7,795 research outputs found
340 years of atmospheric circulation characteristics reconstructed from an eastern Antarctic Peninsula ice core
Copyright @ 2006 American Geophysical Union (AGU)Precipitation delivery mechanisms for Dolleman Island (DI), located off the east coast of the Antarctic Peninsula, are investigated using reanalysis and back trajectory data. The Southern Annular Mode (SAM) and ENSO are both shown to influence precipitation delivery and event size. Precipitation delivery variability is compared against the interannual variation of chemical data from two DI ice cores. Nitrate concentration in the cores is strongly linked with the ratio of easterly to westerly back trajectories arriving at DI, as described by a Cross-Peninsula Index (CPI) defined in this paper. This CPI is used subsequently to reconstruct the atmospheric circulation characteristics for the 340-year ice core record. The analysis highlights a period of increased easterlies during 1720–1780 and an increase in westerlies for 1950–1980, the latter concomitant with a positive SAM trend and western Peninsula warming. The reconstruction also reveals periods when polynyas may have been present in the Weddell Sea
In situ aerosol measurements taken during the 2007 COPS field campaign at the Hornisgrinde ground site
Copyright @ 2011 Royal Meteorological Society.The Convective and Orographically-induced Precipitation Study (COPS) campaign was conducted during the summer of 2007. A suite of instruments housed at the top of the Hornisgrinde Mountain (1156 m) in the Black Forest region of south-west Germany provided datasets that allow an investigation into the physical, chemical and hygroscopic properties of the aerosol particles sampled during COPS. Organic mass loadings were found to dominate the aerosol composition for the majority of the project, exceeding 8 µg m−3 during a period of high pressure, high temperature, and low wind speed. The ratio of organic:sulphate sub-micron mass concentration exceeds 10:1 during the same time period. Back trajectories show air from this time-frame passing slowly over the local forest and not passing over any local anthropogenic sources. Occasional peaks in nitrate mass loadings were associated with changes in the typical wind direction from south-westerly to north-westerly where air had passed over the Stuttgart region. Size distribution data shows a dominant accumulation-mode when the measurement site was free from precipitation events. A sharp increase in ultrafine particle number concentration was seen during most days commencing around noon. The apparent growth of these particles is associated with an increase in organic mass loading, suggesting condensational growth. For the most part, with the exception of the high pressure period, the aerosol properties recorded during COPS were comparable to previous studies of continental aerosol properties.NER
Photonic crystal fibre as an optofluidic reactor for the measurement of photochemical kinetics with sub-picomole sensitivity
Going places
Journeys. We all make them. Often they take us to exotic places. Sometimes they take us even further. They might take us through time. Or they might take us into a new way of life. There are times too, when we go all over the world and back again only to find that home is, after all, where it’s all happening.
This book contains stories about many different types of journey. We hope you will enjoy travelling into it and finding a world that suits you
MeerKAT radio observations of the neutron star low-mass X-ray binary Cen X-4 at low accretion rates
Centaurus X-4 (Cen X-4) is a relatively nearby neutron star low-mass X-ray
binary that showed outbursts in 1969 and 1979, but has not shown a full
outburst since. Due to its proximity and sustained period of quiescence, it is
a prime target to study the coupling between accretion and jet ejection in
quiescent neutron star low-mass X-ray binaries. Here, we present four MeerKAT
radio observations at 1.3 GHz of Cen X-4, combined with NICER and Swift X-ray
monitoring. During the first and most sensitive observation, Cen X-4 was in a
fully quiescent X-ray state. The three later and shorter observations targeted
a brief period of faint X-ray activity in January 2021, which has been referred
to as a 'mis-fired' outburst. Cen X-4 is not detected in any of the four
MeerKAT observations. We place these radio non-detections on the X-ray -- radio
luminosity diagram, improving the constraints on the correlation between the
two luminosities from earlier quiescent radio studies. We confirm that Cen X-4
is radio fainter than the transitional milli-second pulsar PSR J1023+0038 at
the same X-ray luminosity. We discuss the radio behaviour of accreting neutron
stars at low X-ray luminosity more generally and finally comment on future
observing campaigns.Comment: 12 pages, 4 figures, 2 tables. Accepted for publication in MNRA
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