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      Volume 128, Issue 4

      June 2019

    • Potential detection of water resources in karst formations using APLIS model and modification with AHP and TOPSIS

      Mahnaz Zaree Saman Javadi Aminreza Neshat

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      Population growth and water shortage in Iran have highlighted the importance of studies on karst. However, in developing countries such as Iran, studies on the karst region including the construction of piezometric wells, exploratory boreholes, qualitative sampling and tracing tests are performed infrequently due to the huge costs. Hence, it is necessary to conduct karst studies in regions with a high potential of recharge using the map of groundwater recharge potential. In addition, determining and estimating the potential of these resources for management planning is vital in water shortage conditions. In this study, the potential detection of water resources in karst formations using ranking methods is investigated. First, APLIS weighting model was used in Javanroud, Kermanshah region, as the main method of and the basis of this research. Then, analytic hierarchy process (AHP) and TOPSIS techniques were used to modify the weight of the APLIS model and lastly, the three final maps of APLIS, AHP and TOPSIS were matched and compared with maps of spring and fault. Thus, the TOPSIS method, despite five springs with discharge of 38 m$^{3}$/s and four faults with length of 8869 m in a region with very high recharge, was selected as the best method. The results obtained enable us to select the best region for geophysical operation that requires the least amount of time along with the lowest cost.

    • Mesoscopic, magnetic and petrofabric study of the High Himalayan gneisses and leucogranite along oblique and frontal ramps of the Vaikrita Thrust in Satluj and Bhagirathi valleys: Thrust locking and superposed folding

      Kavita Tripathi Dubey A K Jayangondaperumal R

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      Field, microstructural and anisotropy of magnetic susceptibility (AMS) studies were performed along the oblique thrust ramp of the Satluj river valley and frontal thrust ramp of the Bhagirathi river valley. The presence of asymmetric and sheath folds indicates intense shearing near the thrust. The simple shear gradually decreases with an increase in distance from the thrust and pure shear with upright folds becomes prominent. The AMS studies suggest slightly higher pure shear in the frontal ramp region as compared to the oblique ramp region where oblique slip was predominant. The sense of shear criteria and orientation of superposed folds indicate locking of the thrust. Normal faults are the youngest structure.

    • Assessment of aquifer zones and its protection via second-order geoelectric indices in parts of drought-prone region of Deccan Volcanic Province, Maharashtra, India

      Shailaja G Gupta G Suneetha N Laxminarayana M

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      Assessment of aquifer protection was studied in the drought-prone regions of Mann Ganga River basin encompassing the districts of Satara, Sangli and Solapur, in Deccan Volcanic Province of Maharashtra, India, using electrical resistivity technique. The study was also aimed at alleviating the drinking water scarcity in these regions. A total of 118 vertical electrical sounding sites were occupied using Schlumberger electrode configuration and the data analysis revealed two to five layered curve types. The modelled layer resistivity and layer thickness at every station were used to calculate the Dar–Zarrouk parameters (i.e., longitudinal conductance S and transverse resistance T). The S values showed that 67% of the area had a poor aquifer protection, whereas 16% had moderate protective capacity and 13% had weak aquifer protective capacity rating. Only 4% of the study area depicted a good protective capacity rating. This indicates that the study area has a rather poor aquifer protective capacity rating, and thereby more prone to infiltrating contaminants. The regions with good-to-moderate protective capacity are envisaged to be potential groundwater zones. The large variation in electrical anisotropy $\lambda$ ranging from 1 to 2.8 in the study area suggests the anisotropic disposition of the aquifers in basaltic region. The intersection points of several lineaments in the study area are probable to be the most favourable zone for groundwater recharge. This is corroborated by the lineament density of the area, wherein high lineament density reflects high probability of groundwater infiltration. Moreover, the rainfall distribution suggests that the central and eastern parts of the study area receive maximum precipitation, which also coincides with the zones of high lineament density. Particle size analysis was determined from 92 soil samples in the study area and correlated with the longitudinal conductance in order to identify the sub-surface conditions and the aquifer vulnerability. Significant positive correlation was observed between the longitudinal conductance and percentage of clay fraction in the study area. These results could be relied upon for making preliminary estimates of protection from pollution for a sustainable groundwater development and management in future.

    • Evaluation of a radiation-based empirical model for estimating hourly reference evapotranspiration for high-altitude climatic conditions: A case study for the state of California

      Chatzithomas D Constantinos

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      High-altitude (>800 m) climatic conditions for the four stations in arid, semiarid and subhumid climatic zones were examined to evaluate their influence on radiation-based empirical estimations of reference evapotranspiration ($ET_{\rm{o}}$) on an hourly time step. The empirical method utilises the incoming solar radiation and the relationship between a function of relative humidity and vapour pressure deficit. The empirical method overestimated $ET_{\rm{o}}$ by 21.4%, on a yearly basis, 27.0% for the winter period and 16.3% for the summer period, compared with the estimations of the American Society of Civil Engineers Penman Monteith (ASCE PM) (2005) method. Various meteorological variables included in the energy and the aerodynamic term of the ASCE PM (2005) method were investigated with respect to altitude. The increasing trend of incoming solar radiation combined with the decreasing trend of relative humidity, both with respect to altitude were the main causes for the underestimation of the empirical radiation method. The empirical method was adjusted for high-altitude climatic conditions by multiplying the values by the ratio of the atmospheric pressure corresponding to the altitude of the station to the atmospheric pressure at sea level. The adjusted values were overestimated by 3.4% compared to the estimations of the ASCE PM (2005) method (higher overestimation: 9.1% and lower overestimation: 0.8%). The value of 0.073 mm h$^{-1}$ was considered as the upper limit for the satisfactory performance of the empirical method. The root mean square error (RMSE) values ranged from 0.038 to 0.054 mm h$^{-1}$ and the $R^{2}$ values ranged from 0.95 to 0.97. The values of the wind speed and vapour pressure deficit (not included in the empirical method) were divided into intervals and the RMSE values between the values of the estimations of the empirical method and the values of the estimations of the ASCE PM (2005) were calculated for each interval. The RMSE values calculated for the intervals of the values of the wind speed ranged from 0.036 to 0.065 mm h$^{-1}$ and were satisfactory. The vapour pressure deficit values <2.5 kPa also yielded satisfactory RMSE values and accounted for 96.1% of the data.

    • Late Quaternary sediments on the carbonate platform off western India: Analogues of ancient platform carbonates

      Purnachandra Rao V Gopinathan P

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      The Late Quaternary carbonate sediments and sedimentary rocks from the platform off western India were reviewed for their genesis and relationship with their ancient counter parts. Sub-marine cemented and vadose diagenetic limestones were recovered at different locations on the platform and, neomorphic limestones and caliche pisolites were recovered on the continental shelf south of the platform. Dolomites on the platform were primary and formed by microbial processes under hypersaline, sulphate-reducing conditions during the lowered sea levels. Aragonite ooids were formed from the mineralization of microbial filaments that enveloped their cortex portions. Phosphorites were found in organic-rich, aragonite muds on the continental slope adjacent to the platform and formed from the microbial mineralization of organic matter and replacement of carbonate by apatite during early diagenesis. Microbial processes thus played an important role in the formation of dolomites, ooids and phosphorites reported here and those in ancient deposits. Halimeda bioherms on the platform were grown luxuriantly from the nutrients brought by upwelling currents during the Late Pleistocene–Early Holocene sea level transgression and are similar to the Holocene–Recent deposits in the Indo-Pacific region. Lime muds were bio-detrital and formed primarily from the disintegration of Halimeda bioherms and carbonate skeletal on the platform and then exported to the slope. They resemble fine-grained limestones abundantly reported in ancient platforms. Thus, the different carbonate components on the platform are genetically related to their ancient ones and serve as Late Quaternary analogues for the ancient platform carbonates.

    • Extension of flood basalt on the northwestern continental margin of India

      Kumar P Chaubey A K

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      The Deccan Continental Flood Basalt (DCFB) in central western India is a large igneous province that covers almost one-sixth area of India. It is erupted in less than 1 million years during the magnetic chron 29 r ($\sim$65.6–64.8 Ma) through the Cretaceous–Tertiary boundary. It is believed that nearly an equivalent area of flood basalt, adjoining the DCFB, is submerged on the northwestern continental margin of India (NWCMI). Onshore information on the DCFB is widely reported in geological and geophysical studies. However, knowledge on the offshore extent of flood basalt is poorly known because of paucity of marine geophysical data and lack of an appropriate approach to determine the flood basalt. To fill this gap in knowledge, P-wave velocity in flood basalt as a proxy, drilled wells results, and published seaward dipping reflectors are used to delineate flood basalt extent on the NWCMI. The results of the study reveal that P-wave velocity in the flood basalt varies from 4.1 to 5.2 km/s. Apart from some isolated basement-high features, it is found that flood basalt lies below sediment and carpets the entire NWCMI extending up to the Laxmi–Laccadive ridges. The depth of occurrence of flood basalt ranges from 800 to 7400 m, with a maximum thickness of $\sim$3900 m in the eastern part of the Laxmi basin. The article presents preliminary results about the extension of flood basalt on the western continental margin of India which may be useful for researchers and Indian oil industries planning exploration activities in Mesozoic sediment of the margin for hydrocarbon prospects.

    • Facies architecture and depositional evolution of Palaeocene–Eocene, Subathu Formation, Garhwal Himalaya, Uttarakhand, India

      Mishra S R Rabisankar Karmakar Satish C Tripathi Mridul Gupta Rajuram Sarswat

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      The Late Palaeocene–Middle Eocene marine sedimentary sequence of the Himalayan foreland basin, represented by the rocks of Subathu Formation, is enriched with the presence of foraminifera, bryozoa, corals, gastropods, bivalves and so on within both carbonate and clastic dominant lithologies. The carbonate and the shale consist mainly of larger benthic foraminifera (LBF) and the assemblage is composed of Nummulites and Assilina along with the other skeletal and non-skeletal components. The presence of a palaeosol at the base of Subathu indicates a gap in sedimentation. The lithological and biotic assemblages along with the bed form, bed geometry and primary sedimentary features helped us to establish four facies associations, A, B, C and D, and have been corroborated with the shoreline migration (transgression/regression) history. The facies association-A, representing the basal horizons of Subathu Formation, indicates the onset of transgression and deposition in lagoonal condition with carbonaceous shale and oolitic ironstone, followed by the facies association-B and -C deposited in shallow marine shoreface. The uppermost unit, i.e., the medium- to coarse-grained sandstone (facies association-D) of Subathu Formation, represents a fall in relative sea level (progradational stacking pattern), whereas the underlying contact between the facies association-B and -C is represented by an aggradational stacking pattern between the siltstone and the shale, but certainly without exposing the shelf. Petrographic studies based on characteristic features such as framework constituent, the percentage of matrix and grains, nature of cementing material, textural features and fossil content help to deduce a distinct change in depositional setting from an open marine (shelf) to shoal, a lagoon that gradually grades to foreshore/beach environment. The study reveals that the basin has gone through a transgressive (facies association-A and -B), regressive (facies association-C) as well as distinct forced regressive (facies association-D) phase of shoreline migration history.

    • Integrating geochemical and reservoir engineering approach to evaluate reservoir continuity: A case study from Foroozan field, Offshore Iran

      Hassanzadeh P Hezarkhani A Rabbani A R Khajooie S

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      Foroozan field, with seven different reservoir layers, is one of the complex fields in the Persian Gulf. The purpose of this study was to identify intra-reservoir compartmentalisation using geochemical and reservoir engineering evidences. On the basis of this approach, 11 gaseous samples, which belong to different wells producing from the Burgan reservoir of Foroozan field, were selected. Gas composition, gas isotopes and associated oil bulk properties were tested to determine the reservoir continuity through the Burgan reservoir. In addition, fluid contacts and properties are also used to investigate reservoir continuity. Regarding clear differences in gas composition such as hydrogen sulphide concentrations, at least two separate segments in the north and south of the reservoir were detected. Moreover, the percentages of the different gas components indicated two separate compartments. Other evidences such as C$_{1}$–C$_{4}$ alkane isotopic compositions and sulphur and nitrogen isotopic signatures confirmed the Burgan reservoir compartmentalisation. A number of petroleum bulk properties confirmed gradual variations that provide supplementary evidence on the reservoir-filling direction, signifying that fluids equilibrium had not been extended through the Burgan reservoir, laterally. Initial reservoir condition, different original water–oil contacts, solution gas–oil ratio at original pressure and bubble point pressure are other reservoir engineering evidences that support the Burgan reservoir compartmentalisation.

    • Review on estimation methods of the Earth’s surface energy balance components from ground and satellite measurements

      Md Masudur Rahman Wanchang Zhang

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      Accurate estimation of the Earth’s surface energy balance (SEB) components is very much important for characterising the environmental, hydrological and bio-geophysical processes to predict the weather and climate or climate change. This narrative review summarises the basic theories of estimation methods of the solar (shortwave) radiation, thermal (longwave) radiation and evapotranspiration (latent heat flux) from both the ground and satellite measurements, which are inherently complex to measure at large scale. This paper discusses the reviews of prior and recent advances in the estimation methods and models by focusing their advantages, disadvantages and recommendations. Uncertainties associated with satellite estimations and some key directions for further studies are also discussed, including the status of ground-based measurements at regional and global scales and the advent of new satellite technologies for quantifying the SEB components more accurately. This study infers that the further advances in the satellite remote sensing and worldwide ground-based measurement networks will enhance the capabilities for the potential estimation of the SEB parameters as well as monitoring the global water and energy cycles to develop significant environmental studies for the betterment of living on the Earth.

    • Plio-Pleistocene stratigraphic sequences and depositional model using 3D seismic interpretation constrained by well logs in Central Graben, North Sea

      Haris Ahmed Khan Taher Zouaghi Shaista Iftekhar Muhammad Jahangir Khan Muhammad Irfan

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      This work presents depositional and structural model of Plio-Pleistocene delta of southern Central Graben offshore basin of Netherlands, based on seismic reflections and well logs tools. The studied interval of the Plio-Pleistocene delta is divided into 5 seismic super units, 11 seismic units, and 24 seismic subunits. Seismic reflections were correlated with the wire line records that lead to identification of depositional sequences and parasequences. The seismic units contain 27 well log units interpreted as depositional sequences. Each depositional sequence in term is composed of component parasequences corresponding to progradational and aggradational/retrogradational systems tracts. The main regional interpreted units can be correlated with the regional seismo-stratigraphy, chrono-eustatic and chronostratigraphy. Other previous works show that the Mid-Miocene to top Pleistocene interval is divided regionally into 13 seismic units and 18 log units. Coastline shifting and the sediment supply direction through Plio-Pleistocene time have been detected by lateral changes in clinoform geometry captured via construction of seismic unit’s time structure maps. Seismic super unit and seismic unit boundaries have been delineated by onlaps, downlaps, toplaps, truncations of seismic reflectors, which show the significant landward and basinward shifting of coastline. Boundaries of seismic subunits are marked on the basis of depositional cycles. Depositional cycles are characterized on the basis of gamma ray log trends (funnel shape, bell shape, and cylindrical shape) and their associated geometry of parasequences (lowstand, transgressive, and highstand, systems tracts). This work results in a sequential and geometric characterization of the defined deep-seated sedimentary units. It provides a better comprehension of the sedimentary, eustatic, and geodynamic evolution of the North Sea domains, and consequently a better evaluation of its economic interests.

    • Geological and geotechnical characterisation of the Khotila landslide in the Dharchula region, NE Kumaun Himalaya

      Ambar Solanki Vikram Gupta Bhakuni S S Pratap Ram Mallickarjun Joshi

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      On 04 October 2016, a severe landslide had occurred in the vicinity of Khotila village in Dharchula, region of NE Kumaun Himalaya. This landslide may be classified as typical rockslide, involving thin veneer of debris on the slope as well as the highly shattered rockmass. The slide has been divided into three morpho-dynamic zones, viz., (i) Zone of detachment between elevation 1000 and 960 m, (ii) Zone of transportation between elevation 960 and 910 m, and (iii) Zone of accumulation between elevation 910 and 870 m. The landslide had occurred at the end of the monsoon season when the slope was completely saturated. It has been noted that the area received $\sim$88% rainfall during the monsoon months which is about two times more rainfall during 2016 monsoon than during 2015 monsoon. Geotechnical testing of the soil overlying the rockmass, corroborate the soil as ‘soft soil’ with compressive strength of 42 kPa and friction angle of 27.4$^{\circ}$. Granulometry confirms the soil as having >97% sand and silt size particles and <3% clay size particles, indicating higher permeability. Mineralogically, the soil dominantly constitutes quartz, muscovite and clinochore. Though no swelling clay minerals has been observed, the higher permeability and low strength of the soil, and concentrated higher rainfall during 2016 are the main causes for the landslide to occur. This landslide has partially blocked the flow of Kali river that serve as a boundary between India and Nepal and is endangering the habitants of the Khotila and Bangabagar villages, situated downstream in the Indian and Nepalese side of the Himalaya. In order to understand the stability of the slope, finite element modelling of the landslide has been carried out that points towards higher concentration of stresses in the landslide zone, indicating that there is further probability for the failure of landslide mass. It is therefore suggested that the landslide must be monitored continuously, particularly during the rainy season and also the risk posed by this landslide must be evaluated so as to avoid any further loss to life and infrastructure in the region.

    • Study on the change characteristics of regional geoelectric fields

      Fan Y Y An Z H Wang J J Liu J

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      In this study, we illustrate the temporal variations of the geoelectric field and geomagnetic field by data from eight geoelectric field stations and four geomagnetic field stations in Mainland China in 2011. The maximum entropy spectral estimation method (MEM) was used to process the data in our study. The results show that: (i) it is obvious seasonal changes at inland geoelectric field stations and monthly changes at coastal geoelectric field stations; (ii) obvious seasonal changes can be observed at geomagnetic field stations and its seasonal changing curve of component H is most similar to that of the geoelectric field; and (iii) monthly changes of geoelectric field are caused by the combined action of solar and lunar tidal forces, and the seasonal changes of geoelectric field are caused by electromagnetic induction of the seasonal changes of ionospheric current induction intensity inside the Earth.

    • PM$_{2.5}$, PM$_{10}$ and surface ozone over Lumbini Protected Zone, Nepal, during monsoon season of 2012

      Kaushar Ali Trivedi D K Dilip M Chate Gufran Beig Prodip Acharja Trimbake H K

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      Physical characterisation of PM$_{2.5}$, PM$_{10}$ and surface ozone measured during the period from 17 July to 21 August 2012 at four strategic locations in and around the Lumbini Protected Zone, Nepal, is done to assess air quality of the region and understand qualitatively source mechanisms of these pollutants. The measurement locations are Panditarama Lumbini International Vipassana Meditation Centre, Parsahawa, Bhairahawa and Tilaurakot, representing monastic, industrial, urban and control areas, respectively. The overall average concentration of PM$_{2.5}$ at these locations is $\sim$19 $\pm$ 12, 35 $\pm$ 13, 35 $\pm$ 11 and 25 $\pm$ 6 $\mu$g/m$^{3}$ and of PM$_{10}$ is $\sim$25 $\pm$ 11, 103 $\pm$ 41, 58 $\pm$ 15 and 32 $\pm$ 7 $\mu$g/m$^{3}$, respectively. PM$_{2.5}$ never crosses the safe limit of the National Ambient Air Quality Standards of Nepal (NNAAQS) in the monastic and control areas but either crosses the NNAAQS occasionally or remains in its vicinity at the other two locations. The PM$_{10}$ concentration frequently exceeds the safe limit in the industrial area but not in the other remaining areas. The analysis indicates the dominance of the impact of local sources and boundary layer thickness on the atmospheric loadings of the particulate matter. The daily average mixing ratio of surface ozone remains normally low at all the four observational sites although the mixing ratio of ozone at Panditarama Lumbini International Vipassana Meditation Centre is much lower than the NNAAQS but higher than that observed at Tilaurakot.

    • Application of satellite altimetry in understanding river–wetland flow interactions of Kosi river

      Chembolu V Dubey A K Gupta P K Dutta S Singh R P

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      Flood-plain wetlands are the seasonal water bodies formed along a river. These wetlands become active during the monsoon season, which frequently grow in size with seasonal floods and eventually dry up during the non-monsoon season. The flow interaction between flood-plain wetlands and the river sometimes vary over a very short period in response to rapid rise in the river water level due to high precipitation in its upstream catchment. Understanding the complex flow interactions between the river and its associated flood-plain wetlands with field-based measurements of wetland hydrologic characteristics is always a challenging task. To overcome these challenges, an attempt has been made to utilise Topex/Poseidon satellite altimetry-derived water levels into a hydrodynamic model (HEC-RAS) to study river and wetland flow interactions in the lower reach of the Kosi river in India. The satellite altimetry-derived water levels and Landsat satellite images on the Kosi wetlands are used to develop volume-elevation relation. HEC-RAS is setup over the study area and calibrated for different values of manning’s roughness coefficient (n) for the river bank and the main channel of the river for the period of 1993–1996. Unsteady flow simulations are carried out for different monsoon seasons to simulate daily river flow interaction (inflow/outflow) between river and wetlands. Statistical analysis is performed between the altimetry-derived and the model-simulated water levels. It is found that simulated water levels are in good agreement ($R^{2}$=0.87, root mean square error of 0.84 m and Nash–Sutcliffe efficiency coefficient of 0.85) with altimetry-derived water levels. The analysis of simulations indicates that interactions between the wetland and the river are bidirectional with most of the flow coming out from the river during the month of August and leaving out from the wetlands during the month of September. The wetlands respond in three different ways, i.e., (i) gaining stage, (ii) wetland and river in equilibrium and (iii) loosing stage, which is reflected on water levels of the river and wetland. This study demonstrates complex interaction processes happening between the Kosi river and its surrounding wetlands.

    • Coupling of thermocline depth and strength of the Indian, summer monsoon during deglaciation

      Sushant S Naik Divakar Naidu P

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      We investigated the variations in thermocline depth using the difference in $\delta^{18}$Oc values between the two species of planktonic foraminifera, surface dwelling Globigerinoides ruber (s.s.) and thermocline dwelling Neogloboqudrina dutertrei, covering a time span of 9–23 kyr from the sediment core SK218/1 from the western Bay of Bengal (BoB). Here we show that during the strong phase of the Indian summer monsoon (12–9 kyr), a strong stratification leads to a shallow mixed layer and thermocline depth in the BoB as evident from higher $\Delta\delta^{18}$O between the mixed layer and thermocline dwelling planktonic foraminifera species. Thus, a strong coupling between the Indian summer monsoon and thermocline depth in the BoB prevailed at a millennial time scale.

    • Tropical cyclones over the Arabian Sea and Bay of Bengal tracked by Megha-Tropiques SAPHIR during 2011–2018

      Vasudha M P Raju G

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      Monitoring of tropical cyclones (TCs) using the Sondeur Atmospherique du Profil d’Humidite Intertropicale par Radiometrie (SAPHIR) sounder on-board the Megha-Tropiques satellite is attempted on a qualitative basis. The sounder with a high resolution of 10 km at nadir, combined with its high temporal observation ability, 4–6 times a day, and with six channels at 183.31 $\pm$ 11.0 GHz, is used for tracking the cyclones. The study has been performed by applying SAPHIR brightness temperature datasets to the cyclonic regions. In this study, 25 TCs from 2011 to 2018 in the Arabian Sea and the Bay of Bengal over the North Indian Ocean have been observed. A comparison of six channels of SAPHIR shows the clear variations of the eye of the cyclone under various conditions. Furthermore, the positional variations obtained by multiple linear regression models are used to observe the evolution of the cyclone storm from its genesis to dissipation/landfall for all the 25 cyclones. The location accuracy is found to be 0.2–0.3$^{\circ}$, as observed from the SAPHIR dataset that agrees reasonably well with the India Meteorological Department dataset and Advanced Microwave Sounding Unit sounder dataset in cyclone tracking. This study attempts at using the unique features of high temporal resolution, good spatial resolution and more channels and is expected to complement other methods of cyclone tracking.

    • Seasonal and annual variation of AIRS retrieved CO$_{2}$ over India during 2003–2011

      Anju Gupta Dhaka S K Matsumi Y Imasu R Hayashida S Vir Singh

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      The present study shows spatio-temporal variability in carbon dioxide (CO$_{2}$) in the mid-tropospheric region over India (0–32$^{\circ}$N, 60–100$^{\circ}$E) during 2003–2011. The CO$_{2}$ data used in the study is retrieved from Atmospheric Infra-Red Sounder (AIRS). Analysis of 9 yrs of data shows that the CO$_{2}$ exhibits a linear increasing trend of 2.01 ppm/year. Besides displaying the linear increasing trend, data show strong seasonal and annual variability. Concentration of CO$_{2}$ is observed to be highest around April–May (summer months), which decreases by 4–5 ppm during the monsoon months. Seasonal decrease in CO$_{2}$ concentration appeared to be influenced by the monsoonal activity. Low OLR (proxy of convection) associated with high rainfall during summer monsoon via increasing vegetation index (NDVI) appears to be the primary cause for the seasonal decrease in CO$_{2}$ through photosynthesis. Correlation coefficient between CO$_{2}$ and NDVI is of the order of –0.90 suggesting vegetation as a seasonal sink of CO$_{2}$. Decrease in CO$_{2}$ concentration takes place at a delay of 2–3 months of rainfall. However, convection seems to be another component, which causes uplifting of CO$_{2}$ during dry summer (April and May) making high concentration in the mid-troposphere as shown by increase in the planetary boundary layer (PBL) height in this period. Eastward propagating intra-seasonal oscillations with period 30–40 days in OLR anomalies are found to modulate (with a fluctuation of 1–2 ppm) mid-tropospheric CO$_{2}$. Analysis of seasonal anomalies in CO$_{2}$ over four different regions (northern, southern, western and eastern) of India is also being investigated. The regional variability of CO$_{2}$ in northern region show marginal larger values suggesting more anthropogenic activities especially during late winter.

    • Comparison of coastal hydrodynamics in different energy regime coasts along southwest coast of India

      Noujas V Kurian N P Thomas K V

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      Study of the complex physical processes of beach-nearshore system helps to understand the coastal processes and facilitate coastal planning and management. Since the SW coast of India has very dynamic and contrasting hydrodynamic features, the Veli–Varkala stretch of southern Kerala (SK) and Munambam–Chettuwa sector of central Kerala (CK) were selected for a comparative study of their hydrodynamics. SK is a high wave energy coast compared to CK. The contrasting wave energy regimes result from the differences in the inner shelf slope and shoreline orientation. However, just as in the case of SK, waves and wave induced littoral processes are the dominant driving forces in the coastal processes of CK too. Due to the favorable hydrodynamic and sedimentological characteristics, mudbanks set in at different locations of CK affecting the coastal processes of the locations of its occurrence. Mudbanks do not occur along the SK due to the unfavorable sedimentological features. Artificial morphologies such as seawalls, groins, harbour breakwaters have a great role for coastal processes along both the sectors. The long term shoreline change along the SK and CK can be linked to the contrasting characteristics of longshore sediment transport along the coasts.

    • Relative impact of recent climate and land cover changes in the Godavari river basin, India

      Narendra Hengade Eldho T I

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      The Godavari river basin (GRB), the second largest river basin (312,800 km$^{2}$) in India, was considered in this study to quantify the relative hydrological impact of recent land cover (LC) changes and rainfall trends using the variable infiltration capacity hydrologic model. Three scenarios, namely, (i) LC change, (ii) climate change and (iii) LC and climate changes, were considered to isolate the hydrological implications of the LC changes from those of climate change. Results revealed that evapotranspiration is predominantly governed by LC change and that small changes in rainfall cause greater changes in the runoff. Although the spatial extent of LC change is higher, the climate change is the dominant driver of hydrological changes within the GRB. Thus, climate projections are the key inputs to study the impact on the river basin hydrology. The results provide insights into the impacts of the climate and LC changes on the basin. The methodology and results of the present study can be further considered for water resource planning within the river basin in view of the changing environment.

    • An approach to simulate the climate-driven streamflow in the data-scarce mountain basins of Northwest China

      Chong Wang Jianhua Xu Yaning Chen Weihong Li

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      With global warming, the inland river basin in the arid region of Northwest China is facing a serious water supply situation. The headwater basin of the inland river is located in the high-altitude mountainous region, and there are few meteorological observation sites, so it is difficult to apply distributed hydrological models and other models based on the physical mechanism of runoff generation to evaluate climate change and its impact on streamflow. To simulate the climate-driven streamflow in data-scarce mountain basins of Northwest China, we developed an integrated approach by using downscaled reanalysis data, Mann–Kendall test, ensemble empirical mode decomposition and backpropagation artificial neural networks together with the weights connection method. We validated the approach in the Kaidu River basin located in the Tianshan mountains. The results showed that the streamflow increased 12.9% by 2.5 $\times$ 10$^{8}$ m$^{3}$ per decade with the warm and wet climate, while the average annual temperature increased 5.2% at a rate of 0.3$^{\circ}$C per decade and the precipitation increased 37.3% at a rate of 16.4 mm per decade during the period from 1980 to 2015. The impact of temperature variability on streamflow was 44.21 $\pm$ 2.08% and the impact of precipitation variability on streamflow was 55.79 $\pm$ 2.08%.

    • Evaluation of ambient air quality in Dehradun city during 2011–2014

      Amar Deep Chhavi P Pandey Hemwati Nandan Purohit K D Narendra Singh Jaydeep Singh Srivastava A K Narendra Ojha

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      The variations in the ambient concentrations of particulate matter (SPM and PM$_{10}$) and gaseous pollutants (SO$_{2}$ and NO$_{2}$) at Clock tower (CT), Rajpur road (RR) and Inter State Bus Terminal (ISBT) station in Dehradun city, Uttarakhand, India are analysed for the period of 2011–2014. Mean concentrations are observed to be higher during pre-monsoon season as compared to the winter and monsoon. PM$_{10}$ and SPM concentrations with maximum values of 203 $\pm$ 23 and 429 $\pm$ 49 $\mu$g m$^{-3}$, respectively, during winter, are found to exceed the national standards by factors of 2 and 3. Winter-time elevated pollution in Dehradun is attributed to the lower ventilation coefficient (derived from Era interim model fields) and minimal precipitation. Nevertheless, the SO$_{2}$ and NO$_{2}$ levels are observed to be within the criteria notified by the Central Pollution Control Board (CPCB), India. Correlation analysis shows profound impacts of the meteorology and local dynamics on the observed variations in observed trace species. Additionally, the stronger inter-species correlation variations (r=0.79 for SO$_{2}$ with NO$_{2}$, and r=0.89 for PM$_{10}$ with SPM), which may suggest their origin from common sources. Analysis of ‘Air Quality Index (AQI)’ variations indicates unhealthy atmospheric conditions near the major city centers and bus station. More observations in the region are highly desirable to understand the dispersion of the enhanced pollution in the Dehradun valley.

    • Flash flood susceptibility modelling using geomorphometric approach in the Ushairy Basin, eastern Hindu Kush

      Shakeel Mahmood Atta-Ur Rahman

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      This study focuses on flash flood susceptibility modelling using geomorphometric ranking approach in the Ushairy Basin. In the study area, flash floods are highly unpredictable and the worst hydrometeorological disaster. An advanced spaceborne thermal emission and reflection radiometer global digital elevation model was used as input data in a geographic information system environment to delineate the target basin. A total of 17 sub-basins were delimited using a threshold of 4 km$^{2}$. The attribute information of each sub-basin was analysed to compute the geomorphometric parameters by applying Hortonian and Strahler geomorphological models. The results were analysed and categorised into five classes using statistical techniques, and the rank score was assigned to each class of all parameters depending on their relation with flash flood risk. In this study, 16 parameters were analysed to quantify the geomorphometric number of each sub-basin depicting the degree of flash flood susceptibility. The geomorphometric number of each sub-basin was linked to the geo-database for spatial visualisation. The analysis reveals that extremely high, very high, high and moderate sub-basins susceptible to flash floods were spread over an area of 55%, 8.5%, 23.7%, and 11.5%, respectively. It was found that out of total settlements, 53% are located in the extremely highly and very highly susceptible sub-basins. In the study area, the upper reaches are characterised by snow-covered peaks, steep slopes and high drainage densities (>1.7 km/km$^{2}$). The analysis further indicated that the flash flood susceptibility increases with the increase in area, relief and relief ratio of the sub-basins. Model accuracy was assessed using primary data regarding past flood damages and human fatalities. Similarly, socio-demographic conditions of each sub-basin were also compared and linked to the extent of flash flood susceptibility. This study may assist the district government and district disaster management authority of Dir upper to initiate flood risk reduction strategies in highly susceptible zones of the Ushairy Basin.

    • Temporal and spatial characteristics of droughts and floods in northern China from 1644 to 1911

      Shuoben Bi Shengjie Bi Ying Lu Ying Qu Feng Zhao

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      This study analyses the temporal and spatial distributions of droughts and floods in northern China during the Qing Dynasty (1636–1912), with data ranging from 1644 to 1911, or nearly the entire dynastic period. Variations in the intensities of droughts and floods are investigated across different timescales and with respect to their spatial variation. The impacts and physical mechanisms of solar activity as well as surface temperatures of the Pacific Ocean on drought and flood intensities in northern China are analysed using a cross-wavelet method. The results reveal periodicities on scales of 10–11, 20–22, 45–50 and 90–100 yrs. Seven rapid changes are found on the 10-yr scale and four are found on the 30-yr scale. Analysing the spatial distribution of drought and flood intensities, we found a trend of decreasing precipitation from east to west. Precipitation over the Shandong region, which is in the eastern part of the study area, is significantly higher than that of the other regions, which may be explained by its coastal location and the resultant rich water vapour content of the atmosphere. Analyses of cross-wavelet power spectra and coherence spectra among the different drought and flood intensities and the Nino3 regional sea surface temperature (SST) index series and sunspot series indicate significant correlations between the drought and flood series and the Nino3 SST index series at scales of 2–4 and 8–12 yrs, and the phase difference differs across the different timescales. Furthermore, the drought and flood series and the sunspot series are closely correlated at a scale of 8–14 yrs.

    • Multi-model assessment of trends, variability and drivers of terrestrial carbon uptake in India

      Ananya S Rao Govindasamy Bala Ravindranath N H Rama Nemani

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      A multi-model-based assessment is made to assess the trends and variability in the land carbon uptake in India during the period 1901–2010. Data from nine models, used in a recent land surface model inter-comparison project called TRENDY, are used for this purpose. Our analysis is focused on the trends and variability in the net primary productivity (NPP), net ecosystem productivity (NEP) and net ecosystem exchange (NEE). The multi-model mean NPP shows a positive trend of 2.03% per decade during this period. The NEP, which is the difference between NPP and heterotrophic respiration, has a mean value of $-$0.138 $\pm$ 0.086 Pg C yr$^{-1}$ over this region. According to our analysis of TRENDY multi-models, the inter-annual variation in NPP and NEP is strongly driven by precipitation, but remote drivers such as El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) do not have a strong influence. The water use efficiency (WUE) shows an increase of about 25% over the 110-yr period. Our multi-model-based estimate of the cumulative NEE is 0.613 $\pm$ 0.1 Pg C during 1901–2010, indicating that the Indian terrestrial ecosystem was neither a strong source nor a significant sink during this period. However, we caution that our conclusion is based on a limited set of offline land models, and the results presented here have large uncertainties due to model resolution and parameterisation of various land surface processes, the inadequate validation procedures and the use of limited number of models and land use change data sets. Further investigations using more observational data, rigorous validation using extensive observational data sets and a set of comprehensive coupled models that include several feedbacks between land, atmosphere, ocean and the cryosphere are needed to assess the robustness of our results.

    • Modelling of strong motion generation areas for a great earthquake in central seismic gap region of Himalayas using the modified semi-empirical approach

      Sandeep Joshi A Sah S K Parveen Kumar Sohan Lal Kamal

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      Over the past decades, strong motion generation areas (SMGAs) have received significant attention in the modelling of high-frequency records. Herein, we propose the source model for a scenario earthquake ($M_{\rm{w}}$ 8.5) in the central seismic gap region of Himalayas. On the rupture plane, three SMGAs have been identified. Further, SMGA parameters are evaluated using available empirical relations. The spatiotemporal distribution of aftershocks is utilised to locate these SMGAs on the rupture plane. Further, the modified semi-empirical technique (MSET) is used to simulate the strong motion records. It has been observed that the study area can expect peak ground acceleration of >100 cm/s$^{2}$ and its distribution is mainly affected by the location of nucleation point in the rupture plane. Furthermore, the estimated peak ground acceleration (PGA) values are comparable with the earlier studies in the region. This confirms the robustness of generated rupture model with three SMGAs and the reliability of MSET to simulate high-frequency records.

    • Illite crystallinity index from the Mesoproterozoic sedimentary cover of the Kaladgi basin, southwestern India: Implications on crustal depths of subsidence and deformation

      Mrinal Kanti Mukherjee Kunal Modak Jiten Ghosh

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      The grade of metamorphism and thermal maturity of the Mesoproterozoic Bagalkot Group in the Kaladgi basin of southwestern India has been determined using the illite crystallinity (IC) index. IC index was determined from the argillite samples of four stratigraphic levels viz., Ramdurg Formation (basal unit), Yargatti Formation (intermediate lower unit), Yadahalli Formation (intermediate upper unit) and Hoskatti formation (upper unit). IC index (Kubler equivalent) values range between 0.54$^{\circ}\Delta 2\theta$ and 0.24$^{\circ }\Delta 2\theta$ (in a set of 37 samples) and indicate a deep diagenetic to high anchizone metamorphic grade within a temperature range of $\sim$180 to 300$^{\circ}$C. The Mesoproterozoic sedimentary cover of the Kaladgi basin is deformed due to southerly directed gravity gliding of the cover over the basement. The general variation of the IC index along and across the basin as indicated by the distribution of IC index values and isocryst contour patterns is due to the combined effect of deformation and variable subsidence of the Mesoproterozoic cover of the basin. Considering an average Mesoproterozoic geothermal gradient of 35$^{\circ}$C/km, the crustal depth of deformation and/or subsidence of the Mesoproterozoic cover up to the sample point is estimated to vary between 5.14 and 8.57 km.

    • Audio-magnetotelluric investigation of Bakreswar Geothermal Province, Eastern India

      Anurag Tripathi Shalivahan S S Ashish K Bage Shailendra Singh Pramod Kumar Yadav

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      Bakreswar Geothermal Province (BGP) lies over the Archaean gneisses and schists formations. The heat flow and geothermal gradient of BGP are $\sim$230 mW/m$^{2}$ and 95$^{\circ}$C/km, respectively. The Bakreswar hot spring (BHS) (23$^{\circ}$52$^\prime$30$^{\prime\prime}$N; 87$^{\circ}$22$^{\prime}$30$^{\prime\prime}$E) is located over NNW–SSE trending fault. It lies in the eastern flank of BGP and is connected by Sone–Narmada–Tapti (SONATA) and deep-seated ONGC fault systems. Earlier studies indicated that the geothermal fluid flowed towards the same path as that of deep ONGC fault. In view of this, 24 audio-magnetotelluric soundings in the frequency range 10 kHz–10 Hz were conducted at one end of the deep ONGC fault, which is about 20 km northwest of BHS. The data analysis indicated that the data are internally consistent. Analysis of dimensionality and strike are indicative of complex conductivity structures. The 3D inversion of full impedance was performed to obtain a conductivity model of the study area and resulted in root mean square (RMS) for sites close to unity. The results have been discussed by extracting cross-section along 3 to 7 profiles (four of the profiles are perpendicular to strike, whereas three profiles were oblique to the strike direction and are perpendicular to east–west trending ONGC faults). Several low conducting zones are observed in the profiles drawn parallel and perpendicular to the strike. These common conductors show consistent model features but modified resistivity and dimension. Depth slices from 200 to 1400 m suggest that the conductors in the northern part of the study area are deeper than the conductors in the south. The study area is dominated by several shallow conductors which coincide with several fractures present in the study area. The conductors are surrounded by a resistive feature that can act as an impermeable bed and probably restricts the flow of water within the zone. The four major conductors along the oblique profiles (profiles perpendicular to deep ONGC fault) coincide with deep ONGC fault, through which probably the geothermal fluid flows.

    • Petrographic controls on phosphorous distribution in coal seams of the Jharia basin, India

      Atul Kumar Varma Sumit Mishra Balram Tiwari Bodhisatwa Hazra Susheel Kumar Durga Charan Panigrahi Anwita Ojha

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      In recent years, the international coking coal market is experiencing an acute shortage of coal supply which has caused a fluctuation in its price. Degradation of coke, in the blast furnace, is largely controlled by its inherent mineral matter. Phosphorous occurs in all coals in minor or trace amounts and is an important parameter to coal users, particularly in steel industries. The mode of occurrence and distribution of phosphorous minerals in 17 coal samples of the Jharia coal basin were investigated through petrographic examinations, technological characterisation and phosphorous distribution. The results reveal that the dull bands are eight times more enriched in phosphorous than the bright bands. The macerals of the inertinite group and mineral matter positively correlate with the phosphorous content, whereas vitrinite macerals have an apathetic correlation. The impact of the thermal alterations is localised and diminishes away from the contact of the intrusion. In contrast, the faulting does not appear to have any effect on the phosphorous content.

    • The mechanism of the bottom-crashing rockfall of a massive layered carbonate rock mass at Zengziyan, Chongqing, China

      Kai He Yueping Yin Bin Li Chunli Chen

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      Multiple carbonate cliffs are distributed in the karst mountain areas of southwestern China. The dynamic process and failure mechanism of rockfalls in the cliffs are complicated and undefined, and can be dangerous for settlements. Moreover, it is difficult to identify the potential for such failures before they occur. The rockfall of the Zengziyan cliff at Chongqing, China, is used as an example for studying this type of failure and to determine the developmental characteristics of rockfall, expounding on the evolving process from a cliff to an unstable rock mass through to rockfall. A fracturing–crashing failure mode is proposed, based on the evolutionary characteristics of damage development, compression-induced fracturing, rock mass crashing and overall rockfall. Finite difference numerical simulations were used to analyse and validate the failure mode of the Zengziyan cliff under three simulation conditions. The results of the simulations indicated that strength deterioration at the bottom of the cliff was the root cause of its fracturing–crashing rockfall. The outcomes of this paper could provide a new analytical model and theoretical basis for identifying and analysing similar types of geological disasters in the mountainous areas of southwestern China, and may provide valuable reference information for further mechanical analysis, stability evaluation and engineering prevention of unstable rock masses prone to a fracturing–crashing rockfall.

    • Precision mapping of boundaries of flood plain river basins using high-resolution satellite imagery: A case study of the Varuna river basin in Uttar Pradesh, India

      Mallikarjun Mishra Vikas Dugesar Prudhviraju K N Shyam Babu Patel Kshitij Mohan

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      Accurate demarcation of river basin boundaries is an important input for any programme connected with watershed management. In the present study, the boundary of the Varuna river basin is automatically derived using coarse- and medium-resolution digital elevation models (DEMs) of SRTM-30 m, ASTER-30 m, Cartosat-30 m, ALOS Palsar-12.5 m and Cartosat-10 m as well as manually through on-screen digitisation from a very high-resolution 1 m $\times$ 1 m remote sensing data available as Google Earth image. The study demonstrated the efficacy of on-screen digitisation from high-resolution Google Earth image supported by detailed field observations in the precision mapping of the place of origin of the Varuna River, its stream network and basin boundary when compared to the maps generated through automatic methods using DEMs of various resolutions. The Varuna river system takes its headwaters from the areas surrounding Umran and Dain ‘tals’ (shallow, large depressions/basins) but not from the west of Mau Aima town as has been previously reported.

    • The oldest record of the bivalve Dosinisca Dall and its implications

      Borkar V D Kantimati G Kulkarni

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      Certain species of Dosinia occurring in the Miocene of Kachchh and the Pliocene of Balochistan in reality belong to the subgenus Dosinisca (Veneridae, Dosiniinae). This subgenus was hitherto known from the Quaternary of the Western Pacific Zoogeographic Province. The present study reveals that the first occurrence of Dosinisca is in the Khari Nadi Formation (Aquitanian) of Kachchh, India. The faunal affinity of the Kachchh Basin with the Alpine–European region through the Tethys fauna until Oligocene came to an end in the Lower Miocene due to the uplifting of the Himalayas. Later, during Lower Miocene, faunal migration took place between Kachchh and the Barrow Island off the northwestern coast of Australia, through the East Indies and Timor Island. After Dosinisca thrived in the Indian Subcontinent during Lower Miocene, the receding of marine waters endangered its very existence in this part of the globe. It somehow survived in Balochistan during Pliocene due to an episode of marine transgression. However, it must have migrated eastwards to the East Indies to be eventually established in the Western Pacific Zoogeographic Province.

    • Groundwater prospecting by the inversion of cumulative data of Wenner–Schlumberger and dipole–dipole arrays: A case study at Turamdih, Jharkhand, India

      Abhay Kumar Bharti Pal S K Saurabh Singh K K K Singh P K Amar Prakash Tiwary R K

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      The present study deals with groundwater prospecting in hardrock terrain. Initially, the Wenner–Schlumberger array and the dipole–dipole array data have been acquired using Syscal Junior Switch-48. Furthermore, data acquired using both arrays have been merged using Prosys-II data handling software for the inversion of the cumulative data for possible mapping of water-bearing fracture rock masses with different structural distribution in a complex geological environment. The data have been analysed using RES2DINV software, based on the smoothness constrained least-square technique. Two numbers of 2D electrical resistivity tomography profiles (AA$^{\prime}$ and BB$^{\prime}$) have been selected over an official colony of the Turamdih uranium mine for groundwater prospecting, which is located at about 24 km west of Jaduguda, Jharkhand, India. High-resistivity features associated with a dyke-like structure have been delineated in both the profiles. Three low-resistivity features have been delineated as water saturated alluvium/aquifers in profile AA$^{\prime}$. A low-resistivity feature associated with the water-saturated fracture zone has been identified in profile BB$^{\prime}$, which is well correlated with the surficial location of an ephemeral channel at the bottom of the hill across the slope. It is observed that geoelectric sections generated by the inversion of cumulative data of both arrays provide superior results compared with the Wenner–Schlumberger and dipole–dipole arrays, separately.

    • Analysing the characteristic features of a pre-monsoon thunderstorm event over Pune, India, using ground-based observations and WRF model

      Leena P P Pandithurai G Gayatri K Murugavel P Ruchith R D Sakharam S Dani K K Chetana Patil Dharmaraj T Patil M N Thara Prabhakaran

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      In the present work, the characteristic features and factors contributed to the formation of a typical pre-monsoon thunderstorm that occurred over Pune has been studied using various ground-based observations, such as microwave radiometer profiler, wind lidar and surface eddy covariance flux measurements along with weather research and forecast (WRF) model. Initially, the thermodynamic state of atmosphere, variation in fluxes, as well as convective updrafts and downdrafts associated with the thunderstorm event, has been studied using ground-based observations. Thermodynamic indices derived from ground-based microwave radiometer observations showed significant variation before, during and after the development of thunderstorm such as smaller humidity index and higher values of total total index and K-index during the storm. Convective available potential energy (CAPE) and equivalent potential temperature have also shown an increase prior to the event. It is noted that sensible heat flux is higher than latent heat flux before the initiation of storm, however, the latent heat flux increased significantly during the storm. Wind lidar-derived vertical velocities showed strong variation i.e., exceeding 3 m s$^{-1}$ during the event. Signatures of veering effect indicated the transport of moisture to higher levels was noticed from the altitude variability of wind vector. Ground observations suggested strong crosswind wind shear, convergence of moisture that originated at elevated levels in the boundary layer and enhancement of moist static energy in the elevated layer above the surface was pre-storm characteristics that conducive for the storm enhancement. Secondly, the capabilities of a WRF model in simulating the storm development, structure and evolution have been verified. The WRF model was able to recreate major features of the environment in which the storm was developed. The model output was compared with ground observations, which showed that the model has well captured the sensible heat and friction velocity as that of observation compared to mixing ratio and latent heat. It is observed that the water vapour variation in the model is having a lag, about an hour, with that of observations. The detailed analysis of model output did not show triggering of a thunderstorm as noted in the observation at the same location, which may be probably due to model bias in the moisture transport or moisture convergence was weaker in the model.

    • Estimation of coda Q for the eastern Indian craton

      Koushik Biswas Prantik Mandal Prosanta Kumar Khan

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      We herein present new frequency-dependent coda-Q ($Q_{\rm{c}}$) relations ($Q_{\rm{c}}$=$Q_{0}f ^{n}$) (frequency ranges between 2 and 18 Hz) for three regions of the eastern Indian craton (EIC), viz., the Singhbhum Odisha craton (SOC) and the Eastern Ghat mobile belt (EGMB), comprising the Mahanadi basin and the Chotanagpur granitic gneissic terrain (CGGT). The frequency-dependent coda-$Q_{\rm{c}}$ relations are obtained through the single backscattering model for coda waves ($Q_{\rm{c}}$) of local earthquakes which are recorded on 15 three-component broadband seismograph stations in the regions. In this work, we pay special attention to test the lapse time ($t_{\rm{L}}$) dependency of coda-Q ($Q_{\rm{c}}$) estimates for the three regions. Lapse time signifies the sample area of the coda wave of the study region. Generally, the sample area increases with lapse time. To test the lapse time ($t_{\rm{L}}$) dependency, nine different lapse time windows ($t_{\rm{L}}$) from 10 to 90 s with 10 s interval are considered. On the ground of estimated poor correlation coefficients, only six lapse time windows ($t_{\rm{L}}$) from 40 to 90 s with 10 s interval are considered. Our results suggest more heterogeneity in EGMB than that of the SOC and CGGT region. Estimates of $Q_{0}$ and n for the three regions of EIC (SOC, EGMB and CGGT) are found to be consistent with the results of $Q_{0}$ and n for mildly active less heterogeneous seismic zones in different parts of the world. By assuming entirely intrinsic attenuation characteristics, actual hazard parameters, i.e., extinction distance and anelastic attenuation coefficients are also computed for the three regions. The extinction distance ($L_{\rm{e}}$) provides an idea of the distribution of scatterers in the lithosphere and anelastic attenuation coefficients signify the anelasticity of the medium, i.e., fluid movement and grain distribution. The estimate of extinction distance and attenuation coefficients suggests that for all three study regions, the upper mantle is relatively less heterogeneous and attenuation below 110–126 km depth is also comparatively lower. Coda Q indicates the degree of fracture and heterogeneity in the lithosphere related to seismicity. A higher estimate of $Q_{0}$ values in the Archaean SOC region and the Proterozoic CGGT region is found when compared with that of the sedimentary-rich EGMB. It can be inferred that seismically less active cratons in general comprise high $Q_{0}$ values, whereas the sedimentary-rich EGMB is more attenuative, characterised by a low coda $Q_{0}$ value. Moreover, it is found that the estimated $Q_{0}$ values for CGGT region are a little bit higher than that for the SOC region. This can be explained as a comparatively less disturbed and less heterogonous land mass that is present in the CGGT region as compared to the SOC region, which comprises different minerals, ore bodies, fault scarps and shear zones. The developed $Q_{\rm{c}}$ relation for the EIC region could be useful for the study of hazards and ground motion prediction.

    • Impact of Cartosat-1 orography on weather prediction in a high-resolution NCMRWF unified model

      Jisesh Sethunadh Jayakumar A Saji Mohandas Rajagopal E N Subbu Nagulu A

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      The current study reports for the first time an application of orography from the Cartosat-1 satellite digital elevation model (DEM) generated at a source resolution of 30 m in a convection-permitting numerical weather prediction model. The effects of improvements in the representation of orography have been examined in the high-resolution regional National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model predictions for a heavy rainfall event over the city of Chennai. A time-lagged ensemble method is employed to account for the uncertainties associated with the initial conditions, which can better forecast extreme weather events than single forecasts. The simulations reveal that the predictions based on Cartosat-1 DEM capture the local details of the rainfall distribution better than the National Aeronautics and Space Administration shuttle radar topography mission DEM-based predictions, and better represent the orographic and thermal uplifting. The spatio-temporal patterns of the simulated rainfall over Chennai are superior in Cartosat-1 DEM-based simulations mainly due to the enhanced wind convergence and moisture transport. The present study reveals the role of mountains in the enhancement of heavy rainfall events over coastal cities and highlights the potential use of high-resolution orography in the improvement of the operational weather forecasting skill of the NCMRWF Unified Model.

    • Correlation of multiple deformation events in an area: Example from schistose rocks of Lesser Himalayas, NW Pakistan

      Mustafa Yar

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      Integrated micro-, meso- and macro-structural investigations were carried out in the multiply deformed rocks of the Mula Gori area, northeastern Khyber Agency, Lesser Himalayas. These investigations revealed an intricate history of deformation events that have not been formerly recognised. These structural examinations show four successive deformations. These events were identified in the field as well as in oriented vertical thin sections. The first deformation event D$_{1}$ is preserved in the form of inclusion trails in garnet porphyroblasts of foliation intersection axis 1 (FIA 1) and the fold axis of the macroscopic fold indicates NW–SE orogeny-oblique shortening. The D$_{2}$ event produced N–S trending foliations, fold axes and mineral lineations indicating E–W shortening. The D$_{3}$ is preserved as FIA 2 in garnet porphyroblast and E–W trending foliations, mineral lineations and fold axes in the field representing N–S shortening. The D$_{4}$ created NNW–SSE fabrics, which post-dates the main mantle thrust and the main boundary thrust, and likely resulted from the ENE–WSW bulk shortening related to development of the Hazara–Kashmir syntaxis.

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