scholarly journals Objective-Prism Radial Velocities at High Latitudes

1977 ◽  
Vol 4 (2) ◽  
pp. 77-77
Author(s):  
J. Stock ◽  
W. Osborn ◽  
A. R. Upgren
Keyword(s):  
Power Series ◽  
Spectral Line ◽  
High Latitude ◽  
Sufficient Accuracy ◽  
Radial Velocities ◽  
High Latitudes ◽  
Proper Motions ◽  
Third Order ◽  
Latitude Zone ◽  
Objective Prism

Stock and Osborn (1972, 1973) have shown that objective-prism spectra taken with a conventional prism may be measured to produce radial velocities of sufficient accuracy for statistical purposes. They are determined by means of a third-order power series in both x and y coordinates. The same spectral-line measures can also yield positions such that proper motions can be determined if first-epoch positions are also available. For many stars, both tangential and radial velocities can be obtained with about the same error which is of the order of ± 20 km/sec. The field distortions caused by the prism are large but are constant and predictable to the degree that measured residuals are similar in size to those for direct images (Stock and Upgren 1968). A survey of a high-latitude zone between −30° and −35° in declination is underway and a catalogue of about 3000 stars has already been compiled by Stock. For each star, the catalogue lists an accurate 1950 position, spectral and luminosity type, apparent photographic magnitude, relative radial velocity and its weight, and the number of plates on which the star was measured.

Objective-Prism Radial Velocities at High Latitudes

1977 ◽  
pp. 77-77
Author(s):  
J. Stock ◽  
W. Osborn ◽  
A. R. Upgren
Keyword(s):  
Radial Velocities ◽  
High Latitudes ◽  
Objective Prism

On the Inhomogeneity of Chemical Composition over the Surface of 21 Per

1976 ◽  
Vol 32 ◽  
pp. 343-349
Author(s):  
Yu.V. Glagolevsky ◽  
K.I. Kozlova ◽  
V.S. Lebedev ◽  
N.S. Polosukhina
Keyword(s):  
Chemical Composition ◽  
Spectral Line ◽  
Variable Star ◽  
Radial Velocities ◽  
Crimean Astrophysical Observatory ◽  
Line Intensities ◽  
Magnetic Variable

SummaryThe magnetic variable star 21 Per has been studied from 4 and 8 Å/mm spectra obtained with the 2.6 - meter reflector of the Crimean Astrophysical Observatory. Spectral line intensities (Wλ) and radial velocities (Vr) have been measured.

High Latitude Dust: contemporary emissions and geomorphic interactions

2021 ◽  
Author(s):  
Joanna Bullard
Keyword(s):  
Remote Sensing ◽  
Environmental Change ◽  
High Latitude ◽  
Cold Climate ◽  
Sediment Supply ◽  
Future Research ◽  
Similar Proportion ◽  
High Latitudes ◽  
Dust Emissions ◽  
Dust Sources

<div> <p>The world’s largest contemporary dust sources are in low-lying, hot, arid regions, however the processes of dust production and emission also operate in cold climate regions at high latitudes and altitudes.  This lecture focuses on contemporary dust emissions originating from the high latitudes (≥50°N and ≥40°S) and explores three themes before setting out an integrated agenda for future research.  The first theme considers how much dust originates from the high latitudes and methods for determining this.  Estimates from field studies, remote sensing and modelling all suggest around 5% of contemporary global dust emissions originate in the high latitudes, a similar proportion to that from the USA (excluding Alaska) or Australia.  This estimate is a proportion of a highly uncertain figure as quantification of dust emissions from Eurasian high latitudes is limited, and the contribution of local and regional emissions (from any latitude) to the global total is thought to be considerably under-estimated.  Emissions are particularly likely to be under-estimated where dust sources are topographically constrained, and where cold climates reduce vertical mixing of dust plumes restricting the altitudes to which the dust can rise, because both these characteristics present particular challenges for modelling and remote sensing approaches. The second theme considers the drivers of contemporary high latitude dust emissions that reflect complex interactions among sediment supply, sediment availability and transport capacity across different geomorphic sub-systems.  These interactions determine the magnitude, frequency and timing of dust emissions at a range of time scales (diurnal, seasonal, decadal) but both the drivers and response can be nonlinear and hard to predict.  The third and final theme explores the importance of high latitude dust cycling for facilitating cross-boundary material fluxes and its impact in the atmosphere, cryosphere, and terrestrial and marine ecosystems.  This is influenced not only by the quantity and timing of dust emissions but also by dust properties such as particle-size and geochemistry.  Landscape sensitivity, spatial environmental transitions and temporal environmental change are highlighted for their importance in determining how the interactions among drivers and cycles are likely to change in response to future environmental change.</p> </div>

scholarly journals Corrected μβ for stars of Hipparcos catalogue from independent latitude observations over many decades

2011 ◽  
pp. 35-41 ◽  
Author(s):  
G. Damljanovic ◽  
I.S. Milic
Keyword(s):  
International Organizations ◽  
Sufficient Accuracy ◽  
Proper Motions ◽  
Earth Orientation Parameters ◽  
Method Of Calculation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
International Polar ◽  
The Common ◽  
Orientation Parameters

During the last century, there were many so-called independent latitude (IL) stations with the observations which were included into data of a few international organizations (like Bureau International de l'Heure - BIH, International Polar Motion Service - IPMS) and the Earth rotation programmes for determining the Earth Orientation Parameters - EOP. Because of this, nowadays, there are numerous astrometric ground-based observations (made over many decades) of some stars included in the Hipparcos Catalogue (ESA 1997). We used these latitude data for the inverse investigations - to improve the proper motions in declination ?? of the mentioned Hipparcos stars. We determined the corrections ??? and investigated agreement of our ?? and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007). To do this we used the latitude variations of 7 stations (Belgrade, Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering different intervals in the period 1904.7 - 1992.0, obtained with 6 visual and 1 floating zenith telescopes (Mizusawa). On the other hand, with regard that about two decades have elapsed since the Hipparcos ESA mission observations (the epoch of Hipparcos catalogue is 1991.25), the error of apparent places of Hipparcos stars has increased by nearly 20 mas because of proper motion errors. Also, the mission lasted less than four years which was not enough for a sufficient accuracy of proper motions of some stars (such as double or multiple ones). Our method of calculation, and the calculated ?? for the common IL/Hipparcos stars are presented here. We constructed an IL catalogue of 1200 stars: there are 707 stars in the first part (with at least 20 years of IL observations) and 493 stars in the second one (less than 20 years). In the case of ?? of IL stars observed at some stations (Blagoveschtschensk, Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than the corresponding Hipparcos ones and for some of them (stations Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.

scholarly journals Upper tropospheric water vapour variability at high latitudes – Part 1: Influence of the annular modes

2015 ◽  
Vol 15 (16) ◽  
pp. 22291-22329 ◽  
Author(s):  
C. E. Sioris ◽  
J. Zou ◽  
D. A. Plummer ◽  
C. D. Boone ◽  
C. T. McElroy ◽  
...  
Keyword(s):  
Water Vapour ◽  
Atmospheric Chemistry ◽  
High Latitude ◽  
Lower Stratosphere ◽  
Southern Annular Mode ◽  
The Arctic ◽  
Boreal Winter ◽  
High Latitudes ◽  
Annular Mode ◽  
Annular Modes

Abstract. Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60–90 and 60–90° S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in eight of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the mid-troposphere to study the vertical profile of the response of UTLS water vapour to the annular modes. The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % (r = −0.80) of the monthly variability in water vapour at northern high-latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March 2004–2013). Using a seasonal timestep and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record (1950–2015), led to > 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

scholarly journals The Warm Winter Paradox in the Pliocene High Latitudes

2022 ◽  
Author(s):  
Julia C. Tindall ◽  
Alan M. Haywood ◽  
Ulrich Salzmann ◽  
Aisling M. Dolan ◽  
Tamara Fletcher
Keyword(s):  
High Latitude ◽  
Data Model ◽  
Model Comparison ◽  
Co2 Concentration ◽  
High Latitudes ◽  
Warm Winter ◽  
Reconstruction Methods ◽  
Number Of Factors ◽  
Modern Analogue ◽  
Winter Temperatures

Abstract. Reconciling palaeodata with model simulations of the Pliocene climate is essential for understanding a world with atmospheric CO2 concentration near 400 parts per million by volume. Both models and data indicate an amplified warming of the high latitudes during the Pliocene, however terrestrial data suggests Pliocene high latitude temperatures were much higher than can be simulated by models. Here we show that understanding the Pliocene high latitude terrestrial temperatures is particularly difficult for the coldest months, where the temperatures obtained from models and different proxies can vary by more than 20 °C. We refer to this mismatch as the ‘warm winter paradox’. Analysis suggests the warm winter paradox could be due to a number of factors including: model structural uncertainty, proxy data not being strongly constrained by winter temperatures, uncertainties on data reconstruction methods and also that the Pliocene high latitude climate does not have a modern analogue. Refinements to model boundary conditions or proxy dating are unlikely to contribute significantly to the resolution of the warm winter paradox. For the Pliocene, high latitude, terrestrial, summer temperatures, models and different proxies are in good agreement. Those factors which cause uncertainty on winter temperatures are shown to be much less important for the summer. Until some of the uncertainties on winter, high latitude, Pliocene temperatures can be reduced, we suggest a data-model comparison should focus on the summer. This is expected to give more meaningful and accurate results than a data-model comparison which focuses on the annual mean.

scholarly journals Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

2002 ◽  
Vol 20 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
F. Pitout ◽  
P. T. Newell ◽  
S. C. Buchert
Keyword(s):  
High Latitude ◽  
Time Interval ◽  
High Latitudes ◽  
Polar Ionosphere ◽  
Plasma Convection ◽  
Low Latitude ◽  
Svalbard Archipelago ◽  
Cusp Region ◽  
Ionosphere Plasma ◽  
Particle Measurement

Abstract. We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

Investigation of relative motion in the triple system ADS 48 on the basis of Gaia DR2 and Pulkovo 26-inch refractor observations

2021 ◽  
pp. 89-98
Author(s):  
O. V. KIYAEVA ◽  
R. YA. ZHUCHKOV ◽  
I.S. IZMAILOV
Keyword(s):  
High Precision ◽  
Relative Motion ◽  
Apparent Motion ◽  
Triple System ◽  
Radial Velocities ◽  
Proper Motions ◽  
The Family ◽  
Outer Pair ◽  
Motion Parameters ◽  
Gaia Dr2

There are high-precision positions, proper motions, parallaxes and radial velocities at the instant 2015.5 for all three components of the star ADS 48 ABF in the catalogue Gaia DR2 (2018). According to these data relative motions and the family of orbits were calculated by the Apparent Motion Parameters (AMP) method (Kiselev and Kiyaeva, 1980), and the best orbit was chosen for the inner pair AB. A perturbation with the period of 11 years was discovered according to Pulkovo observations of the outer pair. The reasons for the perturbation are discussed.

scholarly journals Southern-Hemisphere high-latitude stratospheric warming revisit

2019 ◽  
Vol 54 (3-4) ◽  
pp. 1671-1682
Author(s):  
Yan Xia ◽  
Weixuan Xu ◽  
Yongyun Hu ◽  
Fei Xie
Keyword(s):  
Southern Hemisphere ◽  
High Latitude ◽  
Recent Decade ◽  
Warming Trend ◽  
High Latitudes ◽  
Stratospheric Warming ◽  
Amundsen Sea ◽  
Maximum Warming ◽  
Dipole Pattern ◽  
The Western Pacific

AbstractPrevious studies showed significant stratospheric warming at the Southern-Hemisphere (SH) high latitudes in September and October over 1979–2006. The warming trend center was located over the Southern Ocean poleward of the Western Pacific in September, with a maximum trend of about 2.8 K/decade. The warming trends in October showed a dipole pattern, with the warming center over the Ross and Amundsen Sea, and the maximum warming trend is about 2.6 K/decade. In the present study, we revisit the problem of the SH stratospheric warming in the recent decade. It is found that the SH high-latitude stratosphere continued warming in September and October over 2007–2017, but with very different spatial patterns. Multiple linear regression demonstrates that ozone increases play an important role in the SH high-latitude stratospheric warming in September and November, while the changes in the Brewer-Dobson circulation contributes little to the warming. This is different from the situation over 1979–2006 when the SH high-latitude stratospheric warming was mainly caused by the strengthening of the Brewer-Dobson circulation and the eastward shift of the warming center. Simulations forced with observed ozone changes over 2007–2017 shows warming trends, suggesting that the observed warming trends over 2007–2017 are at least partly due to ozone recovery. The warming trends due to ozone recovery have important implications for stratospheric, tropospheric and surface climates on SH.

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