Meteorological features associated with unprecedented precipitation over India during 1st week of March 2015

Unprecedented precipitation along with heavy falls occurred over many parts of India from 28th February to 2nd March 2015. Many of the stations of northwest and central India received an all time high 24 hr cumulative precipitation of March during this period. Even the national capital, New Delhi, broke all the previous historical 24 hr rainfall records of the last 100 years to the rainfall record in March 2015. Due to this event, huge loss to agricultural and horticultural crops occurred in several parts of India. In the present study, an attempt is made to understand the various meteorological features associated with this unprecedented precipitation event over India. It occurred due to the presence of an intense western disturbance (WD) over Afghanistan and neighbouring areas in the form of north–south oriented deep trough in westerlies in middle and upper tropospheric levels with its southern end deep in the Arabian Sea, which pumped huge moisture feed over Indian region. Also, there was a jet stream with core wind speed up to 160 knots that generated high positive divergence at upper tropospheric level over Indian region; along with this there was high magnitude of negative vertical velocity and velocity convergence were there at middle tropospheric level. It caused intense upward motion and forced lower levels air to rise and strengthen the lower levels cyclonic circulations (CCs)/Lows. Moreover, the induced CCs/Lows at lower tropospheric levels associated with WD were more towards south of its normal position. Additionally, there was wind confluence over central parts of India due to westerlies in association with WD and easterlies from anticyclone over north Bay of Bengal. Thus, intense WD along with wind confluence between westerlies and easterlies caused unprecedented precipitation over India during the 1st week of March 2015.     

Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism,India: Evidence from volcaniclastic rocks,bentonite, black shales,and oolite

The late Aptian(118-115 Ma) continental flood basalts of the Rajmahal Volcanic Province(RVP) are part of the Kerguelen Large Igneous Province,and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin.The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts,bentonite,grey and black shale/mudstone and oolite,whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material.At the eastern margin and the north-central sector of the RVP,the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites.The pyroclastic rocks are largely felsic in composition,and comprise ignimbrite as well as coarse-grained tuff with lithic clasts,and tuff breccia with bombs,lapilli and ash that indicate explosive eruption of viscous rhyolitic magma.The rhyolites/dacites(68 wt.%) are separated from the andesites( 60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma.On the other hand,partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma,crystallizing orthopyroxene at a pressure-temperature of ~3 kb/1150℃.In contrast,the northwestern sector of the RVP is devoid of felsic-intermediate rocks,and the volcaniclastic rocks are predominantly mafic(basaltic) in composition.Here,the presence of fine-grained tuffs,tuff breccia containing sideromelane shards and quenched texture,welded tuff breccia,peperite,shale/mudstone and oolite substantiates a subaqueous environment.Based on these observations,we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions.The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment.Alignment of the Rajmahal eruptive centers with a major N—S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica.     

Uncertainty in differential settlements of bridge foundations and retaining walls

ABSTRACT

In the bridge design specifications of the American Association of State Highway and Transportation Officials (AASHTO) using the Load and Resistance Factor Design (LRFD) method, the loads and resulting force effects are given two-letter designations, e.g. “SE” for “force effects due to settlement”. The SE load factor is used to develop factored values of the induced force effects such as moments and shears in a bridge structure due to foundation movements. In 2018 AASHTO committees voted to adopt calibrated values of the SE load factors that account for the uncertainty in predicted foundation movements from different analytical methods. However, additional uncertainty can occur in the differential settlements. This paper explores the additional uncertainty in differential settlements of bridge foundations and retaining walls using the datasets for two analytical methods that were used by AASHTO to develop the SE load factors for foundation settlement. Normalised probability exceedance charts (NPECs), that integrate the concept of reliability index and data correlation, have been developed and their application in bridge and wall design process is discussed for a variety of scenarios. Guidance is provided for the practical implementation of differential settlement in bridge analysis through an example problem.     

Delineation and classification of rural–urban fringe using geospatial technique and onboard DMSP–Operational Linescan System

This study aims to analyse the processes and patterns of peri-urbanization using diurnal earth observation data-sets from onboard DMSP–Operational Linescan System. In this study, multiple correlation, simple and conditional linear regression are used to find out the degree of relationship and spatial behavioural pattern of the factors responsible for the urbanization. All the factors are standardized using the Analytical Hierarchy Process (AHP) coupled fuzzy membership functions. AHP is used to derive the weighting of the factors to produce the urbanity index. In total three functional zones – urban, rural and urban shadow are generated based on factor standardization and spatial contiguity index. Urban fringe is sharing ≥ 60% of Urbanity Index followed by rural fringe (39.50–60% of urbanity index) and urban shadow <39.50% of urbanity index. Shape index indicates that the city is going through unplanned development following cross to star shape growth.     

Intraseasonal variability of subsurface ocean temperature anomalies in the Indian Ocean during the summer monsoon season

Ocean Dynamics - The present study focuses on the variability of subsurface ocean temperature and associated planetary waves (oceanic Kelvin and Rossby waves) in the Indian Ocean during the boreal...     

Petrogenesis and Tectonic Significance of the Neoproterozoic Magmatism of the Tusham Ring Complex (NW Indian Shield): Insight into Tectonic Evolution of the Malani Igneous Suite and Rodinia Supercontinent

Geotectonics - The present study is carried out to probe geodynamic evolution and tectonic history of A-type granitoids from the Riwasa and Nigana areas in the Tusham Ring Complex (TRC), western...     

Impact of South China Sea Cold Surges and Typhoon Peipah on Initiating Cyclone Sidr in the Bay of Bengal

In the present study, an attempt was made to understand the role of South China Sea (SCS) convection associated with northerly cold surges and Typhoon Peipah in initiating Cyclone Sidr in the Bay of Bengal (BoB). The variation of air sea fluxes during the entire history of Cyclone Sidr tracking before its landfall over Bangladesh was also studied. The presence of cold surges in the north SCS associated with heavy rainfall episodes has been noticed at the southern Gulf of Tonkin coast prior to the formation of Typhoon Peipah. Subsequently, these surges migrated south, which resulted in intensification of a deep convection on reaching the Vietnamese coast. During the same period in the western Pacific, Typhoon Peipah developed, propagating in the westward direction and entering the SCS. Analysis of geostationary water vapour images, mean sea level pressure, and surface wind maps clearly depicted the transport of convective cloud clusters, moisture, and westward momentum from Typhoon Peipah to the deep convection cells over the SCS. Consequently, the existing deep convection over the Vietnamese coast resulted in a westward direction and entered the Gulf of Thailand and Andaman Sea. The availability of higher latent heat fluxes, warmer sea surface temperatures, and suitable atmospheric conditions over this region favoured the formation of a tropical depression in the Andaman Sea. This depression further intensified in the southeast BoB, resulting in the formation of Cyclone Sidr. NCEP/NCAR wind fields and air-sea fluxes revealed left asymmetry surface winds and higher latent heat flux on the left side of the track during the intensification phase of Sidr.     

Cadmium (II) distribution in complex aquatic systems containing ferrihydrite, bacteria and an organic ligand: The effect of bioactivity

The distribution of Cd²⁺ in the presence of phthalic acid (H₂L_p), ferrihydrite and bacteria (Comamonas spp.) was investigated in biologically active systems involving H₂L_p biodegradation. Tests showed that Cd²⁺ sorption onto bacteria, ferrihydrite and bacteria-ferrihydrite mixture increased with pH in all systems, irrespective of H₂L_p degradation or not. The use of bacterial growth medium, Bushnell Hass Broth modified for low phosphate, had negligible effect on Cd sorption. In the presence of ferrihydrite, no difference was observed between Cd²⁺ sorption in the ferrihydrite-live bacteria and in the ferrihydrite-dead bacteria systems as ferrihydrite proved to be the dominant sorption phase. Cadmium sorption to ferrihydrite and to bacterial cells was described using the diffuse layer model and a nonelectrostatic 4-site model, respectively, which were developed for systems lacking H₂L_p degradation. For systems experiencing H₂L_p degradation this modeling approach predicted the general trend of Cd²⁺ sorption-edge shift and gave good fits to the observed sorption data. The results obtained demonstrate that Cd²⁺ sorption in the biologically active system was reasonably estimated by a model developed for biologically inactive systems, although uncertainty exists due to processes involving H₂L_p biodegradation products and changes in the bacterial population.