Lidar and Sun photometer observations of atmospheric boundary-layer characteristics over an urban area in a mountain valley

We present measurements of the vertical aerosol structure and the aerosol optical depth in the lower troposphere performed above the city of Sofia (an urban area situated in a mountain valley), western Bulgaria by means of a ground-based aerosol lidar operating continuously for a number of years. The lidar measurements were accompanied by measurements of the aerosol optical depth (AOD) in the visible and near infrared regions of the spectrum performed in October 2004 using Microtops II radiometers. The maximum values of the AOD were found to occur 1–2 h before the complete development of the atmospheric boundary layer, i.e. during the residual layer destruction, which confirms our hypothesis concerning the slope circulation effect on the processes taking place in the atmospheric boundary layer. The AOD values obtained by the lidar are lower than those taken by the sun photometer. Further, the AOD exhibits two different types of behaviour. In the case of a ‘clear atmosphere’ (i.e. in the absence of volcanic eruptions and/or dust transport from the Sahara) most of the aerosol accumulated within the atmospheric boundary layer over the urban area considered. The combined use of the two instruments allows the comparison between the optical characteristics of the atmospheric aerosol (e.g. aerosol extinction coefficient, etc.) obtained by the lidar and through an independent method (sun photometer).     

Occurrence of Cordaitales from lower Gondwana sediments of Ib-River Coalfield, Orissa, India: An Indian scenario

The Ib-River Coalfield in Orissa State is a part of Mahanadi Master Basin. Recent extensive investigations were conducted in this Coalfield to locate fossiliferous beds in the Lower Gondwana deposits and as a result a large cache of plant fossils were recovered from Lower Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries. The complete flora includes 23 genera representing nine orders viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Only the Cordaitales, represented by four genera i.e., Noeggerathiopsis, Cordaites, Euryphyllum and Kawizophyllum are discussed in this paper. Cordaitalean leaves are described for the first time from this coalfield; the remaining plant groups will be considered in a subsequent publication. Cordaitalean leaves attributable to Noeggerathiopsis hislopii, Noeggerathiopsis minor, Euryphyllum whittianum, Euryphyllum maithyi, Kawizophyllum dunpathriensis and Cordaites sp. constitute about 13.90% (111 specimens) of the total plant assemblage collected from this Coalfield. Of the cordaitaleans, N. hislopii is most abundant (47.75%; 53 specimens) followed by E. whittianum (40.54%; 45 specimens). A summary of the distribution of Cordaitales throughout the Indian Gondwana is also presented. Floristic composition varies stratigraphically at the two Barakar exposures (Lajkura and Jurabaga Collieries). Cordaitales are preserved only in the lowermost (4th) horizon (lower floral zone). Strata in these collieries have been assigned to the lower and upper Barakar Formation based on floristic content and an Early Permian (Artinskian) age is assigned.     

Urban growth analysis using spatial and temporal data

Urban growth identification, quantification, knowledge of rate and the trends of growth would help in regional planning for better infrastructure provision in environmentally sound way. This requires analysis of spatial and temporal data, which help in quantifying the trends of growth on spatial scale. Emerging technologies such as Remote Sensing, Geographic Information System (GIS) along with Global Positioning System (GPS) help in this regard. Remote sensing aids in the collection of temporal data and GIS helps in spatial analysis. This paper focuses on the analysis of urban growth pattern in the form of either radial or linear sprawl along the Bangalore — Mysore highway. Various GIS base layers such as built-up areas along the highway, road network, village boundary etc. were generated using collateral data such as the Survey of India toposheet, etc. Further, this analysis was complemented with the computation of Shannon’s entropy, which helped in identifying prevalent sprawl zone, rate of growth and in delineating potential sprawl locations. The computation Shannon’s entropy helped in delineating regions with dispersed and compact growth. This study reveals that the Bangalore North and South taluks contributed mainly to the sprawl with 559% increase in built-up area over a period of 28 years and high degree of dispersion. The Mysore and Srirangapatna region showed 128% change in built-up area and a high potential for sprawl with slightly high dispersion. The degree of sprawl was found to be directly proportional to the distances from the cities.     

Seasonal variations in the vertical structure of water vapor optical depth in the lower troposphere over a tropical station

Spatio-temporal variations of water vapor optical depth in the lower troposphere (450-3850 m) over Punt (18o32’N, 73o51’E, 559 m Above Mean Sea Level), India have been studied over a period of five years. The mean ver-tical structure showed that the moisture content is greatest at the lowest level and decreases with increasing altitude, except in the south-west monsoon season (June to September) where an increase upto 950 m has been found. Optical depths are maximum in the monsoon season. The increase from pre-monsoon (March-May) to monsoon season in moisture content on an average is by about 58% in the above altitude range. The temporal variations in surface Rela-tive Humidity and optical depth at 450 m show positive correlation. The amplitude of seasonal oscillation is the larg-est at 1465 m altitude. The time-height cross-sections of water vapor optical depths in the lower troposphere showed a contrast between years of good and bad monsoon.     

Rain induced shallow landslide hazard assessment for ungauged catchments

A physically based distributed slope stability model derived from the integration of hydrologic analysis and slope stability analysis is presented for GIS based modeling on a catchment scale. The catchment is represented by a mesh of squares with vertical columns. The hydrologic model calculates subsurface flow and resulting pore-water pressure during rainfall in each cell for every time step. The slope stability module then calculates the stability of each cell for the changing water pressure scenario. There are very few input data requirements, which makes the model applicable to ungauged catchments, also where the record of the past landslides and associated rainfall are not available. The model was tested in Garjuwa catchment, Nepal where all landslide scars were documented. The model reproduces the observed distribution of landslide locations in a consistent way. Several model runs were conducted, increasing the intensity of rainfall to see corresponding increase in instability. The results show that there is a critical rainfall intensity for the catchment, beyond which increase in rainfall intensity does not increase instability significantly.     

Generalized Expanding and Shearing Anisotropic Bianchi Type I Magnetofluid Cosmological Model in General Relativity

The behaviour of magnetic field in anisotropic Bianchi type I cosmological model for perfect fluid distribution in General Relativity, is investigated. The distribution consists of an electrically neutral perfect fluid with an infinite electrical conductivity. It is assumed that the component ¹ ₁ of shear tensor ^j _i is proportional to the expansion () which leads to A = (BC)ⁿ. The other physical and geometrical aspects of the model are also discussed, Bali (1986) obtained the cosmological model for n = 1 in presence of magnetic field. We have investigated the model for general values of n and discussed the particular case and general behaviour of the model.     

Distribution and enrichment of trace metals in marine sediments of Bay of Bengal,off Ennore,south-east coast of India

In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and range from 1.7 to 3.7% for Fe, 284–460 μg g⁻¹ for Mn, 148.6–243.2 μg g⁻¹ for Cr, 385–657 μg g⁻¹ for Cu, 19.8–53.4 μg g⁻¹ for Ni, 5.8–11.8 μg g⁻¹ for Co, 24.9–40 μg g⁻¹ for Pb, 71.3–201 μg g⁻¹ for Zn and 4.6–7.5 μg g⁻¹ for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I _geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment.     

A simple non-linear model for the investigation of the effects of the gap closure at the abutment joints of short bridges

Closure of the gap at the abutment joints of bridges has been the source of extensive damage during the 1971 San Fernando and more recent earthquakes. In this paper a model for the investigation of the effects of this gap closure is presented and analysed. The focus of the model is the representation of the non-linear response of the bridge abutments, the foundation and the columns. The model is used for the investigation of the response of a short bridge located in California.     

Tropical atmospheric stability and wind structures as inferred from the Indian MST radar observations

Summary The MST (Mesosphere-Stratosphere-Tropospher) Radar Facility at Gadanki (13.47° N, 79.18° E), near Tirupati, Andhra Pradesh, India has been operated over seven diurnal cycles—three in November 1994, one in September 1995 and three in January–February 1996 with an objective to study the wind and stability characteristics in the troposphere and lower-stratosphere. The radar-measured height profiles of both zonal (EW) and meridional (NS) wind components and near-simultaneous radiosonde measurements from Madras (13.04° N, 80.7° E) and Bangalore (12.85° N, 77.58° E), the two stations close to either side of the radar site, have been compared and they are found to be in gross agreement within the limitations of the sensing techniques.The results of the study also indicated multiple stable and turbulent structures/stratification throughout the height region from about 4 to 30 km. It is noticed that the stable layers are well marked around the altitudes 4 km, 12 km and the tropopause while the turbulent layers exist a few kilometers below the tropopause. These stable and turbulent layer structures showed good correspondence with the radar-measured wind gradients and also with the radiosonde-derived temperature and wind distributions over Madras. The maximum positive gradient in the signal-tonoise ratio (SNR) which corresponds to radar tropopause is found to coincide with the greater potential temperature gradient and smaller wind gradient. The time evolution of atmospheric stability structure, derived from the SNR, spectral width and vertical wind revealed a diffused tropopause or tropopause weakening which is found to be associated with broader spectral width and larger gradients of winds. This feature is considered to be due either to the instability associated with large vertical gradients in horizontal winds (dynamical instability) or to the instability generated by the convection (convective instability).With 6 Figures     

Characteristics of landslide in Koshi River Basin,Central Himalaya

Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya(mostly small and medium size landslides in east-west direction) and the TransitionBelt(mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfallinduced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000 m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum(Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations(2000~3000 m) and steeper slopes(40°~50°).