Cloud height determination using satellite stereoscopy from Along Track Scanning Radiometer onboard ERS-1 satellite: A simulation study

The first ERS-1 satellite launched in May 1991 promises to make a substantial contribution towards the cloud stereoscopy. One of its payload, Along Track Scanning Radiometer (hereafter ATSR) has IR split window channels and scans the earth conically leading to earth views at two view angles (0° and 55°) in two curved swaths registered with respect to each other in image frame. This enables us to construct stereoscopic image of a cloud thereby determining its height geometrically. The present paper describes the utility of ATSR onboard ERS-1 in retrieving cloud height by synthetic stereo imaging over NOAA-AVHRR visible and thermal band observations.     

An explanation of induced magnetic variations at Sabhawala,India

Induction vectors calculated for short-period events such as “bays” and “storm sudden commencements” (SSCs) indicate that the conductor causing the anomaly lies to the south of Sabhawala. The nature of vertical transfer functions obtained from spectral analysis of storm-time variations further confirms the presence of such a conductor. The nature of maximum (G_p) and minimum (G₁) response functions suggests that a two-dimensional conductor south of Sabhawala is responsible for anomalies in Z. Invoking a structural model of the Earth's crust beneath the Himalayas, in keeping with accepted orogenic theories, we propose that one structure capable of producing the desired conducting path is a rise of the asthenosphere south of the Himalayan range. Another important factor contributing to the induced variations at Sabhawala is due to a sedimentary trough running parallel to the Himalayas, again to the south. These views are confirmed by a two-dimensional model calculation. It is found that the undulation of the asthenosphere alone does not reproduce the nature of the anomalies in H and Z.     

Induction at short periods in the horizontal field variations in the Indian peninsula

A study of the horizontal components of certain short-period magnetic-fluctuation events, viz., storm sudden commencements and bays, shows appreciable anomalies at two of the five magnetic observatories in peninsular India. The electric current patterns deduced from the magnetic horizontal induced variations imply channelling of induced currents through the Palk Straits and around the southern tip of the Indian peninsula. An interesting feature of these anomalies is that while the induced magnetic vertical variations are strongly correlated with the horizontal northward magnetic field, the electric current concentrations flow parallel to the coast; southwest, near Annamalainagar, and north near Trivandrum. The observations are interpreted in terms of a regional, east-west, induced electric current pattern which is perturbed in the vicinity of the two observatories by the Indian peninsula.     

Calculation of the second vertical derivative of gravity field

Summary Two formulas, using Taylor's series expansion method, have been developed by means of which the second vertical derivative of gravity field may be computed at any point in the horizontal plane of observation. A comparative study of the resolving powers of different approaches by performing numerical and filter response tests suggests that the formulas provide a definite improvement over many existing methods.NGRI Contribution No. 69-130.     

Extensional tectonic activity in the cratonward parts (peripheral bulge) of the Ganga Plain foreland basin,India

Flexural subsidence of the Indian lithosphere created the foreland basin in front of the emerging Himalayan mountain belt. The continued northward push of the Indian plate and thrust sheet loading in the Himalayan orogen caused an up-warping along its cratonward margin, in the form of a regional gentle bulge. In the cratonward peripheral bulge small-scale to moderate size deformation features, e.g., gentle folds (up-arching of the sediment layers), extensional normal faults and uplifted tilted blocks, and incised river channels with 20-60-m-high cliffs, developed. Cliff sections of many rivers in this cratonward part of the foreland basin expose deposits of latest Pleistocene-Holocene age and show evidences of active tectonics in the last few thousand years: vertical uplift leading to deep incision of the river system, development of prominent fractures cutting through the sedimentary succession, bending and tilting of the strata, and tilted blocks. In the Late Quaternary relaxation phase of the Himalayan orogen-foreland, there is increased vertical tectonic activity in the region of the peripheral bulge. The vertical uplift in this part of the Ganga Plain foreland basin caused the rivers (including the axial rivers) to make further deep incision without shifting from their courses. During periods of increased tectonic activity in the Himalayan region, i.e., the addition of thrust slices more rapidly, probably caused the maximum down-bending in the proximal part of the Ganga plain foreland basin. The high amplitude and asymmetric nature of this foreland basin is partly controlled by extensional tectonism.     

Impact of moisture variations on the circulation of the south-west monsoon

The impact of moisture anomalies on the circulation of the south-west Indian monsoon has been studied with a general circulation model. Newtonian relaxation is adopted to subject the model atmosphere under sustained moisture anomalies. The impact of negative anomalies of moisture was seen as a divergent circulation anomaly, while the positive anomaly was a stronger convergent anomaly. Although the humidity fields display a resilient behaviour, and relax back to normal patterns 1–2 days after the forcing terms in humidity are withdrawn, the circulation anomalies created by the moisture variation keeps growing. A feedback between positive moisture anomalies and low level convergence exists, which is terminated in the absence of external forcings.     

Aerial remote sensing application in hydrogeological and geomorphic mapping of a rocky terrain: A case study from Uttar Pradesh

Ground water prospecting in hard rock areas of Uttar Pradesh is quite difficult, owing to the geological and geomorphic controls of sub-surface strata on the occurrence and movement of ground water resources, and, therefore, it requires systematic investigations, mainly with the aid of remotely sensed and data, which undoubtedly provide realistic information on the hydrogeological conditions, geomorphologic features, drainage patterns etc. of any rocky area. In this paper, an endeavour has been made to locate ground water possibilities in the drought-affected, rocky terrain of the southern Mirzapur district of Uttar Pradesh, covering part of block Muirpur which is mainly characterised by the varied geological formations, including Archean complex, pre-Vindhyan matasediments and Gondwana formation, through the application of air photointerpretation technique, primarily based on the geologic/geomorphologic approach. The hydro-investigation in the area was carried out using panchromatic aerial photos of 1∶60,000 scale, chiefly to identify the drainage patterns, major geomorphic geo structural and lithological units; as these may control the ground water regime of the area, Further. the present study was also ably supported with limited field survey and hydrogeological data, for achieving reliable results.     

Quantitative Geomorphic Approach for Identifying Active Deformation in the Foreland Region of Central Indo-Nepal Himalaya

Geotectonics - Globally the remote sensing and geomorphometric analysis are frequently used for the assessment of tectonic activity. We used satellite-driven DEM data to analyze regional scale...     

Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko

Solar System Research - The paper considers the free molecular flow of gas through the dusty porous surface layer of a comet nucleus. The study is based on computer models of generation of a porous...