• PRASHANT KUMAR

      Articles written in Journal of Earth System Science

    • Verification of cloud cover forecast with INSAT observation over western India

      Shivani Shah B M Rao Prashant Kumar P K Pal

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      Since the beginning of the summer monsoon 2009, experimental mesoscale weather forecasts in real time are being generated using WRF model by the Meteorology and Oceanography Group at the Space Applications Centre (ISRO)and are disseminated through MOSDAC (www.mosdac.gov.in) to various users. To begin with, the 12 h, 24 h and 48 h forecasts for the western India region are made available. A study is undertaken to comprehensively assess the cloudiness prediction performance of WRF model. The evaluations have been made over the three months period during monsoon 2009. INSAT cloud imagery data has been used as a reference for these evaluations. The verification strategy includes computation of various skill scores. It is seen that probability of detection (POD)of cloud is 84% and the false alarm rate (FAR) is around 18%. It is hoped that this assessment will provide information on the use of these forecasts in various applications.

    • Impact of additional surface observation network on short range weather forecast during summer monsoon 2008 over Indian subcontinent

      Prashant Kumar Randhir Singh P C Joshi P K Pal

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      The three dimensional variational data assimilation scheme (3D-Var) is employed in the recently developed Weather Research and Forecasting (WRF) model. Assimilation experiments have been conducted to assess the impact of Indian Space Research Organisation’s (ISRO) Automatic Weather Stations (AWS) surface observations (temperature and moisture) on the short range forecast over the Indian region. In this study, two experiments, CNT (without AWS observations) and EXP (with AWS observations) were made for 24-h forecast starting daily at 0000 UTC during July 2008. The impact of assimilation of AWS surface observations were assessed in comparison to the CNT experiment. The spatial distribution of the improvement parameter for temperature, relative humidity and wind speed from one month assimilation experiments demonstrated that for 24-h forecast, AWS observations provide valuable information. Assimilation of AWS observed temperature and relative humidity improved the analysis as well as 24-h forecast. The rainfall prediction has been improved due to the assimilation of AWS data, with the largest improvement seen over the Western Ghat and eastern India.

    • Magnetic susceptibility investigation of the saline water intrusion problem: The LAMP-BHU protocol

      VIRENDRA RANA PRASHANT KUMAR SAYANDEEP BANERJEE ARKOPROVO BISWAS

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      A protocol is presented to perform bulk magnetic susceptibility (BMS) analysis of simulated seawater/saline water using MFK2-FA Multi-Function Kappabridge instrument at Laboratory for Analyses of Magnetic and Petrofabric (LAMP), BHU to obtain a correlation between BMS and hydrogeological data such as salinity and conductivity. This LAMP-BHU Protocol involves the preparation of simulated saline water. It has been developed after BMS measurement of 20 simulated seawater samples in different frequencies, i.e., F1 (976 Hz), F2 (3904 Hz), and F3 (15616 Hz) to prepare a standard data. This standard data is further validated with field data. Fourteen water samples are collected from the field, and hydrogeological data (salinity and conductivity) and BMS at three different frequencies were measured. Further linear regression analysis is performed on the measured data. This protocol yields efficient results with F3, followed by F1 and F2 having an R$^{2}$ value of 0.84, 0.60, and 0.54, respectively, for salinity, and 0.79, 0.51, and 0.40, respectively, for conductivity. Salinity and conductivity are showing a negative trend with all the frequencies. This protocol enables to delineate saline water intruded zone or extent of saline intrusion using BMS analysis. The proposed protocol is a rapid and efficient mode of determination of the saline water intruded zones in the coastal aquifers for prioritisation of groundwater assets facilitating freshwater availability in coastal areas.

      $\bf{Highlights}$

      $\bullet$ Protocol is developed for Saline water intrusion studies using magnetic susceptibility measurements.

      $\bullet$ Magnetic susceptibility, salinity and conductivity was measured for simulated and field samples.

      $\bullet$ Inverse relationship observed between magnetic susceptibility w.r.t. salinity and conductivity.

      $\bullet$ High frequency magnetic susceptibility provides better results for gradual increase in salinity.

    • Ionospheric and atmospheric perturbations due to two major earthquakes (M > 7.0)

      SANJAY KUMAR PRASHANT KUMAR SINGH ROHTASH KUMAR A K SINGH R P SINGH

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      The perturbation produced in the atmosphere/ionosphere associated with earthquake precursors during seismic activity of two major earthquakes which occurred on (1) 24 June 2019 in Indonesia (M = 7.3) and (2) on 19 August 2018 at Ndoi, Fiji (M = 8.2), are studied. Based on statistical analysis of total electron content (TEC) data, the presence of ionospheric perturbations 5 days before and after the main shock are found, which depends on the distance as well as direction of observation point from the epicentre. In general, ionospheric perturbations after the EQ at all the stations are found larger than that before the EQ. Probable mechanisms behind these perturbations associated with EQ are also being discussed. The ionospheric perturbations are observed at stations which are at larger distances from the epicentre, but not observed over other stations in different directions which are comparatively closer to the epicentre. These results suggest that seismic induced ionospheric anomaly is not isotropic in nature. Ozone data from three satellites: AIRS, OMI, and TOMS-like and MERRA-2 model are also analyzed 5 days before the EQ day and compared to the monthly average level. A strong link between anomalous variation in ionospheric TEC and atmospheric ozone data prior to both the EQs is noticed.

    • Barren Island volcanism and seismicity: An intriguing finding

      GOUTHAM KRISHNA TEJA GUNDA PRASHANT KUMAR CHAMPATI RAY MAMTA CHAUHAN PRAKASH CHAUHAN S BALAJI

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      Barren Island volcano (BIV), India has started erupting vigorously from 2018 after a gap of 13 years (last active period 2004–2005) just after the 2004 tsunami. Although there is evidence of coupling between seismicity and earthquake in this region, it is not thoroughly researched. Here, we present satellite-based approach to monitor and understand the volcano dynamics w.r.t. associated seismicity at BIV using multispectral datasets, ${\sim}$ 20 yrs Volcanic Radiative Power (VRP) and ${\sim}$ 70 yrs historical earthquake data (1950–2020 July). The rate of frequency of earthquake has increased to 3.54 times during 1990–2020 as compared with 1950–1989 which signifies seismicity-induced pressure release that may have caused decompression in the region, leading to eruptions or at least modulation of the eruption. The VRP results clearly depicted the changes from low to high thermal regimes that indicate switching from open-vent to effusive activity of Barren Island volcano. The historical data of recent times show correlation of seismic and volcanic activities. The spatial-temporal distributions of earthquake swarm are not associated with volcano, but are clustered near the tectonic regimes. The volcanic activity is preceded by seismic activity along the regional tectonic structures. In addition, the 2018 eruptive phase has been analyzed for better understanding of the proposed event. The present research has provided significant supportive evidences to give adequate credence to this emerging hypothesis and also revealed the location of primary, secondary vents, flow tracts and all evolving volcanic landforms of the region and recorded the changes in flow directions. Further, for a comprehensive risk assessment of the region, volcanism, seismicity, and coastal dynamics along with crustal deformation need to be considered.

      $\bf{Highlights}$

      $\bullet$ The study has analyzed the eruption of Barren Island volcano and associated regional seismic activity from a Multi-Hazard perspective using satellite as well as field-based observations.

      $\bullet$ These results provided stronger supportive evidences for coupling seismicity and volcanic eruptions at Barren Island volcano for the first time in this region and open up new vistas for research in this direction.

      $\bullet$ The understanding of these two natural phenomena is very much needed for better preparedness with respect to disaster risk mitigation and management.

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