Polar cap sporadic E

1969 ◽  
Vol 47 (8) ◽  
pp. 931-948 ◽  
Author(s):  
N. C. Gerson
Keyword(s):  
Auroral Oval ◽  
Skewed Distribution ◽  
The Arctic ◽  
Similar Data ◽  
The West ◽  
Secondary Maximum ◽  
Geomagnetic Pole ◽  
Summer Maximum ◽  
Resolute Bay ◽  
Sporadic E

Backscatter probings (at 28 MHz) of the arctic ionosphere were made at Alert, Canada, for almost two years. A skewed distribution around the site was found with (a) maximum occurrences constrained to the northeast within ±30° of the great circle through Alert and the principal northern magnetic dip pole, (b) a secondary maximum to the south, and (c) a marked dearth of observations as a tongue from the west (250°–280°) to about 800 km in the east. The annual pattern was almost identical with the summer and winter patterns. Equinoctial distributions were distinct. The maximum broadened to include the sector in the northeast within the great circles passing through Alert and the dip pole, and Alert and the geomagnetic pole. The secondary maximum and the tongue from the west of very low occurrences vanished.Seasonally, a pronounced maximum was found in the period June–August, and a weak secondary maximum during the equinoctial months. Diurnally, activity was present from 0700–1900 LST with a single peak near 1300 LST. Slight deviations from this pattern were noted in winter and summer. In the equinoxes, a plateau or double peak seemed present in the afternoon.Returns from the azimuth of Thule correlated with vertical-incidence sporadic E frequencies from Thule multiplied by the secant factor. No correlation with similar data from Resolute Bay was present. Indications of direct backscatter from field-aligned irregularities were found despite the large angles off perpendicularity. Es occurrences, after a lag of 1–2 days, seemed to be associated with appreciable increases in the daily value of ap. None of the results were predicted by standard maximum usable frequency prediction procedures.Two mechanisms seem possible for clarifying the results: (a) for the summer maximum, the Es layer tilted upwards to the principal northern dip pole; and (b) for the secondary equinoctial maximum, the daily swing of the auroral oval through the antenna beamwidth.

Logistic problems in the Canadian Arctic

Polar Record ◽  
1961 ◽  
Vol 10 (67) ◽  
pp. 365-371
Author(s):  
T. A. Harwood
Keyword(s):  
United States ◽  
Canadian Arctic ◽  
The United States ◽  
The Arctic ◽  
Weather Bureau ◽  
Weather Stations ◽  
Resolute Bay ◽  
States Weather

In 1946 the United States Weather Bureau and the Canadian Meteorological Service installed the first of the Joint Arctic Weather Stations at Resolute Bay. The network of satellite stations was extended into the Arctic archipelago in the following years on roughly a 275-mile spacing to Mould Bay, Isachsen, Eureka and Alert.

Accessory and Ore Mineralization of Schists from the Basement of the Yamal Peninsula (Zapadno-Yarotinsky Area, Western Siberia)

2021 ◽  
pp. 49-55
Author(s):  
Yuriy V. Erokhin ◽  
Kirill S. Ivanov ◽  
Anatoliy V. Zakharov ◽  
Vera V. Khiller
Keyword(s):  
Western Siberia ◽  
The Arctic ◽  
Yamal Peninsula ◽  
Metamorphic Rocks ◽  
The West ◽  
Temperature Range ◽  
Ore Minerals ◽  
Ore Mineralization ◽  
Native Silver ◽  
The Yamal Peninsula

The results of studying the mineralogy of metamorphic schists from the Pre-Jurassic base of the Arctic part of the West Siberian plate are presented. The accessory and ore mineralization of schists from the Zapadno-Yarotinsky license area located in the southern part of the Yamal Peninsula is studied. The schists was uncovered by the Zapadno-Yarotinskaya No. 300 well at a depth of 2762 m. Above the section, the metamorphic rocks are overlain by a young Meso-Cenozoic cover. The schists are mainly composed of quartz, plagioclase (albite), carbonates (dolomite and siderite), mica (muscovite) and chlorite (donbassite). The discovered accessory and ore minerals in the metamorphic schists of the Zapadno-Yarotinsky area can be divided into two groups. The first group includes minerals that were formed during the metamorphism of schists, or were preserved as detrital matter. These minerals include zircon, fluorapatite, and rutile as the most stable compounds. The remaining mineralization (pyrite, sphalerite, chalcopyrite, cubanite, galena, cobaltite, barite, xenotime-(Y), goyazite, synchysite-(Nd), native silver and copper) is clearly secondary and was formed as a result of superimposed metasomatic processes. Judging from the described mineralogy, the schists underwent changes as a result of superimposed propyllitization. The temperature range of this process is determined by the formation of cubanite in association with chalcopyrite at a temperature of 200-210 оС.

scholarly journals Similarities and differences in polar mesosphere summer echoes observed in the Arctic and Antarctica

2008 ◽  
Vol 26 (9) ◽  
pp. 2795-2806 ◽  
Author(s):  
R. Latteck ◽  
W. Singer ◽  
R. J. Morris ◽  
W. K. Hocking ◽  
D. J. Murphy ◽  
...  
Keyword(s):  
Noise Source ◽  
Late Summer ◽  
The Arctic ◽  
Occurrence Rate ◽  
Height Distribution ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
The Mean ◽  
Resolute Bay ◽  
Highly Correlated

Abstract. Polar Mesosphere Summer Echoes (PMSE) have been observed in the high latitudes of the Northern and Southern Hemisphere for several years using VHF radars located at Andenes/Norway (69° N, 16° E), Resolute Bay/Canada (75° N, 95° W), and Davis/Antarctica (69° S, 78° E). The VHF radars at the three sites were calibrated using the same methods (noise source and delayed transmitting signal) and identical equipment. Volume reflectivity was derived from the calibrated echo power and the characteristics of the seasonal variation of PMSE were estimated at the sites for the years 2004 to 2007. The largest peak volume reflectivity of about 2×10−9 m−1 was observed at Andenes compared with their counterparts at Davis (~4×10−11 m−1) and Resolute Bay (~6×10−12 m−1). The peak of the PMSE height distribution is 85.6 km at Davis which is about 1 km higher than at Andenes. At Resolute Bay the height distribution peaks at about 85 km but only a few layers were found below 84 km. The mean PMSE occurrence rate is 83% at Andenes, 38% at Davis with larger variability and only 18% at Resolute Bay (in late summer). The duration of the PMSE season varies at Andenes from 104 to 113 days and at Davis from 88 to 93 days. In general the PMSE seasons starts about 5 days later at Davis and ends about 10 days earlier compared to Andenes. In all three seasons the PMSE occurrence suddenly drops to a much lower level at Davis about 32 days after solstice whereas the PMSE season decays smoothly at Andenes. The duration of the PMSE season at Andenes and Davis is highly correlated with the presence of equatorward directed winds, the observed differences in PMSE occurrence are related to the mesospheric temperatures at both sites.

scholarly journals Global atmospheric model for mercury including oxidation by bromine atoms

2010 ◽  
Vol 10 (24) ◽  
pp. 12037-12057 ◽  
Author(s):  
C. D. Holmes ◽  
D. J. Jacob ◽  
E. S. Corbitt ◽  
J. Mao ◽  
X. Yang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Model ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Deposition Flux ◽  
Mercury Deposition ◽  
Photochemical Reduction ◽  
Global Atmospheric Model ◽  
Summer Maximum ◽  
Southeast Us

Abstract. Global models of atmospheric mercury generally assume that gas-phase OH and ozone are the main oxidants converting Hg0 to HgII and thus driving mercury deposition to ecosystems. However, thermodynamic considerations argue against the importance of these reactions. We demonstrate here the viability of atomic bromine (Br) as an alternative Hg0 oxidant. We conduct a global 3-D simulation with the GEOS-Chem model assuming gas-phase Br to be the sole Hg0 oxidant (Hg + Br model) and compare to the previous version of the model with OH and ozone as the sole oxidants (Hg + OH/O3 model). We specify global 3-D Br concentration fields based on our best understanding of tropospheric and stratospheric Br chemistry. In both the Hg + Br and Hg + OH/O3 models, we add an aqueous photochemical reduction of HgII in cloud to impose a tropospheric lifetime for mercury of 6.5 months against deposition, as needed to reconcile observed total gaseous mercury (TGM) concentrations with current estimates of anthropogenic emissions. This added reduction would not be necessary in the Hg + Br model if we adjusted the Br oxidation kinetics downward within their range of uncertainty. We find that the Hg + Br and Hg + OH/O3 models are equally capable of reproducing the spatial distribution of TGM and its seasonal cycle at northern mid-latitudes. The Hg + Br model shows a steeper decline of TGM concentrations from the tropics to southern mid-latitudes. Only the Hg + Br model can reproduce the springtime depletion and summer rebound of TGM observed at polar sites; the snowpack component of GEOS-Chem suggests that 40% of HgII deposited to snow in the Arctic is transferred to the ocean and land reservoirs, amounting to a net deposition flux to the Arctic of 60 Mg a−1. Summertime events of depleted Hg0 at Antarctic sites due to subsidence are much better simulated by the Hg + Br model. Model comparisons to observed wet deposition fluxes of mercury in the US and Europe show general consistency. However the Hg + Br model does not capture the summer maximum over the southeast US because of low subtropical Br concentrations while the Hg + OH/O3 model does. Vertical profiles measured from aircraft show a decline of Hg0 above the tropopause that can be captured by both the Hg + Br and Hg + OH/O3 models, except in Arctic spring where the observed decline is much steeper than simulated by either model; we speculate that oxidation by Cl species might be responsible. The Hg + Br and Hg + OH/O3 models yield similar global budgets for the cycling of mercury between the atmosphere and surface reservoirs, but the Hg + Br model results in a much larger fraction of mercury deposited to the Southern Hemisphere oceans.

scholarly journals Quantifying Climate-Wise Connectivity across a Topographically Diverse Landscape

Land ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 355 ◽  
Author(s):  
Morgan Gray ◽  
Elisabeth Micheli ◽  
Tosha Comendant ◽  
Adina Merenlender
Keyword(s):  
Climate Adaptation ◽  
Temperature Gradients ◽  
Range Shifts ◽  
Temperature Extremes ◽  
Improved Method ◽  
The West ◽  
Biologically Relevant ◽  
Summer Maximum ◽  
Suitable Habitats ◽  
Large Water

Climate-wise connectivity is essential to provide species access to suitable habitats in the future, yet we lack a consistent means of quantifying climate adaptation benefits of habitat linkages. Species range shifts to cooler climates have been widely observed, suggesting we should protect pathways providing access to cooler locations. However, in topographically diverse regions, the effects of elevation, seasonality, and proximity to large water bodies are complex drivers of biologically relevant temperature gradients. Here, we identify potential terrestrial and riparian linkages and their cooling benefit using mid-century summer and winter temperature extremes for interior coastal ranges in Northern California. It is rare for the same area to possess both terrestrial and riparian connectivity value. Our analysis reveals distinct differences in the magnitude and orientation of cooling benefits between the summer maximum and winter minimum temperatures provided by the linkages we delineated for the area. The cooling benefits for both linkage types were maximized to the west during summer, but upslope and to the northeast during winter. The approach we employ here provides an improved method to prioritize climate-wise connectivity and promote landscape resilience for topographically diverse regions.

Spatiotemporal Variation in ΔR on the West Coast of North America in the Late Holocene: Implications for Dating the Shells of Marine Mollusks

2020 ◽  
Vol 85 (4) ◽  
pp. 676-693
Author(s):  
Ian Hutchinson
Keyword(s):  
North America ◽  
West Coast ◽  
Late Holocene ◽  
Southern Oscillation ◽  
Tidal Energy ◽  
Spatiotemporal Resolution ◽  
The West ◽  
Summer Maximum ◽  
High Alkalinity ◽  
High Degree

Radiocarbon ages on mollusk shells, which account for about half of the more than 8,000 dates from cultural deposits on the west coast of North America, need to be corrected for the local marine reservoir effect (ΔR) to yield true ages. Assays on “prebomb” shells show that ΔR increases poleward, echoing the age gradient in offshore waters. The meridional gradient in ΔR is not appreciably affected by the transition either from an upwelling regime to a downwelling regime north of 40°N–45°N or from a winter maximum-high alkalinity river discharge pattern to a summer maximum-low alkalinity pattern at the same latitude, probably because these changes are offset by increasing storminess and tidal energy in coastal areas. Mesoscale variations in ΔR along this gradient are attributable to contrasts in shore morphology and exposure. Data from 123 shell-wood pairs reveal similar patterns of temporal variation in ΔR in the late Holocene in the coastal ecoregions. The characteristic temporal pattern echoes phases of variable El Niño-Southern Oscillation (ENSO) activity. The high degree of variability in ΔR argues against the indiscriminate application of regionally uniform or trans-Holocene ΔR values and demands improvements in spatiotemporal resolution if shell is used to date cultural deposits.

scholarly journals Air Temperature and Precipitation on the Greenland Ice Sheet

1960 ◽  
Vol 3 (27) ◽  
pp. 558-567 ◽  
Author(s):  
Marvin Diamond
Keyword(s):  
Air Temperature ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Warming Trend ◽  
The Arctic ◽  
Mean Annual Precipitation ◽  
The West ◽  
West Side ◽  
Temperature And Precipitation ◽  
Mean Annual Air Temperature

AbstractMean annual air temperatures and precipitation on the Greenland Ice Sheet, as estimated from snow profile studies and long-term meteorological records at coastal stations, have been used to prepare mean annual air temperature and mean annual precipitation charts for the Greenland Ice Sheet. It is shown that melting of surface snow may occur at elevations of about 1,300 m. in north Greenland and up to 2,700 m. in south Greenland. The warming trend in the Arctic, as indicated by increases in mean annual air temperature, may have occurred to a lesser extent on the ice sheet than at sea-level coastal stations. Annual accumulation of precipitation is two or three times as great at 2,700 m. on the west side of the ice sheet as at the crest. South of lat. 66° N., precipitation may be about twice as great on the east side of the crest as on the west side.

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