Comparison of Atmospheric Circulation in the Area of Spitsbergen in 1920–1950 and in the Modern Warming Period

The results of studying the temporal variability of atmospheric circulation in the Western Arctic (the Norwegian and Barents seas) are presented. The daily dataset of Girs-Vangengeim E, W, and C circulation forms for the period of 1891–2016 is used to describe atmospheric circulation. Special attention is given to the estimation of differences in weather conditions during the modern period of warming (1985–2015) and in the period of the first Arctic warming (1920–1950). For the cold (November-March) and warm (April-October) seasons, the trends in the frequency of occurrence of the circulation forms are determined. The occurrence of the number of consecutive days with the same atmospheric circulation form which can be considered as a characteristic of weather stability during the analyzed period of warming, is computed for both seasons. The prevalence of the E circulation form during the warm season is typical of both periods. The modern period of warming in the study area, as compared to the period of the first warming, is characterized by an increase in the occurrence of the C circulation form with a short duration. It is found that the current climate regime is characterized by an increase in surface air temperature against a background of less stable weather conditions.     

Geochemical zoning and magnetic mineralogy at Fe,Ni‐alloy–troilite interfaces of three iron meteorites from Morasko,Coahuila II,and Mundrabilla

We combined high‐resolution and space‐resolved elemental distribution with investigations of magnetic minerals across Fe,Ni‐alloy and troilite interfaces for two nonmagmatic (Morasko and Mundrabilla) IAB group iron meteorites and an octahedrite found in 1993 in Coahuila/Mexico (Coahuila II) preliminarily classified on Ir and Au content as IIAB group. The aim of this study was to elucidate the crystallization and thermal history using gradients of the siderophile elements Ni, Co, Ge, and Ga and the chalcophile elements Cr, Cu, and Se with a focus on magnetic minerals. The Morasko and Coahuila II meteorite show a several mm‐thick carbon‐ and phosphorous‐rich transition zone between Fe,Ni‐alloy and troilite, which is characterized by magnetic cohenite and nonmagnetic or magnetic schreibersite. At Morasko, these phases have a characteristic trace element composition with Mo enriched in cohenite. In both Morasko and Coahuila II, Ni is enriched in schreibersite. The minerals have crystallized from immiscible melts, either by fractional crystallization and C‐ and P‐enrichment in the melt, or by partial melting at temperatures slightly above the eutectic point. During crystallization of Mundrabilla, the field of immiscibility was not reached. Independent of meteorite group and cooling history, the magnetic mineralogy (daubreelite, cohenite and/or schreibersite, magnetite) is very similar to the troilite (and transition zone) for all three investigated iron meteorites. If these minerals can be separated from the metal, they might provide important information about the early solar system magnetic field. Magnetite is interpreted as a partial melting or a terrestrial weathering product of the Fe,Ni‐alloy under oxidizing conditions.     

Cosmic ray exposure and pre‐atmospheric size of the Gebel Kamil iron meteorite

Cosmogenic He, Ne, and Ar as well as the radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁵³Mn, and ⁶⁰Fe have been determined on samples from the Gebel Kamil ungrouped Ni‐rich iron meteorite by noble gas mass spectrometry and accelerator mass spectrometry (AMS), respectively. The meteorite is associated with the Kamil crater in southern Egypt, which is about 45 m in diameter. Samples originate from an individual large fragment (“Individual”) as well as from shrapnel. Concentrations of all cosmogenic nuclides—stable and radioactive—are lower by a factor 3–4 in the shrapnel samples than in the Individual. Assuming negligible ³⁶Cl decay during terrestrial residence (indicated by the young crater age <5000 years; Folco et al. 2011 ), data are consistent with a simple exposure history and a ³⁶Cl‐³⁶Ar cosmic ray exposure age (CRE) of approximately (366 ± 18) Ma (systematic errors not included). Both noble gases and radionuclides point to a pre‐atmospheric radius >85 cm, i.e., a pre‐atmospheric mass >20 tons, with a preferred radius of 115–120 cm (50–60 tons). The analyzed samples came from a depth of approximately 20 cm (Individual) and approximately 50–80 cm (shrapnel). The size of the Gebel Kamil meteoroid determined in this work is close to estimates based on impact cratering models combined with expectations for ablation during passage through the atmosphere (Folco et al. 2010 , 2011 ).     

Axially Symmetric Cosmic Strings in a Scalar-Tensor Theory

Axially symmetric cosmological models with cosmic string source are obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A113, 467, 1985). The models obtained give us axially symmetric geometric (Nambu) string, p-string and Reddy string (Astrophys. Space Sci. 286, 2003b) in Saez-Ballester theory. Some physical properties of the models are also discussed.     

Estimation of actual evaporation using precipitation and soil moisture records in arid climates

There is little knowledge available about infiltration and evaporation processes in wadi channels in arid regions. This work was conducted to determine the actual evaporation from bare soils in wadi channels in the south-western region of the Kingdom of Saudi Arabia. The estimation of soil evaporation is highly dependent on the availability of moisture in the upper layers of alluvial wadis, in which the areal rainfall, flood hydrograph and soil properties play a significant part. The study was conducted by estimating the actual evaporation using soil moisture data, precipitation and runoff depths in a representative basin. The results are compared with potential rates. The actual rates were 1.5 mm/day immediately after a rainy day and then decreased to 0.42 mm/day. The minimum rate was about 0.1–0.2 mm/day during the dry season. The potential rates were about 9.5 mm/day in June and July, decreasing to 3.5 mm/day in December and January.