Are many pulsars processed in binary systems?

A detailed statistical analysis of pulsarcurrent is presented. The conclusions reached are the following: (1) The birthrate of pulsars is about one in 75 ± 15 years. (2) There is evidence forinjection of pulsars into the population of solitary pulsars. Such an injection is particularly pronounced in the magnetic field range 12 < logB < 12.6. (3) This is interpreted as due torecycled pulsars being released into the population. (4) We tentatively conclude that as much as 10 – 15% of all pulsars may have been born and processed in binary systems.     

Probable maximum precipitation for a 2-day duration over the Indian Peninsula

Summary For the purpose of providing information to hydrologists for designing costly and large hydraulic structures, estimates of probable maximum precipitation (PMP) for a 2-day duration for stations in the Indian Peninsula lying between 8° N to 20° N were calculated using the Hershfield statistical techniqe. Maximum annual 2-day rainfall data of 80 years from 1901 for 131 stations in the region were used. In order to obtain values of PMP, an enveloping frequency factor (k _m ) curve based on the actual rainfall data of stations in the region was developed. The enveloping curve was then utilised to estimate 2-day PMP values of all the 131 stations. Based on these PMP estimates, a generalised chart showing the spatial distribution of 2-day PMP was prepared. It was found that 2-day PMP estimates over the Indian peninsula varied from 40 to 95 cm and the average ratio of 2-day PMP to the highest observed 2-day rainfall was found to be 1.76.With 2 Figures     

On the effect of the partial solar eclipse of 29 April 1976 on electron content

Faraday rotation measurements made at a chain of stations and group delay measurements made at Ootacamund from ATS-6 are examined for the partial solar eclipse event of 29 April 1976. There is no evidence of eclipse-induced gravity waves in these measurements extending from Ootacamund near dip equator to Patiala (dip 45° N). Eclipse-induced fluctuations were however reported at Trivandrum, about 300 km south of Ootacamund.     

Weathering impact on the colour of building stones of the ‘Gateway of India’ monument

To understand the effect of monsoon and marine environment on the colour of building stones of the ‘Gateway of India’ monument, 133 samples from different areas were assessed. Colour changes were evaluated using Microflash 200d colour spectrophotometer over a period of 1 year. The alteration in the stones effecting the colour change was studied by petrographic thin section, which shows that the colour change is associated with weathering of the feldspars.     

Design storm studies for the Upper Krishna river catchment upstream of the Almatti dam site

Summary The Almatti dam is the major engineering feature in the development of water resources in the Upper Krishna river forming a storage reservoir of 6425 million m³ at spillway crest level. In this paper, the design storm rainfalls for different return periods and also the Probable Maximum Precipitation (PMP) for the catchment above Almatti dam have been estimated to review the adequacy of the flood spillway design for the dam. The design storm rainfalls of various return periods have been computed from a statistical analysis of point and areal time series of annual maximum rainfall. In evaluating the PMP, the maximum observed rainfall obtained by Depth Duration method were maximized as the orography of the Western Ghats plays profound influence over the catchment. It was found that (area 35925 km²) the highest areal rainfalls over the catchment were 14.0 cm, 21.5 cm and 24.6 cm in 1, 2 and 3-day durations, respectively. These are scaled up by a factor of 1.23 to obtain the PMP rainfalls. The areal PMP estimates for the upper Krishna River (UKR) catchment above Almatti dam have been found to be 18.0 cm, 27.0 cm and 31.0 cm, respectively.With 6 Figures     

Flood Inundation Hazard Modelling Using CCHE2D Hydrodynamic Model and Geospatial Data for Embankment Breaching Scenario of Brahmaputra River in Assam

In many flood prone river basins, water inundates vast areas of land causing loss of life and heavy damage to the dwellings in flood plains. It also impacts agricultural productivity and cause severe economic losses. One of the reasons for flooding in plains of Brahmaputra valley in north east India is embankment breaching. In this study, an attempt was made for probabilistic flood hazard modelling of July 2008 embankment breaching scenario of Brahmaputra river at Matmara village, Lakhimpur district in Assam, based on various numerical simulations with the help of Center for Computational Hydro science and Engineering hydro-dynamic model. The methodology was applied over 2146 km² flood prone area. Data inputs in the study include: Advanced Spaceborne Thermal Emission and Reflection Radiometer Digital Elevation Model, Pre-flood and Post flood satellite images of Landsat Enhanced Thematic Mapper Plus (ETM+) and other ancillary data. The simulation was carried out for various discharge levels based on flood frequency analysis. The result of the model includes spatial variations of inundated water depth and water velocity. The results were validated by comparing it with the post-flood ETM+ data and flood situation status report of National Informatics Centre. Flood hazard maps were prepared by carrying out a spatial analysis of simulated inundation depth and velocity. It was seen that the majority of flooded area fell into the very high and high categories. This information can be used to plan appropriate cost effective flood mitigation schemes.     

Rainfall mechanism over the rain-shadow region of north peninsular India

Climate Dynamics - Rainfall mechanism over the rain-shadow region of north peninsular India during the summer monsoon season has been investigated using dynamic, thermodynamic, cloud microphysics...     

Did the Harappan settlement of Dholavira (India) collapse during the onset of Meghalayan stage drought?

Radiocarbon dating of archaeological carbonates from seven cultural stages of Dholavira, Great Rann of Kachchh (GRK), the largest excavated Harappan settlement in India, suggests the beginning of occupation at ~5500 years BP (pre-Harappan), and continuation until ~3800 years BP (early part of the Late Harappan period). The settlement rapidly expanded under favourable monsoonal climate conditions when architectural elements such as the Citadel, Bailey, Lower and Middle Town were added between the Early and mid-Mature Harappan periods. Abundant local mangroves grew around the GRK sustaining prolific populations of the edible gastropod Terebralia palustris. Oxygen isotope (δ¹⁸O) sclerochronology of Early Harappan gastropod shell suggests seasonal mixing of some depleted (δ¹⁸O ~ −12‰) river water in summer/monsoon months (through ancient Saraswati and/or Indus distributary channels) with seawater that periodically inundated the GRK. Evaporation from this semi-enclosed water body during the non-monsoon months enriched the δ¹⁸O of water/shell carbonates. The humid fluvial landscape possibly changed due to a catastrophic drought driving the final collapse of the settlement of Dholavira exactly at the onset of the Meghalayan (Late Holocene) stage (~4300–4100 years BP ). Indeed, Dholavira presents a classic case for understanding how climate change can increase future drought risk as predicted by the IPCC working group. Copyright © 2019 John Wiley & Sons, Ltd.     

Hydrograph separation and precipitation source identification using stable water isotopes and conductivity: River Ganga at Himalayan foothills

The observed retreat of several Himalayan glaciers and snow packs is a cause of concern for the huge population in southern Asia that is dependent on the glacial‐fed rivers emanating from Himalayas. There is considerable uncertainty about how cryospheric recession in the Himalayan region will respond to climate change, and how the water resource availability will be affected. As a first step towards quantifying the contribution of glacier‐melt water, hydrograph separation of River Ganga at Rishikesh into its constituent components, namely (i) surface runoff, (ii) glacial ice‐melt and (iii) groundwater discharge has been done in this paper. A three‐component mixing model has been employed using the values of δ¹⁸O and electrical conductivity (EC) of the river water, and its constituents, to estimate the time‐varying relative fraction of each component. The relative fraction of the surface runoff peaks (70–90%) during winter, due to the near‐zero contribution of glacial ice‐melt, essentially represents the melting of surface snow from the catchment. The contribution of glacial ice‐melt to the stream discharge peaks during summer and monsoon reaches a maximum value of ～40% with an average of 32%. The fraction of groundwater discharge varies within a narrow range (15 ± 5%) throughout the year. On the basis of the variation in the d‐excess values of river water, it is also suggested that the snow‐melt and ice‐melt component has a significant fraction derived from winter precipitation with moisture source from mid‐latitude westerlies (also known as western disturbances). Copyright © 2010 John Wiley & Sons, Ltd.