Satellite image based quantification of invasion and patch dynamics of mesquite (Prosopis juliflora) in Great Rann of Kachchh,Kachchh Biosphere Reserve,Gujarat, India

The invasion of alien species is a significant threat to global biodiversity and the top driver of climate change. The present study was conducted in the Great Rann of Kachchh, part of Kachchh Biosphere Reserve, Gujarat, India, which has been severely affected by invasion of Prosopis juliflora. The invasive weed infestation has been identified using multi-temporal remote sensing datasets of 1977, 1990, 1999, 2005 and 2011. Spatial analyses of the transition matrix, extent of invasive colonies, patchiness, coalescence and rate of spread were carried out. During the study period of three and half decades, almost 295 km² of the natural land cover was converted into Prosopis cover. This study has shown an increment of 42.9% of area under Prosopis cover in the Great Rann of Kachchh, part of the Kachchh Biosphere Reserve during 1977 to 2011. Spatial analysis indicates high occupancy of Prosopis cover with most of the invasion (95.9%) occurring in the grasslands and only 4.1% in other land cover types. The process of Prosopis invasion shows high patch initiation, followed by coalescence, indicating aggressive colonization of species. The number of patches within an area of < 1 km² increased from 1977 to 2011, indicating the formation of new Prosopis habitats by replacing the grasslands. The largest patch of Prosopis cover increased from 144 km² in 1977 to 430 km² in 2011. The estimated mean patch size was 7.8 km² in 1977. The mean patch size was largest during 2011, i.e., 9 km². The annual spread rate for Prosopis has been estimated as 2.1% during 2005–2011. The present work has investigated the long term changes in Prosopis cover in the Great Rann of Kachchh, part of Kachchh Biosphere Reserve. The spatial database generated will be useful in preparing strategies for the management of Prosopis juliflora.     

Some anisotropic cosmological models in a modified theory of gravitation

Field equations in a modified theory of gravitation proposed by Harko et al. (Phys. Rev. D 84: 024020, 2011) are obtained with the aid of a spatially homogeneous and anisotropic LRS Bianchi type-II metric. Cosmological models corresponding to stiff fluid, disordered radiation, dust and false vacuum are obtained. Some physical and kinematical properties of each of the models are also studied.     

LRS Bianchi type-II bulk viscous cosmic string model in a scale covariant theory of gravitation

A locally rotationally symmetric(LRS) Bianchi type-II space-time is considered in the frame work of a modified theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional cosmic strings. A special law of variation for Hubble’s parameter proposed by Bermann (Nuovo Cimento B 74:182, 1983) is used to obtain determinate solution of the field equations. We have also used the barotropic equation of state and the bulk viscous pressure is assumed to be proportional to the energy density. The physical and kinematical properties of the model are also discussed.     

Compositional variability on the surface of 4 Vesta revealed through GRaND measurements of high‐energy gamma rays

Measurements of the high‐energy gamma‐ray flux emanating from asteroid 4 Vesta by the Dawn Gamma‐Ray and Neutron Detector (GRaND) have revealed variability in the near‐surface elemental composition of the Vestan surface. These observations are consistent with the presence of large (≥8 × 10⁴ km²) regions with distinct, HED‐like elemental compositions. The results agree broadly with other global measurements, such as the macroscopic neutron absorption cross section and spectral reflectance‐derived mineralogic maps. Two distinct regions with eucrite‐like elemental compositions have been identified, the first located primarily within the Lucaria and Marcia quadrangles and the second within Oppia quadrangle. The former region is collocated with some of the oldest, most heavily cratered terrain on Vesta. The interior of the 500 km diameter Rheasilvia impact basin is found to have a composition that is consistent with diogenite‐like material. Taken together, these observations support the hypothesis that Vesta's original crust was composed of basaltic outflows in the form of eucritic‐like material and that the Rheasilvia‐basin‐forming impact exposed lower‐crustal, diogenite‐like material. These measurements also constrain the maximum amount of mesosiderite‐like material to <10% for each 15 × 15° surface element.     

Impact of atmospheric and physical forcings on biogeochemical cycling of dissolved oxygen and nutrients in the coastal Bay of Bengal

Time-series observations were conducted off Visakhapatnam, central west coast of Bay of Bengal, from October 2007 to April 2009 to examine the influence of physical and atmospheric processes on water column nutrients biogeochemistry. The thermal structure displayed inversions of 0.5 to 1.0° C during winter and were weaker in summer. The water column was vertically stratified during the entire study period and was stronger during October–November 2007 and August–December 2008 compared to other study periods. High concentrations of chlorophyll-a and nutrients were associated with the extreme atmospheric events. The strong relationship of nutrients with salinity indicates that physical processes, such as circulation, mixing and river discharge, have a significant control on phytoplankton blooms in the coastal Bay of Bengal. Phosphate seems to be a controlling nutrient during winter whereas availability of light and suspended matter limits production in summer. Formation of low oxygen conditions were observed in the bottom waters due to enhanced primary production by extreme atmospheric events; however, re-oxygenation of bottom waters through sinking of oxygen-rich surface waters by a warm core (anticyclonic) eddy led to its near recovery. This study reveals that atmospheric and physical processes have significant impacts on the water column biogeochemistry in the coastal Bay of Bengal.     

How to characterize terrains on 4 Vesta using Dawn Framing Camera color bands?

We present methods for terrain classification on 4 Vesta using Dawn Framing Camera (FC) color information derived from laboratory spectra of HED meteorites and other Vesta-related assemblages. Color and spectral parameters have been derived using publicly available spectra of these analog materials to identify the best criteria for distinguishing various terrains. We list the relevant parameters for identifying eucrites, diogenites, mesosiderites, pallasites, clinopyroxenes and olivine + orthopyroxene mixtures using Dawn FC color cubes. Pseudo Band I minima derived by fitting a low order polynomial to the color data are found to be useful for extracting the pyroxene chemistry. Our investigation suggests a good correlation (R² = 0.88) between laboratory measured ferrosilite (Fs) pyroxene chemistry vs. those from pseudo Band I minima using equations from Burbine et al. (Burbine, T.H., Buchanan, P.C., Dolkar, T., Binzel, R.P. [2009]. Planetary Science 44, 1331–1341). The pyroxene chemistry information is a complementary terrain classification capability beside the color ratios. We also investigated the effects of exogenous material (i.e., CM2 carbonaceous chondrites) on the spectra of HEDs using laboratory mixtures of these materials. Our results are the basis for an automated software pipeline that will allow us to classify terrains on 4 Vesta efficiently.     

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.     

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.     

Evaluation of trends and predictability of short‐term droughts in three meteorological subdivisions of India using multivariate EMD‐based hybrid modelling

This paper presented trend analysis of droughts in Kerala, Telangana, and Orissa meteorological subdivisions in India and proposed a framework for drought prediction by employing the Empirical Mode Decomposition (EMD)‐based prediction models. The study used 3‐month standardized precipitation index (SPI3) for drought analysis. The trend analysis of SPI3 series for the period 1871–2012 using Mann–Kendall method showed statistically significant increasing trend in Kerala and Telangana subdivisions and a decreasing trend in Orissa subdivision. In addition, the non‐linear trend component extracted from EMD showed statistically significant changes in all the three subdivisions. Then, the study proposed a hybrid approach for prediction of short‐term droughts by coupling multivariate extension of EMD (MEMD) with stepwise linear regression (SLR) and genetic programming (GP) methods. First, the multivariate dataset comprising the SPI3 series of current and lagged time steps are decomposed using the MEMD. Then, SLR/GP models are developed to predict each subseries of SPI3 of desired time step considering the subseries of predictor variables at the corresponding timescales as inputs. The resulting models at different timescales are recombined to obtain the SPI3 values of the desired time step. The method is applied for prediction of short‐term droughts in the three subdivisions. The results obtained by the hybrid models are compared with that obtained by conventional prediction models using M5 Model Trees and GP. The rigorous performance evaluation based on multiple statistical criteria clearly exhibited the superiority of the hybrid approaches (i.e., prediction models with MEMD‐based decomposition over models without decomposition) for prediction of SPI3 in three subdivisions. Further, the study found that MEMD‐GP model performs marginally better than the MEMD‐SLR model due to its efficacy in modelling high frequency modes.