Current Science

Chandra Shekhar Sanwal ¹, Raj Kumar ², Sneha Dobhal ³, Sushma Kerkatta ⁴, S. D. Bhardwaj ⁵

Affiliations
1 Uttarakhand Forest Department, Dehradun 248 001, IN
2 ICAR-Indian Institute of Soil and Water Conservation, RC, Vasad 388 306, IN
3 College of Forestry, Dr Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan 173 230, IN
4 Department of Forestry, Sarguja Vishwavidayalaya, Ambikapur 497 001, IN
5 College of Forestry, Dr Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan 173 230, IN

Abstract

In general, little emphasis is given on the production of medicinal plant species for sustainable harvest and conservation in the understorey of degraded forests. For instance, forests like chir pine which are not managed to grow any medicinal plants, offer an opportunity to produce and conserve native medicinal plants. This article highlights a study focusing on the production of medicinal plants in association with Chir pine forests, involving sustainable management techniques like minimum tillage and selecting suitable aspects for the sustainable harvest and conservation of plants under the canopy of trees. The medicinal plants were grown on three topographical aspects - Northern, North-Western and Western by adopting three tillage depths, viz. minimum (0 cm), medium (up to 10 cm) and deep tillage (up to 15 cm), in open and below tree canopy conditions. From yield and economic point of view, Andrographis paniculata, Mucuna pruriens, Solanum khasianum and Spilanthes acmella were found to be better yielding and more remunerative in comparison to Withania somnifera, Cymbopogon nardus and Ocimum basilicum, when grown outside the tree canopy adopting deep tillage on the Western aspect in Chir pine forests. The study can also be applicable to the other parts of the country to produce and conserve native medicinal plant species using sustainable management techniques like minimum tillage in blank patches or understorey of the degraded forests.

Keywords

Chir Pine, Degraded Forest, Medicinal Plants, Production and Conservation, Sustainable Management.

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Raj Kumar ¹, Mridul Chakraborti ¹, Ngursanzuala Sailo ¹, Tshering Chomu Bhutia ¹, D. R. Singh ¹

Affiliations
1 ICAR-National Research Center for Orchids, Pakyong, Sikkim 737 106, IN

Abstract

Orchids of Paphiopedilum genera, commonly known as lady’s slipper orchids, are popular as potted plants. Nearly 131 species have been reported worldwide, among which 9 are found in the states of North East India. Paphiopedilum villosum (Lindl.) is one such species which is listed under vulnerable category in the latest version of the IUCN Red Data Book. Its area of occupancy (AOO) is limited to only 56 sq. km in the world and its population trend has reduced significantly in recent decades. The species is protected under Schedule VI of the Wildlife Protection Act of India. Utilization of only cultivated specimens in the trade and long-term community-based conservation to protect the habitat and species has been recommended by IUCN.

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Surajit Ghosh ¹, Raj Kumar ¹, Uttara Pandey ¹, Parul Srivastava ¹, Swapan Mehra ¹

Affiliations
1 IORA Ecological Solutions Pvt Ltd, 225B, FF, Indraprastha, Gyanamandir Complex, Lado Sarai Village, New Delhi - 110030, IN

Abstract

The Brahmaputra basin covers a geographical area of 580,000 km², spreading over China, India, Bangladesh and Bhutan. India is the middle riparian country between China and Bangladesh on the Brahmaputra river which originates from the Angsi glacier in Tibet¹. The catchment of the Brahmaputra within India spreads across the states of Arunachal Pradesh, Assam, Meghalaya, West Bengal, Nagaland and Sikkim. Flooding is a regular phenomenon in the lower catchment of the Brahmaputra.

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Neeraj Agarwal ¹, Rashmi Sharma ¹, Pradeep Thapliyal ¹, Rishi Gangwar ¹, Prateek Kumar ¹, Raj Kumar ¹

Affiliations
1 Earth, Ocean, Atmosphere and Planetary Sciences Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

The study presents assessment and potential oceanographic applications of sea-surface temperature (SST), ocean net shortwave radiation (SWR) and chlorophyll concentration (CC) observations obtained from various geostationary platforms. SST and SWR from imager on-board Indian National Satellite (INSAT- 3D) and CC from Global Ocean Color Imager (GOCI) on-board communication ocean and meteorological satellite (COMS) have been used in the analysis. Relative advantages of high temporal resolution obtained from the geostationary platform compared to polar orbiting platforms are demonstrated. Comparison of INSAT-3D SST with observations gives a correlation of 0.85 and RMSE of 0.81 K. These platforms definitely provide a highly reliable source of continuous observations, which is useful in monitoring dynamic oceanic features such as thermal fronts, chlorophyll blooms, air–sea exchange fluxes, etc. on diurnal to daily timescales.

Keywords

Chlorophyll Concentration, Geostationary Satellites, INSAT-3D, Sea-surface Temperature, Shortwave Radiation.

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Tapan Misra , Raj Kumar , Ernesto Rodríguez

Abstract

Ocean surface winds are an important parameter for various meteorological and oceanographic applications. These are utilized not only for the study of severe weather events like cyclones, hurricanes and typhoons, but are also important for assimilation in numerical weather forecast models to improve the forecast. The ocean surface winds also cater to the forcing of ocean wave and circulation models used for ocean state forecasts. In situ measurements of winds by buoys and ships are point observations and also very few in number to provide a synoptic view.

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Suchandra A. Bhowmick ¹, James Cotton ², Alexander Fore ³, Raj Kumar ¹, Christophe Payan ⁴, Ernesto Rodríguez ³, Anuja Sharma ¹, Bryan Stiles ³, Ad Stoffelen ⁵, Anton Verhoef ⁵

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN
2 Met Office, GB
3 Jet Propulsion Laboratory, California Institute of Technology, US
4 CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, FR
5 Royal Netherlands Meteorological Institute (KNMI), NL

Abstract

SCATSAT-1 is a continuity mission for the Oceansat-2 scatterometer, OSCAT-1, which provided useful ocean vector wind observations used in, among others, oceanography, numerical weather prediction (NWP) and nowcasting. The purpose of this paper is to review the findings of the SCATSAT-1 CalVal team regarding the stability and performance of version 1.1.3 of the SCATSAT-1 data. The international CalVal team organized by ISRO included participants from various institutions in India, ISRO’s Space Applications Centre, KNMI from the Netherlands, and from the USA, NOAA, and NASA’s JPL. To perform the evaluation, different centres processed the data independently using heritage processors and made comparisons against NASA’s Ku-band QuikSCAT mission, in situ data, and NWP models. We also provide a preliminary assessment of the impact of the SCATSAT-1 data on operational forecasts in India and Europe. We conclude that the SCATSAT-1 data shows significantly improved performance relative to ISRO’s OSCAT-1 on Oceansat-2, and that the instrument seems to be stable, given the limited period of observation. The CalVal team has also identified features in the data that could benefit from calibration and processing changes, potentially leading to further improvements on data quality.

Keywords

Calibration, OSCAT-1, QuikSCAT, Weather Prediction.

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Raj Kumar ¹, Suchandra A. Bhowmick ¹, Abhisek Chakraborty ¹, Anuja Sharma ¹, Shweta Sharma ¹, M. Seemanth ¹, Maneesha Gupta ¹, Prantik Chakraborty ¹, Jalpa Modi ¹, Tapan Misra ¹

Affiliations
1 Space Applications Centre, ISRO, Ahmedabad 380 015, IN

Abstract

Here we provide a brief description of the post-launch data quality evaluation and calibration–validation chain of the SCATSAT-1, the second scatterometers mission of Indian Space Research Organisation. This chain is of absolute importance to monitor the satellite health and its impact on its measurements. It also provides us overview of the suitability of the data for various applications. The results show that the SCATSAT instrument is having nominal behaviour, the measurements are of very high quality and is comparable to the reference mission QuikSCAT. The ocean surface winds derived using SCATSAT-1 are having errors less than 1 m/s and hence it is suitable for all operational meteorological and oceanographic applications.

Keywords

Calibration, Data Quality Evaluation, Scatterometers, Validation, Wind Vectors.

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Raj Kumar ¹, Robert O. Green ²

Affiliations
1 Space Applications Centre, ISRO, Ahmedabad 380 009, IN
2 Jet Propulsion Laboratory, US

Abstract

ISRO–NASA Airborne Hyperspectral Campaign

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Bimal K. Bhattacharya ¹, Robert O. Green ², Sadasiva Rao ³, M. Saxena ¹, Shweta Sharma ¹, K. Ajay Kumar ¹, P. Srinivasulu ³, Shashikant Sharma ¹, D. Dhar ¹, S. Bandyopadhyay ⁴, Shantanu Bhatwadekar ⁴, Raj Kumar ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN
2 Jet Propulsion Laboratory, California Institute of Technology, CA 91109, IN
3 National Remote Sensing Centre, Indian Space Research Organisation, Hyderabad 500 625, IN
4 Earth Observation Science Directorate, Indian Space Research Organisation, Bengaluru 560 231, IN

Abstract

The first phase of an airborne science campaign has been carried out with the Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG) imaging spectrometer over 22,840 sq. km across 57 sites in India during 84 days from 16 December 2015 to 6 March 2016. This campaign was organized under the Indian Space Research Organisation (ISRO) and National Aeronautics and Space Administration (NASA) joint initiative for HYperSpectral Imaging (HYSI) programme. To support the campaign, synchronous field campaigns and ground measurements were also carried out over these sites spanning themes related to crop, soil, forest, geology, coastal, ocean, river water, snow, urban, etc. AVIRIS-NG measures the spectral range from 380 to 2510 nm at 5 nm sampling with a ground sampling distance ranging from 4 to 8 m and flight altitude of 4–8 km. On-board and ground-based calibration and processing were carried out to generate level 0 (L0) and level 1 (L1) products respectively. An atmospheric correction scheme has been developed to convert the measured radiances to surface reflectance (level 2). These spectroscopic signatures are intended to discriminate surface types and retrieve physical and compositional parameters for the study of terrestrial, aquatic and atmospheric properties. The results from this campaign will support a range of objectives, including demonstration of advanced applications for societal benefits, validation of models/techniques, development of state-of-the-art spectral libraries, testing and refinement of automated tools for users, and definition of requirements for future space-based missions that can provide this class of measurements routinely for a range of important applications.

Keywords

Airborne Science Campaign, Hyperspectral Sensing, Imaging Spectrometer, Surface Reflectance.

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Deepak Putrevu ¹, Sanjay Trivedi ¹, Anup Das ¹, Dharmendra Pandey ¹, Priyanka Mehrotra ¹, S. K. Garg ¹, Venkata Reddy ¹, Shalini Gangele ¹, Himanshu Patel ¹, Devendra Sharma ¹, R. Sijwali ¹, Nikhil Pandya ¹, Amit Shukla ¹, Gaurav Seth ¹, V. M. Ramanujam ¹, Raj Kumar ¹

Affiliations
1 Space Applications Centre, Ahmedabad 380 015, IN

Abstract

Dual-frequency Synthetic Aperture Radar (SAR) operating in L- and S-band frequencies is one of the primary payloads of the Chandrayaan-2 orbiter. This payload with the capability of imaging in dual frequency (L-band: 24 cm wavelength and S-band: 12 cm wavelength) with full polarimetric mode aims for unambiguous detection, characterization and quantitative estimation of water-ice in permanently shadowed regions over the lunar poles. The payload will address the ambiguities in interpreting high values of circular polarization ratio associated with water-ice observed during previous missions to the Moon through imaging in dual-frequency fully polarimetric SAR mode. Various improved system features such as wide range of resolutions and incidence angles, synchronized Land S-band operations, radiometer mode, are built into the instrument to meet the required science objectives, adhering to stringent mission requirements of low mass, power and data rates. Major scientific objectives of dual-frequency polarimetric SAR payload are: unambiguous detection and quantitative estimation of lunar polar water-ice; estimation of lunar regolith dielectric constant and surface roughness; mapping of lunar geological/morphological features and polar crater floors at high-resolution, and regional- scale mapping of regolith thickness and distribution.

Keywords

Circular Polarization Ratio, Dual Frequency, Lunar Polar Water-ice, Synthetic Aperture Radar.

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Surisetty V. V. Arun Kumar ¹, Rakesh Kumar Luhar ², Rashmi Sharma ¹, Raj Kumar ¹

Affiliations
1 Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Ahmedabad 380 015, IN
2 Mechanical Engineering Systems Area, Space Applications Centre (ISRO), Ahmedabad 380 015,, IN

Abstract

Lagrangian drifters are analogues of particles that are relevant to flow-field characterization and therefore they represent realistic surface currents compared to Eulerian techniques. The use of global navigation satellite system (GNSS) in such drifters with Differential Global Positioning System mode at high frequency (5–10 Hz) sampling and post-processing kinematic results in position estimates with centimeter-level accuracy. In the complex nearshore zone, deploying expensive instruments is a risk due to greater chances of loss. To avoid this, two drifters have been designed and developed using a low-cost Emlid Reach® GNSS receivers, antennae and ‘off-the-shelf’ PVC components to measure the surface currents. The dimensions of the drifters were optimally chosen to minimize the wind and wave impacts and to increase the subsurface current drag. An analysis of relative position and velocity errors from stationary observations indicates that the drifter can resolve motion accurately with minimal errors of ±1 cm and ±2 cm/s respectively. These drifters were used to measure surf zone currents at the RK Beach, Visakhapatnam during May 2018 and to successfully identify dangerous rip current zones. This study presents the design, development aspects, error analysis and testing of GNSS drifters. Although these drifters are primarily developed to measure the rip current velocities and trajectories in the nearshore zone, they can also be operated in any marine environment like rivers, lakes, estuaries, etc. without change in the design. An extensive study using a fleet of such drifters is required to understand the complex physical processes in the marine environment.

Keywords

Drifter, Error Estimation, Rip Currents, Relative Position and Velocity.

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Jagdish Prajapati ¹, Abhisek Chakraborty ¹, Bipasha Paul Shukla ¹, Raj Kumar ¹

Affiliations
1 Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

In this study, a method for retrieving ocean surface wind speed using C-band cross-polarization SAR observations has been outlined. A linear least square technique has been used to develop a Geophysical Model Function (GMF), C2P. The GMF was derived using NRCS observations from RISAT-1 and wind-speed observations from ASCAT. The correlation between observed and simulated NRCS values obtained from C2P was 0.66, with a negative bias of 0.01 dB and the corresponding ischolar_main mean square difference of 1.13 dB. Subsequently, the developed GMF was tested with 774 RISAT-1 MRS datasets to retrieve wind speed along the Indian coast and also of the tropical cyclone ‘Megh’. The measured intensity and radius of maximum wind speed were 30 m s^–1 and 16.65 km respectively. Subsequently, the retrieved wind speed was validated with ASCAT wind-speed observations. The statistical comparison of RISAT-1 and ASCAT observed wind speed showed negative biases of 0.90 and 0.34 m s^–1 with the corresponding RMSD of 2.11 and 1.77 m s^–1 respectively, for CMOD5.N and C2P. The developed GMF C2P showed 16% more accuracy than that of CMOD5.N.

Keywords

Cross-polarization, Geophysical Model Function, Ocean Surface, Wind Speed Retrieval.

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Surisetty V. V. Arun Kumar ¹, Ch. Venkateswarlu ², B. Sivaiah ², K. V. S. R. Prasad ², Rashmi Sharma ¹, Raj Kumar ¹

Affiliations
1 Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre (ISRO), Ahmedabad 380 015, IN
2 Department of Meteorology and Oceanography, Andhra University, Visakhapatnam 530 004, IN

Abstract

Determining nearshore bathymetry by traditional surveying methods is a challenging task as it involves huge costs and efforts. Most of the coastal shallowwater zones worldwide either remain unmapped or not updated. Bathymetry estimations from optical satellite imageries have been increasingly implemented as an alternative tool for traditional bathymetry surveys. In this study, we examine the usefulness of freely available, five-day revisit and relatively highresolution Multi Spectral Instruments (MSI) on-board Sentinel-2A and 2B twin satellites. A process workflow has been developed which automatically incorporates a robust atmospheric correction through ACOLITE software and multi-scene compositing of several scenes to improve the reliability and no data gaps. Two study sites in India are explored owing to their variability in submarine morphology. High-resolution bathymetry maps are generated through a log-ratio transform model calibrated with minimal in situ data from the jet ski soundings. The satellite-derived bathymetry obtained has an overall bias of –0.01 and 0.02 m, and ischolar_main mean square error of 1.09 and 0.93 m respectively, at two study sites up to 15 m depth. The consistency in bathymetry retrieval indicates a potential for automated application for the benefit of operational and scientific studies. These high-resolution maps capture small-scale nearshore features like sandbars and rip channels, which are of prime importance for coastal and beach managers.

Keywords

Optical Remote Sensing, Multispectral Imagers, Nearshore Bathymetry Maps, Rip Channel, Twin Satellites.

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R. P. Singh ¹, Shard Chander ¹, Ratheesh Ramakrishnan ¹, Ashwin Gujrati ¹, Rohit Pradhan ¹, Chirag Wadhwa ¹, A. S. Rajawat ¹, Raj Kumar ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

In this study we identify a region of submarine groundwater discharge (SGD) near Okha coast, Gujarat, India using thermal infrared remote sensing technique. Observations of brightness temperature (BT) in the thermal infrared spectral region (10.6–11.19 μm) from Landsat-8 satellite in the coastal region showed unique localized cooling in the Arabian Sea during winter. We observed lowering of BT in the range 0.6°– 2.3°C in the coastal region associated with SGD in comparison to sea surface temperature of the ocean during low-tide conditions. Consistent geographical pattern of thermal contrast was observed near the same location (lat. 22°26′54.43″N, long. 69°00′41.67″E) when multi date (11 datasets) thermal data were analysed between 2015 and 2019 in winter. Generally, low-tide conditions show more cooling of ocean surface at the SGD site compared to high-tide conditions, which indicates the process of SGD. Satellite-based assessment was further validated using field- and ship-based measurements.

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M. Mohapatra ¹, A. K. Mitra ¹, Virendra Singh ¹, S. K. Mukherjee ¹, Kavita Navria ², Vikram Prashar ¹, Ashish Tyagi ¹, Atul Kumar Verma ¹, Sunitha Devi ¹, V. S. Prasad ³, Mudumba Ramesh ⁴, Raj Kumar ⁵

Affiliations
1 National Meteorological Satellite Centre, India Meteorological Department, New Delhi 110 003, IN
2 National Meteorological Satellite Centre, India Meteorological Department, New Delhi 110 003ii
3 National Centre for Medium Range Weather Forecasting, Noida 201 309, IN
4 Master Control Facility, Indian Space Research Organisation, Hassan 573 201, IN
5 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

In order to observe severe weather conditions during cyclones, thunderstorms, etc., IMAGER instruments on-board INSAT3D/3DR have been built with a flexible scanning feature known as ‘rapid scan mode’. Using this feature, the number of scan lines over a given coverage region and the number of repetitions of the selected region can be programmed for scanning. Therefore, to understand the physical processes involved in convective clouds associated with severe weather phenomena, rapid scan of INSAT3DR mode is attempted. It has very high temporal resolution of approximately 4 min and 30 sec. The present study will help in better understanding of the physical processes of severe weather phenomena and in nowcasting. It will also help to improve the accuracy in the NWP model forecast through assimilation of radiances and atmospheric motion wind determined using rapid scan mode.

Keywords

Nowcasting, Physical Processes, Rapid Scan Operations, Severe Weather Conditions, Weather Monitoring.

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V. C. Pande ¹, P. R. Bhatnagar ¹, D. Dinesh ¹, Raj Kumar ², Gopal Kumar ³

Affiliations
1 ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Vasad 388 306, IN
2 ICAR-Central Soil Salinity Research Institute, Karnal 132 001, IN
3 ICAR-Indian Institute of Soil and Water Conservation, 218, Kaulagarh Road, Dehradun 148 195, IN

Abstract

Ravine agro-ecosystems are characterized by degra­ded gullied lands formed over the years due to several natural and anthropogenic factors, surrounded by the adjacent table lands cultivated for the production of food and fibre for humans and livestock. These potential lands not only support the livelihood of marginal and smallholder farmers, but are host to various plants and grass vegetation providing a cushion to the local environment. A two-way relationship exists between the human settlements and ecosystem services in these agro-ecosystems. While the ravines support plants, grasses and human settlements in these agro-ecosystems, the same biophysical pressures over time degrade the ecosystem leading to ecosystem services loss, if not managed sustainably. The present pilot study conducted in the Mahi ravines, Gujarat, India, has examined these issues from the local socio-ecology perspectives and suggests management options for participatory management.

Keywords

Ecosystem Services, Gullied Land, Livelihood, Participatory Management, Ravines.

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