Characteristics of atmospheric turbulence in the surface layer over Antarctica

This paper presents meteorological measurements made during the antarctic summer period, on two 9 m and 3 m towers, on the rocky and ice shelf terrains of the Indian antarctic stations Maitri and Dakshin Gangotri, respectively. The measurements of fluctuations in temperature and wind speed made with relatively lesser precision instrumentation pertain to smaller wave numbers ~10^-2 m^-1 appropriate to outer scale L ₀ of the atmospheric turbulence spectrum. Autocorrelation analysis of the fluctuations in temperature and wind speed has been performed. A new autoregressive scheme has been developed to represent the computed autocorrelation functions by a Yule statistical model, and to estimate the correlation period T ₀ of the turbulent medium. Height profiles of outer scale L ₀ of turbulence may be given in terms of T ₀ and mean wind speed u. Further, the similarity theory of Monin-Obukhov has been used to compute height profiles of temperature structure parameter C _T ². At Maitri, values of L ₀ and C _T ² are higher between 03–22 h local time than between 22–03 h. Values of L ₀ and C _T ² are smaller over the ice shelf terrain of the Dakshin Gangotri station, compared to those over the rocky terrain of the Maitri station.     

Thermal history of the Sonnblick Dome,south-east Tauern Window,Austria: Implications for heterogeneous uplift within the Pennine basement

The Sonnblick Dome is one of several domal structures affecting the interface between basement and cover within the Pennine Zone of the Tauern Window in the eastern Alps. Rb-Sr isotopic data, comprising 19 biotite and 22 white mica ages from variably deformed granitic gneisses, provide new evidence of the thermal and tectonic history of the dome and its relationships with other parts of the south-east Tauern Window. White mica ages generally cluster between 26 and 30 Ma although there are values up to 82 Ma, which appear to reflect incomplete equilibration during Tertiary metamorphism under low amphibolite facies conditions; six closely spaced samples from an intensely sheared gneiss lamella are more tightly grouped between 26 and 27.6 Ma and provide the best estimate of the age of syntectonic crystallization. Biotite ages are systematically younger, ranging from 19 to 23.5 Ma, reflecting closure during post-metamorphic cooling. Sonnblick Dome and the Hochalm Dome approximately 20 km further east, where closure of Rb-Sr in biotite did not occur until 16.5 Ma; the metamorphic peak here is also probably younger, possibly as late as 22 Ma. The Sonnblick Dome was formed before 27 Ma and the deformation style had changed to extension before biotite closure by 19 Ma. In contrast, rapid updoming in the Hochalm Dome was previously dated at 16.5 Ma and the differences in thermal history can be linked to differences in deformation history. Overall the geochronological data from the south-east Tauern Window demonstrate the heterogeneity of thermal history on a geographical scale of 10 km and emphasize the importance of tectonic displacements in controlling temperature within orogenic belts.     

Cosmic strings in a five dimensional spherically symmetric background in $$ gravity

We study the physical behavior of a five dimensional non-static spherically symmetric cosmological models in the presence of massive strings in the framework of \(f(R,T)\) gravity proposed by Harko et al. (Phys. Rev. D 84:024020, 2011). Here \(R\) is the Ricci scalar and \(T\) is the trace of the stress energy tensor and the fifth dimension is not observed because it is compact. We solve the field equations (i) using a relation between the scale factors given by Samantha and Dhal (Int. J. Theor. Phys. 52:1334, 2013) and (ii) equations of state for string models. The models obtained correspond to \(p\)-string, geometric string and massive string models in this modified theory in five dimensions. Cosmological parameters of the models are determined and their dynamical properties are discussed.     

Chemical composition of rain water and influence of airmass trajectories at a rural site in an ecological sensitive area of Western Ghats (India)

Samples of rain water were collected during monsoon season (June to September) of 2006 and 2007 at Hudegadde, a rural site located in an ecological sensitive area of Western Ghats. The collected samples were analyzed for pH, conductivity and major ions. At this site, rainwater pH varied from 4.20 to 7.39 with 5.65 as volume weighed mean. The observed mean was slightly lower than the average pH reported at most of the Indian continental sites. Monthly variation showed that average pH of rain water was the lowest during September (end of monsoon) and the highest during July (peak of monsoon). Overall, marine sources had dominating influence at this site. However, significant influence of anthropogenic and crustal sources from local as well as inter-continental regions was also noticed. As compared to NO₃⁻, higher concentration of SO₄²⁻ was noticed which might be due to contribution from industrial activities responsible for SO₂ emission. At this site, influence of five types of airmass trajectories was noticed i.e. i) C.I.O. (Central part of Indian Ocean)-when air masses blown from Maldives and nearby region of central Indian ocean. These airmasses had higher concentrations of nss Ca²⁺ which did not show any adverse impact on the pH; ii) N.W.I.O.(North-West Indian Ocean)-when airmasses travelled from oceanic region close to north-east Africa. These airmassses had higher concentrations of nss sulphate and nitrate and gave rise to acid rain; iii) S.W.I.O. (South -West Indian Ocean)- when airmasses came from southern part of Indian ocean (close to Mauritius). During these airmasses, rain water samples had almost equal ratio of nss SO₄²⁻ and nss Ca²⁺ similar to N.W.I.O but very low NO₃⁻ ; iv) Gulf-when airmasses were observed coming from Gulf region. Although these airmasses contributed only 2% of the total number of samples but carried high amount of nss SO₄²⁻ which gave rise to acid rain. The second lowest pH was observed during these airmasses which might be due to very high nssSO₄²⁻/nssCa²⁺ ratios; v) N.W.I.O. + S.W.I.C. (North-West Indian Ocean+South-West Indian Continental)- when airmasses originated from north-west Indian Ocean travelling towards south continental part of India and then arriving to the site. During these airmasses, samples showed typical influence of urban activities having high concentrations of nss SO₄²⁻ and NO₃⁻ leading to the lowest pH of rain water.