Observed daily large-scale rainfall patterns during BOBMEX-1999

A daily rainfall dataset and the corresponding rainfall maps have been produced by objective analysis of rainfall data. The satellite estimate of rainfall and the raingauge values are merged to form the final analysis. Associated with epochs of monsoon these rainfall maps are able to show the rainfall activities over India and the Bay of Bengal region during the BOBMEX period. The intra-seasonal variations of rainfall during BOBMEX are also seen using these data. This dataset over the oceanic region compares well with other available popular datasets like GPCP and CMAP. Over land this dataset brings out the features of monsoon in more detail due to the availability of more local raingauge stations.     

Unusual calcareous concretions from the Palaeocene grey-black shales of Palana Formation at Hadla Bhatiyan Southwest of Bikaner, Rajasthan

During the search of some plant and animal fossils a variety of calcareous concretions were collected from the carbonaceous grey-black shales of Palana Formation of the Palaeocene age in a dug well section at Hadla Bhatiyan village Southwest of Bikaner in Rajasthan. The concretions range in size from a few millimetres to 30 centimetres in diameter. These structures exhibit a variety of shapes ranging from spherical, botryoidal, flattened and dumbbell shaped. The calcareous concretions observed here show an unusual internal structure. On the outer surface they show straight laminations but inside these laminations form slump structures. In many cases the central portion of the slump structures has been detached and rotated due to the gravity effect. Secondly, laminations on the outer surface exhibit continuity irrespective of the shape of the concretions.     

Evaluating the impact of artificial groundwater recharge structures using geo-spatial techniques in the hard-rock terrain of Rajasthan,India

Groundwater levels in hard-rock areas in India have shown very large declines in the recent past. The situation is becoming more critical due to a paucity of rainfall, limited surface water resources and an increasing pattern of groundwater extraction in these areas. Consequently, the Ground Water Department with the aid of World Bank has implemented the water structuring programme to mitigate groundwater scarcity and to develop a viable solution for sustainable development in the region. The present study has been undertaken to assess the impact of artificial groundwater recharge structures in the hard-rock area of Rajasthan, India. In this study groundwater level data (pre-monsoon and post-monsoon) of 85 dug-wells are used, spread over an area of 413.59 km². The weathered and fractured gneissic basement rocks act as major aquifer in the area. Spatial maps for pre- and post-monsoon groundwater levels were prepared using the kriging interpolation technique with best fitted semi-variogram models (Spherical, Exponential and Gaussian). The groundwater recharge is calculated spatially using the water level fluctuation method. The entire study period (2004–2011) is divided into pre- (2004–2008) and post-intervention (2009–2011) periods. Based on the identical nature of total monsoon rainfall, two combinations of average (2007 and 2009) and more than average (2006 and 2010) rainfall years are selected from the pre- and post-intervention periods for further comparisons. All of the water harvesting structures are grouped into the following categories: as anicuts (masonry overflow structure); percolation tanks; subsurface barriers; and renovation of earthen ponds/nadis. A buffer of 100 m around the intervention site is taken for assessing the influence of these structures on groundwater recharge. The relationship between the monsoon rainfall and groundwater recharge is fitted by power and exponential functions for the periods of 2004–2008 and 2008–2011 with R ² values of 0.95 and 0.98, respectively. The average groundwater recharge is found to be 18% of total monsoon rainfall prior to intervention and it became 28% during the post-intervention period. About 70.9% (293.43 km²) of the area during average rainfall and more than 95% (396.26 km²) of the area during above-average rainfalls show an increase in groundwater recharge after construction of water harvesting structures. The groundwater recharge pattern indicates a positive impact within the vicinity of intervention sites during both average and above-average rainfall. The anicuts are found to be the most effective recharge structures during periods of above-average rainfall, while subsurface barriers are responded well during average rainfall periods. In the hard-rock terrain, water harvesting structures produce significant increases in groundwater recharge. The geo-spatial techniques that are used are effective for evaluating the response of different artificial groundwater recharge techniques.     

Lead-zinc resource prediction in India: An application of Zipf's law

Resource prediction is necessary for allocation of exploration efforts to keep pace with future demand and the growth pattern of a commodity. Zipf's law, a mathematical relationship between size and rank of discrete phenomena, has been used for resource prediction of oil in Western Canada, uranium, gold, tin, and lead-zinc deposits in Australia, and copper deposits in Zambia. The model, applied to lead-zinc metal accumulation of 24 known precambrain deposits in India, indicates that about 75% of the lead-zinc metal is yet to be discovered. The probability of occurrence of 14 deposits of larger dimensions based on the cumulative percentage frequency for different accumulations lies between 5 and 30%. In future exploration, preference should be given to more effort in the Banded Gneissic Complex of Rajasthan in comparison to Aravalilis of Rajasthan, followed by similar environments throughout the country and Palaeozoic strata of the Himalayas.     

Assimilation of IRS-P4 (MSMR) meteorological data in the NCMRWF global data assimilation system

Oceansat-1 was successfully launched by India in 1999, with two payloads, namely Multi-frequency Scanning Microwave Radiometer (MSMR) and Ocean Color Monitor (OCM) to study the biological and physical parameters of the ocean. The MSMR sensor is configured as an eight-channel radiometer using four frequencies with dual polarization. The MSMR data at 75 km resolution from the Oceansat-I have been assimilated in the National Centre for Medium Range Weather Forecasting (NCMRWF) data assimilation forecast system. The operational analysis and forecast system at NCMRWF is based on a T80L18 global spectral model and Spectral Statistical Interpolation (SSI) scheme for data analysis. The impact of the MSMR data is seen globally, however it is significant over the oceanic region where conventional data are rare. The dry-nature of the control analyses have been removed by utilizing the MSMR data. Therefore, the total precipitable water data from MSMR has been identified as a very crucial parameter in this study. The impact of surface wind speed from MSMR is to increase easterlies over the tropical Indian Ocean. Shifting of the positions of westerly troughs and ridges in the south Indian Ocean has contributed to reduction of temperature to around 30‡S.     

Identification of clusters in tropical cyclone tracks of North Indian Ocean

Tropical cyclones are a key climate-related hazard in South Asia. Assessment of the risk of cyclone impacts requires a comprehensive characterization of historical cyclone climatology. This study analyzes the tracks of tropical cyclones in the North Indian Ocean. Based on their spatial characteristics, cyclone tracks appear to be grouped into five well-defined clusters. These clusters correspond to distinct regions of cyclonic activity and exhibit differences in characteristics such as genesis location, probability of landfall, duration, and maximum intensity. Some of the identified clusters appear particularly important with regard to impacts because events in these clusters have greater landfall probability and are more intense. The clustering approach is likely to provide useful insights for the characterization of cyclone risk.     

Impact of slate quarrying on soil properties in semi-arid Mahendragarh in India

Slate quarrying in Mahendragarh district of Haryana state has resulted in changes in soil properties. Most of the mining area is devoid of vegetation. The soil in and around the mining area (0–1 km) is alkaline (pH 11.2–11.7) but non-saline (electrical conductivity < 4). The alkaline nature of the soil was attributed to the high concentrations of hydroxyl (OH⁻), carbonate (CO₃²⁻) and bicarbonate (HCO₃ ⁻) present in minerals of mined materials. Biotite, limonite, kaolinite, gibbsite, muscovite, geothite, dolomite and so on were the chief minerals added to soil through mining. The physical properties of soil, i.e. porosity, water-holding capacity (WHC), bulk density and particle density represented poor soil health in mining area (34.4, 29.8%, 1.636, 2.496 g/cc, respectively) and they improved with distance away from it (46.4, 38.3%, 1.070, 2.180 g/cc, respectively, at a distance of 1 km). Porosity and WHC were found to be a function of increased organic matter away from the mining area. CO₃²⁻, HCO₃⁻, phosphate (PO₄³⁻), lead (Pb) and iron (Fe) were more in mining area and decreased with distance. On the other hand, sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), sulphate (SO₄²⁻), organic carbon, total Kjeldahl’s nitrogen, cation exchange capacity, chromium (Cr) and cadmium (Cd) increased with distance from mining area. High concentration of heavy metals in mining area was a cause of concern (0.93 μg/g Cd, 22.35 μg/g Cr, 26.25 μg/g Pb, 1,383.75 μg/g Fe). The change in physico-chemical properties could be because of the addition of chemical constituents that are a part of major minerals present in mined material. The soil away from mining area represented comparatively better properties.     

K-dV and Burgers’ equations on DA waves with strongly coupled dusty plasma

A rigorous theoretical investigation has been made on the nonlinear structures, mainly, dust-acoustic (DA) solitary and shock waves propagating in a strongly coupled dusty plasma consisting of strongly coupled correlated positively and negatively charged inertial cold dust fluid, weakly correlated inertialess Maxwellian electron and ion fluids. The presence of arbitrary (negative and positive) charged dust grains in such a plasma system causes the presence opposite potentials (positive and negative) DA solitary and shock structures and significantly modify it’s basic features. The results obtained from this analysis can be employed in understanding the nature of plasma waves both in laboratory and space plasma system.     

Modeling of groundwater draft based on satellite-derived crop acreage estimation over an arid region of northwest India

Over-exploitation of groundwater for agricultural crops puts stress on the sustainability of natural resources in the arid region of Rajasthan state, India. Hydrogeological study of groundwater levels of the study area during the pre-monsoon (May to June), post-monsoon (October to November) and post-irrigation (February to March) seasons of 2004–2005 to 2011–2012 shows a steady decline of groundwater levels at the rate of 1.28–1.68 m/year, mainly due to excessive groundwater draft for irrigation. Due to the low density of the groundwater observation-well network in the study area, assessment of groundwater draft, and thus groundwater resource management, becomes a difficult task. To overcome the situation, a linear groundwater draft model (LGDM) has been developed based on the empirical relationship between satellite-derived crop acreage and the observed groundwater draft for the year 2003–2004. The model has been validated for a decade, during three year-long intervals (2005–2006, 2008–2009 and 2011–2012) using groundwater draft, estimated through a discharge factor method. Further, the estimated draft was validated through observed pumping data from random sampled villages (2011–2012). The results suggest that the developed LGDM model provides a good alternative to the estimation of groundwater draft based on satellite-based crop area in the absence of groundwater observation wells in arid regions of northwest India.