Absorption of radio waves during a solar eclipse

In this paper, the results of our observations on Al-method ionospheric absorption of radio waves on 1.8 and 2.2 MHz during the solar eclipse of 16 February 1980 are presented. The absorption decreased by about 41% and 46% of the normal value respectively at the above two frequencies at Ahmedabad following the maximum phase of the eclipse (about 77% of full disc) with a delay of 18 minutes. The quantityA _T (f) which is a measure of εN vdh is now examined for better clarity of the influence of the changes in theE-layer. The results are discussed in relation to the observations of the ionizing radiations from the sun, changes in the electron density, recombination rate and absorption in the underlyingD andE regions.     

Paleomagnetic results from the Narosura and Magadi volcanics of Kenya

Results of a paleomagnetic study carried out on the exposed volcanic rocks on the western side of the South Kenya Rift Valley are presented. Nine stratigraphic groups ranging in age from Miocene to Pleistocene were sampled. The rocks consist of basalts, trachytes, nephelinites, melanephelinites, olivine melanephelinites and ignimbrites. Paleomagnetic poles obtained for different age ranges are as follows: Period I (0.64–0.72 Ma), 116°E, 85°N (A₉₅ = 6°); Period II (1.6–6.9 Ma), 297°E, 84°N (A₉₅ = 4°); Period III (12.0–15.0 Ma), 34°E, 80°N (A₉₅ = 9°). The results for Period II show large secular variations which are in disagreement with the model predictions for near-equatorial sites.     

Climate and hydrological models to assess the impact of climate change on hydrological regime: a review

Quantitative knowledge about the impacts of climate change on the hydrological regime is essential in order to achieve meaningful insights to address various adverse consequences related to water such as water scarcity, flooding, drought, etc. General circulation models (GCMs) have been developed to simulate the present climate and to predict future climatic change. But, the coarse resolution of their outputs is inefficient to resolve significant regional scale features for assessing the effects of climate change on the hydrological regimes, thus restricting their direct implementation in hydrological models. This article reviews hierarchy and development of climate models from the early times, importance and inter-comparison of downscaling techniques and development of hydrological models. Also recent research developments regarding the evaluation of climate change impact on the hydrological regime have been discussed. The article also provides some suggestions to improve the effectiveness of modelling approaches involved in the assessment of climate change impact on hydrological regime.     

Variability of sensible heat flux over the Bay of Bengal and its connection to Indian Ocean Dipole events

The Bay of Bengal (BOB) is known to possess complex thermodynamics which show distinct seasonal patterns. Surface heat fluxes in the BOB are very much dependant on upper ocean heat exchanges and wind. Sensible heat flux (SHF) is also one among those fluxes that depends on air-sea temperature difference and wind. However, this study further proves that a strong relationship exists between barrier layer thickness (BLT) and SHF variability that has not been focussed on in earlier literatures. This study also investigates the seasonal as well as inter-annual variability of SHF and its relationship with BLT and sea surface temperature (SST) patterns in more detail with statistical analyses. It is found that both SST and BLT are responsible for the evolution of SHF signal in the BOB although their effects are spatially distributed. During the post monsoon period, freshwater induced enhanced BLT is more related to SHF than the summer time when effect of SST is found to be dominant. During Indian Ocean Dipole (IOD) years, the correlation between SHF and BLT in the eastern BOB is more pronounced compared to SHF and SST. The western BOB however is dominated by SST variations for the respective IOD phase which also contribute to SHF signals there. Northernmost BOB shows high standard deviation due to river discharge effects.     

Vesuvianite-wollastonite-grossular-bearing calc-silicate rock near Tatapani,Surguja district,Chhattisgarh

This paper reports the occurrence of vesvianite + wollastonite + grossular + diopside + microcline + quartz assemblage in an enclave of calc-silicate rocks occurring within quartzofeldspathic gneiss near Tatapani in the western part of Chhotanagpur Gneissic Complex. The enclave contains phlogopite-absent and phlogopite-bearing calc-silicate rocks, the latter being much more abundant than the former. The above assemblage occurs in the phlogopite-absent rock. Phlogopite-bearing rock contains the assemblage phlogopite + salite + microcline + plagioclase + quartz. A strong schistosity is developed in both the calc-silicate rocks and the minerals are syntectonic with the major foliation-forming event in the area. The vesuvianite-bearing assemblage is formed by amphibolite facies regional metamorphism of a calcareous protolith at pressure < 4 kbar and X_{CO 2} (fluid) < 0.15.     

Quantifying climate-induced drought risk to livelihood and mitigation actions in Balochistan

Natural Hazards - Climate change-induced disasters show the highest risk for agriculture and livelihoods in rural areas of developing countries. Due to changing rainfall pattern, the arid and...     

Assessment of large aperture scintillometry for large-area surface energy fluxes over an irrigated cropland in north India

Amount of available net energy and its partitioning into sensible, latent and soil heat fluxes over an agricultural landscape are critical to improve estimation of evapotranspiration and modelling parse (ecosystem modelling, hydrological and meteorological modelling). Scintillometry is a peculiar and robust methodology to provide structure parameter of refractive index and energy balance. Scintillometer has proven for assessment of sensible and latent heat flux, which is based on the principle of Monin–Obukhov similarity theory. Scintillometer has been installed in the agricultural experimental farm of ICAR-Indian Agricultural Research Institute, New Delhi, with a spatial covering path length of 990 m of irrigated and cultivable agricultural landscape. This paper discusses the patterns of energy flux as diurnal and seasonal basis at scintillometer path which was mainly covered by maize in Kharif and wheat in Rabi season during a crop growing seasons of 2014–2015. The biophysical parameters (leaf area, soil moisture, crop height) were recorded at a temporal resolution of fortnight basis along the path length at usual sampling distance. The Bowen ratio value for both Kharif and Rabi season was 0.76 and 0.88, respectively by scintillometer. Leaf area index had a significantly positive correlation with latent heat flux (\(R^{2} =0.80\)) while a significantly negative correlation with sensible heat flux (\(R^{2}{=}-0.79\)). Soil moisture had a significant negative correlation with sensible heat flux (\(R^{2}{=}-0.68\)). The average evapotranspiration from crop land was \(1.58 ~\hbox {mm d}^{-1}\) and total evapotranspiration was 543 mm over the 12 months study period. This study defines that large aperture scintillometer is robust instrument which can evaluate energy flux over a large area with a long term series time domain. Moreover, further studied should be conducted to use in crop simulation modelling, developing of new model with calibration and validation of remote sensing energy balance algorithm, etc.     

Ichnology of the Callovian-Oxfordian rocks of the Katrol hill range,Kachchh, western India

On the basis of distinct lithologic features such as composition, grain size, bedding characteristics and sedimentary structures, six facies were identified in Callovian to Oxfordian rocks exposed southwest of Bhuj, Kachchh. They are interbedded calcareous shale-siltstone (ICSSF), limestone (LF), ferruginous sandstone (FerSF), felspathic sandstone (FelSF), grey shale (GSF) and oolitic limestone (OLF) facies. The rich and highly diversified trace fossils reveal a wide range of animal behaviours represented by dwelling, feeding, crawling and resting structures. Horizontal feeding structures are found abundantly in all lithofacies indicating low wave and current energy and deposition of poorly sorted muddy to sandy sediments. A few coarse layers containing Arenicolites, Ophiomorpha and Skolithos indicate the presence of opportunistic animals (due to their first appearance under harsh conditions) under -intermittently moderate wave and current energy or storm wave conditions (due to coarse grain size and dominance/presence of only vertical trace fossils) in the shoreface zone. Taenidium occurs mainly in the lower shoreface to transitional zone suggesting low to moderate energy conditions. Thalassinoides occurs in middle to lower shoreface settings under relatively low-energy conditions. Zoophycos represents offshore environment, where it occupies the deepest bioturbation levels.The characteristic lithofacies and assemblages of trace fossils in the rocks of the Chari/Jumara Formation indicate a depositional environment fluctuating from the upper shoreface to offshore zone.