Selection of optimum frequency of a wind scatterometer

The problem of selecting the optimum operating frequency of a scatterometer, used for remote sensing of sea surface wind speed has been addressed by applying the criteria of maximum sensitivity of backscattering coefficient to wind speed as well as its correlation with wind speed. The backscattering coefficient values for sea surface were computed by the two-scale scattering theory. To compute the atmospheric transmittance, 753 clear sky atmospheres over Indian Ocean were used. While the correlation coefficient was uniform (0.94) throughout the frequency range of 1 to 30GHz, only frequencies above 5GHz were found sensitive enough to yield a wind speed accuracy of ±2msec⁻¹ and better, the accuracy improving with frequency.     

Cosmogenic isotope and track records in meteorites and their implications to cosmic ray fluxes

Study of several cosmic ray effects, such as VH track density, spallogenic²⁶Al and⁵³Mn activity,²¹Ne and²²Ne/²¹Ne ratio, made in the same sample or in cores taken from different meteorites can identify parameters related to the exposure history of meteorites and cosmic ray flux variations. Meteorites with single or multiple exposure can be distinguished from a track production rate —²²Ne/²¹Ne correlation diagram and cosmic ray flux variations over 10⁶–10⁷ years can be deduced from a three-isotope correlation diagram of²⁶Al,⁵³Mn and²¹Ne. Isotopic data based on chondrites with simple, one-stage exposure are consistent with the same average galactic cosmic ray intensity over the past 2 million years as that during the past 10⁷ years.     

Quasi-specular sea scatter with modified reflection coefficient

The paper deals with the relationship between the sea surface wind speed (U) and the backscattering coefficient (σ⁰) for microwave frequencies and quasi specular range of angles. Valenzuela’s effective reflection coefficient based on the theory of scattering of electromagnetic waves from rought dielectric surfaces has been introduced in the expression of backscattering coefficient and the final result compared with the σ⁰-U relationship derived fromSEASAT scatterometer and concurrent sea truth data.     

List of forthcoming papers

Other Index

List of forthcoming papers     

Gis aided demographic analysis of sub-mountain area of indian punjab-A case study

The present study is an attempt to understand the huge demographic data using GIS at village level. Two blocks from the sub-mountain Siwalik region of Punjabviz. Mahalpur and Garhshankar were selected. Various thematic maps were prepared using this technique. The inequality of distribution between various parameters has been studied using Lorenz curve and Ginni coefficient. Both Mahalpur and Garhshankar blocks are moderately populated blocks with highest population in south western parts. Population density is highest in the areas adjacent to the Garhshankar and Mahalpur towns. Schedule caste population is well distributed in both the blocks. The average sex ratio of the study area is 910 females per thousand males which shows that it is not a female deficit area. There are various villages in these blocks which have sex ratio more than 1000 females per thousand males, which is quite a good sign for these blocks. The literacy rate of the study area is nearly 57 per cent, which is quite low as compared to district Hoshiarpur having 81.4 per cent. Comparatively, Mahalpur block has more literate persons as compared to Garhshankar block. Lorenz curve shows that literate persons are quite evenly distributed. NRI families were around 10 per cent of the total number of families out of which 8 per cent are in Mahalpur block while remaining 2 per cent are in Garhshankar block. The study brings out important inferences at the village level by way of pinpointing the exact location of hot spots where action is needed by the planners and the administration.     

River Discharge,Major Ion Chemistry and Sediment Transport of the Bharathapuzha River,Southwest India: Implications on Catchment Erosion

The present study deals with the discharge characteristics, major ion chemistry as well as particulate and dissolved sediment transport of the Bharathapuzha river flowing across the Western Ghats through the Palghat gap - a prominent break in the Western Ghats that acts as a climate corridor in the region. While the western part of the basin in Kerala exhibits a wetter/humid climate, the eastern part in Tamil Nadu experiences a semi-arid climate. This peculiar climatic condition together with human interventions has a decisive role on the discharge characteristics as well as catchment erosion of the river basin. The dissolved and particulate contents of the river waters were found to be directly related to the geo-environmental settings of the river catchments. An intercomparison of elemental loading in the river waters in different seasons reveals notable decrease in monsoon compared to nonmonsoon seasons, which is attributed mainly to dilution of the solute contents by monsoon precipitation. The bivariate plots of Na/(Na+Ca) vs Total Dissolved Solids (TDS) and Cl/(Cl+HCO₃) vs TDS spread generally in the rock dominance sector of Gibb’s model indicating the role of chemical weathering in contributing to the major ion chemistry of the Bharathapuzha river. The intensity of weathering varied significantly among the different sub-basins of the Bharathapuzha river basin. The higher particulate load by dissolved load ratio of the Thuthapuzha and Gayathripuzha tributaries draining the humid areas compared to the Chitturpuzha tributary draining the semi-arid zones of the basin indicates the predominance of physical weathering in the former two sub-basins than the latter.     

Chronology of Late Pleistocene environmental changes in the lower Mahi basin,western India

Sediments exposed in the lower Mahi basin at the southern fringe of the Thar Desert, Rajasthan, India, provide evidence of three distinct depositional environments, namely marine, aeolian and fluvial. These have been used to reconstruct Late Pleistocene environmental and tectonic history of the region. Infrared stimulated luminescence (IRSL) chronology of the fluvial and aeolian litho‐units provides evidence of two major fluvial aggradation phases in the region corresponding to Oxygen Isotopic Stages 5 and 3. The basal marine clay is inferred to represent the last interglacial stage and its present elevation at +20 m a.s.l. is attributed to post‐depositional tectonism. Comparison of fluvial records from other regions indicates interhemispherically documented wetter phases during Oxygen Isotope Stages 5 and 3. Copyright © 2000 John Wiley & Sons, Ltd.     

Eroding islands of Gulf of Mannar,Southeast India: a consequence of long-term impact of coral mining and climate change

Natural Hazards - Lightning is one of the most widespread and deadly hazards in Bangladesh. Bangladesh has among the highest death rates of any country. The main objective of this study is to...     

Protracted river response to medieval earthquakes

Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co-seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after earthquake-induced sediment pulses around Pokhara, Nepal's second largest city. Freshly exhumed cohorts of floodplain trees in growth position indicate rapid and pulsed sedimentation that formed a fan covering 150 km² in a Lesser Himalayan basin with tens of metres of debris between the 11th and 15th centuries AD. Radiocarbon dates of buried trees are consistent with those of nearby valley deposits linked to major medieval earthquakes, such that we can estimate average rates of re-incision since. We combine high-resolution digital elevation data, geodetic field surveys, aerial photos, and dated tree trunks to reconstruct geomorphic marker surfaces. The volumes of sediment relative to these surfaces require average net sediment yields of up to 4200 t km^–2 yr^–1 for the 650 years since the last inferred earthquake-triggered sediment pulse. The lithological composition of channel bedload differs from that of local bedrock, confirming that rivers are still mostly evacuating medieval valley fills, locally incising at rates of up to 0.2 m yr^–1. Pronounced knickpoints and epigenetic gorges at tributary junctions further illustrate the protracted fluvial response; only the distal portions of the earthquake-derived sediment wedges have been cut to near their base. Our results challenge the notion that mountain rivers recover speedily from earthquakes within years to decades. The valley fills around Pokhara show that even highly erosive Himalayan rivers may need more than several centuries to adjust to catastrophic perturbations. Our results motivate some rethinking of post-seismic hazard appraisals and infrastructural planning in active mountain regions. © 2018 John Wiley & Sons, Ltd.