function of latitude and integrated over the visible disk obtained during the period of 1989–2011 at the Kodaikanal Solar Tower Telescope shows that the FWHM of the K1 distribution at different latitudes varies by negligible amount at about 60° latitude whereas it varies significantly at other latitudes. Findings, especially the fewer variations in mid-latitude belts as compared to polar regions and complex variation in the shift in the activity around 60° latitude belt, will have important implications on the modeling of solar dynamos. Further, we have generated a uniform set of digitized Ca-K line images by selecting images considering the intensity distribution of the images corrected for the instrumental vignetting for the data obtained at Kodaikanal during the 20th century. Then, we have determined the percentage of plage and network areas by using the intensity and area threshold values.
24
Qu, Tao, Lifeng Zhang, Yuan Wang, Xu Wang et Jiping Guan. « Seasonal Variations in the Vertical Wavenumber Spectra of Stratospheric Gravity Waves in the Asian Monsoon Region Derived from COSMIC-2 Data ». Remote Sensing 14, no 24 (14 décembre 2022) : 6336. http://dx.doi.org/10.3390/rs14246336.
Texte intégralRésumé :
We used the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) dry temperature profile data from December 2019 to November 2021 to study the vertical wavenumber spectra of the potential energy of stratospheric gravity waves (GWs Ep) in the Asian monsoon region (15–45°N, 70–150°E). The GW Ep decreases with increasing vertical wavenumber, and the spectral slope varies with wavenumber. The spectral slope becomes smaller over a wavenumber range of 0.1–0.45 km−1, and larger from 0.45–1 km−1, with increasing wavenumber. The energy density distribution at middle and low latitudes shows seasonal variations. Over a wavenumber range of 0.05–0.5 km−1, the energy density in winter is higher at middle latitudes than at low latitudes, and the opposite is observed in summer over a wavenumber range from 0.1 to 1 km−1. Both the spectral amplitude and characteristic wavelength exhibit band-like patterns, and the large-value bands and their centers vary significantly with the season. In winter, the middle latitude spectral amplitude is larger than that at low latitudes, and the significant large-value band-like distribution is at 40°N. In summer, the distribution is opposite, with large-value band regions over the Bay of Bengal and Indo-China Peninsula. The large-value region of the middle latitude spectral amplitude corresponds to a longer characteristic wavelength, while the large-value region of the low latitude spectral amplitude corresponds to a shorter characteristic wavelength. There is also significant seasonal variation in the distribution of spectral slopes. Over a wavenumber range of 0.1 to 0.5 km−1, the slope is smaller at middle latitudes and larger at low latitudes in winter; the opposite is observed in summer. There is a significant annual cycle of spectral amplitude at middle and low latitudes, and a 4.8 month cycle at middle latitudes.
25
Zhang, Zebin, Jie Jiang et Haowei Zhang. « A Potential New Mechanism for the Butterfly Diagram of the Solar Cycle : Latitude-dependent Radial Flux Transport ». Astrophysical Journal Letters 941, no 1 (1 décembre 2022) : L3. http://dx.doi.org/10.3847/2041-8213/aca47a.
Texte intégralRésumé :
Abstract The butterfly diagram of the solar cycle is the equatorward migration of the emergence latitudes of sunspots as the solar cycle evolves. Revealing the mechanism for the butterfly diagram is essential for understanding the solar and stellar dynamo. The equatorward meridional flow at the base of the convection zone (CZ) was believed to be responsible for the butterfly diagram. However, helioseismological studies indicate controversial forms of the flow, and even present poleward flow at the base of the CZ, which poses a big challenge to the widely accepted mechanism. This motivates us to propose a new mechanism in this study. Using a data-driven Babcock–Leighton–type dynamo model, we carry out numerical simulations to explore how the latitude-dependent radial flux transport affects the latitudinal migration of the toroidal field, under different meridional flow profiles. The results indicate that when the radial transport of the poloidal field at higher latitudes is sufficiently faster, the toroidal fields of a new cycle at higher latitudes are generated earlier than that at lower latitudes, and vice versa. Thus, the butterfly diagram is suggested to correspond to the time- and latitude-dependent regeneration of the toroidal field due to the latitude-dependent radial transport of the poloidal flux.
26
Longobardi, P., A. Montenegro, H. Beltrami et M. Eby. « Spatial scale dependency of the modelled climatic response to deforestation ». Biogeosciences Discussions 9, no 10 (22 octobre 2012) : 14639–87. http://dx.doi.org/10.5194/bgd-9-14639-2012.
Texte intégralRésumé :
Abstract. Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scale land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we determine effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is registered over low latitude deforested areas. Mid latitude SAT response is mixed. For all simulations deforested areas tend to become drier and have lower surface air temperature, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation, cause an increase in soil carbon large enough to generate a previously not reported net drawdown of CO2 from the atmosphere. Our results support previous indications of the importance of changes in cloud cover in the modelled temperature response to deforestation at low latitudes. They also show the complex interaction between soil carbon dynamics and climate and the role this plays on the climatic response to land cover change.
27
Palter, Jaime B., Stephen M. Griffies, Bonita L. Samuels, Eric D. Galbraith, Anand Gnanadesikan et Andreas Klocker. « The Deep Ocean Buoyancy Budget and Its Temporal Variability ». Journal of Climate 27, no 2 (15 janvier 2014) : 551–73. http://dx.doi.org/10.1175/jcli-d-13-00016.1.
Texte intégralRésumé :
Abstract Despite slow rates of ocean mixing, observational and modeling studies suggest that buoyancy is redistributed to all depths of the ocean on surprisingly short interannual to decadal time scales. The mechanisms responsible for this redistribution remain poorly understood. This work uses an Earth system model to evaluate the global steady-state ocean buoyancy (and related steric sea level) budget, its interannual variability, and its transient response to a doubling of CO2 over 70 years, with a focus on the deep ocean. At steady state, the simple view of vertical advective–diffusive balance for the deep ocean holds at low to midlatitudes. At higher latitudes, the balance depends on a myriad of additional terms, namely mesoscale and submesoscale advection, convection and overflows from marginal seas, and terms related to the nonlinear equation of state. These high-latitude processes rapidly communicate anomalies in surface buoyancy forcing to the deep ocean locally; the deep, high-latitude changes then influence the large-scale advection of buoyancy to create transient deep buoyancy anomalies at lower latitudes. Following a doubling of atmospheric carbon dioxide concentrations, the high-latitude buoyancy sinks are suppressed by a slowdown in convection and reduced dense water formation. This change is accompanied by a slowing of both upper and lower cells of the global meridional overturning circulation, reducing the supply of dense water to low latitudes beneath the pycnocline and the commensurate flow of light waters to high latitudes above the pycnocline. By this mechanism, changes in high-latitude buoyancy are communicated to the global deep ocean on relatively fast advective time scales.
28
Jin, Yu-Song, Yu-Kun Hu, Jing Wang, Dan-Dan Liu, Ying-Hua Lin, Guang Liu, Yun-Hui Zhang et Zhi-Qiang Zhou. « Diversity of Understory Communities in Boreal Forests : Influences of Forest Type, Latitude, and Spatial Scale ». Forests 10, no 11 (9 novembre 2019) : 1003. http://dx.doi.org/10.3390/f10111003.
Texte intégralRésumé :
Understory vegetation hosts high biodiversity and plays a critical role in the ecosystem processes of boreal forests. However, the drivers of understory plant diversity in this high-latitude ecosystem remain uncertain. To investigate the influences of forest type and latitude on understory beta diversity at different scales, we quantified the species composition of Vaccinium uliginosum Linnaeus communities under broadleaf and coniferous forests at two latitudes at the quadrat (2 × 2 m) and plot (10 × 10 m) scales in the Greater Xing’an Mountains, NE China. At the quadrat scale, species alpha diversity of V. uliginosum communities was higher in broadleaf forests than that in coniferous forests at both latitudes. The differences in species beta diversity (the Sørensen’s dissimilarity) in two forest types depended on the latitude: beta diversity in broadleaf forests was higher than that in coniferous forests at the higher latitude, while beta diversity in coniferous forests was higher at the lower latitude. At the plot scale, alpha and beta diversity of V. uliginosum communities decreased from broadleaf forests to coniferous forests at the higher latitude, and they did not show significant differences between forest types at the lower latitude. These results indicate the interactive effects of forest type and latitude on beta diversity of understory vegetation. Moreover, the influences of forest type and latitude on species alpha and beta diversity were different across the two spatial scales, suggesting that the assembly mechanisms underlying species diversity may be different at different scales. Understanding the maintenance of understory vegetation diversity will benefit the conservation and management of boreal forests.
29
Lu, Xinmin, Minyan He, Saichun Tang, Yuqing Wu, Xu Shao, Hui Wei, Evan Siemann et Jianqing Ding. « Herbivory may promote a non-native plant invasion at low but not high latitudes ». Annals of Botany 124, no 5 (18 juillet 2019) : 819–27. http://dx.doi.org/10.1093/aob/mcz121.
Texte intégralRésumé :
Abstract Background and Aims The strengths of biotic interactions such as herbivory are expected to decrease with increasing latitude for native species. To what extent this applies to invasive species and what the consequences of this variation are for competition among native and invasive species remain unexplored. Here, herbivore impacts on the invasive plant Alternanthera philoxeroides and its competition with the native congener A. sessilis were estimated across latitudes in China. Methods An common garden experiment spanning ten latitudinal degrees was conducted to test how herbivore impacts on A. philoxeroides and A. sessilis, and competition between them change with latitude. In addition, a field survey was conducted from 21°N to 36.8°N to test whether A. philoxeroides invasiveness changes with latitude in nature as a result of variations in herbivory. Key Results In the experiment, A. sessilis cover was significantly higher than A. philoxeroides cover when they competed in the absence of herbivores, but otherwise their cover was comparable at low latitude. However, A. philoxeroides cover was always higher on average than A. sessilis cover at middle latitude. At high latitude, only A. sessilis emerged in the second year. Herbivore abundance decreased with latitude and A. philoxeroides emerged earlier than A. sessilis at middle latitude. In the field survey, the ratio of A. philoxeroides to A. sessilis cover was hump shaped with latitude. Conclusion These results indicate that herbivory may promote A. philoxeroides invasion only at low latitude by altering the outcome of competition in favour of the invader and point to the importance of other factors, such as earlier emergence, in A. philoxeroides invasion at higher latitudes. These results suggest that the key factors promoting plant invasions might change with latitude, highlighting the importance of teasing apart the roles of multiple factors in plant invasions within a biogeographic framework.
30
Chandran, A., et R. L. Collins. « Stratospheric sudden warming effects on winds and temperature in the middle atmosphere at middle and low latitudes : a study using WACCM ». Annales Geophysicae 32, no 7 (28 juillet 2014) : 859–74. http://dx.doi.org/10.5194/angeo-32-859-2014.
Texte intégralRésumé :
Abstract. A stratospheric sudden warming (SSW) is a dynamical phenomenon of the wintertime stratosphere caused by the interaction between planetary Rossby waves propagating from the troposphere and the stratospheric zonal-mean flow. While the effects of SSW events are seen predominantly in high latitudes, they can also produce significant changes in middle and low latitude temperature and winds. In this study we quantify the middle and low latitude effects of SSW events on temperature and zonal-mean winds using a composite of SSW events between 1988 and 2010 simulated with the specified dynamics version of the Whole Atmosphere Community Climate Model (WACCM). The temperature and wind responses seen in the tropics also extend into the low latitudes in the other hemisphere. There is variability in observed zonal-mean winds and temperature depending on the observing location within the displaced or split polar vortex and propagation direction of the planetary waves. The propagation of planetary waves show that they originate in mid–high latitudes and propagate upward and equatorward into the mid-latitude middle atmosphere where they produce westward forcing reaching peak values of ~ 60–70 m s−1 day−1. These propagation paths in the lower latitude stratosphere appear to depend on the phase of the quasi-biennial oscillation (QBO). During the easterly phase of the QBO, waves originating at high latitudes propagate across the equator, while in the westerly phase of the QBO, the planetary waves break at ~ 20–25° N and there is no propagation across the equator. The propagation of planetary waves across the equator during the easterly phase of the QBO reduces the tropical upwelling and poleward flow in the upper stratosphere.
31
Isachsen, P. E., J. H. LaCasce et J. Pedlosky. « Rossby Wave Instability and Apparent Phase Speeds in Large Ocean Basins ». Journal of Physical Oceanography 37, no 5 (1 mai 2007) : 1177–91. http://dx.doi.org/10.1175/jpo3054.1.
Texte intégralRésumé :
Abstract The stability of baroclinic Rossby waves in large ocean basins is examined, and the quasigeostrophic (QG) results of LaCasce and Pedlosky are generalized. First, stability equations are derived for perturbations on large-scale waves, using the two-layer shallow-water system. These equations resemble the QG stability equations, except that they retain the variation of the internal deformation radius with latitude. The equations are solved numerically for different initial conditions through eigenmode calculations and time stepping. The fastest-growing eigenmodes are intensified at high latitudes, and the slower-growing modes are intensified at lower latitudes. All of the modes have meridional scales and growth times that are comparable to the deformation radius in the latitude range where the eigenmode is intensified. This is what one would expect if one had applied QG theory in latitude bands. The evolution of large-scale waves was then simulated using the Regional Ocean Modeling System primitive equation model. The results are consistent with the theoretical predictions, with deformation-scale perturbations growing at rates inversely proportional to the local deformation radius. The waves succumb to the perturbations at the mid- to high latitudes, but are able to cross the basin at low latitudes before doing so. Also, the barotropic waves produced by the instability propagate faster than the baroclinic long-wave speed, which may explain the discrepancy in speeds noted by Chelton and Schlax.
32
Luan, X., L. Liu, W. Wan, J. Lei et T. Yu. « A climatology of the F-layer equivalent winds derived from ionosonde measurements over two decades along the 120°-150°E sector ». Annales Geophysicae 22, no 8 (7 septembre 2004) : 2785–96. http://dx.doi.org/10.5194/angeo-22-2785-2004.
Texte intégralRésumé :
Abstract. The vertical equivalent winds (VEWs) at the F-layer are analyzed along the 120°-150°E longitude sector with an emphasis on their latitudinal dependence. The VEWs are derived from the monthly median data of fourteen ionosonde stations over two decades. The results show that the VEWs have considerable dependences on the magnetic latitude with an approximate symmetry about the magnetic equator. They are mostly controlled by the electric field drifts in the magnetic equatorial region, and shift to be mostly contributed by neutral winds at mid-latitudes. The relative contribution of the two dynamic factors is regulated by the magnetic dip in addition to their own magnitudes. The VEWs generally have opposite directions and different magnitudes between lower and higher latitudes. At solar minimum, the magnitudes of VEWs are only between -20 and 20m/s at lower latitudes, while at higher latitudes they tend to increase with latitudes, typically having magnitudes between 20-40m/s. At solar maximum, the VEWs are reduced by about 10-20m/s in magnitudes during some local times at higher latitudes. A tidal analysis reveals that the relative importance of major tidal components is also different between lower and higher latitudes. The VEWs also depend on local time, season and solar activity. At higher latitudes, the nighttime VEWs have larger magnitude during post-midnight hours and so do the daytime ones before midday. The VEWs tend to have an inverse relationship with solar activity not only at night, but also by day, which is different from the meridional winds predicted by the HWM93 model. The latitudinal dependence of VEWs has two prevailing trends: one is a maximum at the highest latitudes (as far as the latitudes concerned in the present work); the other is a mid-latitude maximum. These two latitudinal trends are mostly dependent on season, while they depend relatively weakly on local time and solar activity. The latitudinal gradients of VEWs also show a tendency of a mid-latitude maximum, except that there are much stronger latitudinal gradients at southern higher mid-latitudes in some seasons. The gradients during daytime are much smaller at solar maximum than minimum, whereas they are generally comparable at night under both solar activity levels.
33
Beaton, Laura L. « A latitudinal gradient in herbivore resistance in common sunflower, Helianthus annuus (Asteraceae) ». Plant Ecology and Evolution 153, no 2 (8 juillet 2020) : 199–207. http://dx.doi.org/10.5091/plecevo.2020.1711.
Texte intégralRésumé :
Background and aims – The intensity of herbivory is expected to decline with increasing latitude. As herbivory varies spatially and over time, a reliable method of assessing the intensity of herbivory is to examine the degree of herbivore resistance in the plant community. Latitudinal gradients in resistance to herbivory were examined in wild populations of common sunflower, Helianthus annuus. Materials and methods – Seeds from 23 different latitudes, ranging from 20 to 44°N, were obtained from the USDA’s Germplasm Resources Information Network. Plants were grown in a greenhouse for nine weeks. At that time, the size (height, leaf length, number of leaves) and resistance of each plant to herbivory (determined through a bioassay using a generalist herbivore, Helicoverpa zea was assessed. Key results – Resistance to herbivory decreased significantly with latitude, while plant size, as indicated by height, was positively correlated with latitude and negatively correlated with both temperature and resistance to herbivory.Conclusion – Populations from lower latitudes exhibited elevated resistance to herbivory and slower growth, suggesting first, that herbivory is more intense at lower latitudes and second, that there is a tradeoff between growth and defense.
34
Hiraiwa, T. « Proposal on the Modification of Sailing Calculations ». Journal of Navigation 40, no 1 (janvier 1987) : 138–48. http://dx.doi.org/10.1017/s0373463300000369.
Texte intégralRésumé :
Methods of calculating the course and the distance between two points from a knowledge of their latitudes and longitudes, or calculating the latitude and the longitude of the arrival point from the course and the distance from a known departure point, are called sailings. Middle-latitude sailing and Mercator sailing have been widely used.
35
Fragoso, Yara Dadalti, Tarso Adoni, Sandra Maria Garcia de Almeida, Soniza Vieira Alves-Leon, Walter Oleschko Arruda, Fiorella Barbagelata-Aguero, Joseph Bruno Bidin Brooks et al. « Multiple sclerosis in South America : month of birth in different latitudes does not seem to interfere with the prevalence or progression of the disease ». Arquivos de Neuro-Psiquiatria 71, no 9A (septembre 2013) : 573–79. http://dx.doi.org/10.1590/0004-282x20130098.
Texte intégralRésumé :
Objective To assess whether the month of birth in different latitudes of South America might influence the presence or severity of multiple sclerosis (MS) later in life. Methods Neurologists in four South American countries working at MS units collected data on their patients' month of birth, gender, age, and disease progression. Results Analysis of data from 1207 MS patients and 1207 control subjects did not show any significant variation in the month of birth regarding the prevalence of MS in four latitude bands (0–10; 11–20; 21–30; and 31–40 degrees). There was no relationship between the month of birth and the severity of disease in each latitude band. Conclusion The results from this study show that MS patients born to mothers who were pregnant at different Southern latitudes do not follow the seasonal pattern observed at high Northern latitudes.
36
Camargo, George, et Erich Fischer. « Primeiro registro do morcego Mimon crenulatum (Phyllostomidae) no Pantanal, sudoeste do Brasil ». Biota Neotropica 5, no 1 (2005) : 181–84. http://dx.doi.org/10.1590/s1676-06032005000100017.
Texte intégralRésumé :
Espécies do gênero Mimon Gray, 1847, ocorrem desde o México até a Bolívia central e sudeste do Brasil, entre as latitudes 22º N e 25º S. Aproximadamente entre 14e 25º S de latitude, a ocorrência conhecida de Mimon é restrita ao leste brasileiro, na Mata Atlântica. Apenas em latitudes menores que 14º S as espécies de Mimon adicionalmente ocorrem na região central e oeste da América do Sul, na Amazônia, Cerrado e Caatinga. Mimon crenulatum (E. Geoffroy, 1810) é localmente rara porém ocorre amplamente dentro dos limites de distribuição do gênero. Reportamos aqui a ocorrência de Mimon crenulatum a ca. 20º de latitude sul na planície inundável do Pantanal, oeste do Brasil. Provavelmente este é o primeiro registro do gênero Mimon neste ecossistema, ampliando a distribuição geográfica de M. crenulatum para o oeste brasileiro em latitudes maiores que 14º S.
37
Ternullo, Maurizio. « The Butterfly diagram leopard skin pattern ». Proceedings of the International Astronomical Union 6, S273 (août 2010) : 195–99. http://dx.doi.org/10.1017/s1743921311015237.
Texte intégralRésumé :
AbstractA time-latitude diagram where spotgroups are given proportional relevance to their area is presented. The diagram reveals that the spotted area distribution is higly dishomogeneous, most of it being concentrated in few, small portions (“knots”) of the Butterfly Diagram; because of this structure, the BD may be properly described as a cluster of knots. The description, assuming that spots scatter around the “spot mean latitude” steadily drifting equatorward, is challenged. Indeed, spots cluster around at as many latitudes as knots; a knot may appear at either lower or higher latitudes than previous ones, in a seemingly random way; accordingly, the spot mean latitude abruptly drifts equatorward or even poleward at any knot activation, in spite of any smoothing procedure. Preliminary analyses suggest that the activity splits, in any hemisphere, into two or more distinct “activity waves”, drifting equatorward at a rate higher than the spot zone as a whole.
38
Dunn, Peter O., Kevin J. Thusius, Kevin Kimber et David W. Winkler. « Geographic and Ecological Variation in Clutch Size of Tree Swallows ». Auk 117, no 1 (1 janvier 2000) : 215–21. http://dx.doi.org/10.1093/auk/117.1.215.
Texte intégralRésumé :
AbstractIn many birds, populations breeding at higher latitudes have larger clutch sizes. It has been hypothesized that this relationship results from the greater availability of food at higher latitudes. We examined geographic variation in clutch size of Tree Swallows (Tachycineta bicolor) in relation to latitude, longitude, laying date, breeding density, elevation, and summer actual evapotranspiration (AE). AE is a measure of terrestrial primary productivity, and we assumed that it was correlated with resource abundance. Clutch size data were compiled from nest records throughout the breeding range in the United States and Canada (n = 7,459). Summer AE estimates were made from long-term climatological records, and breeding density was estimated from Breeding Bird Surveys. All variables were averaged for each 1° block of latitude and longitude (n = 85 latilong blocks). We found a strong positive relationship between clutch size and latitude. Absolute levels of resource abundance (summer AE) were not related to clutch size but were related inversely to latitude and longitude. After controlling for the effects of confounding variables, clutch size was related positively to latitude and relative resource abundance (summer AE after controlling for breeding density). Our results are consistent with Ashmole's hypothesis that relative, rather than absolute, levels of resource abundance determine at least some of the variation in clutch size.
39
Jullien, Elsa, Francis Grousset, Bruno Malaizé, Josette Duprat, Maria Fernanda Sanchez-Goni, Frédérique Eynaud, Karine Charlier et al. « Low-latitude “dusty events” vs. high-latitude “icy Heinrich Events” ». Quaternary Research 68, no 3 (novembre 2007) : 379–86. http://dx.doi.org/10.1016/j.yqres.2007.07.007.
Texte intégralRésumé :
AbstractIt has been proposed that tropical events could have participated in the triggering of the classic, high-latitude, iceberg-discharge Heinrich events (HE). We explore low-latitude Heinrich events equivalents at high resolution, in a piston core recovered from the tropical north-western African margin. They are characterized by an increase of total dust, lacustrine diatoms and fibrous lacustrine clay minerals. Thus, low-latitude events clearly reflect severe aridity events that occurred over Africa at the Saharan latitudes, probably induced by southward shifts of the Inter Tropical Convergence Zone. At a first approximation, it seems that there is more likely synchronicity between the high-latitude Heinrich Events (HEs) and low-latitude events (LLE), rather than asynchronous behaviours.
40
Zhai, Xiaoming, Helen L. Johnson et David P. Marshall. « A Model of Atlantic Heat Content and Sea Level Change in Response to Thermohaline Forcing ». Journal of Climate 24, no 21 (1 novembre 2011) : 5619–32. http://dx.doi.org/10.1175/jcli-d-10-05007.1.
Texte intégralRésumé :
Abstract The response of ocean heat content in the Atlantic to variability in the meridional overturning circulation (MOC) at high latitudes is investigated using a reduced-gravity model and the Massachusetts Institute of Technology (MIT) general circulation model (MITgcm). Consistent with theoretical predictions, the zonal-mean heat content anomalies are confined to low latitudes when the high-latitude MOC changes rapidly, but extends to mid- and high latitudes when the high-latitude MOC varies on decadal or multidecadal time scales. This low-pass-filtering effect of the mid- and high latitudes on zonal-mean heat content anomalies, termed here the “Rossby buffer,” is shown to be associated with the ratio of Rossby wave basin-crossing time to the forcing period at high northern latitudes. Experiments using the MITgcm also reveal the importance of advective spreading of cold water in the deep ocean, which is absent in the reduced-gravity model. Implications for monitoring ocean heat content and sea level changes are discussed in the context of both models. It is found that observing global sea level variability and sea level rise using tide gauges can substantially overestimate the global-mean values.
41
Watson, Abigale S., Charles W. Smith, Anastasia V. Marchuk, Matthew R. Argall, Colin J. Joyce, Philip A. Isenberg, Bernard J. Vasquez et al. « High-latitude Observations of Inertial-range Turbulence by the Ulysses Spacecraft During the Solar Minimum of 1993–96 ». Astrophysical Journal 927, no 1 (1 mars 2022) : 43. http://dx.doi.org/10.3847/1538-4357/ac4588.
Texte intégralRésumé :
Abstract We have examined Ulysses magnetic field measurements for the years 1993 through 1996 as the spacecraft moved sunward from 5 au at high southern latitudes, passing through perihelion during the first fast-latitude scan to achieve high northern latitudes, and finally returning to 5 au. These years represent near-solar-minimum activity, providing a clear measure of high-latitude solar-wind turbulence. We apply a series of tests to the data, examining both the magnetic variance anisotropy and the underlying wavevector anisotropy, finding them to be consistent with past 1 au observations. The variance anisotropy depends upon both the thermal proton temperature parameter and the amplitude of the magnetic power spectrum, while the underlying wavevector anisotropy is dominated by the component perpendicular to the mean magnetic field. We also examine the amplitude of the magnetic power spectrum as well as the associated turbulent transport of energy to small scales that results in the heating of the thermal plasma. The measured turbulence is found to be stronger than that seen at low latitudes by the Voyager spacecraft as it traverses the distance from 1 to 5 au during the years approaching solar maximum. If the high- and low-latitude sources are comparable, this would indicate that while the heating processes are active in both regions, the turbulence has had less decay time in the transport of energy to small scales. Alternatively, it may also be that the high-latitude source is stronger.
42
Schoendorf, J., A. D. Aylward et R. J. Moffett. « Modelling high-latitude electron densities with a coupled thermosphere-ionosphere model ». Annales Geophysicae 14, no 12 (31 décembre 1996) : 1391–402. http://dx.doi.org/10.1007/s00585-996-1391-x.
Texte intégralRésumé :
Abstract. A few of the difficulties in accurately modelling high-latitude electron densities with a large-scale numerical model of the thermosphere and ionosphere are addressed by comparing electron densities calculated with the Coupled Thermosphere-Ionosphere Model (CTIM) to EISCAT data. Two types of simulations are presented. The first set of simulations consists of four diurnally reproducible model runs for a Kp index of 4o which differ only in the placement of the energetic-particle distribution and convection pattern input at high latitudes. These simulations predict varying amounts of agreement with the EISCAT data and illustrate that for a given Kp there is no unique solution at high-latitudes. Small changes in the high-latitude inputs cause dramatic changes in the high-latitude modelled densities. The second type of simulation consists of inputting statistical convection and particle precipitation patterns which shrink or grow as a function of Kp throughout a 3-day period 21–23 February 1990. Comparisons with the EISCAT data for the 3 days indicate that equatorward of the particle precipitation the model accurately simulates the data, while in the auroral zone there is more variability in the data than the model. Changing the high-latitude forcing as a function of Kp allows the CTIM to model the average behavior of the electron densities; however at auroral latitudes model spatial and temporal scales are too large to simulate the detailed variation seen in individual nights of data.
43
Zhang, X. J., L. H. Deng, Z. P. Qiang, Y. Fei, X. A. Tian et C. Li. « Hemispheric distribution of coronal mass ejections from 1996 to 2020 ». Monthly Notices of the Royal Astronomical Society 520, no 3 (15 février 2023) : 3923–36. http://dx.doi.org/10.1093/mnras/stad323.
Texte intégralRésumé :
ABSTRACT Solar magnetic structures are known to be asymmetrically distributed between the two hemispheres. To date, the hemispheric variations of the coronal mass ejections (CMEs) at different latitudes, in different cycles, and for different types (regular and specific events) are still unclear. From the list of white-light CMEs in the Coordinated Data Analysis Web catalogue, we investigate the hemispheric asymmetry of high-latitude and low-latitude CMEs in the time interval from 1996 January to 2020 December. The main results are shown for the following: (1) in each hemisphere, regular CMEs are significantly correlated with solar activity, particularly for low latitudes. However, specific CMEs are not correlated with solar activity; (2) the main reason for the hemispheric asymmetry of the CMEs is attributable to specific CMEs, not regular CMEs. The hemispheric asymmetry of high-latitude CMEs appears to have little connection to that of low-latitude CMEs; (3) for the total and specific CMEs, the relationship between the absolute asymmetry index at high and low latitudes has a positive correlation prior to the cycle maximum, but a negative correlation after the cycle maximum; and (4) the dominant hemisphere, the cumulative trend, and the amplitude of the total, specific, and regular CMEs in cycle 23 differ from those in cycle 24. Our analysis results could be useful for understanding the cyclical variation of the magnetic free energy during different solar cycles, and could also provide insight into more physical processes responsible for the solar–terrestrial relationship.
44
Xiong, Chao, Claudia Stolle et Jaeheung Park. « Climatology of GPS signal loss observed by Swarm satellites ». Annales Geophysicae 36, no 2 (26 avril 2018) : 679–93. http://dx.doi.org/10.5194/angeo-36-679-2018.
Texte intégralRésumé :
Abstract. By using 3-year global positioning system (GPS) measurements from December 2013 to November 2016, we provide in this study a detailed survey on the climatology of the GPS signal loss of Swarm onboard receivers. Our results show that the GPS signal losses prefer to occur at both low latitudes between ±5 and ±20∘ magnetic latitude (MLAT) and high latitudes above 60∘ MLAT in both hemispheres. These events at all latitudes are observed mainly during equinoxes and December solstice months, while totally absent during June solstice months. At low latitudes the GPS signal losses are caused by the equatorial plasma irregularities shortly after sunset, and at high latitude they are also highly related to the large density gradients associated with ionospheric irregularities. Additionally, the high-latitude events are more often observed in the Southern Hemisphere, occurring mainly at the cusp region and along nightside auroral latitudes. The signal losses mainly happen for those GPS rays with elevation angles less than 20∘, and more commonly occur when the line of sight between GPS and Swarm satellites is aligned with the shell structure of plasma irregularities. Our results also confirm that the capability of the Swarm receiver has been improved after the bandwidth of the phase-locked loop (PLL) widened, but the updates cannot radically avoid the interruption in tracking GPS satellites caused by the ionospheric plasma irregularities. Additionally, after the PLL bandwidth increased larger than 0.5 Hz, some unexpected signal losses are observed even at middle latitudes, which are not related to the ionospheric plasma irregularities. Our results suggest that rather than 1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value for the Swarm receiver. Keywords. Ionosphere (equatorial ionosphere; ionospheric irregularities) – radio science (radio wave propagation)
45
ANTARKAR, V. N. « On determination of Sun-rise/set time and on construction of a Computer for the purpose ». MAUSAM 15, no 1 (9 mars 2022) : 61–66. http://dx.doi.org/10.54302/mausam.v15i1.5520.
Texte intégralRésumé :
A simple sliding computer determine sun rise/set times for any place within Indian latitudes is described. Its mathematical basis is discussed. A rough and ready method based on Variation of Sun-rise/set times with latitude is also mentioned, Variation in the observed times of sun-rise/set time with latitude is discussed and its importance to aircraft pilots indicated.
46
Bosmans, J. H. C., F. J. Hilgen, E. Tuenter et L. J. Lourens. « Obliquity forcing of low-latitude climate ». Climate of the Past Discussions 11, no 1 (11 février 2015) : 221–41. http://dx.doi.org/10.5194/cpd-11-221-2015.
Texte intégralRésumé :
Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.
47
Bosmans, J. H. C., F. J. Hilgen, E. Tuenter et L. J. Lourens. « Obliquity forcing of low-latitude climate ». Climate of the Past 11, no 10 (9 octobre 2015) : 1335–46. http://dx.doi.org/10.5194/cp-11-1335-2015.
Texte intégralRésumé :
Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.
48
Duarte, Carlos M., et Jacob Kalff. « Latitudinal influences on the Depths of Maximum Colonization and Maximum Biomass of Submerged Angiosperms in Lakes ». Canadian Journal of Fisheries and Aquatic Sciences 44, no 10 (1 octobre 1987) : 1759–64. http://dx.doi.org/10.1139/f87-215.
Texte intégralRésumé :
Both water transparency and lake latitude influence the depths of maximum biomass (Zb) and maximum depth of colonization (Zc) of submerged plants. The differences in the depth distribution of plants in lakes differing in water transparency become more pronounced as latitude decreases. Changes in transparency in low-latitude lakes should result in greater changes in macrophyte cover than similar changes in lakes at higher latitudes. The maximum depth of colonization appears to be largely a function of water transparency, whereas the depth of maximum biomass is best related to latitude. Relationships developed here allow better predictions of Zc and Zb for individual lakes than were possible before.
49
Singh, Jagdev. « Calcium K-Line Profiles as a Function of Latitude and Solar Cycle Phase ». International Astronomical Union Colloquium 141 (1993) : 408–9. http://dx.doi.org/10.1017/s0252921100029523.
Texte intégralRésumé :
AstractHigh resolution spectra are being taken in ionized calcium K-line at different latitudes and integrated over the visible 180 degree longitude. These have been analysed to study the variability of the line parameters as a function of latitude. These spectra are being obtained on a regular basis and large data base will be used to study chromospheric rotation, differential rotation in chromosphere, activity and variability of K-line parameters as function of latitude and solar cycle phase. Further, an optical arrangement has been worked out to obtain the spectra along the latitudes of the solar image in the light integrated over longitudes. This involves the unidirectionally focusing of the image in N-S direction.
50
Prikryl, P., R. Ghoddousi-Fard, L. Spogli, C. N. Mitchell, G. Li, B. Ning, P. J. Cilliers et al. « GPS phase scintillation at high latitudes during geomagnetic storms of 7–17 March 2012 – Part 2 : Interhemispheric comparison ». Annales Geophysicae 33, no 6 (2 juin 2015) : 657–70. http://dx.doi.org/10.5194/angeo-33-657-2015.
Texte intégralRésumé :
Abstract. During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7–17 March 2012 caused geomagnetic storms that strongly affected high-latitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time (MLT), the scintillation was observed in the ionospheric cusp, the tongue of ionization fragmented into patches, sun-aligned arcs in the polar cap, and nightside auroral oval and subauroral latitudes. Complementing a companion paper (Prikryl et al., 2015a) that focuses on the high-latitude ionospheric response to variable solar wind in the North American sector, interhemispheric comparison reveals commonalities as well as differences and asymmetries between the northern and southern high latitudes, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are caused by the dawn–dusk component of the interplanetary magnetic field controlling the MLT of the cusp entry of the storm-enhanced density plasma into the polar cap and the orientation relative to the noon–midnight meridian of the tongue of ionization.